| Forest litter is the general term of all organic matter that producing by the biological components and returning to the woodland surface in forest ecosystem. It maintains the inner material cycle of forest ecosystem through the material and energy transformation of decomposers. Litter has an important significance in the material recycling, energy flow, forest community succession and forest water resource conservation, soil and water conservation of the forest ecosystems.Reserves and decompositions of natural secondary Pinus tabulaeformis litter and Quercus aliena var. acuteserrata litter from Qinling Mountains have been investigated in this study. It has a very important significance in clarifying the material recycling and the sustainable use of Quercus aliena var. acuteserrata and Pinus tabulaeformis. It can also provide theoretical and practical basis for the maintenance of soil fertility and forest productivity, forest health management, natural forest protection and effective utilization of forest resources in this area.The results were obtained as following:(1) There was a significantly different chemical properties of leaf-litters between Pinus tabulaeformis and Quercus aliena var. acuteserrata.The content of N and P in Quercus aliena var. acuteserrata litter were both greater than those in Pinus tabulaeformis leaf-litters. However, the ratio of carbon to nitrogen (C/N), the ratio of carbon to phosphorus (C/P) and the ratio of crude fiber to nitrogen (crude fiber/N) of fresh leaf-litters in Pinus tabulaeformis leaf-litters were all greater than those in Quercus aliena var. acuteserrata leaf-litters, and the difference was significant (P<0.01). The decomposition of leaf-litters in Pinus tabulaeformis and Quercus aliena var. acuteserrata both showed significant seasonal and periodic variations. Loss percentage of dry matters from Pinus tabulaeformis leaf-litters and Quercus aliena var. acuteserrata leaf-litters in the first year were 25.20% and 43.77%, respectively, however, they were only 16.20% and 25.33% in the next year, respectively. It was concluded that the rapid degradation of leaf-litters in the two species was from June to September each year, while the degradation rate was relatively stable in other months. Loss ratio of leaf-litters in Quercus aliena var. acuteserrata was most (28.97%), and those in Pinus tabulaeformis was 20.12% in the first year. Residual percentage of dry matter in Pinus tabulaeformis leaf-litters was much greater than those in Quercus aliena var. acuteserrata leaf-litters after two years (P<0.01). According to Olson decomposition exponential model, the shortest time that the 95 percent leaf-litters could be decomposed was 5.43 years for Q. aliena var. acuteserrata, and 9.87 years for P. tabulaeformis.(2) There were significant binomial regression between the remaining percentage of carbon nutrient (organic carbon) and the remaining percentage of N and P nutrient in Quercus aliena var. acuteserrata leaf-litters and Pinus tabulaeformis leaf-litters. There were significant linear correlation between the remaining percentage of leaf-litters carbon nutrient and C/N, C/P in the two species. When the leaf-litters of Pinus tabulaeformis was placed in Pinus tabulaeformis forest and mixed forest of Pinus tabulaeformis and Quercus aliena var. acuteserrata to be decomposed, the nutrient release rate of N, P, C in the latter were much greater than the former (P <0.01).(3) The decomposition test of Quercus aliena var. acuteserrata leaf-litters under different temperature conditions showed that leaf-litters decomposition rate and N, P nutrients release rate were all highest at 25℃, followed by 35℃, while all those were slowest at 15℃. Leaf-litters was was decomposed rapidly when the soil was added into N, P nutrients at 25℃,and N, P contents in soil increased from 3.41 and 0.29 g·kg-1 to 4.61 and 0.579 g·kg-1, respectively, after decomposing 90 days, however, the supplement rate of N, P contents in soil were relatively slow under other two temperature conditions.(4) The annual amount, nutrient content, nutrient regressed of litter in Quercus aliena var. acuteserrata were all greater than those in Pinus tabulaeformis (P<0.01). Litter reserves in Pinus tabulaeformis was 30 472.31 kg·hm-2, which was 3.4 times as Quercus aliena var. acuteserrata. N, P and C reserves of litter in Pinus tabulaeformis were also higher than those in Quercus aliena var. acuteserrata (P<0.05). The reason that accumulation in Pinus tabulaeformis litter was that the decomposition rate was slow, resulting in a lot of litter accumulating in the Pinus tabulaeformis forest.(5)Woody debris reserves in the two species had 31 649.33 and 9 430.75 kg·hm-2.On CWD composition, snags and fallen trees in natural Quercus aliena var. acuteserrata forests had a same proportion, while the proportion was 85.65% and 14.35% in Pinus tabulaeformis forest, respectively.(6) Decomposition of fine roots in the two species after two years, dry weight residual percentage of fine root and N, P residual percentage were all less than those in Pinus tabulaeformis, (P<0.05). It meant that fine root decomposition percentage and nutrient release percentage in Quercus aliena var. acuteserrata litter were both greater than those in Pinus tabulaeformis. |
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