intervals to control weeds and promote a flush of green grass, and these fires
commonly burn into the understory of adjoining forests. Although of low
intensity, such surface fires can cause dramatic mortality of rainforest trees and
vines, which have thin bark and thus are poorly protected from flames (Uhl
and Kauffman 1990; Kauffman 1991). Once-burned forests become highly
vulnerable to recurring fires of even greater intensity because the mortality of
many plants reduces canopy cover and increases the amount of dry litter on
the forest floor (Cochrane et al. 1999). In two fragmented landscapes of east-
ern Amazonia, surface fires were significantly more common within 2,400 m
of forest edges (Figure 2.3; Cochrane and Laurance 2002). As a result of
repeated fire incursions, the edges of rainforest remnants may recede over
time, leading to fragment “implosion” (Gascon et al. 2000). Unless fires are
controlled, especially in seasonal areas of the tropics, rainforest vegetation
could be largely replaced in many areas by fire-adapted savannas or scrubby
regrowth (Cochrane and Laurance 2002).
42 I. Conservation Biology and Landscape Ecology in the Tropics
Figure 2.3. Estimated fire rotation times (number of years between successive fires)
as a function of distance from forest edge for a fragmented landscape in the eastern
Brazilian Amazon. Data were estimated using 14 years of remote-sensing data. The
curve was fitted with a smoothing function. Dotted lines show the 95% range of
variation (mean ± 1.96 standard deviations) for forest interiors (2,500 m from edge)
(after Cochrane and Laurance 2002).