Author: ecogrow

The deviation is almost zero near Ŵ point and begin to have large value at the momentum at which the Berry curvature and the OAM are also about to increase from almost zero value. This provides experimental evidence that the deviation from the median value of INCDs in geometry-A and -B can be interpreted as the Berry curvature contribution. Although the Berry curvature and the OAM continually increase as they approach the K point, the deviation from the median value from CD-ARPES data seems to be almost constant away from the Ŵ point.Let us briefly touch upon the possible incident photon energy dependence in CD-ARPES or the final state effect. This is because one can wonder if the CD-ARPES pattern we obtained is seen only with the particular photon energy and a different photon energy may give us a different result. In such case, changing the photon energy will also change the CD-ARPES pattern and the CD-ARPES may not be related to OAM or the local Berry curvature. We would like to point out that incident photon energy dependent CD-ARPES has been performed on the same material. The results showed that CD-ARPES features related to the local Berry curvature are the same regardless of the photon energy. Even though it was for a different plane of incidence compared to the current one, the photon energy independence of the pattern provides a good reason to believe that the CD-ARPES pattern is proportional to OAM or the local Berry curvature. In some the other systems such as Bi2Te3, PtCoO2 and Au, CD-ARPES results show a sign change. Yet, growing bags those results still show that node lines in CD-ARPES map remain the same except a special resonant channel is involved.

In addition, characteristic patterns of CD-ARPES map cannot be explained without consideration of OAM. Therefore, we argue that the interpretation of the CD-ARPES intensity in this work should be robust although the data was taken only with a single photon energy. CD-ARPES data on 2H-WSe2were taken with the crystal mirror plane set as the experimental mirror plane. Within the experimental constraint, there are two possible experimental geometries. We found that CD-ARPES data for the two geometries are almost opposite to each other near the BZ corners, and nearly the same near the Ŵ point. The experimental observations are well explained by accounting for the Berry curvature contribution to CD-ARPES. The Berry curvature contribution to the INCDs can be quantitatively extracted through an analysis that compares INCDs for the two geometries. Our results provide experimental evidence that the deviation from the median value between the two experimental geometries can be interpreted as the Berry curvature or the OAM. Our work may be applicable to observations of the Berry curvature or the OAM in topological materials, such as Weyl semimetals and Berry curvature dipole materials.Horticultural crops provide 60 percent of total farm revenue in California agriculture, and California provides 37 percent of the horticultural crop value in the United States. Clearly, these industries comprise an important part of the agricultural economy. This study provides a detailed statistical profile of California’s horticultural crop industries at the farm level, based on a survey of specialty crop growers that was conducted during the spring of 2002. The Risk Management Agency of the United States Department of Agriculture supported the research, and the California Office of the National Agricultural Statistics Service helped conduct the survey. Specialty crops, also referred to as horticultural crops, include tree and vine crops, vegetables, and ornamental crops.

The statistical profile of California’s horticultural farm industries presented here is the most comprehensive ever undertaken for these industries, drawing on survey data collected from approximately one-third of all horticultural crop producers in the state. Specialty crops are diverse. They differ in their product characteristics, production processes, and market environments. Such heterogeneity extends to risk characteristics of the crops and to the ways farmers cope with various risks. As a preliminary step to development of effective risk management tools, it is important to better understand factors that affect these risks. This report is intended to provide such information to help us understand specialty crop industries, the sources of risk, and behavioral risk responses in these industries. The following summary of results is organized by topic.About 86 percent of the farms surveyed produced primarily orchard and vine crops, 5 percent produced vegetable crops, and 9 percent produced ornamental crops. About 25 percent of the farms were located in coastal areas, 13 percent in the Sacramento Valley, and 47 percent in the San Joaquin Valley. The remaining 15 percent were in the northern mountain areas, the Sierra Nevada, the Southern coast, and the deserts. Average farm size was 203 acres, but the median farm comprised only 34 acres. The average number of acres per farm varied substantially among the three crop categories: fruits/nuts, vegetables, and ornamental crops. The average land holding by vegetable growers, 1,106 acres, far exceeded the average of 157 acres for fruits/nuts and 200 acres for ornamental crops. These land figures include land planted to secondary crops . When we examined land planted only in primary crops, our data showed that fruit/nut and vegetable farmers held, on average, about 50 percent of their land in primary crops . However, land for ornamental crops, on average, accounted for only 10 percent of the average 200 acres per farm.

Crop diversification has long been recognized as an important risk management tool. Our data showed that crop diversification was much less common for orchard farms than for vegetable farms. About 70 percent of fruit/nut farmers were single-crop growers as opposed to 26 percent for vegetable farms. The scope of diversification also differed. Fruit/nut farmers predominantly diversified their crops with other varieties of fruits and nuts; only 20 percent of them used crops other than fruits and nuts for diversification. Vegetable farmers, on the other hand, frequently used other crops for diversification; only one-third of the vegetable farms were diversified among only vegetable crops. Our survey also indicated that primary crop acreage increases with crop diversification for both fruit/ nut and vegetable crops. Farms growing five or more vegetables were, on average, four times larger in vegetable acreage than farms growing a single vegetable crop. In California, 6 percent of specialty crop farmers had some organic or transitional-organic land. In terms of crop category, these farms represented 6 percent of orchard farms, 14 percent of vegetable farms, and 4 percent of ornamental crop farms. Our data showed that these farms also engaged in conventional farming and that they devoted, on average, about one-third of their primary crop lands to organic farming. Judging from acreage assigned to primary crops, nursery grow bag the farms were about average in acreage for fruit/nut farms but much smaller than average conventional vegetable farms.Marketing is an important component of risk management. Marketing channels vary by product use . Processing crops are delivered in bulk directly to processing plants, whereas fresh-use crops are sent to operations to be sorted, packaged, cooled , and distributed through marketing channels. California producers were highly specialized in terms of use. Most fruit/nut farms produced mainly for processing use and most vegetable farms produced mainly for fresh use . Only 7 percent of specialty crop farmers supplied both processing and fresh market outlets. In processed-use markets, contracts played a major role with contracts with a predetermined price being the most prevalent form. In fresh-use markets, grower/shippers, which combine the packing/shipping business with field production under one ownership, provide a form of vertically integrated business. Our survey showed that grower/shippers accounted for 13 percent of vegetable farmers and 3 percent of orchard farmers and that they mainly supply mass merchandisers . The other fresh-market growers tended to use diverse marketing channels, including selling directly to consumers, marketing through cooperatives and independent shippers, and selling directly to commercial buyers. For fresh vegetable markets, “directly to consumers” was the most commonly used outlet , not by volume of production but by number of farms using this marketing channel.We investigated year-to-year yield variations using yield information for the preceding five years. Taking the average of the five annual yields as an individual’s normal yield, we calculated the percent deviation from the normal yield and then arrived at sample mean deviations for sample categories. Our data indicated that annual yield deviated, on average, 15 percent for fruits/nuts and 8 percent for vegetables over the previous five years. For price and profit fluctuations, we elicited information on the range of the highest fluctuation experienced over the same five year period . For both price and profit, the median of the accumulated distribution fell in the 25–49 percent range for fruits/nuts and the 10–24 percent range for vegetables, indicating that prices as well as profits tend to fluctuate less for vegetables than for fruits/nuts. In response to a list of options as the main cause for the lowest profit, “poor yield,” “low market price due to high domestic production,” and “low market price due to imports” were the three most often cited causes for all crops except ornamentals. They accounted for 70 percent of the responses for fruit/nut and vegetable farmers. For fruit/nut crops, poor yield was the most cited reason for the lowest profit , but for vegetables, low market price due to high production was cited most , followed by low market price due to imports .

This underscores the relative importance of production risks for orchard crops and of market risks for vegetable crops.Two sources of risk, adverse temperature and output price fluctuation, were listed as most important; input price fluctuation, pests, and disease were considered to be moderately important. Crop insurance was a preferred risk management tool for orchard and vineyard farmers, and crop diversification was preferred by vegetable and ornamental crop growers. Diversified marketing was reported to be the second most preferred tool for all three crop categories. We also surveyed farmers about the availability of risk management tools. As expected, their preferences were closely linked to availability. The most available tools were crop insurance for orchard crops and crop diversification for vegetables and ornamental crops . Orchard and vineyard farmers reported relatively limited availability of other risk management tools.About 53 percent of fruit/nut farmers, 31 percent of vegetable farmers, and 13 percent of ornamental crop farmers said they had purchased crop insurance in the preceding five years and most of those farmers had purchased it for all five years Single-peril insurance is mostly offered by private firms, most commonly for damage from frost, rain, and hail. This insurance was purchased by about 20 percent of fruit/nut farmers and about 10 percent of vegetable farmers. Many farmers suggested that a higher yield guarantee would improve crop insurance. Further, most farmers strongly suggested the need for crop insurance that compensates in value terms, but they expressed no strong preference among compensations based on gross sales, profits, or production costs.Financial variables examined were off-farm incomes, gross sales, debts, and assets. Clearly, the portion of household income risk attributable to variation in farm income decreased as the share of off-farm income rose. For our sample, an average of 63 percent of income came from off-farm sources. A sizable segment of farmers, as many as 25 percent, derived less than 1 percent of their income from farming in the year sampled. This is consistent with the observation that many of the farms were quite small, many farms operated at a loss in any given year, and there was a relatively large number of so-called “hobby” farms in California. Gross agricultural sales averaged about $0.4 million per farm for the entire sample. Vegetable farms averaged $1.1 million in sales, followed by ornamental crop farms with $0.8 million, and orchard farms with $0.3 million. About 6 percent of fruit/nut farms had sales of more than $1 million, compared to 29 percent for vegetable farms and 13 percent for ornamental farms. Agricultural sales were negatively correlated with off farm income share and positively correlated with acreage. Revenue per acre decreased as acreage increased. Given that specialty crops vary widely in unit value and in value per acre, this indicated that farms with fewer acres tended to grow crops with a high value per acre.

When I commented on the apparent lack of urban agriculture activity in Oakland in the mid 1990s compared to what was happening in Berkeley, Daniel Miller, founder of Spiral Gardens, replied, “Oh, there was plenty of urban agriculture taking place in Oakland back then. It was just happening in folks’ yards” . As I explain in Chapter 2 and in my discussion of the Black Panthers in Part 1 above, most of Oakland’s African American population can be traced to a large wave of migration from the rural South during World War Two. Many younger African Americans in the flatlands—second or third generation Oaklanders—talk about how their parents or grandparents grew up on a farm and what they used to grow. Many participants in flatlands urban agriculture programs—City Slicker Farms’ Backyard Gardening Program in West Oakland, for example—are middle-aged African Americans who grew up eating from their parents’ gardens in Oakland, Berkeley, and Richmond. More recent arrivals have carried on such an agrarian tradition. The rolling range and orchards of the Peralta family’s Rancho San Antonio was long ago transformed by several waves of industrial and residential capital. Yet amidst the dense mix of once-stately ramshackle Victorians, craftsman bungalows, and worn out apartment complexes built in the 1960s and 70s, nursery pots tiny patches of Asian bitter eggplants and runner beans and Mexican quelite greens thrive. Fruitvale has long been Oakland’s Latino enclave.

San Antonio is the city’s most ethnically diverse district: 42% Asian and Pacific Islander , alongsidesignificant African American , Latino , and white populations . Many of these residents were settled in the neighborhood in the 1970s and 1980s, fleeing the economic and political repercussions of post-war Southeast Asia. Several refugee relocation organizations such as Lao Family Community Development, the International Rescue Committee, and Refugee Transitions are either located in this part of Oakland or locate families here due to affordable rent, proximity to public transit, and the presence of existing communities . Arrivals of refugees from around the globe—ethnic Nepalis from Bhutan, Burmese Karen and Karenni, Meskhetian Turks from Russia’s Black Sea region, Bosnians, Ethiopians, Eritreans, and Iraqis—have added to San Antonio’s ethnic diversity since the 1990s. Many of these recent immigrants come from agrarian backgrounds and cultivate vegetables in their yards. As I discuss in Chapter 1, immigrants such as these engage in urban agriculture for a number of reasons: to supplement their diets, to sell produce informally to other immigrants, to alleviate boredom, stress, or isolation in a strange new environment. For many it is a way to maintain ties to their homelands and cultural identity through agricultural and culinary traditions . Several coordinated urban agriculture efforts have taken place in this part of Oakland. In 1999 and 2000, garden activist Grey Kolevzon worked with community members and the Friends of Peralta Hacienda Historical Park to start an afterschool educational garden program at the Peralta House in San Antonio, the historic homestead of the Rancho San Antonio. Once the program was up and running, Lao Family Development, one of the resettlement organizations, proposed connecting the schoolchildren with Mien refugees at the Peralta garden, as well.

Lao Family had been having trouble advancing a literacy program for Mien youth. Inspired by a school in nearby Richmond that had created a successful tutoring program that brought Southeast Asian youth together with elders, the organization invited Mien elders to teach the youth about gardening. The project was hugely popular among the youth and their parents and an unexpected outcome was close collaboration between the neighborhood’s African American youth and Mien elders . The educational garden grew into a community garden that remains under the care of a number of Mien, Latino, and African American families . In 2003 the Alameda County Public Health Department, Oakland Unified School District, and EBAYC partnered with a number of other organizations including Cycles of Change, Urban Ecology, Oakland Children’s Hospital, Clinica de la Raza, the City of Oakland Parks and Recreation Department, and several community groups to form San Antonio Neighbors for Active Living. This umbrella organization applied for and acquired a Healthy Eating, Active Communities grant from the California Endowment, a foundation that funds health and wellness projects. While the initiative was broad in scope, one of the program’s goals was to “Establish and expand local and family-operated urban farms to supply organic fresh produce to school-based produce stands and neighborhood stores”. One of the projects funded was the development of the San Antonio Park Community Garden . As with Peralta House, immigrant parents were interested in the afterschool gardening program underway at Roosevelt Middle School in San Antonio. The grant allowed EBAYC/Cycles of Change to expand the program into San Antonio Park, across the street from the school. The grant also helped San Antonio residents establish and run Full Circle Farms in neighboring Alameda and Sunol, a peri-urban community 25 miles from Oakland . This is perhaps because they are growing for household consumption, an act not seen as particularly radical or tied to a particular movement.

Indeed, like the home gardens dotting the yards of Oakland’s industrial garden half a century earlier, the motivation for many is simply to grow food for their families. For many these gardens are also a means of maintaining cultural ties or agricultural and culinary knowledge, rather than an expression of a particular lifestyle politics or a radical rejection of the corporate food regime. Their invisibility, I argue, is also a result of the growing institutionalization of the urban agriculture movement and the development of the “non-profit industrial complex” that has both subsumed and fueled the urban agriculture movement in Oakland. Ironically, while these urban farmers are largely absent within the movement, they serve as material and symbolic inspiration for urban agriculture activists throughout the flatlands, providing concrete examples not only of how and what to grow in the city, but also what the city should look like and how its denizens should feed themselves. By the early 2000s, these various threads had begun to converge. The radical activism of the Black Panther Party and community coalitions of EJ activists laid the foundations of struggle against the devaluation of Oakland’s flatlands neighborhoods and forged the necessary links across race and class to draw attention to their struggles. Urban Habitat’s “flatlands framework” helped to illuminate environmental injustices in the East Bay and aided in this rescaling of the claims of neighborhood activists, expanding their spaces of engagement to include mostly white, mostly Berkeley-centered allies from the environmental, community gardening, and sustainable agriculture movements. The fusion of their concerns resulted in a social, economic, and environmental justice-oriented engagement with gardening that was able to tap into new funding streams for job training and school garden-based nutrition education. Activists sailed freely between projects and organizations, between Berkeley, San Francisco, Oakland, and the Bay Area hinterlands, plastic planters following funding streams and leaving behind new gardens in their wakes. Over the last decade, a new food justice-oriented urban agriculture movement has taken root in Oakland’s devalued flatlands, one that activists have built on a historical foundation of radical activism while drawing on the human and material resources of an increasingly institutionalized network that bridged urban agriculture, nutrition, and economic development and that was legitimate in the eyes of funders. This growing network of radical activists, urban gardeners, and institutions was new; it was more overtly political than the community gardening movement of the past, with more of a multi-racial, cross-class draw. It was even more political than the community food security movement that took hold in mid-1990s, drawing more explicitly on the spatial justice framework to define the inequities of food access in the flatlands and on the historical legacy and symbolism of Oakland’s past and contemporary social justice and EJ activism. Through its increasing connection with institutions, it has also been better positioned to interface with planners and policy makers. The new “food justice” movement has embraced urban agriculture as a key component. Urban agriculture is about more than simply urban gardening. It is a political act, a rejection of the corporate food regime and commitment to overcoming the devaluation of the flatlands. Indeed, even the use of the term “urban agriculture” is an act of scalar politics, whether conscious or unconscious; by calling what they do urban agriculture rather than community gardening, food justice activists in the flatlands are connecting their actions to those of urban residents in the slums of the Global South struggling to mend the metabolic rift inherent to urbanization . Furthermore, the adoption of the term urban agriculture also legitimizes urban food production by tapping into a decade of advocacy for urban agriculture as a sustainable development strategy in the Global South .

By invoking this new “scale frame” , food justice activists have expanded their space of engagement to a global scale, not unlike the BPP succeeded in doing decades earlier . 90 Also like the BPP movement, the city’s food justice activism in has been centered in West Oakland since the dawn of the new millennium, and urban agriculture has, in some ways, provided a new channel for the Panthers ideological legacy. Concerned with the lack of nutritious food in West Oakland, David Roach started up a farmers market at McClymonds High School in West Oakland in 1994. Four years later he started up an organization called Mo’ Better Foods that has worked to cultivate relationships between the few African American farmers still operating in California and West Oakland residents. Roach, an African American and key figure in the history of Oakland’s food justice movement, views agriculture as vital to economic development for black communities. In an address to the Ecological Farming Conference, Roach underscored the centrality of agriculture to a community’s self-sufficiency. African Americans need to actively engage in farming “to take care of ourselves… It’s okay to want to be a farmer. I want independence. I want freedom.” In his address, he was critical of the ways in which social services exacerbate poverty rather than investing in real structural reform: “Every agency has pillaged our community,” creating a system of “handouts that lead either to prison or unemployment” . Urban agriculture, according to Roach, should not be viewed as the solution, but rather should be viewed as only a small part of the solution. The structural issues—the decline of black farmers, the lack of community-owned retail selling healthy food, the lack of economic opportunity—must take precedence . Roach, along with Dana Harvey, a white woman, was heavily involved in organizing one of the first collaborative efforts to think holistically about the food system in the flatlands. In 2001, Roach, Dana Harvey, and the Environmental Justice Initiative, a local EJ program, organized the West Oakland Food Collaborative to come up with a strategic plan to improve food access and food security, while addressing the political and economic conditions of the city’s most devalued area. A nine-month planning process, funded by a grant from UC Davis, brought activists and agencies to the same table. In the end, they identified the following as necessary components of a vibrant West Oakland food system: a farmers’ market, liquor store “conversion”, a cooperative grocery, community green space, and small business development . The Mandela Farmers’ Market, and later the Mandela Cooperative Grocery both arose from this initiative . As Alkon explains, the Collaborative “cast the struggles of African-American farmers and foodinsecure West Oakland residents as manifestations of racism and poverty, which can be addressed through the creation of a local food system” , and ultimately served as a “hub for community organizing” . In 2003 another major food justice organization cropped up. Brahm Ahmadi, Malaika Edwards, and Leander Sellers had been working with City Slicker Farms when they decided to expand the network of urban gardens at other sites throughout West Oakland. Once the organization got off the ground in 2003 they hired neighborhood teens to be peer educators. They eventually set up a “mobile grocery”, a brightly colored panel van filled with fresh vegetables that parked in various locations around the neighborhood.

As István Mészáros explains, “the historically primary relationship between man and nature [is] nature’s relation to itself, on the grounds that man is a specific part of nature.” Since “earth is the first condition of man’s existence, land is, of course, absolutely inalienable from man” , and by extension, inalienable from all sorts of non-quantifiable social significance; precisely why Polanyi considered it inseparable. It follows, then, that the expropriation and commodification of land and nature—a process central to the cleaving of social rift—rends not only a material rift between land and labor, but also an internalized rift in our cognitive and experiential understanding of ourselves as functional organisms existing as a part of a larger ecosystem. This alienation from nature is well documented in developmental psychology, education, and evolutionary biology, as well. The shift from direct to “increasingly abstract and symbolic” contact with the outside environment in the contemporary political economy limits affective, cognitive, and evaluative development in children , leading to a rise in childhood behavioral problems, popularly referred to as “nature deficit disorder” . Several studies have concluded that exposure to vegetation and green space is essential to children’s cognitive development, can reduce attention deficit disorder, and reduce crime and “mental fatigue” or desperation in impoverished urban areas . From the Marxian perspective, black flower buckets the de-alienation of humans both from the fruits of our labor and from the natural or biophysical world depends on our active metabolism of nature through labor.

By physically laboring the soil, sowing seeds, cultivating, harvesting, and preparing food, urban agriculture mends individual rift by reengaging individuals with their own metabolism of the natural environment. Not only do experiences in the garden bring the urban farmer, gardener, or beekeeper into direct contact with the biophysical environment—soil, plants, water, sunshine, rain, worms, insects, birds—as prescribed by the behavioral scientists cited above, but also allows him or her to experience and metabolize the surrounding landscape, transforming it into a product that he or she can consume. The urban farmer’s labor thus sutures individual rift, reintegrating the human with nature as well as de-alienating the laborer from the fruit of his or her labor. In this case, labor’s fruit is more than metaphor, as it may indeed be a fruit, vegetable, honey, milk, eggs, or meat. Several public health and education studies have linked urban agriculture to enhanced natural science and nutritional knowledge, and improved mental and physical health . Recent immigrants to North American cities rely on urban agriculture as a means of alleviating boredom and putting their agrarian skills and knowledge to work. For Hmong women in Sacramento, urban gardening “structured their time, and provided a sense of accomplishment, as they grew their own produce, and supplied their children, grandchildren, and families with food,” countering the culture shock and feelings of dependence and uselessness they felt upon arrival to the US . A study by Airriess & Clawson on urban agriculture practiced by Vietnamese refugees in New Orleans reported similar findings. Such attempts to overcome individual rift by reengaging with the processes of food production and consumption lie at the center of the urban agriculture movement in the Global North. As I argue above, urban agriculture arises as a counter-movement in response to economic crisis and to the commodification of land and labor. Yet viewing urban agriculture in this way alone does not fully grasp urban agriculture’s multiple origins, functions, and forms.

Focusing on individual rift—particularly in the North where a longer history of wage labor has perhaps rendered alienation from manual labor and the biophysical environment more acute— helps to illuminate the important role that urban agriculture serves in late capitalist economies while differentiating its various forms. While guerrilla gardening and food justice initiatives may arise from an explicitly counter-hegemonic challenge to the capitalist food system as described in the previous section, the groundswell of interest in backyard and community gardening appears to be largely linked to efforts to lessen the impact of individual rift and is not necessarily radical. While individual rift is arguably much more widespread in the North than in the cities of the South where linkages to agrarian livelihoods remain intact, within a generation or two, urban dwellers in the South may also experience similar alienation from their food. The words of a young woman from Bamako poignantly illustrate this: “Why should we care about agriculture, about soil erosion? That’s the domain of rural peasants” . While I’m not arguing that everyone can or should grow his or her own food, my intention is to show how the practices associated with urban agriculture—tilling, planting, weeding, watering, harvesting, composting—are a force of de-alienation. Urban agriculture, from this perspective, can help reestablish a conscious metabolic relationship between humans and our biophysical environment by reintegrating intellectual and manual labor. It is also important to emphasize that this dimension of rift is a necessary prerequisite to the ongoing expansion of capitalist modes of production. If, as Marx argued, nature is alienable from humans, we can easily make the link between ecological and human health; damage to the environment is therefore damage to one’s self. Moreover, complacency towards what we would otherwise perceive as self-destructive actions depends on individual rift; to perceive and experience environmental degradation as a solely external process rather than one simultaneously internal and external depends on this alienation.

Recognizing this form of rift and understanding the forces which cleave it is therefore an essential first step to mitigating it. It is precisely in these flat lands neighborhoods that the city’s food deserts can also be found. And it is here that food justice movements have taken root. Yet to better understand Oakland’s food deserts and to recognize the emancipatory potential of urban agriculture and other food justice initiatives that have emerged as a solution, it is helpful first to understand the forces that have hewn the urban landscape into a crude mosaic of parks and pollution, privilege and poverty, Whole Foods and whole food deserts. Few studies move beyond a geospatial or statistical inventory of food deserts to unearth these historical processes. In this chapter I focus on the structural role of capital in order to emphasize the extent to which the history of capital defines the urban environment. Driving down MacArthur or International Boulevards “in the cuts”, the rough and tumble street scapes of the Oakland flat lands, provides a glimpse into how capital’s dynamic cycles—its ebbs and flows—have shaped both the built environment and the social relations woven through it, leaving an almost entirely treeless and worn landscape of used car dealerships, taco trucks, liquor stores, dilapidated storefronts, and the occasional chain linked vacant lot. Understanding the historical and structural roots of this urban landscape is fundamental to understanding the individual and collective agency that adapts to or resists its development. Indeed, the history of the contemporary urban agriculture movement in Oakland really begins here. With this in mind, I tap existing histories of Oakland and urbanization in California, demographic and economic data, and current “grey literature” to broadly trace the historical geography of Oakland’s flatlands during the periods of industrialization and deindustrialization, roughly from the turn of the century to the “neoliberal turn” of the 1980s. I draw on theoretical insights from the growing field of urban political ecology to shed light on the structural processes that have restricted access to healthy food for residents of the flatlands, arguing that a combination of industrial location, residential development, city planning, french flower bucket and racist mortgage lending unevenly developed the city’s landscape and concentrated the impacts of capital devaluation within the flatlands, a process I refer to as “demarcated devaluation” and which ultimately created the city’s food deserts. Nevertheless, at the risk of being seen as an economic determinist, I want to focus on one process that is fundamental to the transformation of the urban landscape and the creation of food deserts: the devaluation of certain types of capital. It under girds the structural processes of uneven development and the social disruption that emerges in response. Nowhere is this process so readily apparent as in post-industrial cities such as Oakland. Cities are ground zero of humans’ transformative power, where the influx of capital is visibly inscribed on the landscape in the form of buildings and infrastructure, as roads, bridges, power lines, rail lines, sewers. During historical moments of capital over-accumulation following economic booms, surplus capital is invested in this kind of fixed or immobile capital, transforming the urban environment. During economic downturns, as capital retreats from urban industrial zones, the post-industrial city nevertheless retains its industrial character, albeit devalued, dilapidated, and scarred by pollution.

The built environment of the past inhibits future investment because it is simply cheaper to go elsewhere. Rents fall, unemployment rises. Both labor and fixed capital are devalued. Harvey writes, “The geographical landscape which fixed and immobile capital comprises is both a crowning glory of past capital development and a prison which inhibits the further progress of accumulation” . These zones left fallow inside the city by capital’s retreat belong to what Richard Walker has called “a lumpengeography of capital,” or “a permanent reserve of stagnant places” awaiting new investment once land and labor values have been sufficiently devalued.44 From this perspective, the contemporary cityscape is a map of previous cycles of capital accumulation and devaluation, a palimpsest of building, decay, and renewal. The walls of this prison of fixed capital are often clearly delineated by planning, policy, property taxes, and political boundaries. These buttresses and ramparts, whether or not they were crafted with intention, effectively demarcate and quarantine devaluation to prevent its impacts from bleeding over, both metaphorically and materially. As environmental justice literature reveals, this process of demarcated devaluation has been highly racialized historically through zoning, redlining, and neighborhood covenants . Human populations viscerally experience these ebbs and flows of capital. As countless cases in the era of deindustrialization illustrate, capital devaluation has historically been the harbinger of social upheaval in the form of migration, poverty, hunger, crime, and declining public health. Given the extent to which the urban landscape is shaped by capital and its crises of accumulation, urban social struggles against the socioeconomic upheaval that follows are interwoven with struggles for a more equitable environment. Perhaps less obvious to many mainstream environmentalists, struggles to protect or clean up the urban environment are equally as entwined within struggles for social justice; as Swyngedouw and Heynen point out, “processes of socio-ecological change are…never socially or ecologically neutral” . Understanding the food justice movement in Oakland and elsewhere therefore depends on understanding the structural forces, generally, and capital devaluation more specifically, that gave rise to the movement in the first place. Applying this analytical framework, I devote the remainder of this chapter to outlining Oakland’s 20th century history of industrialization and deindustrialization, demarcated devaluation, and the consequent creation of the city’s food deserts.In reference to her childhood home of Oakland, Gertrude Stein famously wrote, “there is no there there.” While these words have been used to belittle Oakland for the seventy years that have passed since their publication, they remain poignant when taken in their original context. Stein had returned to the city decades later and was unable to recognize the childhood home of her memories in the vast expanse of new housing sprawling eastwards from downtown . The transformative power that had effaced the “there” of Stein’s turn-of-thecentury childhood home continued to reshape Oakland as industrial and residential capital flowed and ebbed throughout the rest of the twentieth century. Advertising Oakland as a “city of homes,” speculators from the mid-19th century onwards hoped to cash in on its proximity to San Francisco’s bustling commercial center . The promise of the seemingly paradoxical union of Arcadia and Utopia that was the aesthetic hallmark of California development—pastoral landscapes embodied within an ordered, neighborhood logic —fueled a vibrant housing sector in Oakland, drawing the wealthy merchant class to the Oakland hills and foothills. Echoing the language of Mayor Horace Carpentier’s 1852 speech , a booster for housing in Oakland’s lower foothills in 1911 advertised “home sites from which [to] look down on the cities about the bay…far removed from the dirt and turmoil of the work-a-day world” . At the same time, completion of the transcontinental railroad and construction of its terminus in Oakland in 1869 accelerated the expansion of industry from San Francisco to the East Bay; the arrival of iron works, canneries, cotton and lumber mills, breweries, and carriage factories fueled further industrial agglomeration around the rail terminals in West Oakland and the estuary waterfront at the southern edge of downtown .

Optimum values for Fv/Fm are 0.80–0.83 in C3 plants . Mortality of an individual was assessed by using the stress index, inspecting the texture of the leaves, and evaluating gas exchange and dark-adapted fluorescence values. An individual was determined dead and harvested immediately if it had a stress index score of five or higher, leaves were crispy instead of flexible, and if at least two leaves measured Anet and Fv/Fm values of less than 0.5 µmol CO2×m-2 ×s-1 and less than 0.300, respectively. Stems of harvested plants were checked for lesions by scraping the bark away from the POI and looking for darkened, necrotic tissue extending upward from the POI. Lesion length was measured in centimeters from the POI to the farthest advancing margin of the lesion. Soil moisture, plant structure, physiological data, and disease severity were statistically compared using ANOVA in JMP, version 14 Pro , and post hoc analyses of means were performed using Wilcoxon signed rank test. Two-way factorial ANOVAs were conducted on the influence of watering regime , inoculation treatment , and interaction effects between watering regime and inoculation treatment on plant Anet, Fv/Fm, and disease severity. Correlations between disease severity and physiological stress responses were also examined in JMP using a linear regression analysis to determine maximum fit. Survivorship of each treatment group was estimated using the Kaplan–Meier survival analysis with the survival package in R v. 3.5.1 .

A Cox proportional-hazards model was followed by a Peto and Peto post hoc test to test for statistical significance of Kaplan–Meier survivorship. Due to the small sample size of individuals available for the experiment, procona buckets all reported results for survival were based on a 90% confidence level, and P-values above 0.05 but below 0.1 were considered significant trends. All other tests were conducted using a 95% confidence level for significance.Both chlorophyll fluorescence and net photosynthesis declined as hosts were exposed to drought and fungal infection. Each of these factors caused measurable physiological stress in A. glauca individually; however, in combination, stress symptoms showed up earlier and more strongly . Additionally, an important result was the relationship between visible stress symptom severity and physiological function. Both Anet and Fv/Fm were found to be highly correlated with visible signs of stress that ultimately led to plant mortality. This is consistent with previous studies that have found that Fv/Fm correlates strongly with eventual mortality, and therefore, can be an indicator of drought-related mortality risk in natural systems . Furthermore, Anet was shown to decline even with very low levels of visible stress, suggesting it may be valuable as an early detector of plant stress even before major visible symptoms appear. While Anet and Fv/Fm can be useful tools for measuring physiological stress, they are expensive and difficult to measure on the ground at large scales. Therefore, using visible stress severity indices may be a promising and cost-effective method with which to quickly carry out large surveys aimed at predicting drought- and fungus-related mortality in the field. High mortality was observed in all inoculated plants regardless of drought treatment, indicating that N. australe may act as an obligate pathogen on A. glauca, at least in young, small individuals as were used in this study.

However, mortality occurred much faster in the D+ group. Additionally, some individuals in the D- and W+ group at Week 10 survived well beyond the termination of experiment , suggesting the ability of A. glauca to allocate sufficient resources for defense against drought stress, and in some cases, infection by N. australe, but a greater vulnerability in the simultaneous presence of both factors. Therefore, it appears that a synergistic interaction does exist whereby exposure to both drought and infection by N. australe yields more accelerated decline than either factor alone. It is likely that A. glauca susceptibility, or “predisposition” to disease , is due to the interactive roles of water and carbon availability in plant defenses against drought stress and biotic invaders, as modeled by McDowell et al. and Oliva et al. . Their framework describes a system in which plant hosts are able to allocate resources to either survive extreme environmental stress or defend against biotic invasion, but may succumb via depleted carbon resources when exposed to multiple stressors. For example, hosts like A. glauca can persist through drought with high resistance to cavitation . They can also divert carbon resources to block the spread of pathogens . However, the combination of global-change-type drought and infection by pathogens like N. australe may leave these hosts vulnerable when they no longer possess the resources needed to simultaneously resist cavitation and invasion by the pathogen.

Furthermore, extreme drought conditions can enhance optimal conditions for the growth of pathogens like Botryosphaeriaceae fungi that thrive in more negative water potentials than the host can withstand . These factors combined can push the host beyond a threshold, increasing branch dieback and ultimately increasing the likelihood of whole plant mortality. Understanding the role of pathogens and drought stress in native vegetation canopy loss has long been of great interest to ecologists, though research involving such systems has yielded varying results regarding these interactions. For example, a meta-analysis by Jactel et al. found that in studies on the effects of pathogens and insects on forest plant hosts during drought, damage to hosts varied greatly based on the feeding habits and substrate of the pathogen and severity of the water stress. In the case of secondary agents , more damage occurred on hosts experiencing water stress compared to non-stressed controls, and damage severity increased with increasing water stress. These findings are consistent with the results of the present study and support the hypothesis that drought stress predisposes hosts to pathogen impacts. Other studies have found similar results regarding secondary pathogens in drought-tolerant plant systems, including red pine forests , eucalyptus forests , and chaparral shrublands . By contrast, Davis et al. concluded that drought-induced cavitation alone, not infection by Bot. pathogens, caused canopy dieback of southern California Ceanothus sp. during drought, suggesting that secondary agents do not always benefit from drought-related predisposition. Clearly, while secondary pathogens are known to become pathogenic in hosts experiencing environmental stress , the mechanisms driving this relationship in different plant hosts are not fully understood. Although field studies have been conducted on the presence of fungal pathogens on shrubland species during drought , controlled experiments manipulating both drought and fungal treatments in naturally occurring species are rare and typically involve tree systems rather than wildland shrub species . To the authors’ knowledge, this is the first experiment to investigate the influences of drought and infection by N. australe on A. glauca by manipulating both factors.The results of this experiment, along with the identification of N. australe and other Bot. species in the region , suggest that the severe canopy dieback of A. glauca observed in Santa Barbara County between 2012 and 2016 is likely the result of global-change-type drought combined with the presence of opportunistic fungal pathogens like N. australe. While there is evidence to suggest that acute drought alone may cause some mortality in A. glauca , procona florida container the presence of N. australe and other pathogens likely exacerbates stress and accelerates mortality in these hosts. Furthermore, N. australe has long been reported in avocado orchards in Santa Barbara County ; however, there are no known reports or indications of major disease and dieback of A. glauca in surrounding chaparral shrubland system until recently, during the especially dry winters of 2013 and 2014 .

Thus, we suspect that while N. australe has likely been present on A. glauca hosts , the drought of 2011–2018 was the most severe in the region in the past 1200 years and may have been significant enough to push adult A. glauca past a tipping point of defensibility against N. australe. It should be noted that results of experiments on young plants, which may be highly susceptible to drought and drought-related mortality due to limited carbon reserves, may not scale directly to large, mature individuals in the field . This study showed high mortality in 2-year-old A. glauca exposed to a fungal pathogen with and without drought, in contrast with field observations of diseased, large adults exhibit severe canopy dieback and are ridden with fungal cankers, yet still survive . Previous studies have yielded similar results: for instance, photosynthesis was shown to be greatly reduced in oak seedlings compared to adults in drought years compared to wet years , and He et al. reported that responses of red maple and paper birch saplings to a 1995 drought were significantly different than those of mature adults. Similarly, since hosts are often able to allocate carbon reserves to compartmentalize canker-causing agents like N. australe within carbon-rich barriers , larger individuals with more biomass and greater carbon stores are able to utilize and direct more resources to defense than younger, smaller individuals. Thus, mature plants can better persist through biotic attack during environmental stress than their younger counterparts and experience various levels of canopy dieback rather than full mortality. Arctostaphylos glauca are obligate seeders, meaning they are killed by fire and must maintain populations by individuals recruiting from seed rather than resprouting from their base. Therefore, young, small individuals may be of greatest concern for future populations of this species. Because current research is predicting more frequent and extreme drought events , more exotic pathogens , and more frequent fire in these southern California shrublands , populations of A. glauca could decline because small individuals may be highly susceptible to disease and mortality. A valuable next step for understanding these risks and predicting future shifts in vulnerable chaparral communities would be to monitor young recruiting populations of A. glauca for N. australe for signs of stress, infection, and mortality in the wild.In the face of rapid climate change, it is increasingly important to understand the abiotic and biotic mechanisms driving ecological landscape change. Large plant dieback events can produce major ecological consequences, including changes in vegetation cover , increased fire risk , and changes in hydrology , all of which affect ecosystem structure and functioning . Furthermore, the loss of even a few species can trigger effects on the local food web structure , and increase risk of invasion . The results of this study suggest that small individuals of A. glauca, one of the most common and widespread species the southern California chaparral community, are at high risk of disease and dieback due to opportunistic pathogens and extreme drought. The potential for dieback of Arctostaphylos spp., which provide food for animals such as mice, rabbits, and coyotes and are an important component of post-fire woody regeneration in chaparral, raises concerns regarding changes to ecosystem structure and functioning in the coming decades. Many ecosystems today are facing unprecedented drought ; yet, the interactions of drought and pathogens in wild land settings are difficult to study because the multitude of confounding variables and the challenges of manipulating both the pathogens themselves and climate. Thus, greenhouse studies such as this one are increasingly essential to understand the influences of drought and pathogens as they relate to dieback events, as well as to understand the relationship between stress and shrub/tree ontogeny . Critical questions remain regarding the relative tipping points for large-scale dieback among historically drought-tolerant species such as A. glauca that today are facing the combination of extreme drought and novel pathogens. These pathogens may not express themselves until there is drought, highlighting the need for broader field surveys and long-term monitoring of wild land ecosystems. An important step to understanding the role of disease in contributing to vegetation change is also to isolate pathogens and test their pathogenicity under varying controlled conditions. This study provides one such step for what appears to now be a widespread, opportunistic introduced pathogen in an important native California chaparral shrub. Extreme drought events from climate change have produced immediate and dramatic effects in recent years, with costs often exceeding $1 billion due to their widespread economic and ecological impacts . Among the ecological consequences is widespread tree mortality, , event within plant systems that have historically been considered drought-tolerant .

The geographical range, orientation and power dynamics involved in such non-food functions have yet to be assessed . In short, the many highly-valued social and ecological services that farms provide have not been defined spatially or related to marketing practices, though it is these very orientations that are important to theories of localization and its role in the practices of farmland preservation and management.Last, production, relationships and proximity do not necessarily beget mutually beneficial feedback loops between environmental and social justice objectives. Food insecurity in farm workers is more than triple the national household average in multiple areas of the country . Naturally, markets will gravitate toward more wealthy and powerful communities that are better positioned to help farmers achieve their end goals of profitability and secure farm tenure. Indeed, there is evidence that many direct marketing networks target consumers in the wealthiest neighborhoods. Farms involved in direct marketing are more likely to be located in the Northeast or the West Coast, near densely populated urban markets in areas with high median home values . Schupp finds that farmers markets locate in areas where the neighborhood population has attained higher education levels and a higher percentage identify as white than the national average. Direct market customers are more likely to bemiddle-aged, middle-income or above, well-educated, suburban women . However, different types of local food marketing, blueberry in pot beyond direct marketing through farmers’ markets, may differ significantly in demographics of clientele, economics and geographies.

While the local food movement grows, so does demand for food assistance. As the federal government removed welfare programs, non-profit food banks have rapidly grown in number since the 1980s . Today, one in seven Americans rely on food banks to feed their families . To meet the needs, food banks source from nearby farmers, distributors and retailers, and they are increasingly sourcing fresh, local food . Indeed, the market embeddedness that enabled Belo Horizonte, Brazil to achieve food security for all its citizens may be differently oriented spatially and socially than a food system that localized with the objective of influencing production practices. Empiric research on the embeddedness of food supply is growing to help understand how such theories play out in practice. Penker shows the alternate routes for grain from harvest to mill to bakery with unique social and geographic distinctions between whole meal and standard bread chains. Moragues-Faus and Sonnino review three olive oil producers and their sourcing regions to show the socio-spatial place-making in branding. This research will be the first to explore multiple sales and donation practices in relation to one another. The aim of the research is to identify the geo-socially embedded intersections and deviations in the local food system.The research is not exclusively focused on consumers and their relation to farms, but rather on the interplay of a variety of immediate relationships with farms around sales, visits, and donations, referred to collectively as networks. Geo-social network findings are triangulated using comprehensive planning documents and expert interviews. To start, the methods section will provide a description of the case study region and its relevance the research questions raised in the above literature review to help make sense of the methods employed, how networks were coded, and profiles of interviewees selected.

This study focuses on Chester County, PA due to its long history of direct marketing local food. Located in the northeast, near high to median home values in close proximity to large urban markets of New York, Philadelphia and Washington D.C , Chester County has similar characteristics to what the literature defines as the average landscape involved in direct marketing which both grounds this study and broadens its application to similar cases. The county has historically held widely spaced towns and villages surrounded by new growth forest, livestock operations, row crops, horse farms, and mushroom farming activities . Farms face economic pressure from the housing market. Having added 70,000 people from 2000 to 2010, Chester County has the highest population growth rate of any county in Pennsylvania and ranks second in Pennsylvania, only after adjacent Lancaster County, for farm production. Because of heavy development pressure, agricultural land-uses face continual competition from the residential housing market. The 2007 Census of Agriculture reported a 10 percent decline in the number of farms and 14 percent decline in farm acres from the previous census in 2002.Food insecurity is actively tackled by the local food movement. One in 20 of the 500,000 Chester county residents receive Supplemental Nutrition Assistance Programs compared to one in seven for the state . The food bank, which has been in operation for over 80 years, started its gleaning program in 1996 with the help of state Senator Andy Dinniman and the newly hired Larry Welsch, the Chester County Food Bank’s current director.

The concept of gleaning is based on the Biblical description of scavenging for food left in harvested fields. Some farmers’ crops are earmarked for the food bank while others make their leftovers available to be picked by volunteers. Chester County Food Bank has become a national leader in purveying local, fresh food by harnessing the goodwill of a large volunteer base and generous farming community. The food bank supplies fresh, local food through a variety of programs: gleaning, urban gardening, and school-based high-tunnel greenhouses. In addition, the food bank runs several outreach programs whose education and social networking aims dovetail with gleaning program farms. The Chester County Food Bank ranks sixth nationwide in the percentage of fresh food it disperses, with over twenty-two percent of the 2,000,000 pounds of food distributed being fresh, according to a study by the University of Pennsylvania . This amount does not include the many pounds of fresh food grown in raised beds at food cupboard sites and distributed directly to the community without being transferred through the food bank.No comprehensive list of farms and their market connections currently exists in Chester County. I employed a cross-sectional design to create a novel database, which required a range of sources. Farm and market data was gathered from civic documents, market promotion material, media, farm website listings, county farm listings, Local Harvest affiliates, and buyer associations. Farm managers were queried with an IRB-approved electronic questionnaire to identify their geographic coordinates, raw products and direct sale/donation markets. Non-local products sold through the farm and processed products are not included in this study. In turn, markets were queried by an email, which asked them to identify other direct sale farms in a double verified snow-ball sampling technique. Market and farm locations are geocoded by latitude and longitude based on the exact address. The geographic location of farms and markets were virtually site checked using Google Street View imagery from 2007 to 2015 to verify the location. CSA member purchases are coded at the zipcode level to protect client confidentiality. CSA members were not queried to verify zipcode or network connection. This technique allowed the researcher to capture direct farm networks within, moving into or going from Chester County. Email surveys were sent to 700 farms and 2000 markets/users, and responses from 117 farms and 637 unique users/ markets confirmed network connection.This research takes a broader approach in accounting for any immediate relationship with a farm, plastic planters wholesale including sales to distributors and wholesale grocers, donations of unprocessed food, and visits to farms. Relationships, including donations, sales and farm visits, are referred to collectively throughout as “network.” Networks trace the connections formed through the sale or donation of raw product and services produced by the farm to their first point of sale/donation to customers, institutions, and distributors. In this way, the research encompasses a range of the immediate interactions with farms to assess the spatial distribution and typologies of networks in which farms engage in relation to one another. A priori coding is based on theoretical considerations. Informed by the theory of local food’s embeddedness , this study parses direct marketing networks by their social construct. For example, farms can market directly to consumers through Community Supported Agriculture or farmers’ markets. Farmer’s markets are seasonal and represent a direct connection for consumers with the farmer where the farmer usually travels to an urban or suburban location. CSA and Buyer Club networks bring the product and end consumer in contact through drop-off/pick-up locations. Thus, CSAs constitute a different socio-spatial type of farm network when compared to farmers’ markets, but not buyers clubs, and are coded thus. Wholesale networks represent purchases by larger-volume distributors and grocery stores which act as intermediaries between farms and end-users. Institutions are largescale buyers which, like the smaller-scale restaurants, represent a steady relationship between the purveyor and farmer to cater to consumer demand.

Agricultural byproduct, farm-to-farm sales, and educational visits are also noted as important networks between farmers, farms and their communities. School trips to farms bring students to the farm and represent regional knowledge networks captured in the ‘education visits’ variable. Farm-to-farm sales represent the agricultural social networks involved in sales of raw products.The generated network map is an under-estimate of a county’s farm networks for a variety of reasons. Some categories of farm networks are not captured in this data. Many farms allow online purchases through their own website or a crowd-sourcing website. Farms also sell directly from their farm gate. These sales and connections are not documented in this study. Larger direct distribution networks were not captured in this study mainly because large suppliers did not respond to the query nor do they list their outlets online. Conversely, many smaller-scale suppliers readily listed market outlets on their websites and confirmed them in the research query. Additionally, the online query method limited the response to farms whose networks could be verified by email correspondence. Farms that only listed phone numbers were not contacted. For example, numerous Amish farms were not included in this study due to inability to reach the farmers via email. Conversely, many farmers’ markets list Amish farmers asprominent suppliers. This study does not include non-food producing farms, thereby omitting many fiber alpaca farms, greenhouse nurseries, and horse farms that play a vital role in supporting food-producing farms through the sale and purchase of ancillary products such as horse manure for mushroom substrate. The size of the farm and product sold are not noted. Seller, buyer, and market manager characteristics, which may be highly relevant to the social and geographical nature of supply chains were not noted in this study. Further, coding the type of network is imperfect. Some farms sell through supermarkets that they run from their farm gate. Many retail establishments may operate a cafe through which they serve locally-sourced farm products. In these instances, the duplicated forms of retail were noted. For example, if a farmers’ market is operated from the parking lot of a grocery store that uses some of the food in its on-site cafe, food sold through the farmers’ market is coded as a farmers’ market and restaurant though the primary venue use is for wholesale.The 2009 Chester County Comprehensive Plan is divided into urban, suburban, and rural landscape visions which seek to isolate active farming areas from residential developments while connecting these land-uses through local food marketing . In essence, the planning regulations seek to divorce producers from users physically, while promoting their connections socially. Some agricultural activities are included within the suburban landscape vision. Community Supported Agriculture , small specialized farms and nurseries, community gardens, and farmers markets in suburban areas are meant to “provide residents with fresh locally grown food.” The rural landscape vision has three components: small villages that make up rural centers, a rural landscape of scenic vistas without active farming, and an agricultural landscape . The agricultural landscape is largely located in western Chester County, where the character is similar to the large agricultural area in Lancaster and Berks Counties as opposed to the nearby Philadelphia metropolitan urban area. Agricultural production is diverse, including dairy production, horses and other livestock, poultry, mushrooms, nurseries, orchards, and field crops. This landscape is not planned to accommodate future projected growth, and is dominated by a concentration of active farms, Agricultural Security Areas, large clusters of land permanently protected by agricultural easements, and areas with municipal commitment to adopt effective agricultural zoning.

A study that screened livestock at the California state fair in 2005, which usually hosts livestock raised on small farms or in backyards, observed a 3% prevalence of E. coli O157:H7 in pigs, but did not find O157:H7 in any other livestock samples including dairy cows, whereas our study identified O157:H7 in cattle but not pigs. A 2002 study that also collected fecal samples at fairs in three states, identified an E. coli O157:H7 prevalence of 11.4% in cattle, 1.2% in swine and 3.6% in sheep and goats, whereas we measured a 5.31% E. coli O157:H7 in all cattle . Differing STEC prevalence in these aforementioned studies may reflect different management practices on farms or other climate or animal-level factors. Additionally, since ruminants are the main reservoirs for STEC, our results indicating that STEC prevalence in swine is lower comparatively than the other sampled species is in agreement with previous research, however, pigs are still a livestock species of public health concern, as they harbor E. coli O157:H7 as indicated by many studies. Our model results also indicated that cattle and sheep are a significant factor in STEC presence on farms, as compared to goats and pigs. However, differences in location, laboratory methods and sampling methods make comparison between studies challenging. More than half of the identified O-serogroups in this study are on CDC’s list of the top 7 STEC of concern for public health, including six O157:H7, twenty-two O26, nine O103 and one O111. Stx2, blueberry production which is the more virulent form of the Shiga toxin gene that has been implicated in severe human disease, was identified in 16.46% of O-serogroups; 13.92% contained both stx1 and stx2.

The eaeA gene, which allows STEC bacteria to attach to human host cells, was detected in 55.69% of positive STEC samples, contrary to a study conducted by Dewbury et al, which rarely discovered eaeA in their non-O157 isolates from cattle fecal samples. The ehxA gene, which is reported in severe human cases of STEC, was detected in 88.61% of the positive isolates . Compared to a study conducted by Djordjevic et al in adult sheep and lambs, they detected stx1, stx2 and ehxA in 78.2% of their positive serogroups, versus our study which only identified those three genes in 1.27% of positive serogroups. However, they reported 0.8% of their serogroups had just stx2 and ehxA genes, whereas in this current study, 11.39% of the positive isolates contained these two virulence genes. The pathogenic STEC O-serogroups, genes and virulence factors identified in this study highlight the need for continued studies on DSSF, as well as outreach to stakeholders regarding pre-harvest food safety risks and development of onfarm mitigation strategies. Significant risk factors identified by the final mixed effect model included daily maximum temperature °C. The data in our study ranged from 11.7°C – 39.80°C. An experiment that measured the decline of E. coli O157:H7 in inoculated manure at four temperatures, 7°C, 16°C, 23°C and 33°C, reported that E. coli O157:H7 declined significantly faster in manure at 23°C and 33°C, than at 7°C and 16°C, for both oscillating and constant temperatures. This study confirms our model result, which suggested that as the daily maximum temperature increased, the odds of finding STEC in a fecal sample was less likely. A study by Franklin et al also identified daily maximum temperature as a significant risk factor, when conducting a study of STEC in wild ungulates in Colorado.

They detected a positive association between temperature and STEC presence in fecal samples, whereas our model identified a negative association with the daily maximum temperature. However, the range of daily maximum temperatures displayed in their analysis were narrower than our recorded daily maximum temperatures, which may account for this difference. Although many studies indicate that STEC sheds more in summer months, California microclimates differ from each other and from the majority of seasons in other states. California valleys and foothills experience low humidity and temperatures above 37.78°C in the summer and autumn, which may affect STEC shedding from livestock raised on California farms located in different microclimates. For instance, to compensate for the numerous microclimates in California in our study on Campylobacter spp., which included the same farms included in this current STEC study, we divided the California summer season into Coastal and Inland and season was a significant risk factor in that final multilevel logistic regression model. Interestingly, our Campylobacter study also found a significant association between presence of Campylobacter spp. and a farm owning swine, with 13.76% prevalence of Campylobacter spp. measured in pigs raised outdoors. Difference in climate conditions between states in the US reveal a need to report the full range of temperatures and other environmental factors measured for studies estimating the effect of weather on food borne pathogen shedding in livestock. For instance, a study that collected samples from conventional dairy and beef cattle in Michigan revealed that high average temperatures measured one to five days before sampling had a 2.5 times greater odds of STEC than lower temperatures, which differs from our study results that suggested that STEC survival is less likely at higher maximum temperatures.

Michigan results contradict ours, however the highest maximum daily temperature measured in our study is not a temperature normally observed in many areas of the US. The range of daily maximum temperatures for the Michigan study was 22.78 – 32.2°C, with one 36.11°C outlier. Additionally, our study included winter temperatures, while their study was only conducted in summer . Extreme temperature, heat index or humidity values observed in different parts of the world may affect conclusions and interpretations of results, especially between studies. Stanford et al reported the effects of severe weather events on STEC shedding in Canadian cattle. Although they also observed that STEC prevalence increased when ambient temperatures were higher than 28.9°C, a separate finding indicated that the O-serogroup O26 had a significant reduction in prevalence during extreme heat in July and August. Almost 28% of the O-serogroups in our study were O26, and the final model results may have been influenced by this strain. The ways that different non-O157 STEC strains react to varying environmental conditions, such as temperature or humidity, may account for variations in results between studies. Moreover, changes in the host species during various temperature fluctuations or extreme weather events should also be studied. For instance, Dawson et al measured behavioral changes in cattle during increased temperatures, as a possible driver of changes in STEC prevalence, such as increased water consumption or change in grazing habits. Their simulation results indicated that higher summer temperatures may encourage more resting by cattle in crowded areas, such as under shade trees, which can lead to direct transmission of STEC. Since the aforementioned studies differ in conclusions regarding the direction of environmental effects on STEC shedding in livestock, this risk factor needs further investigation, as perhaps there are underlying mechanisms accounting for the difference between results, including microclimates or animal level factors. Our multi-variable model also indicated that livestock sharing a barn with other animals resulted in 3.5 greater odds of a positive STEC sample. Multiple livestock housed in a barn could share pathogens by cross-contamination of food or water troughs or persistence of STEC in a barn environment that may not be subjected to regular cleaning. Other studies have indicated that STEC persists for long periods of time in barns or on surfaces within the farm environment. For instance, blueberry in container one study swabbed multiple barn surfaces at a dairy ranch and measured 14.9% – 19.1% STEC in samples from cattle or calf feeders, and 11.3% – 18% on other surfaces. Another study implicated water troughs as harboring E. coli O157:H7, and inferred that shared water troughs play a key role in the persistence and maintenance of continued E. coli O157:H7 infections in cattle. A British study reported that housed beef cattle shed more STEC than unhoused and suggested that this may be due to shared water sources or feeding bins and an accumulation of pathogens in a shared environment. Finally, the last significant risk factor from the multi-variable final model indicated that livestock in contact with wild areas, such as forests or wetlands, have a higher likelihood of STEC presence in their feces. Wildlife, including feral pigs, deer, rodents and birds are known reservoirs of STEC. 

A study conducted in California identified a low prevalence of E. coli O157:H7 in rodents , however, they did not test for non-O157 STEC in samples, which may have a higher prevalence in rodents. A 2016 published study discovered the stx2 gene in over twenty percent of Canada geese fecal samples and seven percent of nearby water samples from Lake Eric bordering Ohio, USA. A case-control study conducted after 15 human cases of E. coli O157:H7, identified the source of STEC as those who ate fresh strawberries contaminated by deer feces. Livestock that graze in wild areas may be exposed to indirect sources of STEC, for instance through environmental contamination of soil or water, or because wildlife that live in these bordering wild areas enter agricultural areas and contaminate the pastures grazed by farm animals. Limitations of this study include the small sample size of farms that were convenience sampled, so the model results are not generalizable to other regions and farms. Moreover, because we collected the freshest fecal samples available and did not randomize sample collection, we may have added bias to the study results. Unmeasured variables that should be included in future studies include the age of the animal and whether livestock have direct or indirect contact with neighboring livestock. Although a majority of commercial swine production in the United States occurs indoors with high levels of biosecurity, the US is currently experiencing a return to raising domestic pigs outdoors. Before the 1950s, most swine operations in the US were small scale family farms and either a hybrid of indoor/outdoor or solely outdoor-based. Beginning in the 1960s, commercial swine production began transitioning to indoor systems, based on goals to increase efficiency and reduce swine disease transmission as well as a public health mandate to decrease human trichinosis cases.However, consumer demand for sustainable or pasture-raised animal products within the past few decades has revived traditional methods of raising swine outdoors or on pasture . While primarily considered a niche production method in the US, outdoor-raised pig operations are broadly distributed throughout California. A challenge in raising pigs outdoors is the possibility of these animals interacting with wildlife disease reservoirs, such as feral pigs, and the associated risk of zoonotic and/or swine pathogen transmission Both domestic and feral pigs share the same genus and species and can be reservoirs for zoonotic pathogens ,Also, swine diseases eradicated in conventional indoor-raised herds have been documented in feral swine in California and contact between feral pigs and outdoor-raised swine herds is a risk factor for the reintroduction of these diseases to domestic herds in the US. For example, a 2016 human case of brucellosis in New York state was traced to a feral pig intrusion event on a pasture-raised pig farm. Brucella suis was then transmitted to domestic pigs raised outdoors in 13 other states through animal sales. Feral pigs could also play a significant role in the transmission and maintenance of transboundary animal diseases introduced to North America., For instance, African Swine Fever is actively spreading in eastern Europe, with wild boars transmitting this devastating disease between and within countries. Similarly, wild boars abet the transmission of ASF in South Korea, spreading the virus to outdoor-raised swine. And most recently, ASF was identified in domestic swine in the Dominican Republic, which is the closest to the US that ASF as spread in this century. During the past few decades, feral pig populations have greatly increased in the US from 17 to 41 states. California has one of the largest and widest geographic distributions of feral pigs and this invasive species has the broadest habitat range of any large mammal except humans, which is in part due to their ability to adapt to a diverse range of ecological habitats and their opportunistic omnivore diet. Feral pig population distribution and abundance is dynamic yet has not been documented at fine spatial units. Previous presence maps reported feral pigs for an entire county, even if there had only been a single occurrence recorded countywide.

In order to investigate whether the overall distribution and accumulation of small RNA is affected by the interaction between different V. vinifera genotypes [Cabernet Sauvignon and Sangiovese ] and environments [Bolgheri , Montalcino and Riccione ], we investigated the regions in the grapevine genome from where a high number of small RNAs were being produced , by applying a proximity-based pipeline to group and quantify clusters of small RNAs as described by Lee et al. . The nuclear grapevine genome was divided in 972,413 adjacent, non-overlapping, fixed-size windows or clusters. To determine the small RNA cluster abundance, we summed the hits-normalized-abundance values of all the small RNAs mapping to each of the 500 bp clusters, for each library . To reduce the number of false positives, we considered a cluster as expressed when the cluster abundance was greater than the threshold for a given library, eliminating regions where few small RNAs were generated, possibly by chance. Libraries from bunch closure, representing green berries, and 19 ◦Brix representing ripened berries, where used in this analysis. From the 972,413 clusters covering the whole grapevine genome, 4408 were identified as expressed in at least one sample. As showed in Figure 1, CS-derived libraries have a higher number of expressed clusters when compared to SG-derived libraries of the same developmental stage and from the same vineyard. The exceptions were the Sangiovese green berries collected in Riccione and Sangiovese ripened berries collected in Montalcino, big plastic pots which have a higher number of expressed clusters than the respective CS ones.

When Cabernet berries were green, a higher number of sRNA-generating regions were found active in Bolgheri than in Montalcino and Riccione. Differently, ripened berries had the highest number of sRNAproducing regions expressed in Riccione, while Bolgheri and Montalcino show a similar level of expressed clusters . Sangiovese green berries instead show the highest number of active sRNA-generating regions in Riccione, and this number is twice the number found in Bolgheri and Montalcino that is similar. Ripened berries collected in Montalcino and Riccione show almost the same high level of sRNA-generating clusters, whereas those collected in Bogheri present a lower number . We also noted that when cultivated in Bolgheri, neither Cabernet Sauvignon or Sangiovese change dramatically the number of expressed clusters during ripening, while in Riccione Cabernet Sauvignon shows a 2-fold increase of sRNAproducing clusters, which is not observed in Sangiovese. Next, the small RNA-generating clusters were characterized on the basis of the genomic regions where they map, i.e., genic, intergenic and transposable elements. In general, when the berries were green, the numbers of sRNA-generating loci located in genic and intergenic regions were roughly equal in all environments and for both cultivars, except for Sangiovese berries collected in Riccione, which show a slight intergenic disposition of sRNA-producing regions . Differently, in ripened berries on average 65% of the sRNA-generating loci were in genic regions, indicating a strong genic disposition of the sRNA-producing clusters . The shift of sRNA-producing clusters from intergenic to mostly genic is more pronounced in Cabernet Sauvignon berries collected in Riccione, with an increase of approximately 20% of expressed clusters in genic regions when berries pass from the green to the ripened stage.

When comparing the clusters abundance among libraries, we found that 462 clusters were expressed in all libraries. The remaining 3946 expressed clusters were either shared among groups of libraries or specific to unique libraries. Interestingly, 1335 of the 4408 expressed clusters were specific to Riccione-derived libraries . The other two environments showed a much lower percentage of specific clusters, 263 and 140 in Bolgheri and Montalcino respectively . Comparing the expressed clusters between cultivars or developmental stages, we did not observe a similar discrepancy of specific clusters toward one cultivar or developmental stage; roughly the same proportion of specific clusters was found for each cultivar and for each developmental stage . Among the 1335 specific clusters of Riccione, 605 were specific to Cabernet Sauvignon ripened berries of and 499 to Sangiovese green berries. Other smaller groups of expressed clusters were identified as specific to one cultivar, one developmental stage or also one cultivar in a specific developmental stage. When comparing the expressed clusters with the presence of transposable elements annotated in the grapevine genome , we noticed that approximately 23% of the sRNA-generating regions were TE-associated. Sangiovese green berries from Riccione have the highest proportion of TE-associated expressed clusters, while Cabernet Sauvignon ripened berries also from Riccione show the lowest proportion of TE associated expressed clusters. Sangiovese berries have the highest percentage of expressed clusters located in TE when cultivated in Riccione, compared to the other two vineyards. Interestingly, Cabernet Sauvignon berries show the lowest proportion of TE-associated clusters when growing in Riccione , independently from the berry stage. In all the libraries, Long Terminal Repeat retrotransposons were the most represented TE. More specifically, the gypsy family was the LTR class associated with the highest number of sRNA hotspots. The other classes of TE associated with the sRNA-generating regions can be visualized in Figure 3B.To determine the global relationship of small RNA-producing loci in the different environments, cultivars and developmental stages, we performed a hierarchical clustering analysis. As showed in Figure 4, the libraries clearly clustered according to the developmental stage and cultivar and not according to the environments.

Ripened and green berries had their profile of sRNA-generating loci clearly distinguished from each other. Inside each branch of green and ripened samples, Cabernet Sauvignon and Sangiovese were also well separated, indicating that, the cultivar and the stage of development in which the berries were sampled modulate the outline of sRNA-producing loci more than the environment. Notwithstanding the evidence that developmental stage and variety have the strongest effect in terms of distinguishing samples clustering, we were interested to verify the environmental influence on small RNA loci expression in the two cultivars. Thus, for each sRNA-generating cluster we calculated the ratio between cluster abundance in Cabernet Sauvignon and Sangiovese in each environment and developmental stage, thereby revealing the genomic regions with regulated clusters, considering a 2-fold change threshold, a minimum abundance of 5 HNA in each library and a minimum sum of abundance of 30 HNA . Figure 5 shows how different environments affect the production of small RNAs. In Bolgheri, regardless the developmental stage there were many clusters with a very high abundance level in Cabernet Sauvignon . In Montalcino and even more in Riccione we also observed differences between the expressions of clusters in the two cultivars, with ripened and green berries showing an almost opposite profile in terms of number of clusters more expressed in Cabernet Sauvignon or Sangiovese. When the berries were green, in Montalcino Cabernet Sauvignon shows the highest number of up-regulated clusters, while in Riccione, Sangiovese has the highest number of up-regulated clusters. The opposite behavior was noticed in ripened berries, with Sangiovese having the highest number of up-regulated clusters in Montalcino and Cabernet Sauvignon in Riccione . Notably, we observed a small percentage of regulated clusters exhibiting at least a 10-fold higher abundance of small RNA in Cabernet Sauvignon or Sangiovese when compared to each other . An examination of those clusters showed that a substantial difference could exist between the cultivars, depending on the vineyard and the developmental stage. For example, in Riccione, a cluster matching a locus encoding a BURP domain-containing protein showed a fold change of 390 when comparing green berries of Sangiovese with Cabernet Sauvignon. The small RNAs mapping in this region were mainly 21-nt and produced from both strands . Similarly, growing berries in containers the majority of the highly differentially expressed clusters showed a similar profile: strong bias toward 21-nt sRNAs and a low strand bias. These findings suggest that these small RNAs might be the product of RDR polymerase activity rather than degradation products of mRNAs. We applied a pipeline adapted from Jeong et al. and Zhai et al. to identify annotated vvi-miRNAs, their variants, novel species-specific candidates and, when possible, the complementary 3p or 5p sequences. Starting from 25,437,525 distinct sequences from all the 48 libraries, the first filter of the pipeline removed sequences matching t/r/sn/snoRNAs as well as those that did not meet the threshold of 30 TP4M in at least one library or, conversely, that mapped in more than 20 loci of the grapevine genome . Only sequences 18–26-nt in length were retained. Overall, 27,332 sequences, including 56 known vvi-miRNAs, passed through this first filter and were subsequently analyzed by a modified version of miREAP as described by Jeong et al. . miREAP identified 1819 miRNA precursors producing 1108 unique miRNA candidates, including 47 known vvi-miRNA. Next, the sequences were submitted to the third filter to evaluate the single-strand and abundance bias retrieving only one or two most abundant miRNA sequence for each precursor previously identified.

A total of 150 unique miRNA corresponding to 209 precursors were identified as candidate miRNAs. Among these 209 candidate precursors, 61 belonged to 31 known vvi-miRNA that passed all the filters and 148 were identified as putatively novel miRNA candidates. To certify that they were novel candidates rather than variants of known vvi-miRNAs we compared their sequences and coordinates with the miRNAs registered in miRBase . In order to reduce false positives and the selection of siRNA-like miRNAs, we considered only 20, 21, and 22 nt candidates whose stemloop structures were manually evaluated . Eventually, 26 miRNAs homologous to other plant species were identified with high confidence. Twenty-two were new members of nine known V. vinifera families, whereas the other four belong to three families not yet described in grapevine . For 16 homologs we were able to retrieve also the complementary sequence. Finally, excluding these 26 miRNAs and other si-RNA like miRNAs, we identified 7 completely novel bona fide miRNAs. Apart from the 61 known vvi-miRNAs identified by the pipeline, we searched the dataset for others known vvi-miRNAs eliminated throughout the pipeline, looking for isomiRs that were actually more abundant than the annotated sequences. Their complementary 3p or 5p sequence was also retrieved when possible. Hence 89 known vvi-miRNAs were identified in at least one of our libraries . Among the known vvi-miRNAs identified, 24 had an isomiR more abundant than the annotated sequence and 4 have the complementary sequence as the most abundant sequence mapping to their precursor. We found 16 vvi-miRNA isomiRs that were either longer or shorter than the annotated sequence, 7 vvi-miRNAs that mapped in the precursor in a position shifted with respect to the annotated ones and one miRNA that contains a nucleotide gap when compared to the annotated sequence . An extreme case of shifted position was found in vvi-miRNA169c, where the annotated sequence had only 5 TP4M when summing its individual abundance in the 48 libraries. Another sequence, shifted 16 bp as compared to its annotated position on the precursor had an abundance sum of 1921 TP4M, and was retained together with the annotated sequence, and named vvi-miRNA169c.1. For 36 of the 48 V. vinifera miRNA families deposited in miRBase we found at least one member. An in silico prediction of miRNA targets was performed for the 191 mature miRNAs here identified. Using the miRferno tool , and considering only targets predicted with high stringency, 1192 targets were predicted for 143 miRNAs, including six completely novel vvi-miRNA candidates . Two novel candidates seem to be involved in the regulation of important secondary metabolites biosynthesis. Among the six targets predicted for grape-m1191, the TT12 gene is known to be involved in the vacuolar accumulation of proanthocyanidins in grapevine . For grape-m1355, 12 targets were predicted and all of them are involved in secondary metabolism pathways. Nine targets code a bifunctional dihydroflavonol 4-reductase that is responsible for the production of anthocyanins , catalyzing the first step in the conversion of dihydroflavonols to anthocyanins . Another targeted gene codes a phenylacetaldehyde reductase which, in tomato, was demonstrated to catalyze the last step in the synthesis of the aroma volatile 2-phenylethanol, important for the aroma and flavor . Still this same miRNA candidate was predicted to target with high confidence a cinnamoyl reductaselike protein that is part of polyphenol biosynthetic pathway .

A broader range of studies from different cultivars, locations and environments are needed to determine a common set of genes involved in berry and flavor development. A similar study was conducted on the production of volatile aromas in Cabernet Sauvignon berries across many developmental stages, including a detailed analysis of the °Brix levels that was surveyed in this study. They found that the production of alcohol volatiles from the lipoxygenase pathway dominated in the later stages of berry ripening and suggested that the activity of alcohol dehydrogenases also could play an important role. The abundance of the transcript of VviOMT1 decreased in the pulp with increasing °Brix level and was correlated with IBMP concentrations in the late stages of berry development in this study. Both OMT1 and OMT3 have been shown to synthesize IBMP. Furthermore, the transcript abundance of each gene has been correlated with IBMP concentration, but the transcript abundance of each gene cannot fully account for the total IBMP present in all genotypes and conditions. OMT3 was found to be the major genetic determinant for this trait in two independent studies. Nevertheless, it is possible that OMT1 may contribute to the IBMP concentration, blueberries in containers growing because OMT1 can synthesize IBMP and it is located at the edge of a QTL significantly contributing to this trait.

Furthermore, the majority of IBHP , the precursor for the OMT1 and OMT3 biosynthesis of IBMP, is produced in the pulp of the berry complicating the factors that influence IBMP concentration. Our results raise questions that require additional research to clarify this relationship of transcript abundance to IBMP concentration, including determination of the rates of biosynthesis and catabolism, enzyme activities, volatilization of IBMP from the berry, as well as the concentrations of substrates for the enzymes involve. There are a number of other transcriptomic ripening studies in grapes and other fruit species. Many of these have compared broad developmental stages with partial genome microarrays. One study compared transcriptomic responses of the lates stages of ripening of whole berries of Chardonnay. This study used a different microarray platform with only about half of the genome represented on the array. In this study, 12 genes were found to be differentially expressed in each of the 3 different stages investigated. There were approximately another 50 genes that were differentially expressed at one stage versus another. Several genes were proposed as good candidates for markers of ripeness and these were also examined in Cabernet Sauvignon berries using qPCR. Several of these candidate genes are consistent with our results in the present study. They include CCD4a , a late embryogenesis abundant protein , a dirigent-like protein , and an S-adenosyl-L-methionine:salicylic acid carboxyl methyltransferase . Of these, the transcript expression of SAMT was found to be temperature insensitive. Like the previous study, the present study focused on very close stages in the mature berry when fruit flavors are known to develop. In contrast to the previous study on Chardonnay, there were massive changes in the transcript abundance in hundreds of GO categories over this narrow window of ripening.

This may in part be due to using six biological replicates rather than the standard three, which probably improved the detection of significantly changing transcripts. In addition, we used a different threshold level for statistical significance and an improved microarray platform, which was able to detect double the number of transcripts. In the present study, many differences were found between the skin and the pulp, °Brix levels and the interaction of tissue and °Brix. Important fruit ripening processes were affected including ethylene signaling, senescence, volatile aroma production, lipid metabolism and cell wall softening. These data indicate that fruit ripening in the late stages of maturity is a very dynamic and active process.Ethylene is involved in climacteric fruit ripening with a CO2 burst preceding the rise in ethylene. In tomato, this occurs at the time the seeds become mature in the mature green fruit stage. At this stage, tomato fruits become sensitive to ethyene and can continue through the ripening stage. Prior to the mature breaker stage, ethylene cannot promote tomato ripening to full ripeness. In non-climacteric fruit, there is no respiratory burst of CO2 and the ripening of most non-climacteric fruits was thought not to respond significantly to an extra application of ethylene. However, recently some non-climacteric fruit such as strawberry, bell pepper and grape have been found to produce a small amount of ethylene and appear to have responses to ethylene at certain stages. In the study of grapes, this peak was observed just before the start of veraison, followed by decreases in ethylene concentrations for several weeks afterwards; the late mature stages of ripening were not examined. Ethylene action is dependent upon ethylene concentration and ethylene sensitivity or signaling. In this study, there were clear and significant changes in transcript abundance of genes involved in ethylene signaling and biosynthesis in the late stages of berry ripening. Seeds become fully mature at this time .

Perhaps there is a signal from the seeds when they become mature that allows the fruit to ripen and senesce? Perhaps small amounts of ethylene are produced or there is a change in sensitivity to ethylene? Seymour et al. suggested the response of EIN3 might be a common signaling mechanism for both climacteric and non-climacteric fruit. The responses of VviEIN3 in this study and in a pepper fruit ripening study are consistent with this hypothesis. In addition, the transcript abundance of VviEIN3 in grape is very responsive to ethylene and the ethylene inhibitor, MCP. There are many other factors other than fruit development that can influence ethylene signaling. Could chilling of the fruit or other aspects of the processing of the grapes influence these responses? Could there be some influence of other abiotic or biotic stresses? These are questions that can only be addressed in future studies with additional experiments that are designed to answer these questions.The Berry phase reveals geometric information of quantum wave functions via their phases acquired after an adiabatic cyclic process, and its concept has laid the foundation for understanding many topological properties of materials. For example, the ground state fits the description as the limit of a statistical ensemble at zero temperature. At finite temperatures, the density matrix describes thermal properties of a quantum system by associating a thermal distribution to all the states of the system. Therefore, it is an important task to generalize the Berry phase to the realm of mixed quantum states. There have been several approaches to address this problem, among which the Uhlmann phase has attracted much attention recently since it has been shown to exhibit topological phase transitions at finite temperatures in several 1D, 2D, and spin-j systems. A key feature of those systems is the discontinuous jumps of the Uhlmann phase at the critical temperatures, signifying the changes of the underlying Uhlmann holonomy as the system traverses a loop in the parameter space. However, due to the complexity of the mathematical structure and physical interpretation, the knowledge of the Uhlmann phase is far less than that of the Berry phase in the literature. Moreover, planting blueberries in containers only a handful of models allow analytical results of the Uhlmann phase to be obtained. The Berry phase is purely geometric in the sense that it does not depend on any dynamical effect during the time evolution of the quantum system of interest. Therefore, the theory of the Berry phase can be constructed in a purely mathematical manner. As a generalization, the Uhlmann phase of density matrices was built in an almost parallel way from a mathematical point of view and shares many geometric properties with the Berry phase. We will first summarize both the Berry and Uhlmann phases using a fiber-bundle language to highlight their geometric properties. Next, we will present the analytic expressions of the Uhlmann phases of bosonic and fermionic coherent states and show that their values approach the corresponding Berry phases as temperature approaches zero. Both types of coherent states are useful in the construction of path integrals of quantum fields. While any number of bosons are allowed in a single state, the Pauli exclusion principle restricts the fermion number of a single state to be zero or one. Therefore, complex numbers are used in the bosonic coherent states while Grassmann numbers are used in the fermionic coherent states. The bosonic coherent states are also used in quantum optics to describe radiation from a classical source . Moreover, the Berry phases of coherent states can be found in the literature , and we summarize the results in Appendix A. Our exact results of the Uhlmann phases of bosonic and fermionic coherent states suggest that they indeed carry geometric information, as expected by the concept of holonomy and analogy to the Berry phase.

We will show that the Uhlmann phases of both cases decrease smoothly with temperature without a finite-temperature transition, in contrast to some examples with finite-temperature transitions in previous studies. As temperature drops to zero, the Uhlmann phases of bosonic and fermionic coherent state approach the corresponding Berry phases. Our results of the coherent states, along with earlier observations , suggest the Uhlmann phase reduce to the corresponding Berry phase in the zero-temperature limit. The correspondence is nontrivial because the Uhlmann phase requires full-rank density matrices, which cannot be satisfied only by the ground state at zero temperature. Moreover, the fiber bundle for density matrices in Uhlmann’s theory is a trivial one, but the fiber bundle for wavevfunctions in the theory of Berry phase needs not be trivial. A similar question on why the Uhlmann phase agrees with the Berry phase in certain systems as temperature approaches zero was asked in Ref. without an answer. In the last part of the paper, we present a detailed analysis of the Uhlmann phase at low temperatures to search for direct relevance with the Berry phase. With the clues from the previous examples, we present a conditional proof of the correspondence by focusing on systems allowing analytic treatments of the path-ordering operations. Before showing the results, we present a brief comparison between the Uhlmann phase and another frequently mentioned geometrical phase for mixed quantum states proposed in Refs., which was originally introduced for unitary evolution but later extended to nonunitary evolution. This geometrical phase was inspired by a generalization of the Mach-Zehnder interferometry in optics and was named accordingly as the interferometric phase. It has a different formalism with a more intuitive physical picture and has been measured in experiments. In general situations, the interferometric phase can be expressed as the argument of a weighted sum of the Berry phase factors from each individual eigenstate. Thus, its relation to the Berry phase is obvious. However, the concise topological meaning of the interferometric phase is less transparent since it is not directly connected to the holonomy of the underlying bundle as the Uhlmann phase does. The reason has been discussed in a previous comparison between the two geometrical phases. The interferometric phase relies solely on the evolution of the system state while the Uhlmann phase is influenced by the changes of both the system and ancilla, which result in the Uhlmann holonomy. Although Uhlmann’s approach can be cast into a formalism parallel to that of the Berry phase as we will explain shortly, its exact connection to the Berry phase is still unclear. The Uhlmann-Berry correspondence discussed below will offer an insight into this challenging problem. The rest of the paper is organized as follows. In Sec. II, we first present concise frameworks based on geometry for the Berry and Uhlmann phases, using a fiber-bundle language. In Sec. III, we derive the analytic expressions of theUhlmann phases of bosonic and fermionic coherent states and analyze their temperature dependence. Additionally, the Uhlmann phase of a three-level system is also presented. Importantly, the Uhlmann phases of both types of coherent states and the three-level system are shown to approach the respective Berry phases as temperature approaches zero. In Sec. IV, we propose the generality of the correspondence between the Uhlmann and Berry phases in the zerotemperature limit and give a conditional proof. In Sec. V, we discuss experimental implications and propose a protocol for simulating and measuring the Uhlmann phase of bosonic coherent states. Sec. VI concludes out work.

The right side of this plot, labelled with an electron density of zero, corresponds to charge neutrality in this system and lies in the gap of the band insulator. Therefore and both correspond to situations in which the hole band is very slightly filled. The valley and spin subbands of ABC trilayer graphene are presented in schematic form in Fig. 7.4A in the absence of electronic interactions. When we tune the Fermi level into these bands and activate interactions, we cannot produce a gap- the bandwidths of these bands are far too high- but we can produce full spin or valley polarization, as illustrated in Fig. 7.4B. The precise situations in which we find this system at and are presented in Fig. 7.4C and D; these situations correspond repsectively to full spin polarization but no valley polarization in and full spin and valley polarization in . Valley polarization couples strongly to transport, generating a large anomalous Hall effect and ferromagnetic hysteresis, as presented in Fig. 7.4E. Although these magnets occur in an atomic crystal, they are composed entirely of electrons we have forced into the system with an electrostatic gate, and as a result we can expect their magnetizations to be considerably smaller than fully spin-polarized atomic crystals. We will use the nanoSQUID microscope to image these magnetic phases. An optical image of the ABC trilayer graphene device used to produce data for the publications is presented in Fig. 7.5A. A black dashed line outlines the region we will be imaging using the nanoSQUID microscope. A nanoSQUID image of this region using AC bottom gate contrast is presented in Fig. 7.5B. This magnetic image was taken in the same phase in which we observe magnetic hysteresis, as presented in Fig. 7.4E. Clearly the system is quite magnetized; we also see evidence of internal disorder, blueberry pot likely corresponding to bubbles between layers of the heterostructure. We can park the SQUID over a corner of the device and extract a density- and displacement field-tuned phase diagram of the magnetic field generated by the magnetization of the device; this is presented in Fig. 7.5C.

Electronic transport data of the same region is presented in Fig. 7.5D. The spin magnet has only a weak impact on electronic transport, but the valley ferromagnet couples extremely strongly to electrical resistance. The system also supports a pair of superconductors, including a spin-polarized one; these phases are subjects ofcontinued study. Capacitance data over the same region of phase space is presented in Fig. 7.5E. ABC trilayer graphene is the first atomic crystal known to support purely orbital magnetism. Other related systems have since been discovered to host similar phenomena, including bilayer graphene. Our understanding of these magnetic phases is very far from complete, and we expect to encounter more surprises as our magnetic imaging campaign on this class of materials continues. The first systems with nonzero Chern numbers to be discovered were systems with quantum Hall effects. Quantum Hall insulators behave a lot like Chern magnets but are generally realized at much higher magnetic fields, and Berry curvature in these systems comes from the applied magnetic field, not from band structure. The fact that resistance in these materials is an intrinsic property and not an extrinsic one had implications for metrology that were immediately obvious to the earliest researchers that encountered the phenomenon. All of these devices have resistances that depend only on fundamental physical constants, so a resistance standard composed of these materials need not obey any particular geometric constraints, and can thus be easily replicated. The case for quantum Hall resistance standards was strong enough for the the National Institute for Standards and Technology to rapidly adopt them, and today the Ohm is defined by a graphene quantum Hall resistance standard at NIST. There are some downsides to the quantum Hall resistance standard. The modern voltage standard is a superconducting integrated circuit known as the Josephson voltage standard; it uses Shapiro steps to relate the absolute size of a set of voltage steps to a frequency standard. Because the voltage standard and resistance standard are independently fixed to physical phenomena, current standards are necessarily defined by the relationship between these two different standards. Unfortunately, the superconducting integrated circuits used as Josephson voltage standards must be operated in very low ambient magnetic field, because large magnetic fields destroy superconductivity.

This makes them incompatible with the graphene quantum Hall resistance standard, which must operate in large magnetic fields, generally B > 5T. This is a surmountable problem- in practice it is handled by storing the two standards in different cryostats, or with significant magnetic shielding between them- but the significant distance separating the standards reduces the precision with which the current standard can be defined with respect to our current resistance and voltage standards. One possible way to resolve this conflict is to replace the quantum Hall resistance standard with a Chern magnet resistance standard. Chern magnets show quantized anomalous Hall effects at low or zero magnetic field, meaning they can be installed in very close proximity to Josephson voltage standards in calibration cryostats. Unfortunately, doped topological insulators have such small band gaps that even at the base temperatures of dilution fridges, there is enough thermal activation of electrons into the bulk to limit the precision of quantization of the quantized anomalous Hall effect in these systems. This made the class of Chern magnets discovered in 2013 unsuitable as replacements for the graphene quantum Hall resistance standard. Since intrinsic Chern magnets have now been discovered, and are observed to have band gaps considerably exceeding those of doped topological insulators, it might make sense to replace the graphene quantum Hall resistance standard with an intrinsic Chern magnet resistance standard. The ease of replication of the fabrication process of MoTe2/WSe2 makes that material particularly intriguing as a candidate material for a new resistance standard, but over the past few years new intrinsic Chern magnets have been discovered almost every year, so we may soon be discussing much better materials for this application. In any case, it seems possible and perhaps even likely that Chern magnets will supplant quantum Hall systems as resistance standards in the near future.For decades, magnetic memories dominated information storage technology. Magnetic storage media are robust, do not require continuous access to power, survive high temperatures and extreme radiation environments, and are relatively cheap to manufacture. Hard drives, cassette tapes, floppy disks, and other legacy technologies leveraged the many advantages of magnetic information storage to fuel an explosion in affordable information storage, facilitating mass market access to movies, music, and personal computing.

Many of these technologies were in widespread use until quite recently . Since the heyday of these technologies, however, nursery pots magnetic information storage has fallen out of favor, for one simple reason: magnetic bits cannot be easily written electronically. Legacy mag- netic storage media address magnetic bits mechanically, which limits their maximum speed; modern flash memories can access data much faster precisely because each bit can be written and read electronically. Of course, that fact didn’t take away the many advantages of magnetic memories, and magnetic memories still persist in a variety of niche applications that depend particularly strongly on one of these advantages. Many computers destined to spend their lives in space still use hard drives, and sensors designed to operate over a wide range of temperatures and with intermittent access to power often use non-volatile magnetic memories as well. This has led researchers to search for phenomena and device architectures that allow magnetic order to be switched either with electrical currents or electrostatic gates. Until recently, the best technology available capable of electronic switching of magnetism used spin-orbit torques. In a spin-orbit torque device, current through a system with a strong spin Hall effect pumps spin into a separate magnet, which is eventually inverted by the torque exerted by those spins. This technology has matured considerably over the past few years, producing a cascade of new records for low current density magnetic switching and even a few consumer products in the memory market. The exotic orbital magnet in twisted bilayer graphene was found to be switchable with extremely small pulses of current, and the resulting current-switchable magnetic bits displaced previouslyrealized spin-orbit torque devices as the ultimate limit in low-current control of magnetism. A flurry of theoretical investigation of these systems followed, dedicated primarily to identifying and generalizing the mechanism underlying current control of magnetism in these systems. A few years later, AB-MoTe2/WSe2 joined twisted bilayer graphene, with a similarly small magnetic switching current. In the intervening time, a new phenomenon had been observed- switching of a Chern magnet with an electrostatic gate, in twisted monolayer/bilayer graphene. All of these phenomena represent newly discovered and now more or less well understood mechanisms for controlling magnetic bits electronically, and by the performance metrics used in the literature they reign supreme. Several electronic switching phenomena known in intrinsic Chern magnets are summarized in Fig. 8.3. Chern magnets differ from the magnetic materials used in more traditional magnetic memories in a wide variety of intriguing ways other than their electronic switch ability. Chern magnets are not metals and thus don’t have the same limitations as metallic magnetic memories. For example, the resistance of a Chern magnet is independent of its size, depending only on fundamental physical constants. This makes the resistance of a Chern magnet completely insensitive to miniaturization. Dissipation does occur in Chern magnets, but it occurs only at the contacts to the Chern magnet, so once electrons enter the crystal they can undergo very long range transport completely free of dissipation. Chern magnets are atomically thin in the out-of-plane direction, and of course if they are separated by insulators they can easily be stacked to increase magnetic bit density. Chern magnets are two dimensional materials, and two dimensional materials already have small radiation cross-sections relative to three dimensional crystals like silicon, but the conduction path through a Chern magnet is both one dimensional and topologically protected, so it is overwhelmingly likely that Chern magnet memories would be even more radiation hard than the thin semiconducting films that form the current state of the art. All of these ideas make Chern magnets interesting candidates as substrates for magnetic memories of the distant future. Of course none of these ideas have been implemented in technologies yet, and that is because intrinsic Chern magnets have only been realized at fairly low temperatures . All of the magnetic memory applications we’ve discussed depend critically on the discovery of intrinsic Chern magnets at considerably higher temperatures, and ideally room temperature. The Chern number is just a property of a band and does not come with an energy scale, so there is no reason to expect to encounter Chern bands only at low temperatures. Indeed, bands with finite Chern numbers have been shown to support quantized Hall effects in graphene quantum Hall devices at room temperature and high magnetic fields, as illustrated in Fig. 8.5A,B. The energy scale in a Chern magnet is set by the band gap produced by magnetic interactions. So if we’d like to know what the maximum temperature at which we can expect to find Chern magnets is, we need tothink about the energy scales of known magnets. Magnetism is an interaction-driven electronic phase, and interaction-driven phases almost always melt at sufficiently high temperatures. However, among interaction-driven electronic phases ferromagnetism is particularly stable. Many common transition metals, including iron, cobalt, and nickel, support ferromagnetism into the range 600-1200 K, and all of these have found applications in a variety of electronic technologies as a result. These are of course all three dimensional crystals, and Chern magnets are two dimensional crystals. So the next question we can ask is: do two dimensional magnets exist with Curie temperatures as high as room temperature? The answer turns out to be yes, as illustrated in Fig. 8.5C,D. This magnetic system appears not to be a Chern magnet, unfortunately, but the point is that there is nothing in particular stopping a Chern magnet with a Curie temperature above 300 K from existing.

Systems like chromium iodide have properties that are easy to understand in the context of the models we have so far discussed: strong on site interactions and exchange interactions produce full spin polarization, an interaction-driven band gap, and aligned magnetic moments within a single layer. As a result, these systems are electrical insulators. They support magnetic domain dynamics, and there is a temperature TC above which they cease to be magnetized , although they remain insulators far above that temperature. Extremely weak out-of-plane bonds produce highly anisotropic cleavage planes and make it relatively easy to prepare atomically thin crystals mechanically. As in other systems, this does not mean we will always be studying monolayers of the material. Bilayers, trilayers, four-layer crystals, and even thicker flakes can all have properties that differ significantly from those of a monolayer, often for reasons that we can understand, and CrI3 is no exception. Although it isn’t particularly relevant to the physics of magnetism, it’s worth mentioning that all of the chromium halides are highly unstable compounds, and decompose in a matter of seconds when exposed to air or moisture. These materials are difficult to study under normal circumstances, but two dimensional crystalline samples can be prepared inside of an inert-atmosphere glovebox. They can also be sandwiched, plant pot with drainage or ‘encapsulated,’ between other two dimensional crystals. Two dimensional crystals are so flat that this process produces an air- and water-proof barrier and protects the encapsulated crystal from degradation in atmosphere, facilitating easy measurements with tools like the nanoSQUID.

The crystalline structure of CrI3, projected onto a two-dimensional crystal, is visible in Fig. 2.6A. Unlike graphene, CrI3 has two different kinds of atoms in its unit cell; the chromium atoms are responsible for the magnetic moments producing magnetism. CrI3 has fairly strong spin-orbit coupling, and thus strong Ising anisotropy, with magnetic moments pointing out-of-plane . Most of the other chromium halides also support magnetic order, although the precise nature of each of their ground states differs somewhat. Both CrI3 and CrBr3 have ferromagnetic in-plane interactions and strong Ising anisotropy, but CrI3 has antiferromagnetic out-of-plane interactions, meaning that in the magnetic ground state of the crystal adjacent layers have their spins antialigned . Interestingly, CrCl3 also seems to have ferromagnetic in-plane interactions, but it is likely that it is not an Ising or easy-axis magnet, and instead has its spins pointed in the in-plane direction and thus free to rotate. It is evidently the case that although these systems are structurally very similar and all have strong spin-orbit coupling, their magnetic interactions and magnetocrystalline anisotropies vary wildly in response to modest differences in their electronic structure. As a result of all of the arguments discussed previously in this chapter, a CrI3 monolayer has finite magnetization even in the absence of an applied magnetic field, and its magnetic order experiences hysteresis in response to variations in the applied magnetic field, as illustrated in Fig. 2.6D . Antiferromagnetic interactions between adjacent layers in CrI3 mix in an interesting factor that can be easily understood: flakes with an even number of layers have no net magnetization in the absence of an applied magnetic field, but develop finite magnetization at higher magnetic fields as the applied magnetic field overwhelms interlayer interactions and realigns each layer in turn with the ambient magnetic field .

Layer realignments are close analogues of magnetic phase transitions we have already discussed, and they support magnetic hysteresis as well. We will be studying the magnetic phase transition highlighted in yellow with the nanoSQUID microscope. An optical microscope image of a large four-layer CrI3 sample and a much smaller CrI3 monolayer is shown in Fig. 2.6F; this sample has been encapsulated in hBN for protection in atmosphere. We will use this system to get a taste of what the nanoSQUID microscope is capable of. We will use the nanoSQUID to image the region outlined with a white box in Fig. 2.6F. We will be imaging magnetic order across the magnetic phase transition highlighted in yellow in Fig. 2.6E, starting at B = 720 mT and thus in a state in which the four-layer CrI3 sample has finite magnetization and ending at B = 540 mT, in a state in which the four-layer CrI3 sample has no net magnetization. We thus expect the four-layer CrI3 flake to have a finite net magnetization in the first image, and we expect an antiferromagnetic domain with no net magnetization to consume the magnetized region by the final image. The nanoSQUID sensor used to generate these images was about 80 nm in diameter, and was about 100 nm from the surface of the device, producing an imaging resolution of about 100 nm. A characterization of the SQUID used in this imaging campaign is available in Fig. 1.7. The fully magnetized state can be seen in Fig. 2.7A. The magnetic fields generated by the four-layer crystal are comparable to those emitted by the smaller monolayer, at right. In both flakes, the magnetic order is riven with linear defects, which we attribute to wrinkles or cracks in the two dimensional crystals. We can see in Fig. 2.7B that as we decrease the magnetic field, antiferromagnetic domains spread in from the edges of the flake, destroying the magnetization nearthe edges of the two dimensional crystal.

This process continues in Fig. 2.7C, but it is clear that the linear defects present in the magnetic order stop and redirect ferromagnet/anti-ferromagnet domain walls. These defects protect a small patch of magnetization at the center of the flake as the magnetic field continues to decrease in Fig. 2.7D. In Fig. 2.7E, even this internal patch of magnetized material is overwhelmed, and the entire four-layer flake has completed its phase transition to antiferromagnetic order. The monolayer remains fully magnetized. Chromium iodide is a very simple magnetic system, at least at the level of its macroscopic magnetic properties, but there are still a few conclusions we can draw from our nanoSQUID imaging campaign. First, although it is true that CrI3 supports magnetic hysteresis, it does not behave as a single macrospin, instead supporting rich domain dynamics dominated by internal structural disorder. For this reason we cannot expect to learn anything about the energy scale of magnetoelectric anisotropy from the coercive field. This puts CrI3 in a very large class of magnets that includes almost all large polycrystalline samples of transition metal magnets. We will later on discuss several magnets for which the macrospin approximation is more or less valid. Second, it is apparently the case that magnetic domains cost the least energy to nucleate near the edges of the sample. This isn’t surprising, since this region of the crystal experiences the weakest exchange interactions because the nucleated domain is not completely surrounded by the metastable magnetization state, but it is a nice sanity check for our understanding of these systems. Finally, growing blueberries in pots the fact that regions of high disorder remain highly magnetized even in the antiferromagnetic ground state may provide a hint towards the nature of internal disorder in this system. Other experiments have shown that regions of high strain in CrI3 become highly magnetized, so it could be that these one dimensional defects are wrinkles in the two dimensional crystal. We have thus used the nanoSQUID microscope to image magnetic domain dynamics in a two dimensional chromium iodide crystal with approximately 100 nm resolution at magnetic fields as high as 720 mT. This system is a relatively simple one, an uncomplicated magnetic insulator, without the physical phenomena that will form the scientific focus of this thesis. I think it’s useful to illustrate the capabilites of the nanoSQUID microscopy technique under ideal circumstances, i.e. in a system with high magnetization and strong internal disorder, but also to distinguish the physics of magnetism from the physics of Berry curvature, orbital magnetism, and Chern numbers. These phenomenatogether will form the main focus of this thesis, and we will discuss all of them in the next chapter. Let us take a closer look at the crystalline structure of graphene, armed with the knowledge we have gained about spontaneously broken symmetries and magnetism. We have already discussed how each atomic orbital of each atom contributes a band to the crystalline band structure, although of course the orbitals hybridize to produce new, decocalized quantum states. And of course we know that because either spin species can occupy a band, in reality each band can accommodate two electrons. It contains two different atoms, but those atoms have almost precisely the same environment- in fact, the only difference between them is the fact that the distribution of atoms with which they are surrounded is inverted. We can say that graphene has inversion symmetry, and furthermore that there exists a pair of different atoms that are swapped by inversion in real space and time reversal symmetry in momentum space.

Because these two atoms have almost exactly the same environment, they produce bands that are also strikingly similar. In particular, they produce pairs of bands that are related both by inversion symmetry and time reversal symmetry. These are not the same bands, but they do have precisely the same density of states at every energy. As a result, these bands are in practice energetically degenerate. This means that all of the phenomena associated with spontaneously broken symmetry can apply to this pair of bands, which together form a new degree of freedom. For reasons having to do with the shape of graphene’s band structure, we often call this new degree of freedom the ‘valley degeneracy.’ We have already seen how spin degeneracy produced magnetism. This is now joined by the valley degeneracy, so in graphene we can expect to encounter both of these twofold degeneracies, together producing a fourfold degeneracy. Every graphene band can thus accommodate four electrons. There is one more important point to make about the valley degeneracy. I mentioned in passing that these two states can be related to each other by time reversal symmetry in momentum space. In practice, this means that if the function describing one valley’s band structure is E, then we can immediately say that the other valley’s band structure is E. Suppose we found a set of conditions under which one of the bands in a graphene allotrope had finite angular momentum in its ground state. This is actually not so uncommon, so far as physical phenomena go- many atomic orbitals have finite angular momentum, and in condensed matter systems they can hybridize to form delocalized bands with finite angular momentum. The above condition tells us that we can then expect to find another band with equal energies and equal and opposite angular momenta, and thus magnetic moments. These are precisely the conditions satisfied by the electron spin degree of freedom that allowed it to produce magnetism! So, under these circumstances- i.e., assuming we can find conditions under which a band in graphene has finite anguluar momentum in its ground state, strong electronic interactions, and a flat-bottomed or flat band- we can expect to find a new form of magnetism, dubbed by theorists ‘orbital magnetism,’ wherein center of mass angular momentum coupling to the electron charge is responsible for the magnetic moment, instead of electron spin. There are many important corollaries of the arguments we’ve just discussed, and many more of them will appear later, but there are a few I’d like to focus some special attention on. We discussed earlier how the orientation of electron spin generally does not interact with electronic band structure unless we invoke relativistic effects in the form of spin-orbit coupling. Carbon atoms are extremely light, and as a result the energy scale of spin-orbit coupling in graphene is quite low. For this reason condensed matter researchers in the distant past na¨ıvely expected not to find magnetic hysteresis ingraphene systems. The type of magnet proposed here does not invoke spin-orbit coupling; in fact, it does not even invoke spin. Instead, the two symmetry-broken states are themselves electronic bands that live on the crystal, and they differ from each other in both momentum space and real space.