Drought-driven wildfire impacts on structure and dynamics in a wet Central Amazonian forest

While climate and human-induced forest degradation is increasing in the
Amazon, fire impacts on forest dynamics remain understudied in the wetter
regions of the basin, which are susceptible to large wildfires only during
extreme droughts. To address this gap, we installed burned and unburned
plots immediately after a wildfire in the northern Purus-Madeira (central
Amazon) during the 2015 El-Niño. We measured all individuals ≥10cm in
diameter at breast height, and conducted recensuses to track the
demographic drivers of biomass change over three years. We also assessed
how stem-level growth and mortality were influenced by fire intensity
(proxied by char height) and tree morphological traits (size and wood
density). Overall, the burned forest lost 27.3% stem density and 12.8%
biomass, concentrated in small and medium trees. Mortality drove these
losses in the first two years and recruitment decreased in the third year.
Fire increased growth in lower wood-density and larger-sized trees, while
char height had transitory strong effects increasing tree mortality. Our
findings suggest that fire impacts are weaker in the wetter Amazon. Here
trees of greater sizes and higher wood densities may confer a margin of
fire resistance; however, this may not extend to higher-intensity fires
arising from climate change.