Plant–soil feedbacks in a sub-alpine meadow ecosystem with high plant diversity on the Qinghai-Tibetan Plateau

Most plant–soil feedback studies infer mechanisms based on microbes directly affecting plant performance and have been carried out in grasslands with relatively low plant diversity; however, little is known about how plant–soil feedbacks directly affect soil chemistry in grasslands with high plant diversity. In our study, five types of species-origin soils (3 from an old-field and 2 from an undisturbed meadow) were collected, and used to establish an outdoor feedback experiment. Plant performance in home versus away soil, and soil abiotic and biotic properties before and after the feedback experiment was measured to examine patterns of plant–soil feedbacks, and their mechanisms depending on that affecting soil N availability directly. Both old-field and meadow species performed better in old-field soil than meadow soil. On species level, there was no consistent “home” or “away” advantage. In pre-feedback experiment, old-field was substantially higher in soil total phosphorus and NH₄⁺. All soil properties differed significantly among plant species beneath which the soil was collected; however, there was no consistent pattern among species. In post-feedback experiment, old-field soil had larger increases in NO₃⁻, microbial biomass C and N (MBC and MBN) while larger decreases in NH₄⁺ than meadow soil. Each old-field species had the largest decrease in NH₄⁺ in its own soil, while all species had the largest increases in NO₃⁻, MBC, and MBN in Artemisia’s soils. Plant species influenced MBC and MBN, and these microbial biomass differences in turn drove N mineralization and nitrification differences among species. In total, our results showed that plant–soil feedbacks, in a very diverse alpine meadow, were complex and species specific, but were not driven by plant-induced N mineralization and nitrification.