Assessing hurricane-induced tree mortality in U.S. Gulf Coast forest ecosystems



[1] Tropical cyclones disturb forest ecosystems and have the potential to alter forest structure and species composition as well as ecosystem functions including rates of nutrient cycling and biomass accumulation. Quantifying these forest disturbances is necessary to evaluate the extent and severity of damage for estimating biomass loss, developing regional carbon budgets, and making management decisions following hurricanes. In this study, we quantified forest disturbance (downed and dead and snapped trees) produced by hurricanes using a relationship between field-measured tree mortality and Landsat data that can be broadly applied to Gulf Coast forest ecosystems impacted by hurricanes. Field-measured tree mortality data was collected in Gulf Coast forests at 60 inventory plots established to monitor forest disturbance produced by hurricanes Katrina and Rita, which hit the region in 2005, and Hurricane Gustav, which hit the region in 2008. Large-scale disturbance estimates were obtained by regressing Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) data that in turn were associated with Forest Inventory and Analysis (FIA) data from the U.S. Forest Service. The use of the general relationship produced a biomass loss from dead trees of 43.9 ± 8.4 Tg C for Hurricane Katrina and 37.9 ± 6.4 Tg C for Hurricane Rita, which are near the upper limit of the expected values reported in our previous studies across a number of different forest types. Our results provide an important contribution for reliable assessments of large-scale disturbance produced by hurricanes in forest ecosystems. Improving our ability to accurately assess the impacts of hurricanes on forests and on terrestrial carbon cycles is particularly important given that climate projections suggest that hurricane intensity is likely to increase.