Collaborative Research: Understanding the potential for a climate change-driven critical transition from forest to chaparral

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The frequency and severity of wildfires is changing throughout much of the West, impacting humans and forest ecosystem services and the rate of forest recovery after wildfires. These altered wildfire rates and forest recovery patterns may force the dominant vegetation permanently to shift from forests to shrubs. The 25-million acre (10 million hectare) Klamath region of Oregon and California is an area of particular concern. A shift from forest to shrub would impair the ecosystem services of the forest that benefit humans, impair unparalleled botanical diversity of the Klamath region (for example, there are 29 species of conifer trees that support associated assemblages of other plants and animals) and release massive amounts of greenhouse gasses as these high-carbon sequestering forests transition to low-carbon content shrub-chaparral. The scientists working on this project will evaluate the potential for a forest to shrub transition in the Klamath and collaborate directly with the U.S. Forest Service to identify robust strategies for ecosystem management in the face of climate change. Including the participation of Forest Service decision-makers, who manage 80% of the Klamath region, will ensure the transparency and credibility of the science, thereby increasing its impact on environmental outcomes.This project will test the general hypothesis that climate may drive a critical transition in the Klamath from a high-biomass conifer forest dominated region to a self- low-biomass shrub-chaparral-hardwood dominated region because of increased fire activity and decreased forest recovery rate. The project will quantify the potential for, and mechanisms underlying, a climate induced transition using a three-pronged research approach: (1) development of general mathematical models to gain a broad understanding of dynamics underlying critical thresholds in fire-prone ecotones and to identify the functional relationships that control transitions between shrub-chaparral-hardwood and mature conifer forest, at local and landscape levels; (2) field research to characterize the climate- dependence of post-fire recovery and to test and parameterize models; (3) process-based simulations of local, landscape, and regional dynamics to characterize the interactive roles of climate, fire, and management in shaping the region's ecological communities. Improving understanding of critical transitions has been recognized as a fundamental challenge in ecology with global relevance and urgency in the face of climate change. Increased understanding of the potential for a critical transition in the Klamath region will inform the management of fire-prone forests worldwide.