Leaf phosphorus fractionation underlies the plant phosphorus niche and functional adaptation globally

Phosphorus (P) is vital to plant growth and is involved in different leaf physiological processes. However, whether plants strategically allocate P among distinct functions across species and habitats remains unresolved. By synthesizing a global dataset of leaf P fractions across 252 species spanning 8 biomes, we employ a Bayesian phylogenetic Dirichlet framework to decode the rules of relative allocation of leaf P fractions across species and environments. We found that leaf P partitioning is highly phylogenetically structured but also significantly shaped by soil total P. Specifically, the proportions of nucleic acids and metabolites P increase, while phospholipids decrease with soil total P concentration, suggesting a trade-off in the investment between physiological metabolism and membrane structure. Furthermore, lower investment in phospholipids is consistently associated with both higher photosynthetic P-use efficiency and internal leaf P resorption, but balances differently in the investment in other fractions. Crucially, the relationships between leaf P allocation and leaf economic traits challenge the classic growth rate hypothesis, with species possessing conservative traits, such as higher leaf mass per area and lower nutrient concentration, generally showing higher proportional P investment in metabolically active biochemicals. Notably, the directional trade-off in leaf P partitioning appears to be ecologically effective only in evergreen species. These findings are central to understanding how plants adapt to P deficiency through efficient nutrient allocation, with further implications for crop breeding and biodiversity maintenance.