Microbial necromass accrual from newly added labile and native soil carbon in the rhizosphere vs. non-rhizosphere of broadleaved and coniferous trees
Juan Jia,
Guoqing Zhai,
Yufu Jia,
Xiaojuan Liu,
Keping Ma,
Xiaojuan Feng
Affiliations
Juan Jia
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China
Guoqing Zhai
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
Yufu Jia
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China; Institute of Desertification Studies/Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China; Corresponding author at: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Xiaojuan Liu
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China
Keping Ma
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China
Xiaojuan Feng
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; China National Botanical Garden, Beijing 100093, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Corresponding author at: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Microbe-mediated carbon (C) transformation plays a crucial role in the accumulation of soil organic C (SOC). However, microbial conversion efficiency of newly-added labile C and native SOC to necromass remain under-investigated. Here we collected the rhizosphere and non-rhizosphere soils under broadleaved and coniferous trees of varying nutrient availability, and conducted an 80-day soil incubation with 13C-labelled glucose to evaluate ‘microbial C pump’ (MCP) capacity (new C-derived biomass and necromass), phospholipid fatty acids (PLFAs)-based C use efficiency (i.e., new C-derived PLFAs relative to respiration, referred as CUE′ to differentiate from microbial biomass C-based CUE) and amino sugar (reflecting necromass) accumulation efficiency (AAE; new C-derived amino sugars relative to respiration). We found that MCP capacity, microbial AAE and CUE′ had different variation patterns and influencing factors. The amount of added glucose played a decisive role in determining MCP capacity. The key predictors of AAE were the ratio of inorganic nitrogen (N) to added glucose (reflecting N limitation) and bacterial PLFAs, while ratios of fungi to bacteria and C to N were important for predicting CUE′. Furthermore, we found that glucose addition stimulated microbial transformation of native SOC into necromass in C- but not N-limited soils (with a high AAE) without invoking a priming effect, potentially enhancing microbe-mediated SOC sequestration. These findings suggest that the efficiency of microbial necromass accumulation is strongly influenced by N availability and decoupled from biomass synthesis, highlighting nutrient regulations on SOC sequestration via plant–microbe interactions. We argue that AAE is a more reliable indicator to assess the efficiency of MCP fueled by labile C.
