Abstract: We investigated the responses of phosphorus (P) fractions of rhizosphere soil to thinning in a 30-year-old Pinus massoniana plantation after 10 years of thinning. There were four thinning intensities: control (CK, 0%), low intensity thinning (LIT, 25%), moderate intensity thinning (MIT, 45%), and high intensity thinning (HIT, 65%). The results showed that MIT significantly reduced the total P and organic P concentrations, whereas HIT significantlydecreased the concentrations of inorganic P in the rhizosphere soil. LIT and MIT increased soil acid phosphatase activity, available P, microbial biomass P, and easily available P (H₂O-Pi, NaHCO₃-Pi and NaHCO₃-Po) in rhizosphere soil, but decreased NaOH-Po. Thinning had no effect on the non-available P. Except for non-available P, all the P fractions in rhizosphere soil were higher than those in bulk soil, indicating a positive rhizosphere effect. Soil P content was closely correlated with soil moisture, pH, organic matter content and acid phosphatase activity. These results suggest that LIT and MIT improved soil P availability, which could be used asefficient management practices inP. massoniana plantations.

Key words: forest ecological resilience, climate change, boreal forest, fire disturbance, LANDIS.