Ecological Stoichiometric Characteristics of Leaf−Soil Carbon, Nitrogen and Phosphorus in Pinus massoniana Plantations with Different Forest Ages

Taking 5, 13 , 23, 30, 40, and 60-year-old Pinus massoniana plantations in Guangxi centra as objects, the contents of C, N, and P in leaves and soil were analyzed and the redundant analysis was used to explore the stoichiometric characteristics of leaf C, N, and P and their relationships with soil environmental factors. The results showed that the contents of C, N, and P were all expressed as leaf > soil, and the contents and stoichiometry of C, N, and P were significantly different among different forest ages and between leaves and soil. With the increase of forest age, the C and N contents of leaves showed an upward trend and overmature forests(40 and 60-year-old) were significantly higher than other forest ages, P content first increased and then decreased, and 30-year-old was significantly higher than other forest ages. The contents of soil C, N, and P showed a trend of decreasing first and then increasing. Among them, the contents of C and N in young forests(5-year-old) and overmature forests(40 and 60-year-old) was significantly higher than that in other forests. In 60-year-old, the P content was significantly higher than other forest ages. According to the N∶P value in the leaves, the P. massoniana forest is mainly restricted by the P element. P. massoniana shows stronger plant stability for environmental adaptability, but is more sensitive to the N∶P nutrient balance in the system. At the same time, the soil N, AP, AN content and C∶N are the key determinant of changes in the leaf C, N, P stoichiometric characteristics. In summary, during the growth of P. massoniana, special attention should be paid to the balance of N∶P nutrients. In order to improve its productivity, it is recommended to reasonably apply N and P fertilizers in the process of tending management to enhance soil nutrient status and improve plant nutrient utilization efficiency.