Drivers of phosphorus limitation across soil microbial communities

Abstract

Summary Nutrient limitation of soil microbial communities controls the rates of plant litter and soil organic matter decomposition and nutrient mineralization, and as such, it is central to soil and ecosystem models. According to ecological stoichiometry theory, when the carbon (C)‐to‐nutrient (E) ratio of resources used by a microbial community is higher than a critical ratio (C : ECR), that nutrient is limiting. The C‐to‐phosphorus (P) critical ratio (C : PCR) that determines P limitation is largely unknown for soils, and thus, it is the subject of our study. Our results show that the C : PCR in widely different soils ranges from 26·6 to 465·1 or from 20·9 to 740·7 when accounting for 95% confidence intervals. Using constant or narrowly fluctuating C : PCR in ecosystem models is therefore inaccurate. The C : PCR cannot be simply predicted from microbial community C : P or available soil P. C : PCR was only related to relative abundance of phospholipid fatty acids, which reflects microbial community structure and physiology. Our data suggest complex controls over microbial community C : PCR. We further propose that using P storage compounds that allow the microbial community to temporarily buffer variability in available P can represent a widely adopted strategies across soils.