[Effects of harvest residue treatments on soil phosphorus fractions and availability in a young Chinese fir plantation].

Forest harvesting changes the quantity and quality of organic matter inputs into soil, and thus would alter soil nutrient content and availability. Phosphorus (P) is a key element affecting plant growth. The effects of harvest residue treatments on soil P fractions and availability had not yet been evaluated. In this study, harvest residue retainment (RR), residue removal (R) and residue burning (RB) treatments were manipulated after clear-cutting in a mature Chinese fir (Cunninghamia lanceolata) plantation at the Sanming Forest Ecosystem and Global Change Research Station in Fujian, China. This study focused on the dynamics of soil P fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 4-year residue treatments. The results showed that, in RR treatment, the contents of easily-available P, moderately-available P and non-available P at the 0-10 cm soil layer were all significantly higher than those in R treatment, while the contents of moderately-available P and non-available P at the 10-20 cm soil layer was significantly higher than those in RB treatments. The ratios of soil organic carbon (C) to organic P (C:Po) in both layers were over 200 for all the three treatments, with ratios in RR treatment being significantly lower than those in RB and R treatments, indicating that RR could alleviate P limitation in this ecosystem. Moreover, results of the redundancy analysis showed that changes in P fractions were mainly affected by dissolved organic C, free Fe and noncrystalline amorphous Fe. The results suggested that soil organic P and available P were mainly from the decomposition of plant residues, which supported continuous P supply for plant growth. RR could enhance soil P content, thereby improve soil P availability and mitigate P limitation in Chinese fir plantation.