Abstract:

Fallen woods of Pinus tabulaeformis and Toxicodendron vernicifluum were used to study the decomposition process. According to an international classification, nutrient contents of 6 elements (C,N,P,K,Ca,Mg) in five decomposition classes were measured in Huoditang forest region in the Qinling Mountains, and the elements in the soil were also analyzed. The results showed that there were no significant differences among C contents in the decay classes of P. tabulaeformis, but the C content of T. vernicifluum decreased significantly with decaying. N obviously accumulated in the Ⅴ decay class in P. tabulaeformis and T. vernicifluum. There was no significant difference in Mg among the decay classes in P. tabulaeformis, while Mg significantly increased at the late stage of decomposition in T. vernicifluum. No differences were found in P, K and Ca among the decay classes of P. tabulaeformis and T. vernicifluum, however with the decomposition of P. tabulaeformis and T. vernicifluum, the contents of P and Ca linearly increased, the content of K linearly decreased. With the increase of soil depth, the content of soil C under fallen wood decreased significantly, however no difference was observed in K, Ca and Mg. The content of soil C increased significantly from decay Ⅰ to Ⅴ, while the N, P, Ca and Mg were similar. This research reveals the change pattern of various nutrients during the decomposition process of fallen wood, which would be helpful for measurement-making of promoting the nutrient cycling and forest regeneration of forest ecosystems in the Qinling Mountains.

Key words: Qinling Mountains, Pinus tabulaeformis, Toxicodendron vernicifluum, fallen wood, decomposition, nutrients