What are the most important factors determining different vegetation types in the Chapada Diamantina, Brazil?

Abstract

A transect was used to examine the environmental and biological descriptors of a compact vegetation mosaic in the Chapada Diamantina in northeastern Brazil, including the floristic composition, spectrum of plant life forms, rainfall, and soil properties that defined areas of cerrado (Brazilian savanna), caatinga (seasonally dry tropical forest thorny, deciduous shrub/arboreal vegetation) and cerrado-caatinga transition vegetation. The floristic survey was made monthly from April/2009 to March/2012. A dendrogram of similarity was generated using the Jaccard Index based on a matrix of the species that occurred in at least two of the vegetation types examined. The proportions of life forms in each vegetation type were compared using the chi-square test. Composite soil samples were analyzed by simple variance (ANOVA) to examine relationships between soil parameters of each vegetation type and the transition area. The monthly precipitation levels in each vegetation type were measured and compared using the chi-square test. A total of 323 species of angiosperms were collected distributed in 193 genera and 54 families. The dendrogram demonstrated strong difference between the floristic compositions of the cerrado and caatinga, sharing 2% similarity. The chi-square test did not demonstrate any significant statistical differences between the monthly values of recorded rainfall. The organic matter and clay contents of the soilsin the caatinga increased while sand decreased, and the proportions of therophyte, hemicryptophyte, and chamaephyte life forms decreased and phanerophytes increased. We can therefore conclude that the floristic composition and the spectrum of life forms combined to define the cerrado and caatinga vegetation along the transect examined, with soil being the principal conditioning factor determining the different vegetation types, independent of precipitation levels.Keywords: Savanna, seasonally dry tropical forest, biological spectrum, soil, rainfall. Quais são os fatores mais importantes na determinação de diferentes tipos de vegetação na Chapada Diamantina, Brasil? ResumoFoi estabelecida uma transecção para examinar descritores ambientais e biológicos em uma área compacta de vegetação em mosaico na Chapada Diamantina, Nordeste do Brasil. A composição florística, espectro de formas de vida, precipitação e propriedades do solo foram avaliadas na transecção entre cerrado (savana brasileira) e caatinga (floresta tropical sazonalmente seca espinhosa, vegetação arbustivo-arbórea decídua), separados por vegetação de transição cerrado-caatinga. O levantamento florístico foi realizado mensalmente de abril de 2009 a março de 2012. Foi feita análise de agrupamento a fim de determinar a similaridade entre as fisionomias de cerrado, a caatinga e a transição cerrado-caatinga. As proporções de formas de vida foram comparadas utilizando o teste qui-quadrado. Amostras compostas de solo foram analisadas por variância simples (ANOVA) testando a existência de diferenças entre os solos de cada tipo de vegetação....

The roles of rainfall, soil properties, and species traits in flowering phenology along a savanna-seasonally dry tropical forest gradient

“…The present study was conducted in neighboring vegetation types: savanna (centered at 12°26 0 08 00 S and 41°31 0 04 00 W; 884 m asl), savanna-SDTF transition (12°26 0 04 00 S and 41°32 0 01 00 W; 736 m asl), and SDTF (12°27 0 06 00 S and 41°35 0 52 00 W; 697 m asl; Neves et al 2016). These three environments were located along a single 1-hectare transect in the vicinity of the Chapada Diamantina National Park, Bahia State, Brazil.…”

“…The geographical coordinates of the study areas were used to the determine photoperiod and insolation. The physicochemical properties of the soils were presented by Neves et al (2016) from samples obtained in each vegetation type at depths between 0 and 20 cm; each pooled sample was formed by three 330-g subsamples collected every 50 m in each area.…”

“…Patches of savanna and seasonally dry forests often occur side by side in the Chapada Diamantina Mountains in northeastern Brazil (Juncá et al 2005;Funch et al 2009;Neves et al 2016). These vegetation types experience different levels of water availability, created by differences in the physical properties and depths of their soils, although subject to a similar highly seasonal and semiarid condition (rainfall 688 mm year -1 ) (Harley et al 2005).…”

“…These vegetation types experience different levels of water availability, created by differences in the physical properties and depths of their soils, although subject to a similar highly seasonal and semiarid condition (rainfall 688 mm year -1 ) (Harley et al 2005). As such, soil has been considered one of the main conditioning factors selecting for functional adaptations and determining the floristic composition and the spectrum of life forms that define the transition of savannas to seasonally dry forests over reasonably short distances (Neves et al 2016).…”

Leaf phenology and morphofunctional variation in Myrcia amazonica DC. (Myrtaceae) in gallery forest and “campo rupestre” vegetation in the Chapada Diamantina, Brazil

“…The heterogeneity of habitats in the Chapada Diamantina Mountains (the northeastern extension of the Espinhaço Range in central-eastern Brazil) has been the subject of numerous floristic studies of vegetation mosaics associated with wide physiographic spectra, including ''cerrado'' (neotropical savanna), ''campo rupestre'' (open, rocky fields), forests, and ''caatinga'' (seasonally dry, thorny, deciduous shrub/arboreal tropical forest) (Funch et al 2009). Contrasting habitats in terms of water availability and solar radiation (such as ''campo rupestre'' and gallery forest) occur relatively close to one another under similar macroclimatic conditions in this vegetation mosaic (Neves et al 2016). ''Campo rupestre'' vegetation predominates at altitudes over 900 m and represents a complex vegetation type with numerous microhabitats on rocky mountain tops growing on thin sandy soils, exposed to high solar radiation throughout the year, and experiencing water restrictions and a marked climatic seasonality (Conceição et al 2007).…”