2009 Research Highlights
Two phase transitions are better than one
One goal of landscape research is to identify critical thresholds of landscape patterns that signal phase transitions (abrupt changes) in ecological functions. Scientists have known about one type of phase transition for a long time—the abrupt change from a disconnected to a connected landscape (or vice versa) as a result of random changes in landscape attributes. Scientists with the Eastern Forest Environmental Threat Assessment Center recently identified a second, qualitatively different type of phase transition corresponding to an abrupt change of edge context from interior to exterior (or vice versa). Transitions between exterior and interior edge context have ecological implications including, for example, moderation of the ability of edge-adapted invasive species to permeate a landscape. In related work, researchers were able to show the conditions under which the phase transitions do not occur, which is of interest if prevention of abrupt ecological changes is a goal.
The discovery follows several years of international cooperation with the European Commission Joint Research Center on the development and testing of new spatial pattern indicators from mathematical morphology. That research had earlier identified a new technique to automatically identify and map connecting landscape elements (“corridors”), while fostering international compatibility in assessing forest spatial patterns for reporting.
Contact: Kurt Riitters, acting Forest Health Monitoring team leader, (919) 549-4015, kurt.h.riitters@usda.gov
Partners: European Commission, Joint Research Center, Institute for Environment and Sustainability; USDA Forest Service Southern Research Station
