5. Conclusions
Increasing stand ages reduced the N concentrations in litter, soil, microorganisms, and plants but increased their P concentrations, which led to lower N:P ratios in the C. hystrix plantation ecosystem in response to increasing stand ages. Overall, C. hystrixplantations become relatively N deficient over time, and their P limitation may be alleviated with increasing stand age in southern China. Based on the results of this study, the increase in potential N mineralization with increasing stand age did not meet the plant N demand, while the increases in total soil P and MBP facilitated the plant uptake of P. The shift in the nutrient balance under increasing stand age will increase the importance of N availability in subtropical plantation forest ecosystems as well as influence the availability of P.