摘要：

For this study, Platycladus orientalis, a major tree species used in afforestation in the Loess Plateau, was chosen. Leaf litters of the current year were gathered from P. orientalis and 8 other tree species that were planned to be planted in mixed forests , and soil from the humus layer (0~20 cm) of a tract of tree-free waste grassland was used as medium, in which litters were to be decomposed. Mixtures of litter from P. orientalis with others were shredded and packed into nylon mesh bags according to a set ratio, separately. Then the bags were buried into the soil contained in pots for incubation under a constant temperature and humidity for 345 days on end. The litters were analyzed for quality and nutrient contents before and after the incubation. Results show that 1) among the nutrients released during decompostion of the leaf litters, K was the most active and easy to get released, while P was generally dull and difficult to get released, and C and N was moderate and often synchronous in releasing, and the recycle period of these nutrients was 1 ~ 2 a; 2)leaf litter of Ulmus pumila in the mixture acted positively, while that of Amorpha fruticosa, Betula platyphylla and Quercus liaotungensis negatively on C release; leaf litter of Populus simonii did positively, while that of B. platyphylla, Q. liaotungensis and A. fruticosa negatively on N release; litters of P. simonii and U. pumila did positively, while litters from all the other trees negatively on P release; and litter of U. pumila did positively, while that of A. fruticosa did negatively on K release; 3) the Principal Component Analysis of comprehensive effects of decomposition of various mixtures of leaf litters on releasing of C, N, P and K revealed that leaf letter of U. Pumila and P. simonii in the mixture was the most significant in promoting nutrient release, and litters from Caragana microphylla and Q. liaotungensis followed, Litter from A. fruticosa, followed by litter from B. platyphylla, H. rhamnoides and R. Pseudoacacia, showed obvious inhibitive effects on nutrient release.

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