![]() ![]() ![]() Current research emphasizes the efficiency of microbial incorporation of plant carbon into microbial biomass, and adsorption of necromass to mineral surfaces as mechanisms to promote carbon accrual and persistence (Liang et al., 2019). But to quantify how necromass responds to climatic changes, we need to understand some key fundamentals about how, when and where necromass is formed, transformed and lost in soil.Ī new paradigm for soil organic carbon accumulation has developed (Cotrufo et al., 2013), moving away from a traditional focus on the chemical recalcitrance of plant carbon inputs influencing rates of decomposition. Conversely, necromass formation is climate sensitive: higher temperatures increase microbial turnover (death) and increase necromass production (Hagerty et al., 2014 Wang et al., 2020b). Land management can increase soil carbon by optimizing necromass formation (sensu Kallenbach et al., 2015), making necromass a critical component of efforts to mitigate climate change through soil carbon sequestration. Necromass persists in soil due to protection from microbial decomposition and through efficient recycling, in which necromass decomposition contributes towards microbial biomass growth (Buckeridge, Mason, et al., 2020 Creamer et al., 2019 Liang et al., 2019). Microbial necromass accumulates in soil as microbially exuded extracellular compounds or the remains of dead microbial cells and cell fragments. Soil microbial products and residues (hereafter ‘necromass’) contribute, sometimes substantially (15%–80%), to soil organic matter (Angst et al., 2021 Hall et al., 2020 Liang et al., 2019). Read the free Plain Language Summary for this article on the Journal blog. ![]() Our review demonstrates that deconstructing the necromass continuum is key to predicting the vulnerability and persistence of necromass carbon in a changing world. Future mechanistic research focused on the role of biotic and abiotic soil microscale structure in determining necromass process rates and the relative importance of organo–mineral and organo–organo interactions can inform necromass persistence in different climate change scenarios.First, controls on necromass persistence are more clearly defined when viewed through the lens of the continuum second, destabilization is the least understood stage of the continuum with recycling also poorly evidenced outside of a few ecosystems and third, the response of necromass process rates to climate change is unresolved for most continuum stages and ecosystems. From the perspective of the continuum, we draw three conclusions to inform future research.The relative importance of each stage of the continuum is then compared in contrasting ecosystems and for climate change drivers. We discuss the dominant controls on necromass process rates and aspects of soil microscale structure including biofilms and food web interactions. We highlight recent advances, methodological limitations and knowledge gaps which need to be addressed to determine necromass pool sizes and transformations. Current understanding of necromass dynamics is described for each continuum stage.In this review, we define and deconstruct four stages of the necromass continuum: production, recycling, stabilization and destabilization. However, the typical proxies used for necromass carbon do not reveal the dynamic nature of necromass carbon flows and transformations within soil that ultimately determine necromass persistence. Quantification of necromass carbon stocks and its susceptibility to global change is becoming standard practice in soil carbon research. Microbial necromass is a large, dynamic and persistent component of soil organic carbon, the dominant terrestrial carbon pool. ![]()
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