| The sustained and stable development of the ecological environment in the western pastoral areas is of great significance to promoting the prosperity of animal husbandry,maintaining regional ecological security,and protecting the national green barrier.In view of the current problems and challenges in the evaluation and protection of the ecological environment in western pastoral areas,this study selected Otog Banner in Inner Mongolia Autonomous Region,Sunan County in Gansu Province,and Ulan County in Qinghai Province as three typical climate research areas.Adopting single-index evaluation method,"natural resources-social economy"and "pressure-state-response" model evaluation methods,considering the six aspects of meteorology,soil,vegetation,water resources,livestock and socio-economics,the characteristics of changes in typical natural and social ecological indicators are analyzed,and the overall ecological environment changes in typical western pastoral areas are studied.Furthermore,the pros and cons of the ecological environment of the three regions are analyzed comparatively,and divide their ecological environment levels.The main results are as follows:(1)Aiming at the soil ecological health problems in typical pastoral areas in western China,the characteristics of the temporal and spatial changes of soil indicators are analyzed from three aspects:soil physical and chemical properties,soil nutrient content and soil wind erosion.The results show that the overall soil bulk density in the western pastoral areas is relatively large.From April 201 7 to June 2020,the average soil bulk density of Otog Banner,Sunan County,and Ulan County were 1.58 g/cm3.1.38 g/cm3,and 1.42 g/cm3.respectively.The soil in the pastoral area is mostly alkaline sandy soil,and the degree of soil salinization is alleviated.The salt content of the soil surface in the three regions has been reduced by 24.16%,32.93%and 32.41%respectively.Soil nutrient content is a key factor affecting soil quality in pastoral areas.During the study period,the soil nutrient indicators in all regions have increased,and the available phosphorus content has increased the most.Otog Banner increased by 165.17%,Sunan County increased by 35.10%,and Ulan County increased by 79.02%.However,the soil nutrient content in each study area is still low,and the average soil organic matter in the three areas is 7.03 g/kg,7.94 g/kg and 11.22 g/kg,respectively.From the perspective of spatial distribution,the spatial distribution of various soil indicators in Otog Banner is mostly patchy.Sunan County mostly increases or decreases from the north-central area to the surrounding area,showing a belt-like distribution.The spatial distribution of different indicators in Ulan County is quite different,and the distribution of the same indicator in different soil layers is also slightly different.Among the three study areas,Otog Banner has the greatest threat of wind erosion,Ulan County has the least,and Sunan County is in the middle.(2)The inter-annual changes of five factors,including weather,vegetation,water resources,livestock,and socio-economic factors in typical pastoral areas in the west are studied.The results show that the typical pastoral area in the west has a dry climate,with year-round drought,less rainfall and large evaporation.In recent years,the light and heat resources of each typical research region have decreased.The annual active accumulated temperature of Otog Banner has decreased by 24.55%,Sunan County has decreased by 4.05%,and Ulan County has decreased by 10.03%.The degree of drought in Otog Banner has worsened,and its aridity index has decreased by 17.16%,while Sunan County and Ulan County have increased by 21.00%and 32.43%,respectively.From 2016 to 2019,the precipitation anomalies in Sunan County and Ulan County were positive,and the potential evapotranspiration was in a downward trend,while Otog Banner showed the opposite pattern,so the climate conditions in Otog Banner were the worst.The overall vegetation coverage in each region has shown an upward trend,and the proportion of grassland,woodland and farmland in pastoral areas has gradually increased.However,during the study period,the average annual yield rate of vegetation in Otog Banner and Ulan County decreased by 8.37%and 12.69%,respectively,and Sunan County rose by 17.21%.In terms of water resources indicators,Ulan County has the worst water resources.The local water ecological pressure index has increased by 0.32%,and the water use efficiency and water-land resource matching coefficient have been reduced by 17.22%and 14.81%,respectively.The hydrological sensitivity of the other two places is relatively low.The grazing pressure in Otog Banner and Sunan County was reduced,and the actual livestock carrying capacity decreased by 0.87%and 4.14%,respectively,while the actual livestock carrying capacity in Ulan County continued to increase in a linear trend.The social economy of the typical western pastoral areas has improved to varying degrees.Among the three regions,Otog Banner has the best economic situation.(3)The overall eco-environmental quality of typical pastoral areas in the west is showing a trend of continuous improvement.The comprehensive surface soil quality of Otog Banner,Sunan County,and Ulan County increased by 57.3%,41.8%,and 11.4%,respectively.The spatial distribution characteristics of the soil quality are similar to the spatial distribution of physical and chemical indicators and nutrients.The soil quality in the northern part of Otog Banner,the southwest and southeast of Sunan County,and the northeastern part of Ulan County is slightly higher.The evaluation results of the "natural resources-social economy" model show that in 2019,the natural ecological index of each region is greater than 0.60,and the social ecological index ranges from 0.18 to 0.42,and they are all on an upward trend.The degree of regional coordinated development of the three regions is greater than 0.80,which belongs to the category of good coordinated development.Among them,Otog Banner has the highest degree of coordination and Ulan County has the lowest.The evaluation results of the "stress-state-response" model show that in 2019,the comprehensive response health values of Otog Banner,Sunan County,and Ulan County were classified as extremely excellent,poor,and good ecological health levels,respectively.The comprehensive value of pressure health and comprehensive value of state health belong to the category of excellent ecological health,and the comprehensive value of ecological environment health in each region is greater than 0.60,which belongs to the high ecological health level.The evaluation results of the two comprehensive models both show that the ecological environment of the typical pastoral areas in western China has improved.The"pressure-state-response" model shows that water resources are the most important factor restricting the development of ecological environment in typical pastoral areas.The "natural resources-social economy" model shows that Otog Banner and Ulan County should focus on the optimal allocation of water resources,while Sunan County should focus on improving soil quality as the primary goal. |
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