Effects of conversion of Chinese fir forest to broad-leaved forests on phosphorus components and transformation in rhizosphere and non-rhizosphere soils

Phosphorus(P)is one of the essential elements for plant growth and is a key factor in maintaining the productivity of subtropical forest ecosystems. Chinese fir(Cunninghamia lanceolata)is mainly distributed in subtropical areas of China, and its soil acidification and phosphorus utilization efficiency are low. It is of great significance to study the effects of Chinese fir plantation transformation on soil P for the stability of ecosystem and sustainable forest management. In this study, the rhizosphere and non-rhizosphere soils were collected from the replanted Chinese fir plantation, Castanopsis hystrix plantation, Mytilaria laosensis plantation and the mixed plantation of Castanopsis hystrix and Mytilaria laosensis on the cutting-blank of Chinese fir plantation in South Asia, and the effects of soil P component and transformation on the transformation of Chinese fir plantation into broad-leaved forest were studied. The results were as follows:(1)The content of microbial biomass phosphorus and the activity of acid phosphatase in rhizosphere and non-rhizosphere soil of the modified Castanopsis hystrix plantation, Mytilaria laosensis plantation and the mixed plantation of Castanopsis hystrix and Mytilaria laosensis were significantly higher than those of Chinese fir plantation. The contents soil total phosphorus of Castanopsis hystrix plantation and the mixed plantation of C. hystrix and Mytilaria laosensis were more easily converted to quick available phosphorus than those of Chinese fir plantation and M. laosensis plantation.(2)The contents of calcium chloride extraction phosphorus in rhizosphere and non-rhizosphere soils of Castanopsis hystrix plantation and the mixed plantation of C. hystrix and Mytilaria laosensis were significantly higher than those of Chinese fir plantation and M. laosensis plantation, and the contents of enzyme extraction phosphorus, hydrochloric acid extraction phosphorus and citric acid extraction phosphorus in rhizosphere and non-rhizosphere soils of M. laosensis plantation and Castanopsis hystrix/Mytilaria laosensis mixed plantation were significantly higher than those of Chinese fir plantation and Castanopsis hystrix plantation.(3)RDA results showed that soil water content and microbial biomass carbon were the key factors regulating P components in rhizosphere and non-rhizosphere soils, respectively. In summary, the transformation of Chinese fir plantation into broad-leaved forest is conducive to the storage and supply of forest soil P, and this study provides an important scientific reference for tree species selection and management strategies to improve soil P availability in south subtropical plantations.