Quantifying asynchrony between microbial necromass and soil organic carbon for sustainable soil carbon management

Abstract

Microbial products and residues are crucial for soil organic carbon (SOC) formation, ecosystem health, and global climate regulation. Central to this understanding is the concept of the soil Microbial Carbon Pump (MCP), which highlights the role of microbial-derived carbon in SOC transformation and sequestration. Despite the rapid growth in research recognizing the significance of the MCP in SOC storage, direct assessments grounded in the MCP concept have largely lagged behind. Here, we distill important aspects of soil MCP assessment by reviewing relevant literature, showcasing model scenarios, and exploring rational perspectives on sustainable soil carbon management. We introduce the △MCP efficacy metric – a measure representing the change in ratio of microbial necromass to SOC – which captures their varying responses (asynchrony or synchrony) and enables assessment of in-situ SOC storage driven by the soil MCP. Accordingly, we delineate a conceptual, unifying framework that catalogs predictable scenarios involving microbial necromass and SOC, demonstrating how the soil MCP operates and functions in SOC dynamics. We advocate for future studies to extend beyond quantifying the contributions of microbial necromass to SOC to also assess the asynchronous changes in magnitude and direction of them in a dynamic perspective.