Fitossociologia do componente arbóreo em áreas ciliares e de nascentes de um fragmento de floresta ombrófila densa de terras baixas, em Sirinhaém, Pernambuco.

Abstract

Taking into consideration, the scarcity of studies related to forests and springs in the Northeastern region of Brazil, this study is aimed to get an understanding of the composition of phyto tree component in two springs and riparian streams that feed the River Sirinhaém, in the municipality of Sirinhaém, Pernambuco to support programs of restoration and preservation of these configurations. The streams are located in a fragment of tropical rain forest of lowlands, with 272 ha, located in Mill Buranhém in the city of Sirinhaém in the State of Pernambuco, under the coordinates 8° 34' 34.6'' S and 35º 10' 5.7'' W and at an average elevation of 49 m. To collect the data of the tree component in the areas of the springs, they were divided into 10 plots of 10 x 25m, arranged in rays, above the springs and systematically distributed in 5 rows, separated by an angle of 45°. In each line 2 plots were allocated at an interdistance of 25m. The first portions of each line contemplated a Permanent Preservation Area (PPA). The third (3rd) stream was sampled for riparian vegetation, with an allocation of 40 plots (20 on each side), 10 plots were implemented following the banks of the stream with an inter-distance of 25 m and 10 plots distributed in parallel, also with an inter-distance of 25 m, with the same dimensions used at Springs A and B. In total 60 plots were installed, representing a sample area of 15.000 m2. In each plot we sampled all individuals with a circumference, measured at breast height (CBH) ≥ 15 cm. It was found that the number of samples used in the springs A and B and riparian was sufficient to meet the acceptable sampling error of 20% to 95% probability. In the Spring A, we sampled 309 individuals, which correspond to a density of 1236 ind.ha-1, belonging to 27 families, 46 genera and 58 species. The basal area of Spring A is 27.647 m2 ha-1. Sampling performed in Spring B listed a total of 244 individuals, corresponding to a density of 976 ind.ha-1, belonging to 31 botanical families, 42 genera and 58 species. The basal area of Spring B is 21.405 m2 ha-1. In terms of species diversity in the spring, the highlight was the family of Mimosaceae, and in source B, the family of Melastomataceae had the highest number of species. The most abundant species were the Tapirira guianensis and Inga flagelliformis in the Spring A, and Pogonophora schomburkiana and Thyrsodium spruceanum in source B. In the Riparian Forest, we sampled 1307 individuals (a density of 1307 ind.ha-1 and a basal area of 26.735 m2 ha-1), distributed in 40 families, 69 genera and 118 species. Myrtaceae and Sapotaceae were the families with the greatest number of species. Protium heptaphyllum and Pouteria sp.1 were the most abundant species in this environment. Regarding the classification of succession in the three environments, the species of early successional (pioneer + early secondary) had the highest number of species, demonstrating features of a forest at an early stage in the successional development. In terms of Value Importance (VI) species of Eschweilera ovata, Protium heptaphyllum and Virola gardneri are among the ten most ecologically important in the three environments studied. For the sources A and B, the Shannon-Weaner (H') was 3.50 and 3.62 nats/ind., respectively. In riparian forest, the Shannon-Weaner resulted in the value of 4.01 nats/ind. The diameter distribution showed characteristics of secondary environments, where the higher frequency of individuals were found in smaller diameter classes.