Browsing by Author "Grice, Samuel M."
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Item Open Access Is the thermodynamic efficiency of soil microbial communities related to ecosystem maturity and stress?(Cranfield University, 2014-07) Grice, Samuel M.; Harris, Jim A.; Ritz, K.; National Environmental Research Council(NERC); The Swedish Research Council FormasAccording to the second law of thermodynamics, no process can be 100% efficient and all processes must increase the total entropy of the system they occupy. Therefore, living systems require a constant influx of low-entropy energy to survive, giving an evolutionary advantage to those that produce less waste. Odum suggested that ecosystems would therefore develop mechanisms for reducing entropy production per unit biomass, as they matured. Isothermal calorimetry allows the direct measurement of waste heat emitted from any system, including soils and the life within them. However, upon review it became apparent that current methods employed in the analysis of soil microbial communities via isothermal calorimetry are outdated and in need of review. An experiment was conducted to troubleshoot the method and appropriate modifications were made. A second experiment was conducted to test the microbial community response to pre-incubation prior to calorimetric analysis at 20°C, concluding that samples should be pre-incubated for ten to sixteen days prior to analysis at 20°C. Subsequently, experiments were carried out to establish how much waste heat was produced by soil microbial communities in the context of various ecological gradients, following glucose amendment. Results for enthalpy efficiency (ηeff) proved inconclusive, whereas results for substrate induced heat production (SIHP), where heat output is expressed per unit biomass, indicated that soil microbial communities produced significantly more waste heat when subjected to long-term metals induced stress and short-term copper-induced stress. In addition, a reduction in the production of waste heat generated by soil microbial communities associated with primary succession along a glacier foreland was observed. This provides evidence that living systems do indeed evolve towards greater thermodynamic efficiency, manifest via the reduction of energetic waste.Item Open Access Urban meadows as an alternative to short mown grassland: effects of composition and height on biodiversity(Ecological Society of America, 2019-07-22) Norton, Briony A.; Bending, Gary D.; Rachel Clark, Rachel; Corstanje, Ronald; Dunnett, Nigel; Evans, Karl L.; Grafius, Darren R.; Gravestock, Emily; Grice, Samuel M.; Harris, Jim A.; Hilton, Sally; Hoyle, Helen; Lim, Edward; Mercer, Theresa G.; Pawlett, Mark; Pescott, Oliver L.; Richards, J. Paul; Southon, Georgina E.; Warren, Philip H.There are increasing calls to provide greenspace in urban areas, yet the ecological quality, as well as quantity, of greenspace is important. Short mown grassland designed for recreational use is the dominant form of urban greenspace in temperate regions but requires considerable maintenance and typically provides limited habitat value for most taxa. Alternatives are increasingly proposed, but the biodiversity potential of these is not well understood. In a replicated experiment across six public urban greenspaces we used nine different perennial meadow plantings to quantify the relative roles of floristic diversity and height of sown meadows on the richness and composition of three taxonomic groups – plants, invertebrates and soil microbes. We found that all meadow treatments were colonised by plant species not sown in the plots, suggesting that establishing sown meadows does not preclude further locally determined grassland development if management is appropriate. Colonising species were rarer in taller and more diverse plots, indicating competition may limit invasion rates. Urban meadow treatments contained invertebrate and microbial communities that differed from mown grassland. Invertebrate taxa responded to changes in both height and richness of meadow vegetation, but most orders were more abundant where vegetation height was longer than mown grassland. Order richness also increased in longer vegetation and Coleoptera family richness increased with plant diversity in summer. Microbial community composition seems sensitive to plant species composition at the soil surface (0–10 cm), but in deeper soils (11–20 cm) community variation was most responsive to plant height, with bacteria and fungi responding differently. In addition to improving local residents’ satisfaction, native perennial meadow plantings can produce biologically diverse grasslands that support richer and more abundant invertebrate communities, and restructured plant, invertebrate and soil microbial communities compared with short mown grassland. Our results suggest that diversification of urban greenspace by planting urban meadows in place of some mown amenity grassland is likely to generate substantial biodiversity benefits, with a mosaic of meadow types likely to maximise such benefits.