Substrate and environmental controls on microbial assimilation of soil organic carbon: a framework for Earth system models

Abstract

A mechanistic understanding of microbial assimilation of soil organic carbon is important to improve Earth system models' ability to simulate carbon-climate feedbacks. A simple modelling framework was developed to investigate how substrate quality and environmental controls over microbial activity regulate microbial assimilation of soil organic carbon and on the size of the microbial biomass. Substrate quality has a positive effect on microbial assimilation of soil organic carbon: higher substrate quality leads to higher ratio of microbial carbon to soil organic carbon. Microbial biomass carbon peaks and then declines as cumulative activity increases. The simulated ratios of soil microbial biomass to soil organic carbon are reasonably consistent with a recently compiled global data set at the biome level. The modelling framework developed in this study offers a simple approach to incorporate microbial contributions to the carbon cycling into Earth system models to simulate carbon-climate feedbacks and explain global patterns of microbial biomass.

Spatial variability of soil microbial biomass and its relationships with edaphic, vegetational and climatic factors in the Three-River Headwaters region on Qinghai-Tibetan Plateau

“…In addition, the low determination coefficients of the multivariate equations of soil MBC/TOC ratio and soil MBN/TN ratio in this study may suggest that the main determining factors of soil MBC/TOC ratio and MBN/TN ratio were not included in the current study. Yet, Xu et al (2014) found that soil MBC/TOC ratio would be profoundly influenced by soil TOC/TN ratio, and a model in Serna-Chavez et al (2013) that included many edaphic and climatic variables could explain 50.7% of the total variances of soil MBC/TOC ratio around the world. We suggested there are many differences in the mechanisms in determining MBC/TOC ratio and MBN/TN ratio between alpine region and other regions of the world.…”

“…They are closely correlated with each other, and often follow a stoichiometric relationship just like the "Redfield ratio" in marine plankton and other organisms (Cleveland and Liptzin, 2007;Redfield, 1958;Sterner and Elser, 2002;Yang et al, 2014). Although MBC and MBN only contribute to small parts of soil organic matter, MB plays a key role in litter decomposition, nutrient cycling and energy flow in soils (Anderson and Domsch, 1989;Falkowski et al, 2008;Fierer et al, 2009;Xu et al, 2014). Soil MB has become an important ecological indicator due to its close associations with many biotic and abiotic parameters (Chu and Grogan, 2010;Li et al, 2005Li et al, , 2006 and its rapid response to environmental changes (Hargreaves et al, 2003;Marinari et al, 2006;Powlson et al, 1987).…”

Effects of temperature, soil substrate, and microbial community on carbon mineralization across three climatically contrasting forest sites

“…Understanding the roles and underlying mechanisms of soil microbial communities in driving SOM decomposition is critical for modelling the terrestrial carbon cycling in the context of global climate change and environmental perturbations (Bardgett, Freeman, & Ostle, 2008; Schmidt et al., 2011; Xu et al., 2014). …”

Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

“…The heterogeneous distribution of SOC and its bioavailability due to local physical protection and chemical recalcitrance (Six et al 2002), preferential and matrix transport of substrates due to pore connectivity and local moisture content (Hunt 2004;Liu et al 2015aLiu et al , 2014Steefel and Maher 2009), and nonuniform formation of microbial colonies and biofilms due to local substrate availability and predation inhibition (He et al 2014;Kakumanu et al 2013;Or et al 2007;Xu et al 2014) have been observed to affect the rate of heterotrophic respiration and its correlation with moisture content in soils (Franzluebbers 1999;Moyano et al 2012). Understanding the pore-scale physical and biochemical processes associated with these heterogeneous properties as well as their manifestations at large scales is crucial to reduce the uncertainty of predicting the relationship between HR rate and moisture content in soil systems.…”