The availability of BC as a secondary product of bio-energy production and/or waste stream management , as well as lower transportation costs made possible by regional or on-site BC production, could further leverage economic advantages over peat and peat alternatives . Recent studies support the unique ability of BC to mediate biological interactions with benefits for greenhouse production such as enhanced pathogen and pest suppression. For example, 1–5% additions of citrus wood BC to peat-based substrates increased expression of pathogen defense genes in strawberry and as a result suppressed fungal disease ; for tomato and pepper , such additions delayed and reduced disease from fungal pathogens and mites . However, lower susceptibility of plants to pathogens in soil-free substrates with a BC component may be muted by fertilization , and therefore may not be possible under intensive greenhouse production. On the other hand, substrates with a high proportion of BC such as in this study could have detrimental effects on biological processes that support plant productivity , largely due to interference of chemical signals between beneficial microorganisms and host plants . As a result, BC could lessen establishment of rhizobial and mychorrizal associations and reduce nodulation in leguminous species . Strong sorption by BC could afford horticultural advantages, however. For example, bulbet organogenesis of grape hyacinth was enhanced with the use of BC-like material in substrates due to its sorption of inhibitory compounds . Potential plant health benefits of BC-based substrates are relatively under-investigated in evaluations of peat alternatives, despite one of the main uses of soil-free substrates being the avoidance of plant exposure to pathogens . Finally, the ability to replace peat with BC offers potential economic and environmental benefits. The expense of peat is expected to increase in the coming decades due to production costs, competing uses for peat, and its perception as being unsustainable . Such a perception in part stems from the negative impacts on wetland ecosystems of some peat mining operations , though the sustainability of peat harvesting is a subject of debate . Peat mining operations and the eventual decomposition of peat after its use in substrates represents a transformation of a terrestrial C sink of global importance into a net C source, with climate change forcing effects . Assuming a conservative aerobic decomposition rate for peat in substrates of 5% per annum ,vertical hydroponics within one century of mining and use in soil-free substrates 95% of mined peat would be expected to revert from a C sink to source .
In contrast, high-temperature BCs are thought to generally exhibit lower decomposition rates than undecomposed or humified biomass such as compost and peat and exhibit centennial to millennial residence times . The molar O:C = 0.36 for the BC in this study corresponds to a half-life of 100–1000 years , suggesting that one century after production and use in soil-free substrates, at least 50% of C in the softwood BC in this study would be converted to CO2. The use of non-peat biomass or even waste in the form of BC in soil-free substrates is an additional strategy for ‘sustainable bio-char to mitigate global climate change’ due to its greater stability and ability to preserve a key global C sink.In landscape, we form meaning through placefulness; ‘‘place’ places man in that dimension which reveals the revealing meaning of being’. Gardens imply a more accelerated and amplified rendition of this process, while the gardens that we personally make and dwell in further magnify this condition. The garden is in effect the most permanent communion we can make with a piece of the world, whether that patch is on traditional earth or elevated in an artificially constructed environment. Those who have been faced with moving from somewhere they have resided for a long time may confer that vacating the house is one issue, but leaving the associated garden is an altogether more fraught separation. The most fundamental biological fact that plants are rooted and sedentary—while we are not—is laid bare during this process. Accordingly, John Brinkerh off Jackson defines the landscape of place as ‘a space on the surface of the earth … with a degree of permanence’.Nonetheless, we are also remarkably adept and manufacturing meaning on the run. There are countless accounts of how travelers, explorers and refugees have rearranged their immediate surroundings to assemble meaning from the background void. Furthermore, this phenomenon is not restricted to those who move long distances by choice of profession or byproduct of circumstance, since modern urban dwellers also possess this capacity. As Ian Nairn notes, ‘people need to put down roots in a terribly short time’, himself taking ‘about forty-eight hours’. Nairn concludes that movement paradoxically amplifies the sense of place, observing that ports—while being highly fluid—are nevertheless very well defined places. The gardens in a garden show can be considered within this context. Such exhibits are not gardens with which the visitor grows and coinhabits with its meaning, but rather passes through en mass in a matter of minutes.
And not long after they are experienced, the gardens are either wholly deleted or at the very least downgraded to mere residual features in the landscape-park that typically inherits the site once the spectacle of the expo has concluded. Under these circumstances meaning is absorbed and place manufactured on the run. To apply a vegetal analogy, this is less a process of terrestrial rootedness than the ‘continuous-flow solution culture’ associated with hydroponics. This interplay between rootedness and mobility in the place making and meaning-construction of the individual in the garden prefigures a society-scale condition found within Modernity as a whole. That is, the tension between the rapidity of globalism and the romantic yeaning to resist-and-return as Paul Ricoeur describes: ‘how to become modern and return to the sources, how to revive an old dormant civilization and take part in a universal civilization’. While visible in the landscape generally, the tension of this ‘paradox of place’ is manifest most acutely in the garden. The ‘sense’ or ‘spirit of place’ is both a manifestation of this paradox and an attempt to resist or realign it.In the midst of a fast-tracked industrial-to-consumption revolution, this tension is patently visible in the rapidly urbanizing cultural landscape of China. Framed by these dialectics of transience versus groundedness and tradition versus modernity, I focus in this essay on a particular example of a phenomenon that has persevered throughout the West’s Modernity and has found new vigor in China’s; that of the garden show or horticultural exposition. Both an expression of the yearning for otherness within the totalizing fabric of Modernity and a product of the very global reach of Modernity, international garden shows are increasingly commandeered into the mega-events that are used to influence the fortunes of cities. Typically, in the vein of the World’s Fairs and indeed Olympic Games , installments of the World Horticultural Exposition have fulfilled this transformative role, involving themed extravaganzas underpinned by massive quantities of construction far beyond that which is required for the simple promulgation of horticulture. Positioned at the northeastern periphery of the ancient capital, the 2011 Xi’an International Horticultural Exposition continues this bootstrapping city-building logic by leveraging the adjacent development of alluvial farmland and traditional villages into a regional financial centre.
The site preparation for the Expo involved remodeling a clay quarry into a simulacrum of the ancient Guangyun Lake, which was once an important port on the Chan-Ba River. Reinterpreted as a constellation of lined lakes interconnected with weirs,hydroponic vertical farming systems the shorelines inform the necklace structure of the exhibits . While most displays represented other provinces and countries, two areas moved beyond kitsch regional simulacra; the first being the collection of gardens by selected ‘Masters’ of landscape architecture, and the second a collection of University gardens by invited international academic teams. To investigate the state-of-the-art of current garden expo design, I explore these two collections of gardens with several objectives: to position the gardens in relation to contemporary landscape architecture design paradigms; to examine the role of the frame in the contained context of the expo garden with the implicit hypothesis that these tactics have agency in the wider contemporary metropolis; to understand why one set of gardens appeared to function as intended within the Expo, while the other appeared to be dysfunctional; and to create a record of Expo Gardens themselves, since despite pretences of being ‘permanent’ installations, it is highly unlikely that any of the gardens will survive physically or semiotically intact beyond the short extravagance of the Expo event.In the first part of the essay I describe, interpret and theoretically and poetically position a number of exhibits from both the Masters and University collections. In the second part of the essay I explore the issue of framing that so vividly distinguishes the Masters’ from the University Gardens. I develop the argument that dissolving the frame—while relevant in contemporary landscape praxis—does not necessarily translate into the context of individual gardens; rather it is the boundary between the Expo and the city that is the most potent threshold. Extending this argument to the city itself, I conclude the essay with discussion regarding the fate of the horticultural expo and its devolution into the urban fabric. In terms of methodology, I draw on my involvement with the Expo from several perspectives; participation in the design workshop for the University Gardens; observations on site during the construction process; and my experiences at the opened Expo as a member of the public.In regards the latter, when on site I was sensitive to Bernard St-Denis’s critique of the tendency for contemporary garden scholarship to place semantic interpretation over ‘the gratification of spending time in a garden’.To be sure, whereas St-Denis was undoubtedly referring primarily to established gardens, the transient nature of the Horticultural Expo gardens tested this challenge to its practical limits. I made repeat visits to the gardens and loitered insofar as was practical, but never attained a contemplative communion with any one garden. However, the impracticality of experiencing ‘time in a garden’ in the Expo context was offset by the heightened experience of the ‘first encounter-reality’ of the perception that results from the initial visit to each garden. Far from being superficial, first impressions are a potent mechanism in our ongoing formation of a sense of place. They are also rarely isolated as purely experiential events; as Donald Apple yard notes, ‘prior indirect information supplied through social contacts or media are also influential’. Like over-the-horizon radar that allows us to cognitively image un-experienced places, these preconceptions are legitimate component of the construction of an environmental image.In addition to my own experiences—keenly honed but biased as a gardenphile and designer of gardens—I also observed the behavioral tendencies of Chinese visitors in each garden. When visiting other more thematic representative gardens of local provinces, it was clear that on the whole the Chinese knew how to act in each garden, and seemed to be far more in tune with the living cultural narrative of garden history than Westerners in equivalent situations in the West, who as Robert Riley intimated, have lost connectivity with and hence knowledge of what to do in a garden.That said, although the gardens in question are located in China, an apparent deficiency of this essay may appear as a lack of attention to traditional Chinese garden landscape themes and narratives. This is perhaps partially a consequence of my limited command of this material, but most importantly it is a product of the Expo being very much a condition of modern China. Indeed, the modern history of the botanic garden / horticultural expo in China is transplanted from the West rather than emerging from Daoism or Confucianism.That Westerners designed all but one of the Masters Gardens and the majority of University Gardens, but that virtually all Expo visitors were domestic in origin, illuminates this complex condition.In raw form, the 10 000 sq ft plots allocated to each designer are typically flat in profile and trapezial in plan, buffered by thick stands of bamboo with controlled access on two sides. These manufactured site circumstances present a strong case for utilizing the timeless phenomenology of the walled garden as an other world decisively withdrawn from the surrounding landscape.