Unveiling Pervasive Soil Microbial P Limitation in Terrestrial Ecosystems Worldwide

ABSTRACT Soil microorganisms are crucial in terrestrial ecosystems, influencing carbon (C) sequestration, yet their metabolic activities are often constrained by nitrogen (N) and phosphorus (P) availability. Despite this, a global understanding of microbial nutrient limitation remains elusive. We synthesised 1245 observations from 225 articles to elucidate patterns and factors of microbial nutrient limitation. Contrary to convention, soil microbial P limitation is widespread (83.78% of observations), with N limitation mainly in temperate zones and pronounced P limitation in tropical and cold zones. Soil microbial P limitation correlates positively with mean annual precipitation and clay content, while N limitation correlates negatively with soil pH. Importantly, microbial nutrient limitation directly affects C cycling, as microbial C limitation increases with decreasing N or P limitation. This underscores the significance of microbial nutrient limitation in terrestrial C cycling and the need to incorporate it into Earth system models for accurate predictions under changing conditions.