This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Quantifying the Effects of Large-Scale Vegetation Change on Coupled Water, Carbon and Nutrient Cycles: Beetle Kill in Western Montane Forest We are quantifying how rapid, extensive changes in forest structure and composition associated with Mountain Pine Beetle (MPB) infestation of western montane forests affect the coupling of water, carbon, and nitrogen cycles. MPB infestation and associated fungal pathogens radically change ecosystem structure by killing host trees, altering surface energy and water partitioning, reducing carbon uptake, and putting organic matter into soil on short and long time scales. The widespread extent of this disturbance presents a major challenge for governments and resource managers who must respond to the changes, yet lack a predictive understanding of how these systems will respond to the disturbance over various temporal and spatial scales. This disturbance allows us to test emerging theories of direct and indirect effects of vegetation change on coupled biogeochemical cycles following a disturbance that initially changes only the amount of living biomass while leaving soil hydrologic and chemical characteristics unchanged. By working at sites with different levels of MPB impact, we are evaluating how the dramatic loss of tree function both directly (i.e. transpiration and carbon fixation) and indirectly (i.e. snow capture, redistribution, and surface energy balance) affects water, carbon and nitrogen cycling.
Our work is organized around two, broad questions that require both an interdisciplinary approach and close integration of observation and modeling. How do changes in vegetation structure associated with MPB alter the partitioning of energy and water? And How do these changes in energy and water availability affect local to regional scale biogeochemical cycles? We have assembled a diverse team of biogeochemists, ecologists, hydrologists, and atmospheric scientists to address these questions using measurements, modeling tools, and conceptual approaches from each discipline. Our approach includes intensive, coordinated hydrological, biogeochemical, and ecological observations designed to quantify the internal coupling of water, carbon, and nutrient cycling, as well as how these processes are expressed in both land surface-atmosphere exchanges and catchment solute export. These observations are closely integrated with two process models, one from the landsurface community and one from the catchment community, to evaluate our current understanding of how vegetation change alters coupled cycles. To extend our work beyond the relatively short time-scale of our observations, we coordinate with several ongoing projects, including the Boulder Creek CZO and the Niwot Ridge LTER.
By quantifying both the biological and physical controls that forest vegetation has on water and biogeochemical cycles, our project will both improve our basic understand of the coupling between water, energy, carbon, and nitrogen. Through coordination with land surface and catchment modeling communities we will incorporate this knowledge into the broader community. Our educational activities build on successful efforts at all institutions, while coordination with land and water resource managers will ensure our knowledge is transferred to the applied science community.
