Research On The Carrying Capacity Of Water And Grass Resources In Alpine Desert Grassland Pastoral Areas Based On System Dynamics

In recent years,due to climate change,unreasonable grazing methods,and intensity,the coverage of alpine desert grasslands has decreased,productivity has decreased,water conservation capacity has weakened,livestock carrying capacity has decreased,and the carrying situation of water grass resources is severe.In order to ensure the ecological security of grasslands,the carrying capacity of water grass resources should be taken as a constraint to seek sustainable economic and social development in pastoral areas.This study selected Ulan County as a typical alpine desert grassland pastoral area.Firstly,based on the investigation of resource endowment conditions and development utilization,the current situation of water grass resource supply and demand balance was analyzed,and the problems faced were identified.Then,based on key influencing factors,an evaluation index system for water grass resource carrying capacity was established.Then,the combined weighted TOPSIS model and SD model were comprehensively used,following the principle of "water determines grass and water determines livestock" and constrained by "grass animal balance",Conduct research on the evaluation,prediction,determination and optimization of water grass resource carrying capacity,with the aim of exploring ways to maximize the total benefits of pastoral areas within the range of water grass resource carrying capacity.The conclusions are as follows:(1)From 2015 to 2019,the total water use in Ulan County showed an increasing trend,mainly for agricultural irrigation,with water use levels lower than the national level;The Xisai Basin is the main water consuming area with relatively high water usage levels.The planting area of artificial grasslands has been increasing year by year,with wheat,silage corn,and alfalfa as the main crops.In 2019,the overall water and grass resources were in an overloaded state,with an overload rate of 3.4%-52.5%.As the incoming water increased from abundant to dry,the degree of overload increased.Water resource overload is concentrated in the Xisai Basin,while grass resource overload is concentrated in the Chaka Basin,with warm season being higher than cold season.The main problems faced by water grass resources are uneven spatial and temporal distribution,poor coordination between resources,and poor matching with the scale of economic and social development.(2)From the perspective of the entire county,from 2015 to 2019,the carrying capacity of water and grass resources showed a "U" shaped fluctuation and decreased,with a cumulative decrease of 20.75%.Among them,the carrying capacity of the resource subsystem increased,while the carrying capacity of the living,production,and grassland ecosystems decreased significantly,with the living subsystem showing the most significant decline.From the perspective of each partition,the carrying capacity of the water grass resources in the Xisai Basin shows a "V" shaped fluctuation and decrease,with the fluctuation of the carrying capacity of the resource subsystem increasing,and the differential reduction of the carrying capacity of the living,production,and grassland ecosystem subsystems.The carrying capacity of water grass resources in the Chaka Basin fluctuates in an "N" pattern,with a decrease in the carrying capacity of the living subsystem and a differential increase in the carrying capacity of the resource,production,and grassland ecosystem subsystems.(3)Under the current development mode,the population of Ulan County showed negative growth from 2025 to 2035,and the urbanization rate has been increasing year by year.The total population in 2035 was 32000,with an urbanization rate of 58.1%;The scale of artificial grassland planting has been expanding year by year,from 35800 mu to 61700 mu;The livestock inventory at the end of the year has been increasing year by year,reaching 652500 sheep units by 2035;The total benefits are mainly industrial,supplemented by agricultural and animal husbandry benefits,increasing from 2.983 billion yuan to 26.109 billion yuan,with a growth rate of 104.76%.The water grass resource carrying pressure in the Xisai Basin is relatively low,and the carrying situation in the Chaka Basin is severe.The current water grass resource problem has not been solved.(4)From 2025 to 2035,the water grass resources in Ulan County can carry the same population and grassland ecological benefits as planned,and are not affected by the frequency of incoming water;The planting area of artificial grassland that can bear is 717-152300 acres,and the agricultural benefits that can bear are 390-541 million yuan,all higher than the planned value;The year-end stock of livestock that can be carried is 6041 to 800200 sheep units,with a total carrying benefit of 3.244 to 6.416 billion yuan and an industrial benefit of 2.736 to 3.219 billion yuan,all of which transform from being equal to the planned value to being lower than the planned value with incoming water from abundant to dry.(5)Among the optimization schemes,Scheme 3(water-saving scheme)has the largest planting area for artificial grasslands;The plan that can bear the maximum stock of livestock at the end of the year will change from plan 5(productivity+water-saving plan)to plan 3(water-saving plan)as the incoming water flows from abundant to dry;The plan that can bear the maximum total benefit will change from Plan 4(benefit+water-saving plan)to Plan 3(water-saving plan)as the development scale expands.(6)For alpine desert grassland pastoral areas,with the expansion of development scale and the enhancement of resource constraints,adjusting the proportion of grass planting alone will result in changes in irrigation water consumption,leading to a decrease in the scale of planting and livestock breeding that can be carried,and a decrease in overall benefits.Improving the level of irrigation water will increase production costs and reduce the output of artificial grasslands,but the irrigation water cost will be reduced,which can expand the carrying capacity and have the most significant effect on overall efficiency improvement.It can be seen that improving the level of irrigation water is a necessary path to achieve greater economic benefits.