Avaliação da recuperação natural de áreas degradadas pelo garimpo de diamante no Vale do Rio São José em Lençóis/BA

Abstract

The present work examined the floristic compositions and structures, and the similarities between seven areas degraded by mechanized diamond mining along the São José River Valley (12o34’ to 12º36’ S - 41o22’ to 41º35’ W), in the municipality of Lençóis, Bahia State, Brazil, after 23 years of abandonment and natural regeneration and compared them to an area of intact gallery forest along the same river. The collections were made between the months of April and December/2011 along 1 x 100 m transects established in each of the seven areas, applying the point method. A previously compiled species list was used to compare the seven recovering areas with an intact riverine forest site. A total of 62 species were encountered, distributed among 53 genera and 26 families. The families demonstrating the greatest species richness were Leguminosae (16), Poaceae (11), Cyperaceae (7), Melastomataceae (6), Malvaceae (4), and Lycopodiaceae (2). The sum of the richnesses of these families represented fully 74% of the total number of species recorded in the present study. In terms of the plant habits, 11 species (15%) were arboreal, 17 (26%) shrubs, 28 (42%) herbaceous, 07(11%) sub-shrubs, and 04 (6%) vines. The species demonstrating the greatest Relative Vigor and Cover were Sebastiania corniculata, Aristida setifolia, and Homolepis aturensis. The slow natural regeneration of these areas was apparently due to the modification of the soil structure by the mechanized mining, as judged by the greater similarity (although low) between the areas regenerating for the longest periods and the intact gallery forest site along the same river as performing solo one little more structured.c