CAREER: Effects of Prolonged Droughts, Severe Fires, and Forest Parasites on Regional Ecosystem Pattern in the Rocky Mountains Over the Past 5,000 Years

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Climate change is an ongoing outcome of human activity. Regions such as the Rocky Mountains have already experienced significant warming in the past decade. The warming has reduced snowpack and related runoff, facilitated extensive forest damage from insects and other pathogens, and increased areas burned by wildfires. Such effects on water and ecosystems are likely to generate substantial societal challenges for decades or longer, but are poorly understood and hard to predict. Characterizing past climate changes and their impacts provides a means to place such regional changes in a long-term context and to anticipate how such impacts on ecosystems and the goods and services they produce will continue to develop in the future. This project focuses on the role of disturbances (i.e., fires and forest-parasite infestations) in mediating vegetation responses to persistent droughts over the past 5000 years. The goal is to document the types of interactions and regional differences that can influence regional responses to climate change. To do so, the project will study sediments from six lakes in the Park Range of northern Colorado, which were chosen to represent different aspects of the region. Sedimentary evidence of episodes of low lakes-levels in the past will be used to document past droughts, and then will be compared with fossil evidence of vegetation change, forest fires, and forest-parasite outbreaks to document possible climate-disturbance-vegetation interactions and their spatial patterns. Two lakes are located at the lower margins of the range near the border between pine forests and sagebrush steppe, two are within dense pine forests at mid-elevations, and two are within open forest parklands at high elevations along the Continental Divide. The results will show how the lower border between forest and steppe was shifted through time by drought, fire, and parasites, and how the density of forest cover at mid- and high-elevations affected the sensitivity of fire regimes, and thus forest composition, to climate change. Climate change is altering the patterns of ecosystems from local to continental scales. Because changes in precipitation, vegetation, and fire regimes in the Rocky Mountains during the past decade have been dramatic, the project will document these recent changes with repeat photography, and then place the changes in a long-term context via studies of ancient climate changes and their impacts on the forested landscape. To enhance public understanding of climate change impacts, the results of the study will be displayed and explained in an on-line atlas of environmental change in the Rockies along with photography of the ongoing changes in the region (using new photos as well as others taken more than ten years ago). The photos and other results will be made available through a web-based atlas of environmental change in the region, which will be designed to aid K-12 teachers in understanding and explaining the geography and potential outcomes of climate change.