Rui Yichao, Murphy Daniel V, Wang Xiaoli, Hoyle Frances C
Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
College of Agriculture, Guizhou University, Guizhou 550025, China.
Sci Rep. 2016 Oct 18;6:35496. doi: 10.1038/srep35496.
Rebuilding 'lost' soil carbon (C) is a priority in mitigating climate change and underpinning key soil functions that support ecosystem services. Microorganisms determine if fresh C input is converted into stable soil organic matter (SOM) or lost as CO. Here we quantified if microbial biomass and respiration responded positively to addition of light fraction organic matter (LFOM, representing recent inputs of plant residue) in an infertile semi-arid agricultural soil. Field trial soil with different historical plant residue inputs [soil C content: control (tilled) = 9.6 t C ha versus tilled + plant residue treatment (tilled + OM) = 18.0 t C ha] were incubated in the laboratory with a gradient of LFOM equivalent to 0 to 3.8 t C ha (0 to 500% LFOM). Microbial biomass C significantly declined under increased rates of LFOM addition while microbial respiration increased linearly, leading to a decrease in the microbial C use efficiency. We hypothesise this was due to insufficient nutrients to form new microbial biomass as LFOM input increased the ratio of C to nitrogen, phosphorus and sulphur of soil. Increased CO efflux but constrained microbial growth in response to LFOM input demonstrated the difficulty for C storage in this environment.
重建“流失”的土壤碳（C）是缓解气候变化和巩固支持生态系统服务的关键土壤功能的优先事项。微生物决定了新鲜碳输入是转化为稳定的土壤有机质（SOM）还是以二氧化碳形式流失。在这里，我们量化了在贫瘠的半干旱农业土壤中，微生物生物量和呼吸作用是否对添加轻组有机物质（LFOM，代表近期植物残体输入）产生积极响应。将具有不同历史植物残体输入的田间试验土壤[土壤碳含量：对照（耕作）=9.6吨碳/公顷，耕作+植物残体处理（耕作+有机物质）=18.0吨碳/公顷]在实验室中与相当于0至3.8吨碳/公顷（0至500%LFOM）的LFOM梯度进行培养。随着LFOM添加速率的增加，微生物生物量碳显著下降，而微生物呼吸作用呈线性增加，导致微生物碳利用效率降低。我们推测这是由于随着LFOM输入增加了土壤中碳与氮、磷和硫的比例，养分不足以形成新的微生物生物量。响应LFOM输入，二氧化碳通量增加但微生物生长受到限制，这表明在这种环境中碳储存存在困难。
