Levantamento da vegetação campestre em áreas cultivadas com acácia-negra (Acacia mearnsii De Wild.) na região sul do Brasil

Abstract

Black acacia (Acacia mearnsii De Wild.) forests of different ages of cultivation and a native field characteristic of the Jaguarão region were evaluated through botanical surveys of the established vegetation and the soil seed bank to verify the changes occurred in the forage of the Mixed Field of the Eastern Crystalline due to the cultivation of black wattle. The study was carried out in the municipality of Jaguarão, RS, Brazil, in two properties, both near the border with Uruguay. The study was divided into three stages: botanic survey through the point method, collection of soil seed bank and botanical separation of aerial biomass. Black wattle forests were planted in native field areas and evaluated initially with 2, 6 and 8 years of planting; while the native field characteristic of the region served as a witness and its management was considered a conservationist. The areas were compared using the Jaccard Similarity Index. Thirty - nine species were identified, among the different evaluation areas. The areas with presence of black acacia presented smaller amount of poaceae and fabaceae. Under the forage aspect, the negative impact of black acacia cultivation on the native field was considered low, due to the disappearance of only three important forages, Paspalum pumilum, Paspalum lepton and Briza sp. until the 9th year of cultivation. However, there is a high potential for regeneration of the country vegetation even after 15 years of cultivation of the black wattle, through the persistent vegetation in the understory and by the soil seed bank. In this sense, the Axonopus affinis, the Dichantelium sabulorum, the Hymenachne sp, and the Piptochaetium montevidense stand out.