Southern Pine Beetle Herbivory in the Southern United States: Moving from External Disturbance to Internal Process

Abstract

The southern pine beetle (SPB) (Dendroctonus frontalis) is an important pest of southern U.S. pine forests. During most years, SPB populations occur at low densities and cause little or no damage. However, unpredictable regional outbreaks occur during which tree mortality is extensive and unevenly distributed across a forest landscape. Because the southern forest is a managed, productive ecosystem, SPB outbreaks can have a large impact on forest stakeholders. Although SPB pestilence has led to considerable research, the ecological processes that drive its population dynamics remain uncertain. In this chapter, we discuss how the related concepts of ecological disturbance and systems modeling could be used to address the SPB problem. We describe the importance, scale, and complexity of the system; define our concept of ecological disturbance; and discuss model types that could be applied to the SPB problem. We suggest that characteristics of the system may naturally influence and sometimes impede effective SPB modeling. Specifically, we argue that: (1) instead of conceptualizing SPB damage as an external disturbance, models should be developed that represent SPB as an endogenous property of the system; (2) because the structure and composition of forests are largely driven by human management, it may be useful to model SPB as a coupled social–ecological system; and (3) although the economic importance of SPB naturally drives the need for models that can be used as management and decision support tools, its complex ecology suggests that a broader range of model types is useful to organize, integrate, and communicate data and ideas among researchers.