Opposite responses of soil phosphorus fractions to two dominant species during early succession in subtropical phosphorus-enriched degraded mountain ecosystems

Abstract

Understanding the effects of plant species on characteristics of the soil phosphorus (P) distributions in high soil P content areas is particularly important for land recovery and eutrophication control of adjoining freshwater ecosystems. We investigated the plant attributes, soil physicochemical properties, and soil P fractions and sorption characteristics outside and under the canopies of Saccharumrufipilum (SR, a perennial grass) and Pinus yunnanensis (PY, a coniferous tree) in a P-enriched degraded mountain area. The results showed that soil carbon and nitrogen concentrations and root biomasses under the canopies of the two species were higher than outside the canopies. Compared to the area outside the canopy, organic P (Po), labile and intermediate inorganic P (Pi) concentrations increase and decrease under the canopy of SR and PY, respectively, which indicated the positive effects of SR and negative effects of PY on these soil P fractions. The biologically available P index showed that the mean values of this index under the canopies of the two species in the 0–20 cm soil layer were as high as 0.2–0.3, which suggests the importance of biological processes in soil P cycling. The soils under the canopies of the two species had higher soil P sorption index (PSI) values. The main factors that influenced the soil P fractions and PSI were soil nitrogen, iron oxides, and root biomass, which indicated that different plant and sampling effects significantly influenced the soil P fraction distributions and P loss potential primarily by changing the plant root biomass and soil nitrogen and Fe oxides.