Vegetation structure across fire edges in a Neotropical rain forest

Abstract

Human-induced wildfires are one of the greatest threats to tropical forest and are predicted to increase in importance due to altered regimes associated with climate change. Wildfires promote high tree mortality, thus modifying forest structure and composition, and lead to habitat loss and fragmentation. Wildfires may also have effects on the adjacent unburnt areas due to edge influence; conversely, proximity to unburnt forest stands may favor regeneration in the burnt areas. We evaluated wildfire effects on the forest structure of Brazilian Atlantic forest remnants. We established 244 plots along eight 360 m-long transects distributed among three burnt patches, where we measured structural attributes of overstory, understory, and deadwood. The wildfire promoted very high mortality of trees, saplings, and lianas, changing substantially the forest structure. Our analyses showed clear differences between the burnt and unburnt areas but no clear gradients, highlighting the incipient stage of edge influence-related processes. The Neotropical bracken fern Pteridium arachnoideum was dominant in the burnt areas, which can possibly arrest secondary succession. Our results highlight the importance of wildfires as a menace to Brazilian Atlantic Forests remnants, as well as to tropical rainforests elsewhere - an ever-rising concern in a future of increased fire frequency.