Effects of mix-leaf litter decomposition of different trees in the Loess Plateau

Effects of mix-leaf litter decomposition of different trees are important bases of evaluating interspecific relationship and mix-foresting suitability of trees. Experiments of mix-leaf litter decomposition between main tree species in the Loess Plateau have been carried out in laboratory and the results show that: (1) Leaf litter of Hippophae rhamnoides, Ulmus pumila, Caragana microphylla and Populus simonii decompose the most quickly (Turnover periods Ts are 1 a around), leaf litter of Salix matsudana, Platycladus orientalis and Betula platyphylla decompose the second quickly (Ts are a little longer than 1 a), leaf litter of Amorpha fruticosa, Quercus liaotungensis and Robinia pseudoacacia decompose a little slowly (Ts are 1.5 a around), leaf litter of Pinus sylvestris var. mongolica, Larix principis-rupprechtii and Pinus tabulaeformis decompose the most slowly (Ts are a little longer than 2 a). (2) For needle-leaved trees, mixed with litter of P. tabulaeformis, the trees most obviously promoting decomposition are P. orientalis and L. principis-rupprechtii, followed by B. platyphylla, H. rhamnoides and R. pseudoacacia, and no trees obviously restraining decomposition. Mixed with litter of P. sylvestris var. mongolica, the trees most obviously promoting decomposition are L. principis-rupprechtii, P. orientalis, H. rhamnoides and U. pumila, followed by C. microphylla, A. fruticosa and P. simonii, but the trees most obviously restraining decomposition are R. pseudoacacia followed by B. platyphylla and Q. Liaotungensis. Mixed with litter of L. principis-rupprechtii, the trees most obviously promoting decomposition are U. pumila, B. platyphylla and Q. liaotungensis, but the tree obviously restraining decomposition is R. pseudoacacia. A. fruticosa would obviously restraining decomposition mixed with litter of P. orientalis. (3) For broad-leaved trees, mixed with litter of P. simonii, the trees most obviously promoting decomposition are A. fruticosa followed by Q. liaotungensis and R. pseudoacacia. Mixed with litter of R. pseudoacacia, the trees most obviously promoting decomposition are U. pumila and H. rhamnoides, the trees obviously restraining decomposition are C. microphylla followed by Q. liaotungensis and B. platyphylla. Mixed with litter of B. platyphylla, the trees most promoting decomposition are Q. liaotungensis and A. fruticosa, the tree obviously restraining decomposition is C. microphylla. U. pumila would obviously promote decomposition mixed with