Functional and taxonomic alpha and beta diversity responses to burning grasslands in southern Brazil

摘要

Questions Grasslands in subtropical Brazil are known as potentially fire-prone ecosystems. Aiming to better understand the effects of fire on biodiversity, we addressed the following questions: does fire benefit all alpha and beta components of taxonomic and functional diversity in grasslands; which functional groups are affected; does diversity foster recovery of above-ground biomass after fire? Location Campos grassland, southern Brazil Methods The effects of fire were investigated using a before/after control/impact experimental design. A randomized block design with seven replicates was set up, where a fire experiment was established after three years of both grazing and fire exclusion. Each block contained two paired 10 m x 10 m plots. We assessed plant species composition, plant functional trait composition, plant functional groups, and above-ground biomass before and after fire in both burnt and control plots. Results Both taxonomic and functional alpha diversity increased in burnt plots and decreased in unburnt plots across time. Taxonomic species richness considering total species increased more than considering common species only. Functional beta diversity increased in burnt plots while taxonomic beta diversity stayed similar between treatments. Forb total cover increased after fire while graminoids and shrubs remained unchanged. Burnt plots with high initial functional richness presented greater biomass recovery, whereas species richness presented no relation with above-ground biomass. Conclusions Fire increases species and functional richness in plots of subtropical Campos grasslands (alpha diversity component), and while it increases functional beta diversity, taxonomic beta diversity remained unchanged. Functional diversity is important for maintaining grassland biomass recovery after fire.