Relationships of phosphorus fractions to organic carbon content in surface soils in mature subtropical forests, Dinghushan, China

Abstract

Exploring the relationship between the accumulation of soil organic carbon (C) and the form and availability of soil phosphorus (P) is important for improved understanding of soil P availability and its regulation of C storage in forest ecosystems. Here, we investigated the relationships among soil organic C, sequentially extracted P fractions and P sorption index in 32 surface soils (0-0.15 m depth) across eight mature subtropical forests (80-400 years) in Dinghushan, China. Results showed that soil organic P (Po) accounted for 40-63% (mean 54%) of soil total P. Soil organic C was significantly positively correlated with both the content and the percentage of soluble inorganic P (Pi), Al-Po and Fe-Po fractions and the content of the Al-Pi fraction. The content of soil total Po increased significantly with soil organic C, whereas the percentage of soil total Po tended to increase with soil organic C only when soil organic C was low (<30 Mg/ha) but was relatively stable when soil organic C was high (=30 Mg/ha). Moreover, soil organic C was highly correlated with P sorption index. Our results suggest that accumulation of organic C may increase, rather than decrease, the availability of P in surface soil in mature subtropical forests.