Species-dependent phosphorus acquisition strategy modulates soil phosphorus cycle in the subalpine forest of eastern Tibetan Plateau

Abstract

The availability of phosphorus (P) in soils will ultimately determine forest productivity because of increasing P limitation in terrestrial ecosystems. However, it is still unclear how and to what extent of different plant P-acquisition strategies affect soil P cycling in the subalpine ecosystems. Here, bulk soils (BS) and rhizosphere soils (RS) under Abies fabri and Rhododendron decorum were respectively collected in the early-, mid- and late-growing seasons in a subalpine forest of eastern Tibetan Plateau, and low molecular weight organic acids, microbial biomass P and P fractions were analyzed to decipher the effects of the plants on soil P availability. The P fractions in both BS and RS showed a distinct difference between A. fabri and R. decorum because of their different P acquisition strategies. The ericoid mycorrhiza-associated R. decorum sequestered soil available P through organic P mineralization, while the ectomycorrhizal mycorrhiza-associated A. fabri directly or indirectly acquired both the organic and inorganic P pools. Seasonal variations in soil available P further revealed that the difference in the P acquisition by the two species was closely associated with their growing stages. Inorganic P dissolution by citric acid determined available P supply for A. fabri in the mid-growing season, while organic P mineralization contributed to available P for R. decorum in the early-growing season. Our results indicate that mycorrhizal types and plant growing stages drive plant P acquisition, which results in the coexistence patterns of different species in the same habitat.