The soil microbial carbon pump: From conceptual insights to empirical assessments. (13th September 2020)

• Record Type: Journal Article
• Authors: Zhu, Xuefeng; Jackson, Randall D.; DeLucia, Evan H.; Tiedje, James M.; Liang, Chao
• Is Part Of: Global change biology. Volume 26:Number 11(2020)
• Page Start: 6032
• Page End: 6039
• Publication Date: 2020-09-13
• Subjects: amino sugars -- bioenergy cropping systems -- MCP capacity -- MCP efficacy -- microbial necromass -- soil organic carbon; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15319
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: The global soil carbon (C) pool is massive, so relatively small changes in soil organic carbon (SOC) stocks can significantly alter atmospheric C and global climate. The recently proposed concept of the soil microbial carbon pump (MCP) emphasizes the active role of soil microbes in SOC storage by integrating the continual microbial transformation of organic C from labile to persistent anabolic forms. However, the concept has not been evaluated with data. Here, we combine datasets, including microbial necromass biomarker amino sugars and SOC, from two long‐term agricultural field studies conducted by large United States bioenergy research programs. We interrogate the soil MCP concept by investigating the asynchronous responses of microbial necromass and SOC to land‐use change. Microbial necromass appeared to preferentially accumulate in soil and be the dominant contributor to SOC accrual in diversified perennial bioenergy crops. Specifically, ~92% of the additional SOC enhanced by plant diversity was estimated to be microbial necromass C, and >76% of the additional SOC enhanced by land‐use transition from annual to perennial crops was estimated to be microbial necromass. This suggests that the soil MCP was stimulated in diversified perennial agroecosystems. We further delineate and suggest two parameters—soil MCP capacity and efficacy —reflecting the conversion of plant C into microbial necromass and the contribution of microbial necromass to SOC, respectively, that should serve as valuable metrics for future studies evaluating SOC storage under alternative management in changing climates. Abstract : Understanding the mechanisms of soil organic carbon (SOC) formation has shifted from a focus on the role of partially degraded plant detritus as an input to persistent organic compounds derived from microbial anabolism via the soil microbial carbon pump (MCP, a recently proposed concept that describes the continual microbial transformation of organic carbon from labile to long‐lasting anabolic forms). Effective assessment of soil MCP aids SOC projection and climate change mitigation. By investigating the asynchronous responses of microbial necromass and SOC to land use changes, we find microbial necromass appears to preferentially accumulate in soil and dominantly contributes to SOC accrual in diversified perennial bioenergy crops.