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Title: Integrating a process-based ecosystem model with Landsat imagery to assess impacts of forest disturbance on terrestrial carbon dynamics: Case studies in Alabama and Mississippi

Author
item CHEN, GUANGSHENG - Auburn University
item TIAN, HANQIN - Auburn University
item Prior, Stephen - Steve
item PAN, SHUFEN - University Of Maryland

Submitted to: Journal of Geophysical Research-Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2013
Publication Date: 10/23/2013
Citation: Chen, G., Tian, H., Prior, S.A., Pan, S. 2013. Integrating a process-based ecosystem model with Landsat imagery to assess impacts of forest disturbance on terrestrial carbon dynamics: Case studies in Alabama and Mississippi. Journal of Geophysical Research-Biogeosciences. 118:1208-1224.

Interpretive Summary: Based on high resolution (30 m) forest mortality information and a process-based biogeochemical model, this study estimated changes in C storage for Mississippi and Alabama after continuous forest disturbance events. Annual forest mortality in these states was about 1.3% during 1985-2007. The accumulated mortality for some areas could be 100%. The continuous forest mortality resulted in large C release to the atmosphere which accounts for about 2.4% of the total C storage in this region. Most of this C release was caused by the changes in forest biomass following disturbance. Disturbed forests may take a long time to recover to pre-disturbed levels, suggesting a long-term legacy effect of disturbance. Forest systems in the US were reported as a large C sink during the recent decade; however, disturbance may have greatly reduced this C sink size. To accurately estimate future regional C budgets, it is critical to take forest disturbance into consideration.

Technical Abstract: Forest ecosystems in the southern United States are dramatically altered by three major 26 disturbances: timber harvesting, hurricane, and permanent land conversion. Understanding and quantifying effects of disturbance on forest carbon, nitrogen, and water cycles is critical for sustainable forest management in this region. Based on forest mortality data classified from Landsat TM/ETM+ images and a process-based Dynamic Land Ecosystem Model (DLEM), this study estimated the impacts of continuous forest disturbance on carbon dynamics in Mississippi and Alabama during 1985-2007. Mean annual forest mortality rate for the two states was 1.3%; however, the cumulative mortality rate could be 100% in some areas. This continuous but small forest disturbance has resulted in a large carbon source (199.75 Tg C, 8.3 Tg C yr-1; 1 Tg = 1012 34 g) for both states during 1985-2007, accounting for 2.44% (4.10% if disregard carbon storage changes in wood products) of the total forest carbon storage in this region. Large decreases and slow recovery of forest biomass were the main causes of the carbon release. Although small disturbance events may not significantly change forest structure, the legacy effects on carbon storage could last over 50 years. This study implies that understanding forest disturbance impacts on carbon dynamics is of critical importance to assessing the regional carbon budget.