Dr. Monica G.Turner
Department of Integrative Biology
University of Wisconsin
430 Lincoln Dr.
Madison, WI 53706
Ecosystem and
Landscape Ecology Lab
 


Postfire Carbon Dynamics

Contacts

Monica Turner

Keywords

biomass, net primary production, chronosequence, climate change

Research Overview

Our current research on fire, vegetation and ecosystem processes includes two main projects

described below. We have learned a tremendous amount about nature’s mechanisms for recovery from what people consider “catastrophic” disturbances. Wilderness areas like Yellowstone permit scientists to study ecosystems that have been minimally impacted by humans. Fires are likely to increase in number and size with global warming, and long-term studies may help scientists and land managers anticipate what may happen in the future. For a summary of key findings geared for a general audience, read "Rising from the Ashes" from the Summer 2008 issue of On Wisconsin.

Postfire Carbon Dynamics

With funding from the Joint Fire Sciences Program, we are examining carbon balance across the entire Yellowstone landscape, how it might change under future climates and fire regimes, and how cycles of carbon and nitrogen interact. Climate, fire (frequency and intensity), and forest structure and development are strongly linked, but our knowledge of the interactions of these factors is poor. We lack the ability to make robust predictions about how changes in climate will alter these interactions and change the carbon balance of a landscape. Our objective is to estimate how changes in fire frequency, pattern, and intensity will alter the distribution of forest age and structure across a landscape and how these changes, in turn, will change the landscape carbon balance. We are determining the current carbon balance for the Yellowstone National Park (YNP) landscape and how much carbon was lost in the 1988 fires. We are also determining how NEP will change for the YNP landscape with changes in climate and fire regimes by calibrating the Century biogeochemical model to assess how changes in climate will alter NEP across stand development, and using models developed in past research to simulate fire frequency, fire spread, and the resulting landscape structure (the distribution of stand age and tree density) for alternative climatic condition. We hypothesize that variation in tree establishment after a fire and the legacy of the prior stand will control the trajectory of NEP through time, and that climate and fire frequency will change the distribution of forest age and structure, and these changes will alter net carbon storage for the landscape. We completed several modeling analyses as well as field data collection; analyses of the empirical data are under way. View PDF of research proposal....

Kashian et al (2006) examined the potential for changes in landscape carbon storage as a result of changing fire frequency in Yellowstone National Park.  The heterogeneity of stand ages and structures across this landscape creates resistance to large changes in carbon storage even with drastic increases in fire frequency based on changes in age structures alone.  However, our study suggests that widespread changes in postfire stand structure (i.e., especially a substantial reduction in stand density) could move the Yellowstone landscape from a carbon sink to a carbon source (Kashian et al. 2006).

To explore the potential effects of disturbance and climate change on C and N cycling, we modeled (using CENTURY version 4.5) mature and regenerating lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Wats.) stands that vary in post-fire tree density following stand-replacing fire (Smithwick et al. in press).  Results showed that both young (post-fire) and mature stands had elevated forest production and net N mineralization under future climate scenarios relative to current climate.  Forest production increased 25% (Hadley) to 36% (Canadian Climate Center), compared to 2% under current climate, among stands that varied in stand age and post-fire density. Although our simulations indicated strong positive responses of lodgepole pine productivity to future changes in climate, C flux over the next century will likely reflect complex relationships between climate, age structure, and disturbance-recovery patterns across the landscape (Smithwick et al. in press).

The most recent climate model projections suggest that, by the end of the 21st 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. With recent funding from the JFSP New Initiatives program and in collaboration with Dr. Tony Westerling (UC-Merced), we are extending our research to explore the implications of these current projections for vegetation and C in Greater Yellowstone. 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. View PDF of our research proposal…

Selected publications:

Arcano, R. 2005. Allometric model development, biomass allocation patterns, and nitrogen use efficiency of lodgepole pine in the Greater Yellowstone Ecosystem. MS Thesis, Department of Botany, University of Wyoming, Laramie.

Kashian, D. M., W. H. Romme, D. B. Tinker, M. G. Turner and M. G. Ryan. 2006. Carbon cycling and storage across coniferous landscapes: linking fire frequency, post-fire recovery, and ecosystem processes.  BioScience 56:598-606.

Smithwick, E. A. H., M. G. Ryan, D. M. Kashian, W. H. Romme, D. B. Tinker and M. G. Turner.  Modeling the effects of fire and climate change on carbon and nitrogen storage in lodgepole pine (Pinus contorta) stands. Global Change Biology (In press).

Funding source

Joint Fire Sciences Program