The Carbon Cycle Researches In The Recovering Mountainous Grassland Ecosystem In XinJiang

Xinjiang is one of the largest natural grassland regional distribution in China, whose area of the natural grassland accounts for 14.58% of that of China. Now we are confronted with one major ecological problem in Xinjiang—the degradation of the nature grassland generated by overgrazing. This test is one of the important topics of the Global Environment Fund, Its main objective is the adoption of a global significance to the project area Altay and Tianshan mountains inland ecological zones of the arid zone grass ecosystem carbon cycle research. It aims to provide the sustainable development of the natural grassland with a theoretical basis in Xinjiang through the carbon cycle research of the grassland ecosystem of the interior arid region in the project area Tianshan mountain and Altay. This test has made the following main conclusions.1. According to the results of this test, fencing add greatly to the prairie biomass and the soil organic. In the meanwhile, the change or the soil ecological condition promotes the formation of the soil organic and increases the reserving of the soil organic carbon and nitrogen. It is of great benefit to the enhancement and the restoration of soil organic carbon and nitrogen in the natural grassland. While due to the slowness in the accumulation of the soil organic carbon and nitrogen, the majority of that remains in the soil surface layer. In this case, further research should be done on the time scale for fencing.2. The CO₂ fluxes from the plant communities of outside fence of Alpine meadow and subalpine meadow are significantly positively correlated with the air temperature and 5cm and 10cm soil depth temperature and have no correlation with 15cm and 20cm and 25cm soil depth temperature. The CO₂ fluxes from the plant communities of in side fence of Alpine meadow and subalpine meadow are only significantly positively correlated with the air temperature and 5cm soil depth temperature. The CH4 fluxes have no correlation with the air temperature and 5cm and 10cm soil depth temperature . The average CO₂ flux of inside fence are higher than that of outside in Alpine which fenced a long time, but that of inside fence are lower than that or outside in Subalpine which fenced a short time. Moreover, our results also showed that there are 71% of the CO₂ flux emitted in Alpine outside the fence coming from the soil breath and there are 64% of them emitted in Alpine inside the fence coming from the above mentioned thing. There are 67% of them emitted in Subalpine outside the fence coming from the soil breath and in Subalpine inside the fence there are 65% of them coming from that.3. Under the condition of animal raising shut with fencing, the Alpine and Subalpine meadow ecosystem are the weak source of CH₄. The average CH₄ flux of them are 0.000399 g/m².h, 0.000228 g/m².h. Under the natural pasturing condition, the Alpine and Subalpine meadow ecosystem are weak sink of CH₄. The average CH4 flux of them are -0.000251 g/m².h, -0.000978 g/m².h.4. The plant carbon density within the fencing is higher than that out of it. The plant carbon density increased from the subalpine meadow to the Downland and to the Alpine meadow. The plant carbon density inside and outside Downland fencing is respectively 0.8845 kg/m² ,0.5666 kg/m² ;that inside and outside Subalpine meadow is respectively 1.2506 kg/m² ,1.0192 kg/m² and that inside and outside Subalpine meadow is respectively 2.3055 kg/m² ,1.4454 kg/m².5. The soil organic carbon density inside Alpine meadow which fenced a long time is higher than that outside the fencing. That in Subalpine meadow which fenced a short time and that in Downland which fenced for cutting grass is lower than that outside the fencing. This proves that the fencing helps to remarkably increase the primary productivity of the carbon fixation. But the accumulation of soil organic carbon is relatively slow. The fencing has a little influence on the soil inorganic carbon density.