TY - JOUR
T1 - A stoichiometric approach to estimate sources of mineral-associated soil organic matter
AU - Chang, Yi
AU - Sokol, Noah W.
AU - van Groenigen, Kees Jan
AU - Bradford, Mark A.
AU - Ji, Dechang
AU - Crowther, Thomas W.
AU - Liang, Chao
AU - Luo, Yiqi
AU - Kuzyakov, Yakov
AU - Wang, Jingkuan
AU - Ding, Fan
N1 - Publisher Copyright:
© 2023 John Wiley & Sons Ltd.
PY - 2024/1
Y1 - 2024/1
N2 - Mineral-associated soil organic matter (MAOM) is the largest, slowest cycling pool of carbon (C) in the terrestrial biosphere. MAOM is primarily derived from plant and microbial sources, yet the relative contributions of these two sources to MAOM remain unresolved. Resolving this issue is essential for managing and modeling soil carbon responses to environmental change. Microbial biomarkers, particularly amino sugars, are the primary method used to estimate microbial versus plant contributions to MAOM, despite systematic biases associated with these estimates. There is a clear need for independent lines of evidence to help determine the relative importance of plant versus microbial contributions to MAOM. Here, we synthesized 288 datasets of C/N ratios for MAOM, particulate organic matter (POM), and microbial biomass across the soils of forests, grasslands, and croplands. Microbial biomass is the source of microbial residues that form MAOM, whereas the POM pool is the direct precursor of plant residues that form MAOM. We then used a stoichiometric approach—based on two-pool, isotope-mixing models—to estimate the proportional contribution of plant residue (POM) versus microbial sources to the MAOM pool. Depending on the assumptions underlying our approach, microbial inputs accounted for between 34% and 47% of the MAOM pool, whereas plant residues contributed 53%–66%. Our results therefore challenge the existing hypothesis that microbial contributions are the dominant constituents of MAOM. We conclude that biogeochemical theory and models should account for multiple pathways of MAOM formation, and that multiple independent lines of evidence are required to resolve where and when plant versus microbial contributions are dominant in MAOM formation.
AB - Mineral-associated soil organic matter (MAOM) is the largest, slowest cycling pool of carbon (C) in the terrestrial biosphere. MAOM is primarily derived from plant and microbial sources, yet the relative contributions of these two sources to MAOM remain unresolved. Resolving this issue is essential for managing and modeling soil carbon responses to environmental change. Microbial biomarkers, particularly amino sugars, are the primary method used to estimate microbial versus plant contributions to MAOM, despite systematic biases associated with these estimates. There is a clear need for independent lines of evidence to help determine the relative importance of plant versus microbial contributions to MAOM. Here, we synthesized 288 datasets of C/N ratios for MAOM, particulate organic matter (POM), and microbial biomass across the soils of forests, grasslands, and croplands. Microbial biomass is the source of microbial residues that form MAOM, whereas the POM pool is the direct precursor of plant residues that form MAOM. We then used a stoichiometric approach—based on two-pool, isotope-mixing models—to estimate the proportional contribution of plant residue (POM) versus microbial sources to the MAOM pool. Depending on the assumptions underlying our approach, microbial inputs accounted for between 34% and 47% of the MAOM pool, whereas plant residues contributed 53%–66%. Our results therefore challenge the existing hypothesis that microbial contributions are the dominant constituents of MAOM. We conclude that biogeochemical theory and models should account for multiple pathways of MAOM formation, and that multiple independent lines of evidence are required to resolve where and when plant versus microbial contributions are dominant in MAOM formation.
KW - meta-analysis
KW - mineral-associated organic matter
KW - particulate organic matter
KW - plant carbon
KW - soil carbon
KW - soil organic matter dynamics
UR - http://www.scopus.com/inward/record.url?scp=85179307883&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85179307883&partnerID=8YFLogxK
U2 - 10.1111/gcb.17092
DO - 10.1111/gcb.17092
M3 - Article
C2 - 38273481
AN - SCOPUS:85179307883
SN - 1354-1013
VL - 30
JO - Global change biology
JF - Global change biology
IS - 1
M1 - e17092
ER -