中文摘要：

以黄土高原区典型植物刺槐、小叶杨、沙棘、沙柳、苜蓿和长芒草的凋落物为对象，采用网袋法研究了半干旱区（神木）分解过程中，单种、两种及3种凋落物等质量配比混合后其质量、碳和氮的动态变化．结果表明：在整个分解过程中，不同处理凋落物的质量损失率，全碳、全氮的释放速率以及可溶性有机碳和可溶性总氮的含量均表现为前期大于后期．经过412d的分解，3种凋落物混合后的平均质量损失率高于两种混合凋落物，单种凋落物最低．到分解试验结束时，不同处理凋落物的全碳、全氮平均释放率均表现为单种〉两种混合〉3种混合；而不同处理的可溶性有机碳平均含量表现为两种混合〉单种〉3种混合，但未达到显著水平；可溶性总氮含量则为3种混合〉两种混合〉单种，达到显著水平．凋落物的质量损失率与可溶性有机物，特别是可溶性有机碳具有一定的相关性．从质量损失率来看，小叶杨、沙棘与苜蓿凋落物的组合为最佳组合．建议在黄土高原区退耕还林还草工程建设中，合理增加植物种类多样性，促进土壤改善养分状况．

英文摘要：

Taking the litters of species Hippophae rhamnoides, o sativa, Populus simonii, Robinia pseudoacaci, Salix psammophila, and Stipa bungeana in the Loess Plateau of Northeast China as test objects, and by using mesh bags, this paper studied the dynamic changes of the litters mass, carbon, and nitrogen during decomposition after buried in the field in semiarid region. The litters buried were from one, two, or three of the plant species, and mixed thoroughly with equal proportion of masses. During decomposition, the mass loss rate, total carbon and nitrogen release rates, and total soluble carbon and nitrogen contents of different litters were higher at the early than at the later decomposition stage. After 412 d decomposition, the average mass loss rate of the litters was in the order of mixed litters of three plant species 〉 mixed litters of two plant species 〉 one plant species litter. By the end of this experiment, the average release rates of the litter total carbon and nitrogen ranked as one plant species litter 〉 mixed litters of two plant species 〉 mixed litters of three plant species, the litter soluble organic carbon content was mixed litters of two plant species 〉 mixed litters of three plant species 〉 one plant species litter, while the litter soluble total nitrogen content was mixed litters of three plant species 〉 mixed litters of two plant species 〉 one plant spe- cies litter. Correlation analysis showed that the litter mass loss rate had definite correlation with the litter soluble organic matter, especially soluble organic carbon. From the viewpoint of mass loss rate, the mixture of the litters of P. simonii, H. rhamnoide, and M. sativa was the optimum. It was suggested that in the process of returning farmland into forestland and grassland in the gully and valley region of Loess Plateau, it would be required to rationally increase plant species diversity to imnrove soil fertility.