The twentieth century was a period of significant change in climate, land use (e.g., grazing and fire suppression), forest structure, and fires throughout most of western North America, culminating in increasingly large and severe forest fires in the late twentieth century. The frequency and ecological effects of fires are determined by a complex interplay of climate, fuels, and ignitions. Unfortunately, the compounding effects of fire suppression have hindered research progress; natural fire regimes have been altered, making climate-fire and land use relationships nearly impossible to decipher. Yet, to manage forests for potentially novel climate conditions, land managers need improved understanding of the linkages among climate, land use, vegetation, and topography and how these linkages influence fire regimes. Understanding the synergy of these linkages requires documenting fires prior to 1900, as well as fires that would have occurred in the absence of anthropogenic fire exclusion.
Doctoral student Jed Meunier, under the supervision of Professor William Romme at Colorado State University, will integrate ecological and dendrochronological methods to collect data on fire history and climate for the past 300+ years for several unique sites in northern Mexico to explore these linkages. This project investigates the following questions: 1) What is the relative importance of top-down (e.g., climate) and bottom-up (e.g., land use, topographical position, fuels) controls on fire regimes locally, among sites, and regionally? 2) How do intra-annual patterns of precipitation (winter westerly vs. summer monsoon) impact stand dynamics and fire regimes, and have these patterns remained consistent or changed over time? 3) What has been the role of stand-replacing fire vs. low-severity fire, and has that role changed in the past century? This work will elucidate disturbance and climate controls of forest stand dynamics in both pre-1900 and in the twentieth century, an era of extreme climate variability and paucity of climate-fire information, providing an ecological analogue to forests north of the border.
The results of this study will contribute to our understanding of the influences of climate and anthropogenic controls on fire and forest stand dynamics. The U.S. and Mexico face similar threats of ecological degradation, including lack of fire in fire-dependant ecosystems, increasing population pressures, excessive demands on natural resources, and climate change. A fundamental understanding of long-term trends in precipitation variability and historical vegetation shifts in the borderlands region, including recent twentieth century changes, will help prepare for future climate variability. Lack of available data on long-term trends and climate variability hinders the planning and appropriate use of resources. Understanding twentieth century changes in climate, land-use, stand structure, and fire and their interactions may provide an analogue for future climate variability. As a Doctoral Dissertation Research Improvement award, this award will provide additional support to enable a promising student to establish a strong independent research career.
