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Tipping Points and Landscape Vulnerability in the Greater Yellowstone Ecosystem

Funded By: USDI/ Joint Fire Science Program, $ 140,653


Current model projections suggest that, by the end of the 21
st C, climate conditions like those of 1988 (the year of the well-known Yellowstone Fires) will represent close to the average year rather than an extreme year. The consequences of a climate shift of this magnitude for the fire regime, post-fire succession and carbon (C) balance of western forest ecosystems are well beyond what scientists have explored to date, and may fundamentally change the potential of western forests to sequester atmospheric C.  In this project, we hypothesize that vegetation communities will contribute differentially to future landscape C flux because of different sensitivities to future climate and fire combinations, and the net result could qualitatively change the C dynamics of western forests.
 
To explore this idea, we are focusing on the Greater Yellowstone Ecosystem (GYE) to address three overarching questions that are broadly relevant for many Rocky Mountain forests: (1) How great a change in climate and fire regime would be required to shift each of the dominant vegetation communities in the GYE from a net C sink to a net C source? (2) Do current projections indicate that changes of this magnitude are likely to occur in the next century, and if so, where in the GYE do they occur? (3) What are the integrated effects of changing climate, vegetation, and fire on spatial patterns of carbon flux across the GYE landscape as a whole?  


To answer these questions, we are using observed relationships between climate and fire occurrence and downscaled climate data from general circulation models (GCMs) to determine future climate and fire regimes and develop spatially explicit maps of landscape C flux based on individual contributions of vegetation types to future climate and fire – determined from the CENTURY ecosystem model.  


Collaborators:


Monica G. Turner – University of Wisconsin, Madison

Anthony Westerling - Sierra Nevada Research Institute and UC-Merced

William H. Romme - Colorado State University

Michael G. Ryan - USDA Forest Service RMRS