Abundância e raridade de espécies em uma floresta ombrofila aberta com bambu no Estado do Acre.

Abstract

Species do not have the same abundance in ecological communities. An almost universal pattern that has been published in the literature and that few species are common within a given area, others moderately common and a great majority are rare species. However, defining rarity and abundance still generates much controversy in thescientific milieu; These conflicts are a serious problem, because the results produced can both reflect the actual differences in the patterns of abundance and rarity or simply are merely objects of methodological differences. The aim of this work is to determine the abundance and rarity patterns of tree species in an open tropical forest with bamboo, located in the Macauã National Forest (FLONA), in the state of Acre, using data of 15 different hectares inventoried in two forest strata, constituted by individuais with circumference at breast height > 30 (Stratum 1, trees) and individuais with 10 < circumference at breast height <30 (Stratum 2, sapling).We compared abundance and rarity in three methods of analysis (Hubbell, Martins and Kageyama) and between the two strata, in addition to comparing the results obtained with results extracted from several floristic inventories of the Amazon. To describe abundance and rarity, a descriptive statistical analysis was performed. In order to compare the abundance and rarity between the three methods and the two forest strata, a variance analysis was performed, at a levei of 5%. At the transects, 513 species and 8561 individuais were inventoried. The Kageyama method presented a higher percentage of rare species compared to the Hubbell and Martins method, both for trees and for saplings. The strata presented similar percentages of common species by the Hubbell method, the only method applied to analyze common species. When considering a single list of species, considering the 15 hectares inventoried, the percentage of rare species was very similar between the Hubbell and Kageyama methods, both in stratum 1 and stratum 2; however, using the Martins method the percentage of rare species was much lower. There is a difference between the average percentages of rare and common species per hectare comparing to the 15 ha summed up as if it were a continuous area. The averages per ha were greater than the sum of the 15 ha. When comparing with other arcas of the Amazon, the average percentages of common species showed great variation. The Martins method showed a percentage of species smaller than Hubbell, while Kageyama method showed the highest percentage. The Hubbell method, besides separating the common species of intermediate and rare, was also best in relation to the others analyzed methods.