Evaluating the habitat factors of Pristiphora laricis infestation: an information load model

Larch defoliation by Harig (Pristiphora laricis) has caused great damage in China. In this study, an attempt is made to analyze the relationships between Harig infestation and various habitat factors via the analysis of representative needles and other environmental metrics that were collected from Saihanba Mechanical Forestry Farm of Hebei Province between 2007 and 2010. The population density per tree (PD), the percentage of insect-infected trees in one sample plot (PIIT), and the infected area (IA) are treated as dependent variables when analyzing the degree of infection. The study concludes: PD and PIIT differ significantly between areas with varying species composition; canopy density and stand density negatively correlate with PD; Harig appears not to infect young growth; and infections have the tendency to spread to high altitudes. In order to provide a basis for macro prevention and control of insect attack, the habitat factors most closely related to the occurrence of insect attack are inputted into an information load GIS model to estimate the potential damage from infection.