Trait-mediated rhizosphere phosphorus strategies drive functional complementarity among coexisting desert shrubs

Phosphorus (P) limitation is a pervasive constraint in desert ecosystems, fundamentally shaping plant nutrient strategies, community structure, and biogeochemical cycling. However, the trait-based mechanisms that enable plant coexistence and ecosystem stability under chronic P scarcity remain poorly understood. In this study, we investigated rhizosphere and bulk soil P fractions, organ-level C: N: P stoichiometry, and δ13C signatures in three co-dominant desert shrubs—Kalidium gracile, Reaumuria soongarica, and Salsola passerina, —to identify divergent P acquisition strategies and assess their ecological implications. Our results revealed distinct functional strategies among species. S. passerina, a C4 chenopod, employed a P-acquisitive strategy, characterized by rhizospheric enrichment of labile P (resin-P). K. gracile adopted a conservative strategy, marked by limited P mobilization, high leaf C: P ratios, and reliance on organic P mineralization and increased phosphatase activity. R. soongarica exhibited an intermediate buffering strategy, uptake moderate labile P with stem P storage, likely facilitated by root–microbial interactions. These species-specific strategies corresponded to differential root–soil–trait linkages and spatial variation in P availability. Despite divergence in rhizospheric processes, organ-level stoichiometric traits remained relatively conserved, indicating phylogenetic or biomechanical constraints on internal nutrient allocation. The coexistence of acquisitive, conservative, and intermediate strategies reflects functional complementarity in phosphorus use, which enables rhizospheric niche differentiation, minimizes interspecific competition, and supports community-level phosphorus cycling. Our findings highlight how trait-mediated rhizosphere activation and stoichiometric coordination underpin plant coexistence and resilience in P-depleted arid environments. This mechanistic understanding provides a conceptual framework for predicting nutrient acquisition strategies in dryland ecosystems and offers valuable insights for biodiversity conservation, ecosystem restoration, and nutrient management under climate-induced resource stress.