Long term post-fire recovery of woody plants in savannas of central Brazil

Abstract

Although fires have occurred in the Brazilian savannas (Cerrado) without human influence, current human activities are changing the fire regimes and negatively affects the vegetation resilience and recovery rates. Contrasting effects of fire on biodiversity and structure of vegetation in the Cerrado are dependent on fire frequency. Some anthropogenic fire regimes have increased fire frequency with shorter intervals between fires. However, the dynamics post-fire and the time needed for vegetation recovery are still poorly understood for the woody plants of Cerrado. We aimed to respond to two questions: Do the structure, floristic, and functional composition of woody species recover eight years post-fire? Do two consecutive fire events with seven years interval affect the floristic and structure of woody plants over time? We evaluated the woody dynamics in Cerrado savannas under three different fire regimes in central Brazil. We measured all trees and shrubs in 10 plots (totaling 1 ha) from 1997 to 2019 (22 years) and in 10 additional plots from 2008 to 2019 (11 years) in three areas: unburned area (fire exclusion for 30 years – fire regime 0), burned area 1 (one fire event in 2011 – fire regime 1), and burned area 2 (burned in 1998 and 2005 – fire regime 2). We analyzed the vegetation structure, floristic, and functional composition through multiple inventories to evaluate the vegetation recovery status. Density, basal area, and biomass increased similarly over time in the burned area 1 and the unburned area, showing that the woody vegetation parameters has recovered eight years after one fire event. Our results also showed that vegetation structure (i.e., density, basal area, and aboveground biomass) remained relatively constant between 2006 and 2013 (8 years after the occurrence of two fires). The data indicate growth only in the inventory after 14 years without fire.