The mountain pine beetle (Dendroctonus ponderosae Hopkins) is native to pine (Pinus) forests throughout western North America. Periodic population eruptions occur when an abundance of susceptible host trees coincides with climatic conditions amenable for beetle survival (e.g., Taylor and Carroll 2004). Although epidemic populations are a natural component of forest disturbance, large infestations have substantial impacts and provide unique challenges to forest managers (Safranyik et al. 1974; Safranyik and Carroll 2006). At present, Western Canada is experiencing the largest mountain pine beetle epidemic on record. By 2006, over 9 million ha of lodgepole pine forest had been infested (Westfall 2007).
To date, stand-scale mountain pine beetle relationships have been used to develop landscape-scale management models (see Nelson et al. 2006c for a discussion). However, using relationships observed at a stand scale for landscape-scale management may be problematic as the general principle of ecological fallacy indicates that relationships do not necessarily hold across spatial scales (Wiens 1989; Levin 1992). By locating and exploring high-intensity infestations (termed “hot spots”in this paper), it is possible to characterize landscape conditions favourable for hosting large beetle populations. Such analysis is important in improving our knowledge of mountain pine beetle dynamics over large areas.
Our goal is to present an exploratory spatial data analysis approach that characterizes the nature of the environment associated with the most intensely infested locations. Following a growing trend in geographic data analysis (e.g., Fotheringham et al. 2000; Le Gallo and Ertur 2003), we explore and describe trends in the associations between hot spots and the environment as a first step towards developing hypotheses for further testing. To begin, we demonstrate a practical method for identifying hot spots over the landscape. This method is designed for use with point data collected from a helicopter where visual estimates on insect species and number of affected trees are recorded (Wulder et al. 2004; Nelson et al. 2006a). We also examine hot spots using data on management activity. Our methods are demonstrated for a Timber Supply Area (tsa) in British Columbia. Analysis carried out on a data set spanning 8 years of insect activity highlights how these methods can be used to investigate the changing interaction between beetles and the environment over the course of an infestation. The methods we outline can be applied in any forest management area; however, by demonstrating our approach on a specific tsa , we generate new information on the spatial and temporal trends associated with intense infestations over large areas.
Download
PDF Ebook Environmental characteristics of mountain pine beetle infestation hot spots
