Comprehensive Ecological Risk Assessment Of Grassland Ecosystems In Gannan Prefecture

The grassland ecosystem in Gannan Tibetan Autonomous Prefecture(hereinafter referred to as Gannan Prefecture)is an important component of the grassland ecosystem on the Qinghai-Tibet Plateau and also an important ecological security barrier in Northwest China.In recent years,with the intensification of global climate change and human activities,the grassland ecosystem in Gannan Prefecture is facing unprecedented threats.Ecological risk assessment can identify the types of risk sources that threaten the safety of the grassland ecosystem,quantify and analyze the impact of risk sources on the grassland ecosystem,and provide scientific decision-making support for the protection and risk management of the grassland ecosystem,promoting the sustainable utilization and development of grassland resources in the region.In this paper,the grassland ecosystem of Gannan Prefecture is taken as the risk receptor,and five risk sources,including drought,rodent infestation,non-grazing human activities,overgrazing,and soil erosion,are selected.The probability of risk and ecological endpoint are calculated using multi-source data,and based on the probability-loss model,an ecological risk assessment is conducted on the five risk sources.Based on entropy,coefficient of variation,analytic hierarchy process,Monte Carlo simulation,and grassland ecosystems resilience index,a comprehensive ecological risk assessment of the grassland ecosystem of Gannan Prefecture is conducted from 2000 to 2020.The main research findings are as follows:(1)The results of risk probability analysis show that the probability of drought occurrence,potential rodent infestation rate,non-grazing human activity risk,and soil erosion risk all show a trend of first decreasing,then increasing,and then decreasing again,while the risk probability of overgrazing shows a trend of first decreasing and then increasing;in terms of ecological endpoint analysis,the potential loss of aboveground biomass(AGB),the potential loss of fractional vegetation cover(FVC),and the potential loss of the grassland ecosystem all show a trend of first decreasing,then increasing,and then decreasing again.(2)The results of the ecological risk assessment for individual risk sources show that the ecological risk of drought is mainly low(34.71%),showing a trend of first increasing and then decreasing over time,and a distribution pattern of higher risk in the northern part of Gannan Prefecture and lower risk in the southern part.The proportion of low-risk and medium-risk areas is gradually increasing,while the proportion of highrisk and medium-high-risk areas is gradually decreasing.The ecological risk of rodent damage is mainly low(78.68%),with a trend of gradually decreasing over time and a distribution pattern of higher risk in the southwest and lower risk in the east of Gannan Prefecture.The proportion of low-risk areas is gradually increasing,while the proportion of medium-low-risk and medium-risk areas is gradually decreasing.The ecological risk of non-grazing human activities is mainly medium-low risk(39.29%),with a trend of gradually decreasing over time and a distribution pattern of higher risk in the west and lower risk in the east of Gannan Prefecture.The ecological risk of excessive grazing is mainly medium risk(28.48%)and medium-high risk(26.98%),showing a trend of first decreasing and then increasing over time,and a distribution pattern of higher risk in the west and lower risk in the east of Gannan Prefecture.The ecological risk of soil and water loss is mainly low risk(54.35%),showing a trend of gradually decreasing over time,and a distribution pattern of higher risk in the northwest and lower risk in the southeast of Gannan Prefecture.(3)The results of the comprehensive ecological risk assessment show that the primary risk level is low(54.51%),which gradually decreases over time.Spatially,the risk level is higher in the western part of Gannan Prefecture and lower in the eastern part.The low-risk areas of alpine meadows are increasing,while the areas of secondlow,medium,second-high,and high risk are decreasing.The low-risk areas of mountain meadows are increasing,while the proportion of second-high and high-risk areas are decreasing.The risk level of temperate grassland and meadow is gradually decreasing.The center of gravity and standard deviation ellipse analysis show that the centers of gravity of high and second-high risk are shifting north,while the centers of gravity of second-low and low risk are shifting south.The standard deviation ellipses of high and second-high risk are relatively flat,indicating a greater distribution variation and dispersion,while the change in the areas of second-low and low risk are relatively small,with a more concentrated distribution.(4)The results of the future comprehensive ecological risk prediction show that the overall ecological risk of the grassland ecosystem in Gannan Prefecture will increase by 2040.The medium-risk and second-low-risk areas will increase,while the proportion of low-risk,second-high-risk,and high-risk areas will decrease.Spatially,the risk level will show a pattern of higher in the southwest and lower in the southeast.The low-risk and high-risk areas of the alpine meadows will decrease,while the secondlow,medium,and second-high-risk areas will increase.The second-low and mediumrisk areas of the mountain meadows will increase,while the low-risk,second-high,and high-risk areas will decrease.The temperate grassland and meadow will mainly remain at the second-low and low-risk levels.