Heterogeneity of forest landscapes and the distribution and abundance of the southern pine beetle

A fundamental and unanswered research question in landscape ecology centers on how the spatial arrangement of ecosystems influences the distribution and abundance of organisms across complex landscape mosaics. In this study our god was to examine how the southern pine beetle (SPB) perceives and responds to heterogeneity in forest landscape mosaics. The study was based on the use of extant knowledge of SPB's natural history and a spatially referenced database that included explicit information on landscape structure as well as distribution and abundance of the insect. Both the content and context of the spatial elements forming the forest landscape were considered, as human-caused fragmentation and natural disturbances create mosaic patterns where the specific arrangement of components can enhance or inhibit herbivory by the SPB. To examine how heterogeneity influences epidemiology of the SPB, we identified the elements of landscape structure that serve as targets for SPB. The principal targets include three types or arrangements of host trees: acceptable species, susceptible habitat patches, and lightning-struck hosts. Using a spatial database and a statistical approach we evaluated the number and arrangement of these targets in the context of existing population centers. The product was a functional heterogeneity map that portrayed how the spatial arrangement of landscape elements (habitat targets) influences the distribution and abundance of the SPB across complex mosaics of ecosystems. (C) 1999 Elsevier Science B.V. All rights reserved.