The Effects of Landscape Structure and Stand-Scale Factors on Dendroctonus Valens Damage Under Disturbance Conditions in North China

Abstract

Background In recent years, the red turpentine beetle (Dendroctonus valens, RTB), an invasive pest species has spread northward along the distribution of pine forests, forming a potential threat to healthy pine forests in North China. Previous studies have shown that natural (e.g., fire) and human (e.g., felling) disturbances can significantly promote bark beetle damage. However, few studies have considered the effect of multi-scale factors on bark beetle damage under disturbance conditions. Here, we investigated RTB damage (entrance holes) in 98 forest stands with and without disturbance (fire or stolen felling) in the Heilihe National Nature Reserve, Inner Mongolia, which is considered to be in the early stage of RTB outbreak. We assessed the effects of forest landscape structure (forest proportion and host connectivity) and stand-scale characteristics on RTB damage under different disturbance conditions (presence or absence). In addition, we also explored the effects of fire and stolen felling disturbance on RTB damage and the significant differences between them. Result Disturbance (i.e., fire and stolen felling) could significantly promote the occurrence of RTB and there was no significant difference between the two types of disturbance. In the absence of disturbance, small stand-scale factors (i.e., aspect and canopy cover) played important roles in the prediction of RTB damage. In the presence of disturbance, forest proportion within a radius of 250 m was the main factor affecting RTB invasion. Higher forest coverage could reduce the migration of RTB from the surrounding environment to the disturbance area, thus reducing RTB damage. In addition, we observed a positive relationship between elevation and RTB invasion. Conclusion Landscape structure and stand-scale factors had different effects on RTB invasion under different disturbance conditions. This study not only provides new insights into understanding the roles played by multi-scale factors in RTB damage but also assists in the implementation of pest management programs.