Phytosociology of the caatinga in Floresta Nacional de Açu, Rio Grande do Norte, Brazil, and surroundings: diversity and biogeography of the woody layer

ABSTRACT

The semiarid region of Rio Grande do Norte State in the Northeast region of Brazil can be divided into two main geoenvironmental units: Sertaneja Depression and Potiguar Sedimentary Basin. Although the flora of sandy sedimentary basins is usually different from that of crystalline terrains, part of the Potiguar Basin has stony paleo-alluvial deposits, with rolled pebbles, imposing different edaphic conditions to the species. The Floresta Nacional de Açu is located on a stretch of the edge of the Potiguar Basin with pebble deposits, which make the soil stony. The objective of this work was to characterize the phytosociological structure of the caatinga in Floresta Nacional de Açu and its surroundings and to understand the biogeographic links of the local flora with other areas of the Caatinga. We selected areas in the interior and surroundings of FLONA and sampled 1,500 woody individuals, belonging to 33 species. The biogeographical links show that the stony edge of the Potiguar Basin is closer to the flora of the crystalline terrains than to the sandy terrains of other sandy sedimentary basins.

Keywords:
brazilian semiarid region; plant biodiversity; xeric vegetation