Study On Grassland Quality Grading Method

Grassland is the largest terrestrial ecosystem and strategic resource in China,and an important component of the life community of mountains,rivers,forests,farmlands,lakes,grasslands and deserts.As the main body of the national green ecological security barrier,grassland has important ecological functions such as soil and water conservation,wind prevention and sand fixation,carbon fixation and oxygen release.At the same time,grassland,as the basis for the development of animal husbandry,has important production and living functions.In addition,in the context of the development of the national concept of big food,scientific and rational use of grassland is of great significance for grain saving and efficiency improvement,ensuring national food security and realizing a win-win situation of grain and grassland.To find out the quality and distribution of grassland is not only the basis for realizing the protection and rational utilization of grassland,but also the requirement for implementing the construction of ecological civilization.It is also an important measure to improve the grading and grading price evaluation system of natural resources assets and implement the 20th National Congress of the Communist Party of China"Pursuing green development and promoting harmonious co-existence between humanity and nature".Based on the provincial pilot work on grassland grading in Shaanxi Province,this study takes the difficulties and problems encountered in the pilot work as the source of practical experience,uses the data from the 2020 annual land change survey,meteorological observation data,soil survey data and digital elevation model of Lintong District as data sources,takes natural grassland and other grassland as research objects,adopts the factor method to comprehensively select evaluation indicators affecting the natural quality of grasslands according to the actual situation in Lintong District and combines with expert arguments,and scientifically determines the weights of grassland grading evaluation indicators based on the Telfer method to construct an evaluation indicators system for grassland grading.The basic data on grassland quality grading are collected through multiple channels such as field surveys and departmental discussions,and multiple data sources are compared to determine the optimal data sources and data processing methods,to scientifically assign values to the attributes of grassland quality grading indicators,and to use the equal spacing method to classify grassland grades and complete the analysis of grassland quality grading in Lintong District.The main research results are as follows:（1）The natural resource zoning of grassland grading in Shaanxi Province is proposed to be divided according to two major zones,the warm temperate humid and semi-humid zone and the subtropical humid zone.（2）According to grassland grading evaluation indicators,grassland vegetation degradation,grassland desertification,grassland salinization and other ecosystem succession outcome indicators are considered inappropriate to be included in the evaluation indicators system.Based on the practical experience of the pilot work,this study established a grassland grading evaluation indicators system consisting of five factors and eight indicators:climate（average annual temperature A₁,average annual precipitation A₂）,terrain（slope B₁,slope direction B₂）,soil（effective soil layer thickness C₁,soil texture C₂）,resource（grassland comprehensive vegetation coverage D₁）and biodiversity（biodiversity E₁）.（3）According to the weight of grassland grading evaluation indicators,Delphi method are used to determine the weight.It is concluded that the grassland grading score can be calculated according to the following formula:the total grassland grading score=A₁×0.1278+A₂×0.1589+B₁×0.1222+B₂×0.0944+C₁×0.1333+C₂×0.1101+D₁×0.1289+E₁×0.1244.（4）According to the data source and processing method,it is suggested to adopt the measured data of Meteorological Bureau for climate factors.When taking districts and counties as research areas,considering the small differences in climatic conditions within the regions,unified evaluation can be carried out.Due to the obvious difference of soil factors in different soil conditions,it is suggested to use grassland soil survey data as data source.In order to unify the data source of the same factor,it is suggested to adopt the digital elevation model as the data source for terrain factor,and obtain specific indicator data through Arc GIS surface analysis function.It is suggested that resource factor should be obtained by remote sensing interpretation method,and the interpretation results should be revised by combining with measurement.It is suggested to use multi-factor interpretation combined with field investigation to evaluate and obtain biodiversity factor.（5）The grassland in Lintong District is divided into grade 2 and 3,accounting for57.82%and 42.18%respectively,and the grassland quality is relatively good.In summary,for grassland quality grading,data acquisition difficulties are the main problem.Grassland system management and protection should be further strengthened,grassland investigation and monitoring should be actively carried out,and a national data interaction platform should be established to improve work efficiency.According to grassland grading evaluation indicators,it is suggested to delete or replace grassland vegetation degradation,desertification,salinization and other indicators,which are consistent with the grading work of garden land and forest land carried out in the same period,and focus on reflecting the natural background quality of grassland.It is necessary to further coordinate and manage the grading work of natural resources,unify the selection principle of natural resources evaluation indicators and equal division,etc.,so as to lay the foundation for the unified management of natural resources in the later period.Combined with the pilot work experience,this study is carried out in order to further optimize the grassland quality grading method,and provide a reference for the development of grassland quality grading in Shaanxi Province and even in the same areas of China.