Microbial utilization of low molecular weight organic carbon substrates in cultivated peats in response to warming and soil degradation

Dr Huadong Zang1, Dr Yuan Wen1, Dr David  R. Chadwick2, Dr Chris  D. Evans3, Dr Davey  L. Jones2

1China Agricultural University, Beijing, China, 2School of Natural Sciences, Bangor University, Bangor, UK, 3Centre for Ecology and Hydrology, Environment Centre Wales, Bangor, UK

Peatland soils hold approximately one third of the carbon (C) stored in the global terrestrial biosphere. Drainage and cultivation of peat soils lead to rapid soil degradation and C losses, and this may worsen under warming as the soils are no longer protected by anaerobic conditions. To predict the rates of soil C loss and design effective mitigation strategies, it is important to understand what controls organic matter mineralisation in these soils. Central to this is a knowledge of how C is processed through the microbial community. Using the 0-10 cm soil depth of deep and shallow agricultural peat soils, we investigated the fate of low molecular weight organic substrates (LMWOS) and how the microbial biomass consuming these substrates responded to temperature. We incubated the soils under increasing temperatures (4, 10, 20, and 30 °C). Either 14C-labelled glucose or amino acids were added to the soils and their speed of breakdown and microbial C use efficiency (CUE) were determined. The total 14CO2 loss from soil increased significantly with increasing temperature, regardless of peat soil depth. Warming altered the dynamics of LMWOS decomposition by increasing C allocation into the fast cycling C pool and also accelerated the turnover of the slow cycling C pool. The half-life of LMWOS decreased more than 50% when temperature increased from 4 to 30 °C for both substrates. CUE was always higher for shallow than deep peat soil and both declined by 0.002–0.005 °C-1 with temperature increase. Shallow peat decreased substrate C allocation into the fast cycling pool, but had no overall effect on pool turnover rate. Increased temperatures reduced the difference in CUE of glucose between deep and shallow peat soils, but enlarged the difference in CUE of amino acid, at least in short-term. Our work suggests that climate warming will accelerate C mineralisation and turnover in drained peat soils, with larger effects expected in deep peat soil. This study provides an important initial step in characterizing the response of the microbial utilization of labile C to temperature change and soil degradation in cultivated peatlands.

Biography: Dr. Huadong Zang is an associate professor at China Agricultural University. He has finished his PhD under the supervisor of Prof. Yakov Kuzyakov and Michaela Dippold at University of Goettingen, Germany. After that, he has working with Prof. Davey Jones as a Sêr Cymru Fellow at Bangor University within the Climate-Smart Grass Cluster. His research focused on N and C cycles in the plant-soil system, specifically, how N fertilization, temperature, and crop management influence C sequestration, organic matter stabilization, turnover, and priming effects in agroecosystem. He has a solid background in agronomy and soil science, and extensive experience in 13C natural abundance techniques and multiple stable/radioactive isotope (13C, 14C, 15N, 18O) labeling approaches.

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