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Diagnosis and attribution of the contemporary North American terrestrial CO2 sink: the role of disturbance and land use change
Project Funding: 2010 - 2013
NRA: 2009 NASA: New Investigator Program
Funded by NASA
Abstract:Studies suggest that North American forests have had a significant influence on the global carbon budget by acting as a large sink of atmospheric CO2 over the latter part of the 20th Century (Fan et al., 1998; Myneni, 2001). The operation of this sink has been attributed to a combination of mechanisms, including fertilization by elevated atmospheric CO2 concentration and rates of anthropogenic N deposition, the effects of climate warming, woody encroachment, and increases on forest productivity via reforestation and post-disturbance recovery. However, recent changes in these driving factors - particularly the observed and expected increases in disturbances - have the potential to alter the C balance of North America forests (Kurz et al., 2008; Balshi et al., 2009; Hayes et al., in review). Whether these ecosystems continue to sequester atmospheric CO2 in the face of these changes is a key question in global change science and policy, as any changes to the strength of this key terrestrial sink will have important consequences for the global C cycle. The goal of this proposed study is to address the question on the state of the North American terrestrial sink in the early 21st Century by conducting research designed to improve our understanding of the role of disturbance and land use change in the continental-scale land-atmosphere C balance. To address this goal, we will employ a process-based ecosystem modeling framework designed to diagnose the contemporary C balance of North American terrestrial ecosystems. Model experiments will be conducted to explicitly attribute the dynamics in this balance to the major driving forces of the C cycle, with a particular focus on the role of disturbance (fire, insect outbreaks, forest harvest and agricultural conversion and abandonment). The availability of several recently developed tools and datasets provides an excellent opportunity to: (1) apply novel methodologies for characterizing disturbance dynamics from Lansdat data sets (Kennedy et al., 2007) and extrapolating these patterns to larger area coverage with MODIS data (Hayes et al., 2008) in order to develop spatially- and temporally-explicit driving data sets on fire, insect outbreaks, and forest harvest; (2) advance modeling capabilities with improved parameterization of the impacts of disturbance on C fluxes and post-disturbance recovery (e.g., Johnstone and Kasischke, 2005); and (3) reduce uncertainties in continental-scale C budget accounting by analyzing our model simulations in the context of the various inventory-, forward- and inverse- based estimates compiled by the MAST-DC for supporting North American Carbon Program activities. An international team of collaborators will be assembled to contribute expertise on remote sensing analysis, disturbance ecology, inventory-based C budget accounting, and process-based ecosystem modeling.
Publications:
Hayes, D. J., Turner, D. P., Stinson, G., McGuire, A. D., Wei, Y., West, T. O., Heath, L. S., Jong, B., McConkey, B. G., Birdsey, R. A., Kurz, W. A., Jacobson, A. R., Huntzinger, D. N., Pan, Y., Post, W. M., Cook, R. B. 2012. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data. Global Change Biology. 18(4), 1282-1299. DOI: 10.1111/j.1365-2486.2011.02627.x
Hayes, D., Turner, D. 2012. The need for "apples-to-apples" comparisons of carbon dioxide source and sink estimates. Eos, Transactions American Geophysical Union. 93(41), 404-405. DOI: 10.1029/2012EO410007
2011 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)
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