AGRIFOOD_Biochar and bio-trophic carbon storage in temperate soils

Governments are calling for geo-engineering methods of carbon capture and sequestration (CCS) to help reduce CO2 emissions and mitigate dangerous climate change. One CCS approach being currently advocated is the treatment of soils with biochar. This involves the capture of carbon from the atmosphere in bio-energy or agricultural crops, and subsequent conversion of biomass by pyrolysis to a stable form of carbon 'biochar' which is then sequestered in soil for thousands of years. Advocates claim that if launched on a large scale, this process has the potential to convert agricultural soil from a net carbon source to a net large and long term sink. Moreover, they also claim that biochar treatment may have added benefits for soil fertility leading to subsequent gains in crop productivity. The evidence in support of these claims is either anecdotal or lacking. There is an urgent need to scientifically establish if this emerging CCS land-use does represent a win-win option in adaptation to climate change. Moreover, virtually nothing is known about the impact of biochar on soil biodiversity and the functions that this drives. Some effects of biochar on soil microbes have been examined in the humid tropics and recently in boreal forest, where it was shown that biochar may actually stimulate losses of existing soil carbon by promoting microbial decomposition. There has been, however, no research on biochar effects on soil food webs and the processes that they drive, such as decomposition and nutrient cycling, in temperate soils. This represents a serious knowledge gap, given the proposed benefits of biochar and the known links between soil communities and soil ecosystem function. This PhD studentship aims to redress this by studying the effect of biochar treatment in UK soils on soil communities and the functions that they drive. This PhD will test the following hypotheses: H1. Addition of biochar to grassland and cropland soils will alter faunal and microbial communities as a result of changes in physical and chemical micro-habitat heterogeneity, arising from the large surface area of biochar H2. Biochar will decrease rates of soil C and N cycling and biotic-mediated greenhouse gas emissions (CO2, CH4, N2O) in high C soils and soils subjected to N additions H3. Biochar will reduce positive feedbacks between plant rhizodeposition and soil communities and associated biogeochemical cycling, and that climate resilience of native soil organic matter will be diminished. This project will be the first ecological assessment of the impacts of a CCS land-use on biodiversity and function in UK soils. We will measure with stable isotope signatures and tracers the response of soil biodiversity (microbes, microarthropods, oligochaetes, nematodes) and processes (decomposition & respiration rates, nitrogen mineralization). It brings together complimentary expertise and a research team of proven effectiveness, leading to significant new discoveries that will be published in foremost scientific journals. The impact of this PhD will be to provide needed insights into the effectiveness of a land-use advocated as a climate change mitigation strategy. The project will show if biochar soil treatment of UK soils is likely to lead to successful carbon sequestration and the consequences for the stability of soil communities and the functions they underpin. This research will meet an aim of the NERC strategic plan to enable society to respond urgently to global climate change by providing timely evidence-based recommendations to policy makers charged with climate change adaptation and mitigation. Moreover this work will contribute to the NERC biodiversity theme to understand the role of biodiversity in key ecosystem processes by studying the response of soil biodiversity to a perturbation - addition of biochar - and the consequences for the cycling of chemical nutrients.