Abstract
We evaluated the structural and floristic characteristics of a Brazilian savanna fragment occupied by cerradão (CD) and cerrado sensu stricto (CS) in response to the influence of rainfall and long-term fire suppression. We carried out floristic, phytosociological and remote sensing studies in a cerrado fragment located in Corumbataí (SP, Brazil) after 43 years of complete fire suppression. We surveyed 43 plots of 200 m2 each (17 plots in CS and 26 plots in CD) and all individuals ≥ 0.32 cm diameter measured at 30 cm from the ground were included in the sample. We calculated phytosociological parameters for each species and classified them in three ecological groups, namely savanna, generalist and forest species. The remote sensing analysis used aerial photographs and satellite images from 1962 to 2019 (i.e. 59 years). The structural study of community revealed high predominance of forest and generalist species when compared to savanna species. Non-linear correlation between CD expansion rates and total rainfall within the study period indicated a positive influence of the rainfall (R2 = 0.42). Thus, our analysis indicated a tendency of a continuous and fast expansion of CD over areas of CS in the long-term absence of fire combined with periods of heavy rain.
Highlights
The Brazilian tropical savanna, known as Cerrado, is composed by different vegetation types, such as cerrado sensu stricto and cerradão (Furley 1999, Ratter et al 2006)
The sum of the Importance Value Index (IVI) species of the same ecological group highlighted their importance for the studied community: generalists (IVI = 223), forest species (49) and savanna (28)
Some species were abundant in few plots, e.g. Baccharis dracunculifolia, represented by 44 individuals occurring in four plots, with 40 of them sampled in a single plot of cerrado sensu stricto
Summary
The Brazilian tropical savanna, known as Cerrado, is composed by different vegetation types, such as cerrado sensu stricto (discontinuous tree cover with a herbaceous shade-intolerant vegetation) and cerradão (forest vegetation type) (Furley 1999, Ratter et al 2006). The dynamics and structure of different vegetation physiognomies in Cerrado are mainly influenced by climatic and edaphic factors (Eiten 1972, Goodland & Pollard 1973, Puigdefabregasand & Pugnaire 1999, Wiegand et al 2006, Meyer et al 2007, Wright 2007). Large-scale fire disturbances frequently affect extensive vegetation areas, favoring the establishment of fire-prone plant species and the occurrence of savanna formations with less woody cover (Coutinho 1990, Hutchings 2007). Fire suppression in plant savanna communities (Miranda et al 2009) can influence the natural vegetation dynamics by increasing the prevalence of plant formations with greater coverage of woody plants (Coutinho 1990, An Acad Bras Cienc (2021) 93(1). The long-term absence of fire can trigger ecological succession tending to an edaphoclimatic climax of greater phytomass (Pinheiro & Durigan 2009) frequently dominated by fire-sensitive forest species (van der Maarel 1988, Hoffmann et al 2012, Veldman et al 2015a)
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