Browsing by Author "Whitmore, A. P."

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    Defining and quantifying the resilience of responses to disturbance: a conceptual and modelling approach from soil science
    (Nature Publishing Group, 2016-06-22) Todman, Lindsay; Fraser, Fiona; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Ritz, Karl; Whitmore, A. P.
    There are several conceptual definitions of resilience pertaining to environmental systems and, even if resilience is clearly defined in a particular context, it is challenging to quantify. We identify four characteristics of the response of a system function to disturbance that relate to “resilience”: (1) degree of return of the function to a reference level; (2) time taken to reach a new quasi-stable state; (3) rate (i.e. gradient) at which the function reaches the new state; (4) cumulative magnitude of the function (i.e. area under the curve) before a new state is reached. We develop metrics to quantify these characteristics based on an analogy with a mechanical spring and damper system. Using the example of the response of a soil function (respiration) to disturbance, we demonstrate that these metrics effectively discriminate key features of the dynamic response. Although any one of these characteristics could define resilience, each may lead to different insights and conclusions. The salient properties of a resilient response must thus be identified for different contexts. Because the temporal resolution of data affects the accurate determination of these metrics, we recommend that at least twelve measurements are made over the temporal range for which the response is expected.
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    Distinct respiratory responses of soils to complex organic substrate are governed predominantly by soil architecture and its microbial community
    (Elsevier, 2016-10-13) Fraser, Fiona; Todman, L. C.; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Whitmore, A. P.; Ritz, Karl
    Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils’ respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.
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    Evidence for functional state transitions in intensively-managed soil ecosystems
    (Nature Publishing Group, 2018-08-01) Todman, L. C.; Fraser, F. C.; Corstanje, Ronald; Harris, Jim A.; Pawlett, Mark; Ritz, K.; Whitmore, A. P.
    Soils are fundamental to terrestrial ecosystem functioning and food security, thus their resilience to disturbances is critical. Furthermore, they provide effective models of complex natural systems to explore resilience concepts over experimentally-tractable short timescales. We studied soils derived from experimental plots with different land-use histories of long-term grass, arable and fallow to determine whether regimes of extreme drying and re-wetting would tip the systems into alternative stable states, contingent on their historical management. Prior to disturbance, grass and arable soils produced similar respiration responses when processing an introduced complex carbon substrate. A distinct respiration response from fallow soil here indicated a different prior functional state. Initial dry:wet disturbances reduced the respiration in all soils, suggesting that the microbial community was perturbed such that its function was impaired. After 12 drying and rewetting cycles, despite the extreme disturbance regime, soil from the grass plots, and those that had recently been grass, adapted and returned to their prior functional state. Arable soils were less resilient and shifted towards a functional state more similar to that of the fallow soil. Hence repeated stresses can apparently induce persistent shifts in functional states in soils, which are influenced by management history.
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    Is it possible to increase the sustainability of arable and ruminant agriculture by reducing inputs?
    (Elsevier, 2009-02) Glendining, M. J.; Dailey, A. G.; Williams, Adrian G.; van Evert, F. K.; Goulding, K. W. T.; Whitmore, A. P.
    Until recently, agricultural production was optimised almost exclusively for profit but now farming is under pressure to meet environmental targets. A method is presented and applied for optimising the sustainability of agricultural production systems in terms of both economics and the environment. Components of the agricultural production chain are analysed using environmental life-cycle assessment (LCA) and a financial value attributed to the resources consumed and burden imposed on the environment by agriculture, as well as to the products. The sum of the outputs is weighed against the inputs and the system considered sustainable if the value of the outputs exceeds those of the inputs. If this ratio is plotted against the sum of inputs for all levels of input, a diminishing returns curve should result and the optimum level of sustainability is located at the maximum of the curve. Data were taken from standard economic almanacs and from published LCA reports on the extent of consumption and environmental burdens resulting from farming in the UK. Land-use is valued using the concept of ecosystem services. Our analysis suggests that agricultural systems are sustainable at rates of production close to current levels practiced in the UK. Extensification of farming, which is thought to favour non-food ecosystem services, requires more land to produce the same amount of food. The loss of ecosystem services hitherto provided by natural land brought into production is greater than that which can be provided by land now under extensive farming. This loss of ecosystem service is large in comparison to the benefit of a reduction in emission of nutrients and pesticides. However, food production is essential, so the coupling of subsidies that represent a relatively large component of the economic output in EU farming, with measures to reduce pollution are well-aimed. Measures to ensure that as little extra land is brought into production as possible or that marginal land is allowed to revert to nature would seem to be equally well-aimed, even if this required more intensive use of productive areas. We conclude that current arable farming in the EU is sustainable with either realistic prices for products or some degree of subsidy and that productivity per unit area of land and greenhouse gas emission (subsuming primary energy consumption) are the most important pressures on the sustainability of farming.
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    Technologies for increasing carbon storage in soil to mitigate climate change
    (Wiley, 2014-04-23) Whitmore, A. P.; Kirk, Guy J. D.; Rawlins, B. G.
    Means to enhance storage of carbon in soil or avoid its loss from soil are discussed and examined from the viewpoint of policy. In particular, technologies that have until now received little attention are assessed. The main means by which soil carbon might be increased are first listed. These are the following: (i) increasing the rate of input of organic matter; (ii) decreasing the rate of its decomposition by biological or chemical means; (iii) increasing the rate of its stabilization by physico-chemical protection within aggregates and organo-mineral complexes; and (iv) increasing the depth or more correctly the total soil volume sequestering carbon at maximum rate. Immediate gains in carbon storage might be made by switching to more perennial crops, especially grasses that, as a result of breeding, are able to put more carbon into soil. In the longer term, targets for research such as understanding the role of enzymes in carbon turnover and the exploitation of the capacity in subsoils are suggested. Increased fixation of CO2 as inorganic carbonate in soils by application of silicate wastes may have some role.
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    What do we need to know to enhance the environmental sustainability of agricultural production? A prioritisation of knowledge needs for the UK food system
    (MDPI, 2013-07-17T00:00:00Z) Dicks, Lynn V.; Bardgett, Richard D.; Bell, Jenny; Benton, Tim G.; Booth, Angela; Bouwman, Jan; Brown, Chris; Bruce, Ann; Burgess, Paul J.; Butler, Simon J.; Crute, Ian; Dixon, Frances; Drummond, Caroline; Freckleton, Robert P.; Gill, Maggie; Graham, Andrea; Hails, Rosie S.; Hallett, James; Hart, Beth; Hillier, Jon G.; Holland, John M.; Huxley, Jonathan N.; Ingram, John S. I.; King, Vanessa; MacMillan, Tom; McGonigle, Daniel F.; McQuaid, Carmel; Nevard, Tim; Norman, Steve; Norris, Ken; Pazderka, Catherine; Poonaji, Inder; Quinn, Claire Helen; Ramsden, S. J.; Sinclair, Duncan; Siriwardena, Gavin M.; Vickery, Juliet A.; Whitmore, A. P.; Wolmer, William; Sutherland, William J.
    Abstract: Increasing concerns about global environmental change and food security have focused attention on the need for environmentally sustainable agriculture. This is agriculture that makes efficient use of natural resources and does not degrade the environmental systems that underpin it, or deplete natural capital stocks. We convened a group of 29 ‘practitioners' and 17 environmental scientists with direct involvement or expertise in the environmental sustainability of agriculture. The practitioners included representatives from UK industry, non-government organizations and government agencies. We collaboratively developed a long list of 264 knowledge needs to help enhance the environmental sustainability of agriculture within the UK or for the UK market. We refined and selected the most important knowledge needs through a three-stage process of voting, discussion and scoring. Scientists and practitioners identified similar priorities. We present the 26 highest priority knowledge needs. Many of them demand integration of knowledge from different disciplines to inform policy and practice. The top five are about sustainability of livestock feed, trade-offs between ecosystem services at farm or landscape scale, phosphorus recycling and metrics to measure sustainability. The outcomes will be used to guide ongoing knowledge exchange work, future science policy and funding.