不同种植年限尾巨桉人工林叶片-凋落物-土壤碳氮磷化学计量特征

目的]为了解雷州半岛尾巨桉速生人工林生态系统的C、N、P分配格局及化学计量特征。方法]采用空间换时间的方法,选取雷州半岛4种不同林龄(1、3、5、7 a)的尾巨桉人工林为研究对象,对尾巨桉叶片、凋落物及土壤的C、N、P含量及化学计量特征进行测定分析。结果]表明:C、N含量表现为叶片凋落物土壤,P含量表现为叶片土壤凋落物,且3个库间差异显著;土壤的C含量随林龄增加而增加,N、P含量差异不显著,土壤C∶N随林龄的增加而增加,说明土壤有机质分解速率逐渐下降;凋落物的C∶N为54. 07 92. 18 ( 25),表明尾巨桉林下凋落物分解速率较慢,N元素成为主要限制凋落物分解的元素,凋落物的C∶N随林龄的增加先增加后下降,凋落物分解速度先降低后升高;叶片的N∶P为10. 80 12. 98,说明中幼林龄尾巨桉受N限制较明显。相关性分析表明:凋落物养分元素含量受叶片限制,土壤养分含量受凋落物限制,表明生态系统内部C、N、P元素在植物、凋落物与土壤之间实现了运输和转换。结论]雷州半岛尾巨桉中、幼林龄时期土壤有机质及凋落物分解速率较慢;随林龄的增加,土壤有机质、凋落物分解速率下降,N元素成为其主要分解限制性元素,林分生长受N限制明显。

The Stoichiometric Characteristics of C, N and P in Leaf-litter-soil of Different Aged Eucalyptus urophylla×E. grandis Plantations

Objective] To understand the distribution pattern of carbon, nitrogen and phosphorus and the stoichiometric characteristics of Eucalyptus urophylla×E. grandis fast-growing plantation ecosystem in the Leizhou Peninsula.Method] The temporal-spatial method was used to select four E. urophylla×E. grandis fast-growing plantations with different ages (1, 3, 5, 7a) as the subjects. The contents of C, N, P and their ratio were analyzed in the leaf, litter, and soil.Result] The results revealed that the C and N contents followed the pattern of leaf > litter > soil, the content of P followed the pattern of leaf > soil > litter and there was an obvious difference among the three warehouses. Soil C content could increase with the raising of plantation age; but N and P differed little. The ratio of soil C:N increased with rising age, indicating that soil decomposition rate declined gradually. The ratio of litter C:N varied in the range of 54.07-92.18 (>25), increased at first and then declined. It showed that litter decomposition rate was comparatively low and restricted by N. The ratio of N:P in leaf was between 10.8 and 12.98 which also demonstrated that plant growth was limited by N. The correlation analysis showed that the litter N content was limited by the leaf, and the soil N was limited by the litter. Inside the ecosystem, the C, N and P elements had realized the transportation and transformation among the plants, litter and soil.Conclusion] The decomposition rate of soil organic matter and litter of young and middle aged E. urophylla×E. grandis plantations on the Leizhou Peninsula is comparatively slow. The soil organic matter and litter decomposition rate decline with age and is restricted by N. The growth of plantation is also limited by N.