Impacts Of Insect Intensity On The Relationship Between Vegetation Attributes And Leaf Area Index (LAI)

Forest insect has been known as the "Fire without Smoke" due to their major damages on forest resources and therefore is of great significance for ecosystem safety.Current remote sensing based monitoring of forest insect outbreak mainly focus on its distributions,reasons and consequent influences on productivity.Using insect outbreak data acquired at British Colombia in Canada over 2002-2012,we here provide an analysis on the impacts of insect intensity on relationship between leaf area index(LAI)and the normalized difference vegetation index(NDVI)and the enhanced vegetation index(EVI),further,the relationship between leaf area index(LAI)and the gross primary productivity(GPP)and the gross primary productivity(NPP).We showed that for pixels converting from light to moderate and from moderate to severe,correlations between LAI and NDVI became higher first,then lower after evidently and correlations between LAI and EVI became higher consistently.Furthermore,for severe affected regions,the correlation became stronger.EVI-LAI correlation was much higher than NDVI-LAI for the pixels belonging to same intense groups.No result shows which is stronger between the GPP-LAI and the NPP-LAI relationships after finding the fact that the two kinds of relationship,GPP-LAI and NPPLAI,both intend to become more significant with the forest pest severity being worse.Our results provide a good reference for the future assessment of insect damage on ecosystem function using remote sensing observations.