Recurrent wildfires drive rapid taxonomic homogenization of seasonally flooded Neotropical forests

Abstract

SUMMARYRecent evidence has shown that most tropical species are declining as a result of global change. Under this scenario, the prevalence of tolerant species to disturbances has driven many biological communities towards biotic homogenization (BH). However, the mechanisms that drive communities towards BH are not yet thoroughly understood. We tested effects of recurring wildfires on woody species richness and composition in six seasonally flooded Amazonian forests and whether these fires reduce species composition (i.e., taxonomic homogenization) over short periods of time. Our results show that these forests are undergoing taxonomic homogenization in response to recurring fire events. Species richness decreased as a result of local extinctions and floristic similarity increased among forest communities. Fire was selecting tolerant (‘winner’) species and eliminating the more sensitive (‘loser’) species. BH leads to biodiversity erosion, which can deeply alter ecosystem processes such as productivity, nutrient cycling and decomposition, resulting in important consequences for conservation.

Spatial Assessment of Wildfires Susceptibility in Santa Cruz (Bolivia) Using Random Forest

“…The detailed investigation of the relative importance of each categorical class belonging to the variables ecoregions and land cover reveals that "flooded savanna" and "shrub or herbaceous cover, flooded, fresh/saline/brakish water" are the two classes most related with wildfires. This important outcome confirms recent findings, that seasonally wet and dry climate, coupled with hydrologic controls on the vegetation, create in this ecoregion conditions favorable to the ignition and spreading of large wildfires during the driest period, when the biomass is abundant [75,76]. The occurrence of large fires, initiated by slash-and-burn practice getting out of control, is predicted to increase in the near future and the development of new tools for fire risk assessment and reduction is thus needed.…”

Fire Affects Asymbiotic Nitrogen Fixation in Southern Amazon Forests

“…Between 2007 and 2016 (the most recent survey), aboveground biomass loss (Nogueira et al, ), increased floristic similarity, and higher plant mortality than recruitment (da Silva et al, ; Maracahipes et al, ) were reported for the same stands included in this study (Table ). The most recent survey data (2014 and 2016), including trees with a diameter at breast height‐DBH ≥ 10 cm in each stand, are presented in supporting information Tables S1 (species abundance), S2 (beta diversity matrix), and S3 (density, basal area, and relative basal area of trees belonging to Fabaceae).…”

“…Those forests are sensitive to fire because trees adapted to humid tropical forests are generally not fire‐adapted (Franco et al, ); thus, high tree mortality can occur as a result of fire (Hoffmann et al, ). Ongoing long‐term (>12 years) ecological research has indicated above‐average tree mortality and diversity loss in seasonally flooded forests due to fire (da Silva et al, ; Maracahipes et al, ). Fire disturbance can disrupt biological processes and biogeochemical cycles, notably those concerning N (Pellegrini et al, ), which can influence natural succession in dystrophic, nutrient‐poor soils (de Oliveira et al, ; Nardoto et al, ; Taylor et al, ).…”

Impacts of Fire on Forest Biomass Dynamics at the Southern Amazon Edge

“…In riparian forests, fires deliberately set to stimulate grass regrowth (Silvério et al 2013) may invade forest areas more frequently and intensively in drier years. Associated with organic fuel sources of riparian forests, soils may magnify burning intensity, causing biodiversity erosion and biomass loss with a clear tendency towards the biotic homogenization of tree taxonomic composition (Da Silva et al 2018).…”