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Vulnerability of landscape carbon fluxes to future climate and fire in the Greater Yellowstone Ecosystem


Smithwick, Erica A. H.; Westerling, Anthony L.; Turner, Monica G.; Romme, William H.; Ryan, Michael G. 2011. Vulnerability of landscape carbon fluxes to future climate and fire in the Greater Yellowstone Ecosystem. In: Andersen, C., ed. Questioning Greater Yellowstone's Future: Climate, Land Use, and Invasive Species; Proceedings of the 10th Biennial Scientific Conference on the Greater Yellowstone Ecosystem; October 11-13; Yellowstone National Park. Yellowstone National Park, WY: Yellowstone Center for Resources. 9 p.

More frequent fires under climate warming are likely to alter terrestrial carbon (C) stocks by reducing the amount of C stored in biomass and soil. However, the thresholds of fire frequency that could shift landscapes from C sinks to C sources under future climates are not known. We used the Greater Yellowstone Ecosystem (GYE) as a case study to explore the conditions under which future climate and fire regimes would result in tipping points of C source-sink dynamics. We asked: How great a change in climate and fire regime would be required to shift conifer forests in the GYE from a net C sink to a net C source? To answer this question, we developed downscaled climate projections for the GYE for three general circulation models and used these projections in a dynamic ecosystem process model (CENTURY version 4.5). We simulated C storage to year 2100 for individual forest stands under three fire-event pathways (fires at 90, 60, or every 30 years) and a reference simulation (no fire, representing the historical fire interval) under both future and current downscaled climate scenarios. Our results show that fire intervals less than approximately 90 years will cause lodgepole pine (Pinus contorta var. latifolia) forest stands to shift from a net C sink to a net C source, because the time between fires would be less than the time required to recover 85 percent of the C lost to fire. The capacity for fast post-fire regeneration of lodgepole pine from an aerial seedbank (serotinous cones) and the projected increase in lodgepole pine productivity under warmer climate conditions would not counter the consequences of fire-return intervals that were less than 90 years. In all future climate scenarios, decreases in fire-return interval are likely to reduce the potential of the GYE landscape to store C. The magnitude of this shift will depend on the future distribution of forest and non-forest ecosystems across the landscape, other constraints on fire patterns not considered here (fuels, ignition factors, and landscape management), and the accuracy of the fire-climate model as future climate diverges increasingly from the past.

Keywords: terrestrial carbon, climate warming, fire, Greater Yellowstone Ecosystem (GYE)


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Title: RMRS Other Publications: Vulnerability of landscape carbon fluxes to future climate and fire in the Greater Yellowstone Ecosystem
Electronic Publish Date: September 19, 2011
Last Update:
September 19, 2011

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