Study On The Relationship Between The Locust Plague And Vegetation Spectrum In Ar Horqin Banner,Inner Mongolia Autonomous Region

Grassland is one of the important natural ecosystem types.It is not only important geographical barrier,but also the largest surface protecting natural defenses.It plays an integral role in the protection of ecological environment and biodiversity conservation.But in recent years,due to a variety of reasons,such as abnormal climate and human activity causing the deterioration of ecological environment.The locust plague in Inner Mongolia occurred frequency,gradually increased,and seriously hindered the normal growth of grassland vegetation and animal husbandry in the healthy development of the local herdsmen caused serious economic losses,affecting autonomous region the healthy development of animal husbandry and grassland ecology.Ar Horqin Banner is one of the locust plague prone areas in Inner Mongolia Autonomous Region.It has different degrees locust plague every year.Taking this as the research region,we study on the relationship between locust plague and vegetation index NDVI,and establish the relation model between grasshopper population density and NDVI.It is can provide the scientific basis and data support for the locust plague monitoring and early warning research.This paper takes MODIS data as basic data,using MRT and ENVI software to perform a series of preprocessing of MODIS image data,including format transformation,projection transformation and geometric processing.Inversion of the vegetation index value,namely the normalized difference vegetation index NDVI.The characteristics of the spatial and temporal changes of NDVI in the Ar Horqin Banner were analyzed to reveal the relationship between the occurrence of locusts and the growth of vegetation.Taking vegetation spectral data as an entry point,a model for the relationship between locust population density and NDVI was established.Based on the above studies,locust distribution map is extracted from MODIS remote sensing image to realize the monitoring of large scale of locust plague.After a series of studies,the following conclusions are drawn.(1)The area of locust plague and the area of severe locust plague had the highest correlation with NDVI in August,which were-0.88(p<0.05)and-0.977(p<0.01).The disaster-prone areas are in the north central region,which provides suitable habitat and food plants for grasshoppers.This is consistent with the actual situation.(2)The original spectral curve of the vegetation in the high insect population density gradually tends to be horizontal in the"green peak"to"red valley"bands.At the same time,The spectral reflectance of vegetation is significantly decreased in the near infrared band.The"red edge"shifted to the short-wave direction to the left,and the"blue edge"shifted to the long-wave direction to the right.The"red edge"slope is significantly lower.Vegetation caused changes in leaf structure due to grazing by locusts,which affected the pigment content.Vegetation appeared“chlorosis”.The“green peak”moved 2.8 nm to the long wave direction,resulting"red-shift".The area of green peak was reduced by 13.9%.The position of"Red Valley"of the vegetation with the population density of 80 head/m~2 was shifted to 4.0nm in the short-wave direction,resulting in a"blue-shift",and the reflectance increased,that is,the change rate of Red Valley is 84.9%.Change law of vegetation spectral curve in accordance with diseases and insect pests.(3)The description of vegetation growth with only single or multiple single band data cannot meet the needs of the research.In this paper,through the band calculation,the average reflectance values of the 650-670nm and760-850nm wavelength bands are taken as the reflectance values of the red and near-infrared bands,respectively,and the NDVI values are calculated.In order to eliminate part of the human factors,the NDVI variation is used.The equations were fitted to the population density of locust worms and a relational model wasestablished.The bestfitting model was Y=54.42+402.311X-1471.66X~2(R=0.999,P=0.003),where Y was the population density and X was NDVI variation.Based on the changes of NDVI in the July to August in the MODIS remote sensing image of Ar Horqin Banner,and the classification standard of the plague locust,the regional map of the locust infestation was made,and the large scale monitoring of the locust plagues was completed.