Fitossociologia e aspectos ecofisiológicos do componente lenhoso em fragmentos de caatinga na sub-bacia hidrográfica do rio Bodocongó-Paraíba.

Abstract

The plant characterization in Caatinga remainings in Bodocongo River Sub-basin -PB, was made through a floristic and phytossociologic survey of the tree stratum and by the analyses of physiologic variables of species that were founded in the area, aiming to recognize and registry vegetal potentialities, identify possible extinction menace and observe characteristics to explain these species resistance facing weather and soil conditions in Caatinga area. Forty plots of 4 x 50m were used, distributed in four vegetal remnants, Fezenda Caicara (Pi), Fazenda Bodopita (P2), Serra de Bodocongo (P3) e Fazenda Pocinho (P4), and it was also taken information about total height and stalk diameter at the soil level (DNS) of the individuals included in parcels which heights were > lm and DNS > 3 cm. The vegetal species in dilatory stages founded on the area which presented organs that could be analyzed about physiologic variables, water potential and photosynthetic quantical efficiency, were studied in relation to these parameters. It was registered 2331 individuals belonged to 22 families and 45 species. The families that had the higher specific representation were Mimosaceae (5), Euphorbiaceae (5), Caesalpiniaceae (4), Cactaceae (4) e Anacardiaceae (3). The total density was 2655 individuals ha"1 in Pi, 3180 individuals ha"1 em P2, 3010 individuals ha"1 in P3 e 2815 individuals ha"1 in P4. The basal area was 25,851 m2 ha for P,, 29,163 m2 ha"1 in P2, , 32,073 m2 ha"1 in P3, and in P4, 25,250 m2 ha"1. The similarity between the vegetal remainings of the Sub-basin reveal the homogeneity of the vegetation what characterizes it as a unique Caatinga physiognomy. The most important species on the four remnants have been related as the most important in other surveys. Among the ten most important species, four were coincidents, Croton sonderianus. Muell. Arg, Caesalpinia. pyramidalis Tul, Myracrodrum urundeuva Allem, Piptadenia stipulaceae (Benth.) Ducke., and another four species were coincidents in three fragments, Aspidosperma pyrifolium. Mart., Jatropha pohliana Muell. Arg., Bauhinia cheilantha (Bong.) Steud e Manihot glaziovii Muell. Arg., evidencing the importance of these species to the total area. The majority of species concentrate their individuals on the smaller diametric strip of land. It's unquestionable the antropic influence on the area, expressed mainly by the presence of characteristic species of itermediate sucecssional stages, what means perturbation and recuperation of the ambient. The species available about physiologic variables indicated that they are sensitive to water soil variation. However it doesn't occur sufficient physiologic stress at dry period to endanger photosynthetic efficiency, proving a survival capacity consolidated in anatomo-morfophysiologic characteristic modifications in each specie. It demonstrates the high capacity of resistance facing dry period that is genetically condicionated, confirming the importance of the conservation of these natural resources to the study area.