Fire and Carbon Storage in Forests

Collaborators: Bill Romme, Colorado State University; Monica Turner, University of Wisconsin; Dan Kashian, Wayne State University; Erica Smithwick, Pennsylvania State University; Dan Tinker, University of Wyoming

Understanding the interactions between climate, fire and forest characteristics-- and how carbon dynamics are affected by these factors--remains an important challenge in ecology. As the size and severity of fires in the western US continues to increase (Westerling et al. 2006), it has become increasingly important to understand carbon dynamics in response to fire. In this study, we investigated these key interactions in the landscape of Yellowstone National Park (YNP). We asked how initial post-fire heterogeneity in forest structure (especially tree density and stand age) controls carbon dynamics over the full life cycle of individual forest stands, and how climate-mediated changes in the fire regime might potentially alter the behavior of the YNP ecosystem as a net sink or source of carbon in the global carbon cycle. We focused on net ecosystem production (NEP), which is the annual net change in carbon stored in the ecosystem— that is, the difference between net primary production (NPP) and heterotrophic respiration. Our research embraced a landscape perspective by considering how NEP varies with spatial variability in structure and forest development. To address our overarching question, we combined a broad-scale chronosequence study of 77 stands distributed widely across the YNP landscape with simulation modeling that incorporated projected climate change. We also developed new allometric equations to predict biomass of the lodgepole pine trees in this region, since existing equations (developed in other regions) were found to be inadequate. Our research has produced one MS thesis (Arcano 2005), two peer-reviewed journal articles to date (Kashian et al. 2006, Smithwick et al. 2008), one submitted manuscript (Tinker et al. Submitted), two in draft form (Kashian et al. Draft, Smithwick et al. Draft), and six manuscripts are in preparation. Major findings: In a landscape characterized by a natural stand-replacing fire regime, equilibrium carbon storage will change only minimally--as long as the forest regenerates after a fire (Kashian et al. 2006). The carbon lost in the 1988 fire and in the subsequent decomposition of the trees killed in the fire will be recovered quickly, relative to the current fire interval (See final report for figure). Climate change projected for the next 100 years in YNP (more precipitation and warmer temperatures) will increase the production and carbon storage of YNP lodgepole pine forests (Smithwick et al. 2008). Carbon storage on the YNP landscape would be reduced only if stand-replacing fires become much more frequent (e.g., return intervals < 50 yrs) than is projected (Smithwick et al. 2008). Recovery of the carbon lost in the 1988 fires is projected to occur in 100-230 years, depending on modeling approach used and the simulated post-fire stand density (Smithwick et al. 2008). Recovery of nitrogen content in post-fire lodgepole pine ecosystems mirrors that of carbon, and forests > 100 years old do not appear to be nitrogen limited (Smithwick et al. submitted). Allometric equations developed for this study reflected the effects of age and tree density and performed better than other published equations for lodgepole pine ((Tinker et al. submitted). Chronosequence studies are not perfect, even in a ‘pristine’ landscape such as the Yellowstone plateau.		Dan Kashian and Bill Romme Dan Tinker
Publications and Presentations MG Ryan, Kashian DM, Smithwick EAH, WH Romme, MG Turner and DB Tinker. 2008. Final Report, Carbon cycling at the landscape scale: the effect of changes in climate and fire frequency on age distribution, stand structure, and net ecosystem production. JFSP Project Number: 03-1-1-06 Smithwick EAH, DM Kashian, MG Ryan and MG Turner. In Press. Long-term ecosystem nitrogen storage and soil nitrogen availability in post-fire lodgepole pine ecosystems. Ecosystems, December 2008. Tinker DB, RM Arcano, MG Ryan, DM Kashian, and WH Romme. Allometric model development and biomass partitioning in lodgepole pine forests near Yellowstone National Park, WY. Submitted to Forest Ecology and Management, July 2008. Smithwick EAH, MG Ryan, DM Kashian, WH Romme, DB Tinker and MG Turner. Modeling the effects of fire and climate change on carbon and nitrogen storage in lodgepole pine (Pinus contorta) stands. In Press, Global Change Biology (December 2007). Kashian DM, WH Romme, DB Tinker, MG Turner, and MG Ryan. 2006. Carbon storage on coniferous landscapes with stand-replacing fires. BioScience 7:598-606.
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