Divergent Drivers of Various Topsoil Phosphorus Fractions Across Tibetan Alpine Grasslands

Abstract The storage and dynamics of various soil phosphorus (P) fractions could determine soil P availability, and thus regulate terrestrial carbon cycle and its feedback to climate warming. However, little evidence is available about patterns and drivers of soil P fractions in alpine ecosystems which could play a crucial role in terrestrial carbon cycle. Here we evaluated various topsoil P fractions and their determinants in Tibetan alpine grasslands using systematic measurements along a 3,000 km transect. Our results showed that topsoil P concentrations in Tibetan alpine grasslands were higher or equivalent than those in temperate and tropical‐subtropical ecosystems. Our results also revealed distinct drivers among various soil P fractions: microbial properties and soil pH were dominant drivers of labile P and secondary mineral P fractions, respectively. Mineral properties were key determinants of occluded P and organic P fractions, whereas primary mineral P fraction was largely predicted by precipitation and mineral properties. The large‐scale evidence obtained in this study offers new insights for better predicting the trajectory of soil P availability and its interactions with ecosystem carbon cycle in alpine ecosystems under changing environment.