| Forest litter is a part of the forest ecosystem productivity, the major nutrient cycling way of the forest ecosystem is the decomposition of forest litter, so the deep understanding of the ecosystem function can not be separated from the research of the decomposition of forest litter. The major impact factors of the litter decomposition rate are environmental factors and the own characters of the forest litter: the environmental factors, including the climatic factors and biological factors of the place where the forest litter was. Climate change will affect the temperature, air humidity and precipitation and other changes, hydrothermal conditions will directly impact the eluviation and the microbial activity during the litter decomposition, thus the dynamic of litter decomposition will be impacted significantly. In addition, the litter decomposition rate will be indirectly regulated through the impact of litter quality, soil microorganisms and animals activities. The own character of litter, that is the own chemical and physical properties of litter, when the environment condition is the same, the litter decomposition was controlled by its own character. Litter of different tree species are different because of their own biological character, so the character of litter before decomposition has very important influence on the decomposition process. The litter quality is reflected in two main aspects, one is the chemical characteristics of litter, such as the various elements of litter, crude fiber, fat content and so on. On the other hand refers to the physical characteristics of litter, such as the surface characteristics of litter.Nutrient element, organic matter and caloric value of litter leaf of Pinus armandii,Pinus tabulaeformis,Quercusaliena var. acu teserrata,Larix principis-rupprechtii in qinling forest area were studied. The results showed that:(1) Before decomposition, crude fiber, crude fat and caloric value of four kinds litter leaf all properly had the relationships of Pinus tabulaeformis > Pinus armandii > Larix principis-rupprechtii>Quercusaliena var. acu teserrata. Both total N and total P had the relationship of Quercusaliena var. acu teserrata > Larix principis-rupprechtii > Pinus armandii>Pinus tabulaeformis. C/N, C/P and crude fiber/N of Pinus tabu laeformis,Pinus armandii,Larix principis-rupprechtii were all higher than those of Quercusaliena var acu teserrata forest (P<0.01), the highest was Pinus tabulaeformis forest, the ratios were 72.33, 1311.28 and 36.98, they were 1.9～2.5 times of Quercusaliena var. acu teserrata forest respectively. The quality of litter leaf of four tree species were different, but the change of elevation didn't have significant influence on the quality of litter leaf in the same forest (P>0.05).(2) The N and P content took on a rising trend in the early stage of decomposition, and the increasing ratios ranged from 158.51% to 125.20% and from 185.13% to 125.85%, respectively. The relative content of crude fiber increased 104.64%, 103.70%, 121.85% and 110.46% compared to that before decomposition, respectively. With the decomposition of emarcid leaf, the content of Crude fat, organic carbon and caloric value declined gradually, and the decrease ratios ranged from 32.93 to 24.10g·kg-1 from 26.30 to 68.50g·kg-1 and from to 4.15 to 2.78kJ·g-1, respectively. The comparison of the changing trends of the contents of all kinds of nutrients showed that the decomposition of emarcid leaf in different forest lied on its own character when the environment was the same.(3) During the one year decomposition of leaf litter of the same species at different altitudes, nitrogen, phosphorus, crude fiber and organic carbon contents showed no significant differences (P>0.05). While the decomposition rate of leaf litter of the same tree species in low latitude was higher than the decomposition rate of leaf litter in high latitude, and the four tree species all had significant difference (P<0.01). During the one year decomposition, the caloric value of both Pinus armandii and Pinus tabulaeformis had a significant change (P<0.05),and the caloric value of Larix principis-rupprechtii and Quercusaliena var. acu teserrata had a best significant difference (P<0.01).
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