Severe storms and blow-down disturbances in the Amazon forest
Large natural disturbances (> 1 ha) in old-growth tropical forests are caused by a variety of processes such as landslides, fires, wind, and cyclonic storms. We analyzed the pattern of large forest disturbances apparently caused by severe winds (blow-downs) in a mostly unmanaged portion of the Brazilian Amazon using a longitudinal transect of Landsat images (27 scenes between 6°43'W 68°50'S and 2°16'W 51°51'S) and daily precipitation estimates based on NOAA satellite data. We found 170 blow-downs with an average area of 3 km2. Most blow-down disturbances occurred in the Western Amazon between 67°W and 58°W. A map of heavy rainfall (> 20 mm d-1) showed that the maximum frequency of heavy daily rainfall (~80 days y-1) occurred around 63°W in our study region. We found a close relationship between the frequency of heavy storms and the occurrence of blow-down disturbances events. This, in turns, suggests a close connection between severe weather and the rate of forest turnover caused by blow-down disturbances. The forest turnover time calculated for these disturbances within 9 Eastern Landsat scenes studied was almost 9000 years whereas for the 18 scenes in the Western Amazon, turnover time was closer to 1200 year. Large disturbances may have a significant influence on the spatial pattern of forest dynamics and productivity of the Amazon.
Earth Sciences, Earth Systems Research Center
EOS, Transactions American Geophysical Union, Fall Meeting, Supplement
American Geophysical Union Publications
Espirito-Santo, F., Keller, M., Braswell, B., Nelson, B., Vicente, G. and Frolking, S. (2007), Severe storms and blow-down disturbances in the Amazon forest, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract B43C-1456.