解析库 > 2021年考满分GPO新题模考
To assess the impact of severe drought and drought-related fire on rain-forest vegetation, Leighton and Wirawan studied eastern Borneo following the 1982-1983 drought (when rainfall was nearly 70 percent below normal) by comparing postdrought data from various rain-forest plots with 1977-1979 data from the same plots. Some of the plots had been burned; others were only affected by drought. The large, normally evergreen canopy trees had begun shedding their leaves in February 1983 and were leafless when fires began in April 1983. The study revealed that canopy trees suffered more from drought than from fire: there was no difference in mortality between burned and unburned plots. Drought impact was greatest (37 to 71 percent of canopy trees killed) on steep slopes and ridges due to the limited water reserves of the shallow soil in such sites, while drought damage was least (11 percent of canopy trees killed) in a valley-bottom plot, which had deeper soil. Small trees and vines were largely unaffected by drought but were more easily killed by fire than were canopy trees. Thus, areas affected by drought alone witnessed a decline in larger trees' importance, whereas areas affected by drought and fire saw an increase in their relative importance because of their greater survival rate.