不同人工林凋落叶混合分解速率及其C,N释放动态

对岷江上游连香树、糙皮桦、云南松和云杉4种主要人工林凋落叶进行了凋落叶混合分解试验,探讨了凋落叶混合分解过程中的残留率以及分解过程中C,N含量和C,N释放率的动态变化,为试验区最佳混交树种的选择提供理论指导.结果表明,不同凋落叶分解速率存在显著差异.糙皮桦与云杉,糙皮桦与云南松,连香树与云南松凋落叶混合后对分解过程具有明显的促进作用,连香树与云杉凋落叶的混合对分解的促进作用不明显.放置于阔叶林地的针阔混合凋落叶分解速率较之放置于针叶林地快,且针阔混交有益于凋落叶的分解.在分解过程中凋落叶C含量呈减小趋势,但其释放率反之；N含量在分解过程中,连香树、云杉、云南松凋落叶表现为增加(富集)减小(释放)趋势,糙皮桦表现为减小—增大—减小的变化趋势.针阔林地凋落叶混合后促进了针叶林地凋落叶C和N的释放.

Decomposition Rate and C,N Release Dynamics of Mixed Leaf Litters Under Different Artificial Forests

In this study,we selected leaf litters of four planted forests including Cercidiphyllum japonicum,Betula utilis,Pinus yunnansinsis,and Picea asperata as test objects.Their residual rate,total C and Ncontents,and the release dynamics of C and N at decomposing stage were determined in order to provide theoretical guidance for selecting the best tree species in the experimental area.The results indicated that thedecomposition rates of different withered leaves varied significantly.Mixture leaf litters of Picea asperatawith Betula utilis,Pinus yunnanensis and Betula utilis,Cercidiphyllum japonicum with Pinus yunnanensshowed obvious positive interaction in decomposition.No interaction was observed in those of P .asperataand C.japonicum.Furthermore,the decomposition rate of the mixed leaf litters from broad-leaved forestswas larger than that from needle-leaved forests.It is proved that broad-leaved forest stand was propitious tothe decomposition of leaf litter.The C contents of littered leaves showed decreasing trends while their C releasing rates increased during the decomposition process.Both the contents and releasing rates of C werehigher in needle-leaved forests.In contrast,the N content of leaf litter of the Cercidiphyllum japonicum,the Picea asperata and the Pinus yunnansinsis increased at the beginning then decreased,while that of theB.utilis showed a complex decreasing-increasing-decreasing trend.The mixture of the needle-leaved forestsand the broad-leaved forests promoted the releases of C and N from the needle leaf litters.