The Method Of Grassland Quality Evaluation Based On Jilin-1

Because over the years for unreasonable development and utilization of grassland resources,cause as a solid foundation for the development of grassland animal husbandry in our country has experienced different degree of degradation,degradation of grassland area accounts for some 90%of the national scope of the grass.In order to better monitor the situation of grassland,this study introduced red-edge band to construct synthetic index to timely and accurately grasp the growth status of grassland.The red-edge spectrum can obviously reflect the vegetation affected by diseases and insect pests,and the background influence has little interference to it.Finally,the grassland quality index synthesized by principal component analysis was used to evaluate the grassland.This study took Tongyu County Xianghai Nature Reserve as the research object,and used the index method of principal component analysis and synthesis of normalized vegetation index（NDVI）,normalized difference red edge index（NDRE）and red edge chlorophyll index(CI_red-edge)commonly used in remote sensing to monitor vegetation to evaluate the grassland in the study area.This paper evaluates the grass quality based on the red edge band for the reflectivity of leaves.The data of Jilin-1 satellite 04-07 in 2018 and Spectral 02 in 2021 in May and August were used for calculation.Meanwhile,taking Jilin-1SP04-07 satellite as an example,different grassland grade ranges were counted and the results were verified.The remote sensing images of Jilin-1 Spectral 02 satellite in May and August were supervised and classified,and the latest land use map was formed based on the grassland area of the third National land survey.The whole grassland area was extracted from the land use map,and the single vegetation index was calculated,and then the grassland quality index（GQI）was constructed according to the principal component analysis.The results show that the effect of the composite index map of Spectral 02 satellite in May with the introduction of red-edge band was better than that in August,which was caused by the difference of month and band selection.In August,the grassland entered the dry grass season and the red-edge band was not introduced,so the result was worse than that in May.Based on the pickled film extraction of Jilin-1SP04-07 remote sensing images of grassland,a single vegetation index was calculated according to the characteristics of B4 red-edge band and the grassland quality index（GQI）was constructed.The grassland quality was graded according to the Jilin-1SP04-07 satellite image:1.In the reserve,80%of the grassland quality is at the medium level,which is widely distributed everywhere.2.The proportion of good grassland quality is about 15%,mainly located in the central and southern region of the reserve;3.The poor areas in the protected area tend to be scattered,and most of the land types are saline-alkali land and sandy land with serious land degradation and insufficient water supply.In order to further verify this result,biomass was measured at selected sample points in the study area and verified by comparison with field biodiversity measurement methods.A total of 26 sample points were selected in the study area.In order to prevent individual differences,a buffer zone was established with each sample point as the center and a radius of 50 meters.Then,GQI values of 3 sample points were randomly selected in the buffer,and the calculated average value was the quality index of the sample points.The calculated Pearson,Kendall and Spearman correlation coefficients were 0.752,0.680 and 0.807,respectively,indicating that biomass was closely correlated with GQI index,which further confirmed the rationality of this index.Finally,the results of Jilin-1SP04-07 satellite synthesis were compared with the results of previous studies and relevant data,and it was proved that the comprehensive index GQI was basically consistent with the grassland growth in Xianghai Nature Reserve.Grassland quality index（GQI）is of practical significance for monitoring grassland growth status timely and accurately,and can be used as a dynamic indicator of grassland monitoring,which is beneficial to the development of animal husbandry and ecological environment protection in north China.