Tracking Changes in Vegetation Structure Following Fire in the Cerrado
Biome using ICESat-2
Abstract
Fires mediate grass and tree competition and alter vegetation structure
in savanna ecosystems, with important implications for regional carbon,
water, and energy fluxes. However, direct observations of how fire
frequency influences vegetation structure and post-fire recovery have
been limited to small experimental field studies. Here, we combined
lidar-derived canopy height and canopy cover from NASA’s Ice, Cloud and
land Elevation Satellite-2 (ICESat-2) with over two decades of
satellite-derived burned area data to provide the first biome-wide
estimates of post-fire changes in canopy structure for major vegetation
types in the Cerrado. Mean canopy height decreased with increasing burn
frequency for all natural cover types, with the greatest decline
observed for forests and savannas. The ability to separate changes in
fractional canopy cover from height growth using lidar data highlighted
the long time scales of vegetation recovery in forests and savannas
after fire. For forests in medium and high precipitation areas, canopy
cover returned to unburned values within five years following fire,
whereas mean canopy height remained below unburned values, even in the
oldest fires (14-20 years). Recovery was slower for savannas, with
average values of both fractional cover and canopy height below unburned
areas after 14-20 years, and recovery times increased with decreasing
rainfall. Our results suggest only gradual increases in woody vegetation
height and fractional cover over decades, even in mesic or wet savanna
regions like the Cerrado. Infrequent fire activity, particularly in
areas with greater land management, influences ecosystem structure
across the biome, with important consequences for biodiversity
conservation.