Study On Hyperspectral Characteristics And Hazard Level Evaluation Model Of Jujube Canopy Under The Damage Of Tetranychus Truncatus

Ziziphus jujuba is a unique economic forest tree species in China,Xinjiang’s unique photothermal resources are very suitable for jujube planting,so it is known as "the world jujube to see China,Chinese jujube to see Xinjiang ".With the rapid development of forest and fruit industry in Xinjiang,in recent years,Xinjiang jujube production accounts for nearly 40.0%of the national output,becoming the largest province in the country.However,due to the low level of field management and the lack of plant protection measures,the annual jujube planting area will have a "red spider "—Tetranychus truncatus pest,which seriously affects the jujube yield.In this paper,the spectral estimation model of physiological parameter content and hazard grade of jujube canopy under pest stress was constructed by combining field canopy spectral determination and indoor physiological parametric chemical analysis,The main results are as follows:The spectral characteristic analysis of jujube canopy showed that the general trend of the spectral characteristic curve of jujube healthy plants was basically consistent with that of plants under pest stress,but the spectral characteristics of canopy under pest stress in different hazard periods were obviously different.It is mainly manifested in the near infrared region that Early outbreak>Outbreak period>Late outbreak,During the same period,with the increase of pest grade,the spectral reflectance of canopy decreased gradually,and the values of chlorophyll content and water content of jujube decreased accordingly.It can be found that"blue shift" occurs in the differential spectrum of red edge position after the first order derivation of canopy spectrum.Through correlation analysis,the first order differential treatment can effectively improve the correlation between the physiological parameters of j ujube crown and the canopy spectrum.There are spectral sensitive bands in hazard period.The sensitive bands of chlorophyll content in the early,late and the canopy were mainly concentrated at 1 501～1606 nm、480～349 nm and 1 501～1 749 nm、550～850 nm and 1 173 nm,The sensitive band with canopy water content is mainly concentrated in 1 550～1 770 nm and 2 224 nm、1214～1 220 nm and 1 600～1 779 nm、550～1 200 nm.The first function,quadratic function,exponential function and multivariate stepwise regression model are established by using the sensitive band.The correlation analysis between canopy spectrum and hazard level showed that the sensitive bands of canopy spectrum and hazard level were mainly concentrated at 750～900 nm、1 000～1 349 nm and 2 220～2 349 nm,This coincides with the spectral sensitive band of jujube physiological parameter sieve.As a result,physiological parameters and spectral sensitive bands were selected as independent variables and hazard grade as dependent variables.Fisher discriminant analysis was used to construct a spectral estimation model for the hazard grade of jujube crown under the harm of truncated leaf mites.The accuracy reached 76.30%.