Savannas of the Brazilian semiarid region: what do we learn from floristics?

Izaíra Vasconcelos Nepomuceno,Marcela Cruz Moreira,Daniela Cristina Zappi,Francisco Álvaro Almeida Nepomuceno,Elnatan Bezerra De Souza,Marcelo Freire Moro

doi:10.1590/0102-33062020abb0259

Abstract

The Cerrado represents the largest extension of savanna in South America. It occupies large stretches of central Brazil, being fragmented towards the Northeast, Southeast, and South regions of the country. Examples of disjunct patches of vegetation with savanna physiognomy within the Caatinga can be found in the Chapada Diamantina, the Chapada do Araripe, in small areas of southern Ceará State, and also in the coastal plains. This study recorded the floristic composition of four savannas within the Caatinga in northern Ceará State and evaluated the floristic relationships between these and other savannas, Cerrado and Caatinga sites. Periodic floristic collections recorded 247 species distributed among 162 genera and 55 families. Fifty-seven percent of the recorded species were of herbaceous or sub-shrubby habit, while the majority of the flora was of the therophytic life-form. Biogeographic analyses revealed that the study sites differ from typical Cerrado in flora and life-form spectra and have closer floristic relationships with Caatinga vegetation. The presence of floristic elements from the Cerrado, together with species from the Caatinga, in the study sites allows us to conclude that these savanna enclaves in the Caatinga are composed of a mixed flora with typical elements of these two Brazilian biomes.

Highlights

Savannas are a group of phytophysiognomies dominated by open habitats, where trees and shrubs are found sparsely distributed in the landscape and the ground is covered by a continuous herbaceous layer, often associated with natural fires (Eiten 1982; Pennington et al 2006; Walter et al 2008; Townsend et al 2009)
We found Borreria sp. nov., a new species yet to be described and 76 species endemic to Brazil, of which six are recorded only for Northeastern Brazil: Stilpnopappus cearensis, Croton anisodontus, Mimosa ulbrichiana, Schultesia angustifolia, Hexasepalum gardneri (and Mitracarpus fernandesii (BFG 2018)
Other examples of very common species in typical cerrado sites that were recorded in the studied caatinga-savannas were Bouwdichia virgilioides, Byrsonima coccolobifolia, Curatella americana and Hirtella ciliata (Tab. 2, Fig. 3), but typical caatinga species like Cereus jamacaru, Encholirium spectabile, Copernicia prunifera and Combretum leprosum were found in our sites, making them a mixture of floristic elements from both the Cerrado and Caatinga biomes (Moro et al 2011)

Summary

Introduction

Savannas are a group of phytophysiognomies dominated by open habitats, where trees and shrubs are found sparsely distributed in the landscape and the ground is covered by a continuous herbaceous layer, often associated with natural fires (Eiten 1982; Pennington et al 2006; Walter et al 2008; Townsend et al 2009). This vegetation typically occurs under seasonal climate where rainfall is more regular and the dry season is less strong than in deciduous Seasonally Dry Forests (Pennington et al 2006). The Brazil Flora Groups current data (BFG 2018) listed 33,099 angiosperm species for the whole of Brazil and, of these, 12,113 were recorded for the Cerrado biome, with 7,800 species listed for the cerrado s.s. vegetation (Souza et al 2018)

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Discussion

Conclusion