Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Abstract

The analysis of the influence of edaphic finer textures, as a facilitating factor for the expansion of forest formations in the absence of fire, was possible thanks to rare characteristics found in a savanna fragment located in the State of São Paulo, Brazil. The total suppression of fire for over four decades, and the occurrence of two savanna physiognomies, cerrado sensu stricto and cerradão, allowed the conduction of this study based on the hypothesis that cerradão, a physiognomy of forest aspect consisting of fire-sensitive tree and shrubs species, is favored by fire absence and higher soil hydric retention capacity. Edaphic samples were collected from a regular grid of 200 m 2 for the production of isopletic maps of the distribution of clay, fine sand, coarse sand and silt edaphic textures by the geostatistic method of ordinary kriging. Changes in the areas occupied by both savanna physiognomies, defined on the basis of aerial photographs taken over a period of 43 years, were assessed through mean variation rates. Besides corroborating the hypothesis of edaphic hydric retention as a facilitating factor for the expansion of forest physiognomies in savanna areas, we were able to infer the positive influence of higher precipitation on the increase in cerradão expansion rates.

Factors influencing seed germination in Cerrado grasses

“…Changing these factors in nature can lead to a reduction in germination success for Cerrado grasses and, thus, may compromise the persistence of these species in the long term. Woody plants encroachment into Cerrado grasslands due to fire suppression, which has been shown by some studies (Durigan & Ratter 2006;Cardoso et al 2010;Pinheiro & Durigan 2009;Pinheiro et al 2010;Silva et al 2013), probably alters important environmental conditions, by narrowing the amplitude of daily temperature and decreasing the availability of light. Another factor that may modify the conditions of light and microclimate close to the ground in the Cerrado is the invasion by exotic grasses (Hoffmann & Haridasan 2008;Mendonça et al 2015), which accumulate much more biomass on the soil surface than the native grasses.…”

The need for a consistent fire policy for Cerrado conservation

“…Dense uniform tall vegetation (cerradão or forest) has replaced open Cerrado in many sites in the absence of fire (Cardoso et al 2009;Pinheiro & Durigan 2009;Pinheiro, Azevedo & Monteiro 2010). Estimating the proportion of the biome where forest vegetation could never establish even after fire suppression due to shortage or excess of soil water (e.g.…”

Ecological thresholds at the savanna‐forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes

“…; Durigan & Ratter ; Pinheiro et al . ). In drier savannas, climate alone may prevent the development of a closed forest canopy (Sankaran et al .…”