Análise da cobertura vegetal em áreas de caatinga susceptíveis a desertificação, município de Jataúba – PE

Abstract

The objective of the research was generate information necessary to a scientific base to identify the standard of the vegetation of caatinga, in environments with different levels of degradation, proceeding from the performance of the man, in the city of Jataúba- PE, located in Pernambuco State, Brazil. Three environment categories had been selected in agreement the decreasing degree of degradation enviromment, sorrunding medeiun degraded and surrounding conserved (that it represented the vegetation certification). In each environment the community of caatinga was showed. Established 4 plots of 10 x 20 m for environment had been, a total of 12 plots that had been used for the floristc and phytosociological survey. Using the method point-intersection, in a pairo of transects of 20 m, esteem the canopy and the superficial substratum of the soil. The vegetation was showed in three vertical stratus: 1o- individuals with heighter until 0,5 m; 2o - individuals with height of 0,51 m – 3 m and 3o - individuals that had presented highest 3 m. In the floristic survey had been showed to 88 species, pertaining the 54 genera and 32 botanical families. Of the total of the showed species, 70 had been identified the specifc level, 8 the level of genera, 8 the family level and 2 had not been identified nor the family level. 6015 individuals had been showed: 2121 in the conserved environment, where they had been registered 40 species; 1813 in the environment mediun degraded, having 43 species; e 2081 in I degraded it, with register of 39 species. N 1o stratum, Aristida setifolia got the biggest specific covering and was present only in degraded environment. Begin able to be considered as indicating of degradation and how much bigger species the level of bigger degradation its density, 13,56 and 57,78 ind./m2, respectively. The measure that the degradation level grew, Cyperus uncynulatos increased in density, 10,22, 16,22 and 20,89 ind./m2, respectively. Evolvulus filipis showed to be better suitable to occupy more surrounding conserved. Alternanthera tenella only contributed in the vegetal canopy in degraded environments. Neoglaziovia variegate was present in 22 stratum of the conserved environment, in the four plots, with relative density of 74,97%, not occurring in excessively surrounding ones. Caesalpinia pyramidalis and Sida galheirensis, found in three environment, had considerable increase in the density, as bigger the stadium of degradation of environment. In 33 stratum, in the environment medium degraded, Caesalpinia pyramidalis presentedthe biggest values of covering and importance, followed of Aspidosperma pyrifolium. Together with Neoglaziovia variegate. Cordia leucocephala was present only the conserved environment. With relation to superficial substrat of the soil, the number of timeswas counted that each type of substratum was intercepted with a steel rod of 4 mm of diameter. The conserved environment presented the biggest covering with organic substance 66,13%; the degraded one presented the biggest covering with encrostament in the surface of soil 66,56%. The levels of degradation of environment characterized here in this work, had directly affected the structure of vegetation. This influence if disclosed on the density of the species and in the floristic composition of environments.