Abstract
Abstract The Brazilian semiarid region is dominated by caatinga. However, other vegetation formations occur, including deciduous and semi-deciduous forests. This study describes physiognomy and structure of a forest on the sedimentary Ibiapaba plateau. All plants within one hectare were separated into three components: woody plants with perimeter at soil level (PSL) ≥ 9 cm (WCLP), woody plants with PSL ≥ 3 and ≤ 8.9 cm (WCSP), and herb/subwoody plants (HSwC). WCLP included 88 species (33 families), WCSP 50 species (23 families) and HSwC only 7 species (5 families). Total density, basal area, and maximum and average height of WCLP were 5683 plants/ha, 47 m2/ha, 18 and 5 m respectively. Total density and basal area of WCSP were 17500 plants/ha and 2.8 m2/ha, respectively. Density of HSwC was 9 plants/m2 and only 31% of the sampled area was occupied by this component.
Highlights
The heterogeneity of the flora and physiognomies of the different vegetations types in the Brazilian semiarid region is caused by two rainfall gradients, one in the South-North and the other in the East-West direction, and by marked geologic differences (Rodal et al 2008)
The description and classification of plant communities generally focuses on features such as floristic composition, structure and relative species abundances (Box & Fujiwara 2005)
Species with the highest importance value (IV) and relative basal areas were Gymnanthes sp.1, Bauhinia pulchella and Piptadenia moniliformis, which accounted for 28% of the total IV (Tab. 3)
Summary
The heterogeneity of the flora and physiognomies of the different vegetations types in the Brazilian semiarid region is caused by two rainfall gradients, one in the South-North and the other in the East-West direction, and by marked geologic differences (Rodal et al 2008). At higher altitudes, where aridity is less accentuated, the seasonal non-thorny formations occur (Araújo et al 1998; Araújo et al 1999; Rodal & Nascimento 2002; Ferraz et al 2003; Araújo et al 2005b). They belong to two physiognomic types: 1) non-forest formations, mainly savanna (cerrado) and closed shrubland (carrasco), on the sedimentary plateaus; and 2) perennial, seasonal forest formations, both on sedimentary and crystalline substrates (Rodal & Nascimento 2002; Araújo et al 2005b). The vegetation can be managed in order to maintain maximum local biological diversity
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