Comparative Study On Litter Decomposition Between The Typical Steppe Communities And The Wetland Communities Of Xilinhe River

Material recycling is one of the most basic features of the ecosystem. Litter decomposition is the main process of the material that is fixed by primary productivity returning to the environment. The study on litter decomposition of forest and humid grassland ecosystem has been conducted earlier, and also achieved more broad understanding. At present, those kind of study on arid and semi-arid ecosystem is less, especially in the Asian steppe region. The process and mechanism of litter decomposition has only got limited knowledge. While the comparative study between the wet and dry habitat in the same region has been reported rarely. It is also controversial on the effects of grazing on litter decomposition in steppe region. Based on our understanding above, this paper developed the comparative study of the litter decomposition between the degraded-restored typical steppe communities and the wetland communities in Xilin River, Inner Mongolia. Through the in-situ decomposition experiments on the different restoration gradient of the typical steppe communities and the different hydrological gradient of the wetland communities, this paper determined the decomposition rate of each community and measured the content of carbon, nitrogen, phosphorus, lignin, cellulose and ash in litter at different stages. The main conclusions are as follows:1. The effect of the litter bag aperture used in this study (70 mesh and 100 mesh) on litter decomposition was not significant. The role of soil animals on litter decomposition is small.2. There is difference in original material composition of litter of different communities in typical steppe and wetland communities.3. The rate of litter decomposition in the overgrazed steppe community is lower, while the loss of total organic carbon in litter is higher than other steppe communities.4. Alternating wet and dry has accelerated litter decomposition, also did the cycle of phosphorus in ecosystem.5. Although at the early stage (0-75 d) of decomposition the decomposition rate of wetland plant communities is greater than the typical steppe plant communities, long-term weight loss rate is lower than the typical steppe plant communities. This may explain the turnover rate of the material of the typical steppe ecosystem is higher than the wetland ecosystem.6. Whether typical steppe communities or wetland communities, the turnover rate of element nitrogen was faster than the elemental carbon and phosphorus. This shows that the use efficiency of element nitrogen of the two communities is higher. Winter is a primary period of the litter nitrogen loss .7. According to the regression relationship of the typical steppe litter decomposition weight loss rate and time speculated that the litter completed decomposition time of typical steppe is 2.4 years, but according to the regression relationship of the wetland litter decomposition weight loss rate and time speculated that the litter completed decomposition time of wetland is 25.1 years. It can be seen that wetland possesses the attribute of carbon sink.