Study On Early Warning Methods Of Pinus Yunnanensis Damaged By Pests Based On Thermal Infrared Remote Sensing

The area of forest land affected by pests in China is increasing,Tomicus yunnanensis and Tomicus minor have caused serious shoot damage in Yunnan pine forests in the Yunnan Province of China,causing a large number of deaths of Yunnan pine,which restricts the local ecological balance.It is extremely important to realize the early identification of pests.Early detection of forest pests using thermal infrar-ed remote sensing is a research hotspot in recent years.Land surface temperature(LST)can directly est-imate long-wave radiant flux,and can also estimate the latent heat and sensible heat flux affecting the atmosphere,ocean and land indirectly,it is the basic physical quantity for studying the radiation and energy balance of the gas system and the interaction of the earth and air.LST are widely used in forest pest monitoring.This study mainly attempts to explore an early warning system for pests based on tem-perature anomalies in Yunnan.In this paper,the daily variation of temperature of forest land with different degrees of damage is analyzed by the thermal image taken continuously at a fixed position,the study also discussed the distribution of surface temperature;Then,through the Landsat temperature products for many years before and after the pest outbreak,the differences in temperature distribution between healthy forest land and the affected forest land and the temperature difference between healthy forest land and the affected forest land were analyzed.Based on the measured data and NCEP meteorological data,the relationship between the stand parameters and the surface temperature thermal anomaly was verified by the ENVI-met microclimate model;Finally,the research attempts to establish the correlation between the DN value of GF-4 in the mid-infrared band and the surface temperature product(LST)obtained by Landsat datas(level 1),which provides a theoretical reference for obtaining temperature-related products with high spatial and temporal resolution.The main conclusions of the paper are as follows:1)Analysis of the daily variation of the component temperature of the plots with different degrees of damage found that,regardless of the forest temperature or the surface temperature,from 9 to 13 o'clock,the temperature rise of the healthy plots is irregularly changed.,the temperature rise of the shadow surface of the healthy sample gradually increases;Compared with healthy plots,the self-regulation ability of forest temperature and surface temperature of the affected plot is poor,the temperature persistence increases or decreases,and the more serious the damage,the worse the self-regulation ability of the stand;In addition,the use of infrared thermal images to obtain surface temperature information is affected by the type of surface coverage under the forest.2)The analysis of the difference in the distribution of surface temperature grades shows that the average surface temperature of the affected forest land in the dry season is lower than that in the healthy forest land.Before the outbreak of pests in 2013,the temperature difference increased continuously,after the outbreak of pests,the temperature difference began to decrease and gra-dually stabilized;After the severe drought in 2009,the difference in temperature distribution between the affected forest land and the healthy forest land further increased,and then gradually stabilized;Since 2012,the percentage of pixels with higher temperature grades has decreased,and the percentage of pixels with lower temperature grades has increased.However,compared with healthy forest stands,the percentage of pixels with lower temperature grades increased more in the affected forests;In the study of the correlation between stand parameters and surface temperature thermal anomalies,there may be a correlation between tree height,LAI,plant density and other forest stand parameters and surface temperature thermal anomalies.These parameters may mainly affect the surface temperature distribution by affecting the distribution of soil component temperature;At around 12:00,it may be the time period in which the temperature distribution of the victim plot and the health sample are the most different.3)The DN value of the mid-infrared band of GF-4 is linearly related to the temperature product obtained by the Landsat data inversion,with a correlation coefficient of 0.66.This attempt provides a theoretical reference for the generation of temperature dependent parameters with high spatial and temporal resolution.