Integrated Ecological Assessment Of Farmland System And Trade-offs Analysis Of Functions

As the development of ecological civilization construction,homeland security,ecological security and food security have become a prominent problem for the sustainable development of China.There have been long-standing problems that paying more attention to the quantitative factors rather than qualitative and ecological ones during the exploitation of land resources.At present,the management,protection and research of cultivated land resource are mainly focused on the quantitative and qualitative factors,thus the externality and multi-function features of the cultivated land are being overlooked,so are the integrity,openness and dynamics of the farmland ecosystem.However,there is no consensus in terms of the definition of the farmland system,ecological assessment and ecological stewardship,nor a perfect system of scientific research for them.Therefore,this thesis makes a verifying research on the theory framework,index system,which integrated ecological assessment,trade-offs analysis and ecological stewardship to suffice the demand of the land management and the protection of cultivated land.Da’an City in Jilin province is taken as the study area in this thesis.The theories,methods and results from this study are of scientific reference and decision support for the trinity protection with regard to quantity,quality and ecology for cultivated land resource.The research has important theoretical and realistic significance for regional sustainable development.Specifically,the contributions from this study are as follows.(1)The study develops a theory framework for multi-level ecological assessment of farmland system.It makes a systematic explanation on the conception,connotation and characteristics of the farmland system,and defines the contents,principles and general evaluation program of the farmland system ecological assessment.Based on the trinity protection of farmland system,this study discusses the ecological function,production function and living function of the farmland system,and establishes the theoretical framework.It also proposes the theory and model in the conflict and coordination of farmland system functions.The framework of integrated ecological assessment is proposed on the basis of the framework of ecological evaluation system of farmland system,which is derived from ecological security,ecological health and ecological service respectively.(2)The study establishes a multi-scale ecological evaluation index system for farmland system.Based on the characteristics of farmland system and guided by the demands in the reality,this index system brings up a guiding ideology and principles.For the safety,this index system establishes the ecological security assessment index system on the basis of geological,hydrological and biological security;for the stress,stability and structure,it establishes the ecological health assessment index system on the basis of environmental quality,and farmland landscape and spatial structure.For the "ecological-production-living";it establishes the ecological service assessment index system from the functions.And then,it analyzes the spatial scale characteristics of the various indicators and the relationship of the index systems,and introductions the determination and calculation approaches of each indicator.(3)The study carries out multi-aspect research upon the integrated ecological assessment of farmland system.It presents the process and method of the farmland system partition from the perspectives of the farmland ecosystem,the agricultural production system and the socio-economic system.The weight of each index of ecological security and ecological health is determined by the combination of subjective and objective methods,including sorting method,entropy weight method and analytic hierarchy process.The ecological security index and ecological health index are derived from the calculation leveraging comprehensive index method and TOPSIS model.And the ecological service value with regard to each function of each farmland system and the whole study area is estimated respectively by a combination method of matter and value quantities.The results indicate that,the ecological security of the farmland system is at the safe rating,the geological safety is in good condition,the hydrological safety is basically stable,but the biological safety is comparatively low;the ecological health of the farmland system is in the healthier rating,the environmental quality is comparatively good,and the spatial structure is organized to a certain extent,whereas the stability of the farmland landscape is somewhat weak.The ecological service of the farmland system is above-average.The results of the dominant function show that the predominant function of the farmland system is the production function,the followed by ecological function and assisted by living function.(4)The study analyzes the multi-dimensional trade-offs with regard to ecological-production-living functions of farmland system.It proposes the method of trade-offs and synergies analysis of ecological-production-living function of the farmland system.It analyzes the cultivated land quality and production capacity in the study area,and conducts comparative analyses towards the ecological assessment index of the farmland system and the average grain output.It makes the trade-offs and synergies of ecological-production-living functions of the farmland system utilizing the integrated ecological assessment result.The results show that,precipitation is the main limiting factor affecting the cultivated land productivity,underground water resources and irrigation are the main factors ensuring food security,the drought obviously influences the agricultural production,and good habitat quality plays a positive role in improving the production capacity.The soil environmental quality is the foundation of the farmland system for production capacity.But the farmland system is affected by the stress from saline-alkali land and construction land expansion.The applications of the chemical fertilizers and pesticides are positive for promoting the grain production,but also bring more pollution to the farmland.The food supply service is still the most important function of the farmland system,the crop pollination and soil conservation conditions can influence grain production,and the biomass energy supply is associated with the growth of crops.The consumption of water resources is mainly caused by agricultural production in the study area,so the relationship between the need for water supply and food production needs to be coordinated.Through the analysis of outliers and Trade-off index(TOI),about 10%of the farmland systems has abnormal ecological status,so the ecological-production-living functions need to be balanced.By comparing with the regional average level,improving ecological function,stabling living function and controlling the production function are the main directions to optimize the farmland system functions.Finally,the paper comes up with the ecological function regionalization scheme of farmland system.(5)The study builds a multi-channel trinity ecological stewardship of farmland system.It elaborates the definition and connotation of ecological stewardship of farmland system.The main objective of ecological stewardship is achieving the trinity protection of cultivated land,and the ultimate goal is enabling the farmland system to be used sustainably.And the trinity integrated ecological stewardship of the farmland system is constructed from a variety of ways such as legal,economic,political,and technology.Finally,the implementation strategy of farmland management is provided from the fields of ecological security pattern,ecological farmland construction and ecosystem service management.