Biocomplexity: Carbonshed Studies of Carbon Sequestration in Complex Terrain

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

0321918 Monson Recent estimates that regionalize the US carbon sink suggest that a significant fraction is in the Western US, in ecosystems that occur in hilly to mountainous regions. We have used satellite data and ecosystem models to show that Western US montane regions contribute disproportionately to the US carbon sink; we estimated that 25 to 50% of the total continental US carbon sink, and up to 75% of Western US carbon sink occurs in mountainous terrain. Our ability to validate these predictions with measurements, or to build on them with improved mechanistic models, is limited. Although the scaling of biogeochemical processes was pioneered in mountain watersheds, recent research has focused more on the "tower footprint" paradigm than the watershed approach; unfortunately, our current capabilities with tower-based measurements are not adequate to develop accurate mass balance predictions in complex topography, and this has diminished efforts to understand biogeochemical fluxes in the mountains. In this proposal, we develop a "carbonshed" approach for the study of the ecosystem carbon balance of montane landscapes. We define a carbonshed within the same context as a watershed - a mountainous tract in which the slopes and valleys cause complex topographic patterns, which directly influence the drainage and accumulation of CO2, as well as patterns in the redistribution of energy and water, which indirectly influence the exchange of CO2 across the landscape. We make the case that the carbonshed scale is crucial for linking local, ecosystem-level CO2 fluxes to regional, landscape-level CO2 fluxes. In this proposal, we present a plan to measure carbonshed CO2 fluxes in the Front Range of the Rocky Mountains in Colorado. Recognizing that direct measurement of carbon budgets using atmospheric techniques will be impossible in complex landscapes, we focus on modeldata integration, using measurements to calibrate and constrain models, and models to interpolate observations. Recognizing also that carbon and water exchange are closely coupled, especially in this semi-arid Western environment, we focus on linking carbon and water measurements. We will challenge process models with measurements at multiple time and space scales, utilizing seasonal to interannual flux measurements, carbonshed scale campaigns to scale up (10's of km), and regional (1000's of km) airborne measurements. Large fires in 2002 will allow us to make airborne measurements of carbon dynamics in recently burned systems, a unique test of the upscaling of fluxes in disturbance-based models. The project's modeling will use a coupled ecosystem-atmosphere model, allowing simulated fluxes to be translated into concentration patterns for comparison to surface and airborne observations. The proposal addresses the intellectual merit criteria by 1) identifying a new phenomenon in carbon science: the tendency for carbon sinks to develop in high-relief ecosystems, as a result of the interaction of climate with land use patterns, 2) proposing innovative and cross-disciplinary methods to measure this phenomenon, and 3) assembling a team including biophysicists, meteorologists, ecologists and educators to study this problem. Broader Impacts The studies will provide training opportunities for two graduate students and two, postdoctoral students. The funded activities will serve as the catalyst to develop a new course on human-environment coupling that will include an analysis of the combined roles of land use history, water resources, fire suppression and biophysical controls over carbon in the mountains. The research will support a significant K-12 and teacher training program coordinated by the University of Colorado CIRES Office of Education and Outreach. The proposed research will contribute to scientific infrastructure by adding a greatly enhanced carbon cycle instrumental capability to the NSF Facilities at NCAR ATD, which are available to the general scientific community. Additionally, a greatly improved 4-dimensional model for analyzing regional carbon sink activity will be made available to the general scientific and public policy communities for use in analyzing US carbon sinks and their relevance to global carbon cycle issues.