Floristic composition and soil fertility in gold mining of Lavrinha, Pontes and Lacerda, MT, Brazil

Abstract

The mining activities cause intense environmental degradation, especially to the soil and vegetation. This study evaluated attributes of floristic composition and soil fertility in areas of open gold mining areas. One hundred plots of 10 × 10 m were distributed in the area effectively mined and in its surroundings. Stem circunference measures (AGC) of all identified woody individuals with greater than or equal to 9 cm were taken at 0.3 m height above the ground. In all plots soil samples at 0-20 cm depth were collected for analysis of fertility attributes that are routinely evaluated. In total we observed the occurrence of 92 species and 43 families. The most abundant families were Myrtaceae, Fabaceae and Dilleniaceae; and families that had the greatest numbers of species were Fabaceae (10), Malpighiaceae (7) and Vochysiaceae (5). In the area effectively mined the species with higher importance value index (IVI) were Curatella americana (89.1) Cecropia hololeuca (40.9), Roupala montana (12.5) and Pouteria ramiflora (10.2) while in surrounding of the mined area the species with the highest IVI were Myrcia multiflora (25.6), Caryocar brasiliense (15.7), Magonia pubescens (14.8) and Vatareia macrocarpa (14.4). In both areas, the soil had low pH, low availability of P, K+, Ca2+ and Mg2+ and high Al3+ saturation. In spite of the low soil fertility of the studied area, it was able to maintain an overall density of vegetation with AGC > 9 cm of 430 individuals per hectare in the effectively mined area and of 2,220 individuals per hectare in their surroundings.