Increasing stand age increases N deficiency but alleviates relative P limitations in Castanopsis hystrix plantations in Southern China

Abstract

AbstractForest productivity usually declines with the increase in the age of stand, which may be associated with the disturbance in the balance of nitrogen (N) and phosphorus (P) nutrients. However, the effects of stand age on plantation nutrient balance and productivity in plantation is still unclear. Therefore, an experiment was conducted in this study to investigate the influence of the increase in the age of stand (6‐, 10‐, 15‐, 25‐, 30‐, and 34‐year‐old stands) on plant growth and the dynamics of N and P in Castanopsis hystrix plantations of Southern China. The increase in the age of stand reduced plantation productivity and leaf N:P. Moreover, productivity was found to be positively correlated with leaf N:P, reflecting that the decrease in productivity was related to changes in N and P contents in leaves. Reduction in leaf N:P was associated with declining N content and stable P content in leaves. The decrease in leaf N content may be due to the declining –N and microbial biomass N contents in soil, although activities of N‐acetylglucosaminidase, cellobiohydrolase, and polyphenol oxidase decreased with the increase in stand age. The stability of leaf P content may be associated with the increase in soil total P and microbial biomass P, boosting P supply to plants. In contrast, decreased soil phosphatase activity with the increase in the age of stand likely suggests that no additional P was needed through P mineralization. The findings indicate that increasing stand age would improve N consumption but alleviate relative P limitations. Thus, more attention needs to be paid to N fertilizer management (e.g., 10–15‐year stages) to sustain C. hystrix productivity with stand age.