A pantropical analysis of fire impacts and post-fire recovery on
tropical plant diversity and species composition
Abstract
Fire is increasingly driving loss and degradation of tropical habitats,
but factors influencing biodiversity responses to fire are inadequately
understood. We conduct a pan-tropical analysis of systematically
collated data – 5257 observations of 1705 plant species (trees and
shrubs, forbs, graminoids and climbers) in burnt and unburnt plots from
28 studies. We use model averaging of mixed effect models assessing how
plant species richness and turnover (comparing burnt and unburnt
communities) vary with time since fire, fire type, protected area status
and biome type. More long-term studies are needed, but our analyses
highlight three key findings. First, prescribed and non-prescribed burns
have contrasting impacts on plant communities, the direction of which
depends on focal life form and biome. Forb richness, for example,
increases following non-prescribed (but not prescribed) burns in
savannahs and flooded grasslands, but in moist broadleaved forest forb
richness increases strongly following prescribed (but not
non-prescribed) burns. Second, protected areas mitigate fire impacts on
plant communities. Species richness of trees/shrubs increased (by
~50%) following fires in non-protected sites but tended
to remain similar in protected sites. Similarly, ten years after a fire
event graminoid community composition had recovered fully to resemble
non-burnt communities in protected areas, but remained highly divergent
in unprotected sites. Finally, this persistence in divergence of
community composition following fire events occurs across a number of
life forms. Composition of tree/shrub communities remained divergent
from unburnt communities ten years after a fire, and composition of forb
communities only returned to those of unburnt sites after ten years.
Fire intervals are already less than ten years in some tropical
locations, and future climate and land use change are predicted to
further shorten these intervals. Plant communities across much of the
tropics are thus likely to change substantially in response increased
exposure to fire.