Composição florística e fitossociologia de uma área ciliar de caatinga, município de Livramento, Paraíba, Brasil.

Abstract

The objective of this research was to evaluate the floristic composition and the phytosociological parameters of the adult woody component in an area of degraded riparian forest in the municipality of Livramento, Semiarid region of Paraíba. The ecological system chosen to carry out the work was the riparian forest of the Verde creek (7º19'5.46'' S and 36º55'29.28'' W; 568 m altitude), with a total of 50 contiguous plots of 10 x 10 m, distributed along the watercourse. The inclusion criteria were to sample shrub-tree individuals, living and dead, standing, with stem diameter at ground level (DNS) ≥ 3 cm and total height ≥ 1 m. The absolute and relative values for density, frequency and dominance were calculated, and the values of coverage and importance too. Diversity and equability values were also calculated. The individuals were systematized into diametric and hypsometric classes. The shrub-tree community of the riparian area sampled was represented by 23 species, one of which remained undetermined. The identified species were distributed across 20 genera and 11 families. The families with the largest number of species were Fabaceae (eight), Euphorbiaceae (four) and Cactaceae (two). A total of 1050 individuals belonging to the shrub-arboreal component were registered in the phytosociological structure. The species that presented the greatest abundance were Mimosa tenuiflora (Willd.) Poir. (508), Croton blanchetianus Baill. (173), Jatropha mollissima (Pohl) Baill. (81) and Cenostigma pyramidale (Tul.) Gagnon & G.P. Lewis (58). M. tenuiflora presented the highest values in phytosociological parameters. Particularly related to the Importance Value (VI), the species that stood out the most were M. tenuiflora (123.56), C. blanchetianus (32.32), J. mollissima (24.28), C. pyramidale (18.39) and C. flexuosa (12.90), in addition to the category of the dead with 20.69. The diversity and equability values were 1.86 nats.ind.-1 and 0.59 respectively. Considering the diameter distribution, a predominance of individuals in the third (9.1 to 12 cm), fourth (12.1 to 15 cm) and fifth class (15.1 to 18 cm) was observed. Thus, these three classes corresponded to a total of 688 individuals, representing 65.52% of the total number of individuals sampled. Evaluating the hypsometric distribution data, it was observed that the largest number of individuals was also included between the third and fifth class (range of 3 to 6 m in height), with these intervals containing 679 individuals, which represents 64.67% of the total number of individuals sampled. Therefore, the data obtained is defined as relevant to support conservation and restoration strategies for riparian areas in the context of the Brazilian Semiarid region, thus adhering to objectives 6 and 15 of the SDGs of the 2030 agenda.