Does fire exclusion lead to woody encroachment of savannas in the Cerrado?

Abstract

Fire is a key factor in structuring and maintaining fire-prone ecosystems. Among them are the grasslands and savannas like the ones found in the tropics and subtropics. This is the case of the Brazilian Cerrado, a global biodiversity hotspot, with emphasis on its herbaceous and shrub vegetation cover, where 75% to 80% of its diversity can be found. The Cerrado grasslands and savannas formations remain open because of fire that occurs with high frequency in these areas. The frequency of fire influences the structure of plant communities, thus fire exclusion allows the increase of woody plant densities in a process known as woody encroachment. This phenomenon, beyond changing the original characteristics of typically open areas, reduces the diversity of the herbaceous and shrub layer. Thus, the main objective of this work is to explore if fire exclusion can lead to the increase of density and number of woody plant species in open areas of Cerrado. For this, it will be sampled Cerrado areas of Campo Sujo physiognomy under different fire frequencies (annual fire, biennial fire since 2013 and fire exclusion since 2011), bounded by 30x30m plots, with three replicas for each treatment. Surveys will be performed in 10x10m subplots (9 subplots/plot, 3 plots/treatment) to collect the following variables: height and perimeter at 10 cm from the ground for each plant, number of species and number of woody plants with height equal or above 1,5 m. The results should contribute to the understanding of the importance of fire as a necessary disturbance in maintaining these ecosystems.