The association between stand and landscape level factors and red turpentine beetle damage in different infestation stages

Abstract

The red turpentine beetle (RTB), an invasive pest species, has infested large areas of pine forests and caused extensive tree mortality in North China. The ensuing substantial economic and ecological losses make understanding the development and spread of RTB infestations critical. Although some studies have postulated how multiple factors affect bark beetle damage at different stages of population development, knowledge about this mechanism from empirical research is still limited. In recent years, RTB infestations in Heilihe Town of Inner Mongolia and Dahebei Town of Liaoning Province were at different phases (incipient and epidemic stages), which allowed us to explore the possible change mechanism of influencing factors. The present study aimed to identify the critical factors influencing RTB damage and determine whether the primary influencing factors changed during different RTB infestation stages. We established 42 and 40 sample plots in the Heilihe and Dahebei areas and measured the sample plots’ canopy cover, slope, aspect, average diameter at breast height (DBH), elevation and RTB attack rate. Sentinel-2 images and trap data were used to obtain landscape-level variables, including host area, edge density and beetle pressure. We then developed generalized linear models to determine the impact of these explanatory variables on RTB damage. Our results found that the average RTB attack rate of the incipient and epidemic areas was, respectively, 5.35% and 31.45%. At the incipient stage, RTB infestations were mainly related to stand-level factors, including canopy cover and aspect. However, at the epidemic stage, RTB infestations were associated with stand (DBH) and landscape-level factors, in which host area and beetle pressure played an important role. Stand and landscape-level factors played diverse roles during different periods of RTB infestations. Such findings are valuable for understanding the colonization pattern of RTB and taking appropriate management interventions in different infestation stages.