Study On Ecological Effect Evaluation Of Soil And Water Conservation On Slope Scale In Typical Small Watershed Of Tibet

Soil erosion that would pose a threat to the sustainable development of ecological environment is a major problem restricting the human development and social progress.It is an important reason for deterioration and poverty of ecological environment,which not only destroys the natural structure of soil,reduces soil fertility,and results in land desertification and rocky desertification,but also leads to frequent natural disasters.In recent years,the ecosystem stability of Tibet is decreasing and soil erosion is further intensified due to the effects of global climate change and natural activities of human.At present,there are few studies on the ecological effect of soil and water conservation about Tibet because of the lack of soil and water conservation monitoring sites and monitoring data.Based on the public-spirited water resource project "The monitoring and evaluating technology of ecological effects of the water and soil conservation in Tibet Plateau",comprehensively and scientifically evaluate the ecological effects of soil and water conservation on the slope scale in small watershed of RiLang river and ChaBaLang in Tibet region.Build an evaluating indicators system of the ecological effects of soil and water conservation which apply to the Tibet region,and carry out quantitative evaluation of the ecological effects of soil and water conservation,to provide planning basis and technical support for the ecological environment construction in the region.The main contents and conclusions are as follows:(1)According to analyzing the soil erosion characteristics and the status of soil and water conservation in the study area,the ecological effect evaluating index base with 14 indicators was identified by the methods of frequency statistical analysis and expert experience.Using the principal component analysis to obtain the comprehensive load of each index,removed the total phosphorus and soil effective thickness for lower comprehensive contribution rate;According to the results of correlation analysis,removed the soil moisture content index with high repeatability of soil water storage.Analyzing the sensitivity of the indexes by the combination of the coefficient of variation and the degree of response,and the weak sensitivity index soil pH was eliminated.The evaluation system of slope scale ecological effect is obtained eventually,which includes 10 indexes,such as soil water storage,soil erosion modulus,maximum moisture capacity,soil bulk density,organic matter,total nitrogen,total potassium,vegetation coverage,biodiversity and soil carbon fixation.(2)On account of the characteristics of ecological effect evaluation,the weights of 10 indexes in the index system are determined by the combination of the analytic hierarchy process and the entropy weight method.The weights of the indexes are as follows:soil water storage(0.109),soil erosion modulus(0.251),maximum moisture capacity(0.059),soil bulk density(0.021),organic matter(0.105),total nitrogen(0.113),total potassium(0.024),vegetation coverage(0.113),biodiversity(0.041)and soil carbon fixation(0.164).(3)Build a comprehensive evaluation model to get the results of quantitative evaluation of ecological effects of soil and water conservation under different measures.The result shows that the ecological effect of the controlling region is better than non-measures area,which indicates that the soil and water conservation measures is beneficial to the soil erosion control.The ecological effects forest land,cultivated land and stone hilly terraces are better than those of non-measures area.the ecological effect of forest land is the best,and the cultivated land and stone hilly terraces are inferior to woodland because of man-made disturbance and short implementation time;In view of the different soil and water conservation measures,the ecological effect of the soil and water conservation measures area was better than that of the non-measures area,except the Kaer village and the grass-grid in Qushui,because of the climate and soil conditions in the study area.(4)The analysis of different single index by one-factor analysis of variance found that under the soil and water conservation measures,the indexes in the controlling region are better than those without treatment,except the Kaer village.The abnormal situation is related to the short implementation time,less population,less man-made disturbance and thicker soil crust.In addition,in view of the soil bulk density in Nuo village and the soil erosion modulus of the polar in Qushui County,need for long-term dynamic monitoring of the study area,and further research.