Post-fire dynamics of the woody vegetation of a savanna forest (Cerradão) in the Cerrado-Amazon transition zone

Simone Matias Reis,Fernando Elias,Mônica Forsthofer,Letícia Gomes,Beatriz Schwantes Marimon,Ted R Feldpausch,Ben Hur Marimon Junior,Eddie Lenza,Paulo Sérgio Morandi

doi:10.1590/0102-33062015abb0009

Abstract

Fire can change the species composition, diversity, and structure of savanna vegetation, thus altering growth and mortality rates. Such changes in the woody vegetation of burned savanna forest were evaluated over four years in comparison to unburned savanna forest. All woody plants with a diameter at breast height > 10 cm were measured in 100 permanent plots. Six months later, 38 of these plots were burned. Three and a half years later, all surviving individuals were re-sampled. Species richness, diversity, and the number of individuals did not change in the burned plots, although they had significantly higher (p < 0.05) increases in basal area and mortality rates (5.1% year-1) than the unburned plots (3.0% year-1).Tachigali vulgarishad the greatest post-fire increase in basal area (53%). The results indicate that fire alters the dynamics and structure of the savanna forest, excluding the less fire-tolerant species and smaller individuals (? 15cm). Tachigali vulgaris is a key species for the recovery of savanna forest biomass due to its considerable post-fire gains in basal area, at least over the short term due to its short life cycle. It follows that frequent burning of savanna forest would result in a marked change in the species composition and structure of its woody vegetation.

Highlights

Forest and savanna are alternative stable states, maintained by the positive feedback between fire and vegetation (Staver et al 2011)
The savanna forest habitats of central Brazil are relatively vulnerable to fire (Moreira 2000; Hoffmann & Moreira 2002), and wildfires provoke high mortality rates (Hoffmann & Moreira 2002) and may affect habitat dynamics
The occurrence of a wildfire in the savanna forest provided an opportunity to evaluate the responses of individual species and overall changes in community structure, providing potential guidelines for management and conservation

Summary

Introduction

Forest and savanna are alternative stable states, maintained by the positive feedback between fire and vegetation (Staver et al 2011). Forest formations located in the transition zone between Amazon forest and the Brazilian savanna (Cerrado), generally known as transitional forests (Balch et al 2011; Brando et al 2014), are less affected by fire (Barlow et al 2003; Haugaasen et al 2003) than “core” Amazon forests (Balch et al 2011) This is due to the presence of less flammable materials (Balch et al 2011) and tree species typical of the savanna, which are better adapted to fire (Hoffmann et al 2012). Wildfires result in an increase in the availability of combustible material, intensifying the risk of new fires and the complete degradation of the forest (Fearnside 2005; 2006)

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