Research On Grassland Ecological Security Evaluation In Central And Southern Ningxia Hui Autonomous Region

Grassland,which provides important goods and services such as animal products(e.g.meat,milk and leather),but also ecosystem services,is an important part of the terrestrial ecosystem.Grassland is also the largest terrestrial ecosystem and ecological security strategic resource in China.Climate change and human activities are two factors that have important effects on the grassland degradation of terrestrial ecosystems.To reduce the deterioration from the source of the ecological environment,a series of ecological protection projects have been implemented in China since 1999,such as the "Grain for Green" Project,cultivated land to pastures,which has effectively improved the function of grassland ecosystem.Temperate grasslands are the mainly biomes in Central and Southern Ningxia Hui Autonomous Region,which belongs to the agro-pastoral ecotone of northern China.However,local farmers have formed planting and breeding habits,and it is difficult to quickly change the production mode and livelihood strategy of wide planting and low yield and grazing,resulting in a game between local economic development and ecological environment protection,which affects the implementation effect of grassland ecological projects.It is an important part of grassland science research in the agro-pastoral ecotone to find the balance point of the game between ecological environment protection and local economic development,realize the harmonious development of man,grass and livestock,and promote regional ecological security.Based on the grassland ecological security and sustainable development,this study constructed an ecological security database with the aid of field survey data,remote sensing data,statistical data and literature materials in the temperate grassland area in Central and Southern Ningxia Hui Autonomous Region.Based on the dynamic change of land use,grassland vegetation characteristics,and spatial pattern of soil nutrients,the study compared the utilization of natural capital such as regional grassland,cultivated land,and forest land,quantitatively analyzed the temporal and spatial pattern of grassland ecological security,analyzed its influencing factors and mechanisms,and discussed the management strategy and security system of sustainable grassland utilization.The research enriches the theory and method of ecological security research.The main research conclusions are as follows:(1)The grassland area accounted for the largest proportion.In 2018,grassland accounted for 49.81%,cultivated land 34.25%,forest land 5.16%,construction land 1.95%,and water area 1.00%.From 2000 to 2018,cultivated land,grassland and unused land decreased by 6.68%,0.31%and 3.08%respectively,construction land increased by 128.16%,forest land and water area increased by 29.86%and 10.30%respectively;the grassland area in Yuanzhou District,Pengyang,Xiji,Longde and Jingyuan,Haiyuan and Yanchi County increased by 34330.20 hm2;the grassland area in Tongxin,Hongsipu,Zhongning and Shapotou districts decreased by 40090.92 hm2 totally.The transfer relationship between cultivated land,grassland and construction land was the main body of land transfer.(2)Compositae accounted for the largest proportion of grassland species composition in meadow steppe,about 25%,and Gramineae and Leguminosae accounted for 12.5%;Compositae,Leguminosae and Gramineae accounted for 25.27%,15.38%and 10.99%of typical steppe plants;the desert steppe plants were mainly Leguminosae,Compositae and Gramineous plants,accounting for about 60%.The coverage of meadow steppe,typical steppe and desert steppe were 97.81%,85.97%and 39.53%respectively,the heights were 29 cm,23cm and 17 cm respectively,Shannon-Weiner diversity index were 2.51,2.06 and 1.40,Pielou evenness index were 0.85,0.83 and 0.87,and aboveground biomass is 307.61 g/m2,146.56 g/m2 and 88.16 g/m2.The soil organic carbon contents of meadow grassland,typical grassland and desert grassland were 30.69 g/kg,11.47 g/kg and 5.62 g/kg,and the soil organic carbon densities were 25.81 kg/m2,10.71 kg/m2 and 6.44 kg/m2.The surface aggregation was significant on the soil profile.Soil organic carbon decreased gradually from the southern Liupan Mountain to the central arid wind sandy belt.Amos analysis found that environmental factors could explain 91.4%of the spatial variation of soil organic carbon.Altitude had the greatest influence on the total effect of soil organic carbon;the direct positive effect of aboveground biomass on soil organic carbon was the largest;the effect of precipitation on soil organic carbon can be divided into direct effect and indirect effect on biomass and soil water content;the temperature had a negative effect on soil organic carbon indirectly through aboveground biomass.Soil organic carbon in Central and Southern Ningxia Hui Autonomous Region was mainly controlled by precipitation.(3)The improved three-dimensional ecological footprint model was used to analyze the use of natural capital in Central and Southern Ningxia Hui Autonomous Region.From 2010 to 2020,the ecological footprint of each county increased by 26.30%on average.The proportion of grassland footprint increased from 39.89%to 54.46%.Ecological deficits occurred in each county successively and kept growing.The average proportion of grassland footprint size increased from 17.92%to 21.90%.The ecological footprint depth of each county exceeded the original length of 1,showing an increasing trend.Shapotou,Zhongning and other counties have steadily increased their footprint depth and were in the forefront,while Haiyuan,Longde,Jingyuan,Xiji,Yuanzhou and other counties had low footprint depth.The depth of grassland footprint was more than 1,showing an upward trend,and the consumption of grassland capital was serious;the footprint depth of cultivated land,forest land,water area and other land categories was 1,mainly occupied by flow capital.GDP per capita,proportion of secondary industry,urbanization rate,consumption level of rural residents had significant positive driving effects on ecological footprint;the output value of the tertiary industry and the agricultural population presented negative impacts.(4)Based on the pressure-state-response model,comprehensive evaluation method and entropy TOPSIS method were used to study grassland ecological security.Evaluation results of comprehensive index method:from 2005 to 2020,the average comprehensive index of grassland ecological security increased from 0.39 to 0.41.The ecological security index of Jingyuan,Pengyang,Longde,Yuanzhou District,Xiji and Haiyuan counties increased by 84.78%,66.59%,50.55%,30.89%,32.45%and 22.00%,and the ecological security level improved;the ecological security indexes of Hongsipu,Shapotou,Yanchi,Zhongning and Tongxin decreased by 13.68%,10.49%,29.34%,47.23%and 51.11%respectively.In 2020,Jingyuan,Longde,Yuanzhou District and Pengyang County had higher ecological security indexes,and the grassland ecological security level were high;the ecological security of Yanchi,Haiyuan and Xiji were in the middle;the grassland ecosystems of Shapotou,Tongxin,Zhongning and Hongsipu were not safe.The weighted TOPSIS model evaluation showed that the average closeness of grassland increased from 0.38 to 0.41.The ecological security of Jingyuan,Longde,Yuanzhou District,Haiyuan,Xiji and Pengyang improved,and the closeness of Tongxin,Hongsipu District,Zhongning,Yanchi and Shapotou District decreased.In 2020,Jingyuan County had the highest level of ecological security,Longde,Yuanzhou,Pengyang and Yanchi County had a high level of ecological security,Haiyuan,Xiji and Shapotou District were basically safe,and Hongsipu Zhongning and Tongxin grasslands were unsafe.The evaluation results of the two methods were basically consistent.(5)The driving factors of grassland ecological security were revealed by principal component analysis and obstacle degree model.The variables that had a greater impact on grassland ecological security were:soil organic carbon density,annual precipitation,soil moisture,aboveground biomass,proportion of tertiary industry and per capita grassland area.The obstacle degree model was used to diagnose the obstacle factors of grassland ecological security in each county.Jingyuan,Longde,Yuanzhou District and Pengyang were mainly affected by per capita GDP,per capita grassland area,per capita disposable income of farmers,proportion of agricultural population and artificial grassland area per unit of livestock.The grassland was basically safe in Haiyuan,Xiji and Yanchi,where the main obstacle factors were soil moisture,aboveground biomass,annual precipitation and artificial grassland area per unit livestock;Tongxin,Shapotou,Zhongning and Hongsipu,where the grassland was ecologically unsafe,the obstacle factors were:aboveground biomass,soil moisture,annual precipitation per capita grassland area and artificial grassland area per unit livestock.According to the spatial pattern of grassland ecological security and the analysis results of obstacle factors,the grassland in the study area was divided into different areas and the optimal management strategies of grassland ecological security were proposed,which provided a scientific basis for ecological restoration and sustainable development of regional economy and society.