Sustaining trajectories towards Sustainability: Dynamics and diversity in UK communal growing activities     

Rebecca White  Andrew Stirling 《Global Environmental Change》2013,23(5):838-846

Civil society is a critical arena both for exploring Sustainability itself and for sustaining trajectories towards it through innovation, experimentation and debate. Innovations can be mould breaking and can challenge local institutions. Concurrently, initiatives may be fragile due to the development of new working relationships, reliance on voluntary labour and goodwill, and dependence on grant funding. Here we examine different aspects of what it takes to sustain grassroots trajectories for ‘communal growing’, given the pressures that groups and intermediary organisations practicing and supporting this activity experience, and the consequential need to build qualities like ‘resilience’. Attending carefully to the definition of this otherwise slippery concept, a particular focus is given to how contrasting aspects of temporality and agency lead to divergent constructions of ‘resilience’ and strategies for sustaining growing. We draw on fieldwork that explores the practice and support of communal growing in East Sussex, England, and directly associated activities at a national level.We find important interdependencies between communal growing projects and the intermediary organisations supporting them. Additionally there is huge diversity within and between both projects and the organisations that support them, including with respect to the ends to which growing is seen as a means. These ends link growing initiatives – both antagonistically and synergistically – to food, education and health systems. This diversity can be seen positively as: a source of innovation; facilitating the open and bottom up nature of growing; and, enabling the securing of greater financial support for the endeavour. What is less clear is how this plays into framing and configuring communal growing specifically in relation to achieving a more Sustainable and localised food system. We discuss the conceptual and methodological implications of these empirically derived observations with regards future research on grassroots innovations.  相似文献   

Short-term environmental variability in cold-water coral habitat at Viosca Knoll,Gulf of Mexico     

Andrew J. Davies  Gerard C.A. Duineveld  Tjeerd C.E. van Weering  Furu Mienis  Andrea M. Quattrini  Harvey E. Seim  John M. Bane  Steve W. Ross 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(2):199-212

The Lophelia pertusa community at Viosca Knoll (VK826) is the most extensive found to date in the Gulf of Mexico. As part of a multi-disciplinary study, the physical setting of this area was described using benthic landers, CTD transects and remotely operated vehicle observations. The site was broadly characterised into three main habitats: (1) dense coral cover that resembles biogenic reef complexes, (2) areas of sediment, and (3) authigenic carbonate blocks with sparse coral and chemosynthetic communities. The coral communities were dominated by L. pertusa but also contained numerous solitary coral species. Over areas that contained L. pertusa, the environmental conditions recorded were similar to those associated with communities in the north-eastern Atlantic, with temperature (8.5–10.6 °C) and salinity (～35) falling within the known species niche for L. pertusa. However, dissolved oxygen concentrations (2.7–2.8 ml l^?1) and density (σ_Θ, 27.1–27.2 kg m^?3) were lower and mass fluxes from sediment trap data appeared much higher (4002–4192 mg m^?2 d^?1). Yet, this species still appears to thrive in this region, suggesting that L. pertusa may not be as limited by lower dissolved oxygen concentrations as previously thought. The VK826 site experienced sustained eastward water flow of 10–30 cm s^?1 over the 5-day measurement period but was also subjected to significant short-term variability in current velocity and direction. In addition, two processes were observed that caused variability in salinity and temperature; the first was consistent with internal waves that caused temperature variations of 0.8 °C over 5–11 h periods. The second was high-frequency variability (20–30 min periods) in temperature recorded only at the ALBEX site. A further pattern observed over the coral habitat was the presence of a 24 h diel vertical migration of zooplankton that may form part of a food chain that eventually reaches the corals. The majority of detailed studies concerning local environmental conditions in L. pertusa habitats have been conducted within the north-eastern Atlantic, limiting most knowledge of the niche of this species to a single part of an ocean basin. Data presented here show that the corals at VK826 are subjected to similar conditions in temperature, salinity, and flow velocity as their counterparts in the north-east Atlantic, although values for dissolved oxygen and density (sigma-theta: σ_Θ) are different. Our data also highlight novel observations of short-term environmental variability in cold-water coral habitat.  相似文献   

The effect of composition,temperature and pressure on the stability of the 1Tc and 2M polytypes of sapphirine     

Andrew G. Christy 《Contributions to Mineralogy and Petrology》1989,103(2):203-215

Microprobe analyses and structural characterisation by means of transmission electron microscopy and powder X-ray diffraction are presented for a suite of natural and synthetic sapphirines. Most sapphirines appear to consist of intergrowths of the common 2M polytype with minor amounts of the 1Tc phase, although the converse situation is found in some cases. Attempts to correlate the structural state of the mineral with other factors reveal that: (i) There is no strong relationship between mean tetrahedral cation radius or mean octahedral cation radius and the preferred polytype. The Tschermak substitution M²⁺M⁴⁺-M³⁺M³⁺ does not appreciably influence the 1Tc-2M equilibrium, (ii) However, the total content and mean oxidation state of iron in sapphirine are important in this respect. Fe²⁺ stabilises the 2M phase, whereas Fe³⁺ stabilises the 1Tc phase. (iii) P-T estimates for the host rocks, and estimates for the conditions of sapphirine crystallisation, where obtainable, suggest that the 1Tc phase is stable at lower T and higher P than the 2M phase. Some quantitative constraints are inferred.  相似文献   

Stream-driven, high-density gravelly traction carpets: possible deposits in the Trabeg Conglomerate Formation, SW Ireland and some theoretical considerations of their origin   总被引：1，自引：0，他引：1  

SIMON P. TODD 《Sedimentology》1989,36(4):513-530

Within high-density flood flows a prominent mechanism of gravel transport and deposition is by stream-driven, high-density traction carpet (with a rheology similar to grain flow). These gravel carpets are envisaged to form the basal portion of a bipartite high-density flood flow, decoupled from an overlying sand- and silt-laden turbulent flow. Several examples already documented in the literature are reviewed and an additional case from the Lower Old Red Sandstone of southwest Ireland is presented. Two mechanisms of traction carpet initiation are discussed: by rapid entrainment of gravel into suspension on rising stage, followed by settling into the gravel traction carpet at peak and falling stage; and by overconcentration of a ‘normal’, low-density bedload. Gravel entrainment, suspension and traction carpet development are significantly easier if the flood water already carries a high concentration of sand and silt in suspension. Theoretical consideration further shows that gravelly traction carpets can be maintained in channels of relatively low gradient by the shear stress exerted by the high-density, sand-bearing turbulent flood flow above. This tangential shear stress is converted to dispersive pressure, which aids buoyancy and quasi-static grain-to-grain contacts in the support of the clasts within the gravel carpet. The carpet is thought to have a quasi-plastic rheology but behave much like a viscous fluid at high shear rates. Stream-driven gravelly traction carpets are expected to produce sheet-like units of clast- to matrix-supported conglomerate, characterized by a parallel or an a(p)a(i) clast fabric. These units may be ungraded, normally or inversely graded, depending on the rate of shear, the viscosity of the flow and the celerity of deposition.  相似文献   

Si,Al ordering in leucite by high-resolution 27Al MAS NMR spectroscopy     

Brian L. Phillips  R. James Kirkpatrick  Andrew Putnis 《Physics and Chemistry of Minerals》1989,16(6):591-598

High-resolution ²⁷Al MAS NMR spectra of natural leucite recorded at H ₀=11.7T contain three resolvable resonances at ²⁷Al δ _i = 69.2, 64.7, and 61.0±0.5 ppm. These three resonances are assigned to the three inequivalent framework positions of leucite: T3, T2, and T1, respectively. Fitting the observed spectra yields a Si,Al distribution for leucite in which approximately one-half of the Al is in T1 and one-quarter in each of T2 and T3. This Si,Al distribution differs substantially from those obtained by previous workers using ²⁹Si NMR spectroscopy and X-ray diffraction. New ²⁹Si NMR spectra and revision of previously reported ²⁹Si NMR peak assignments, however, make the ²⁷Al and ²⁹Si NMR results consistent. The ²⁷Al δ _i correlate linearly with the mean T-O-T′ bond angles of the average structure, which allows the peak assignments to be made. However, this correlation lies distinctly toward higher frequency and larger bond angles than correlations for Si,Al ordered aluminosilicates, suggesting that the mean T(Al)-O-T′(Si) bond angle for each site in leucite is smaller than the mean bond angle of the average structure, which is averaged over T(Al)-O-T′(Si) and T(Si)-OT′(Si,Al) angles.  相似文献   

A short-range interaction model for polytypism and planar defect placement in sapphirine     

Andrew G. Christy 《Physics and Chemistry of Minerals》1989,16(4):343-351

The concept of short-range interlayer interactions, fundamental to spin-analogue models for polytypism, is examined in the case of sapphirine. Consideration of interactions out to fourth-nearest neighbours provides a rationale for the difference between the polytype suites observed for sapphirine and wollastonite. In each case, the observed long-period structures are consistent with those predicted to be stable by the appropriate mappings onto the axial next-nearest neighbour model. Short-range interaction parameters may also be used to express stacking fault energies. This approach, combined with a simple nucleation-andgrowth model, is used to examine the possibility of metastable generation of complex polytypes in sapphirine. Statistical analysis of defect distributions and frequencies in sapphirine suggests that interactions over several hundred Ångstroms must be considered if the stacking energetics are to be accurately modelled.  相似文献   

Correspondence     

Ismail Gultepe  Andrew Heymsfield 《Boundary-Layer Meteorology》1988,44(3):305-305

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Desertification as a Global environmental issue     

Andrew Warren 《GeoJournal》1993,31(1):11-14

Compared to other environmental issues, such as Global Warming/Climatic Change, and the Ozone Hole, Desertification has been neglected by both scientists and funding agencies. The reasons are the complexity of the problem and the poverty and marginality of the arid lands. The author suggests a policy-oriented definition and draws attention to the differences between drought, desiccation and dry-land degradation.  相似文献   

Carbon fluxes resulting from U.S. private timberland management     

Andrew J. Plantinga  Richard A. Birdsey 《Climatic change》1993,23(1):37-53

A carbon budget model was developed to examine the effects of forest management practices on carbon storage in U.S. private timberlands. The model explicitly incorporates the demand for wood products and its impact on harvesting and other management decisions. Forest carbon is divided into four components: carbon stored in trees, soils, forest litter, and understory vegetation. Changes in the forest carbon inventory result from tree growth and management activities, in particular harvesting. Harvesting of timber for wood products is determined by demand and supply forces. The model then tracks carbon in timber removals through primary and secondary processing and disposal stages. Harvesting also has effects on carbon in soils, forest litter, and understory vegetation. A base-run scenario projects increases in carbon storage in U.S. private timberlands by 2040; however, this increase is offset by carbon emissions resulting from harvesting.  相似文献   

Characterization of Transmissive Fractures by Simple Tracing of In-Well Flow   总被引：1，自引：0，他引：1  

Andrew Michalski  George M. Klepp 《Ground water》1990,28(2):191-198

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