Composição, riqueza e variação espaço temporal de macrófitas aquáticas do Lago Trevo, Município de Boa Vista, Roraima

Abstract

This study was undertaken aiming at characterizing environmental components, soil and water, as well as determining composition, richness, time and spatial distribution of aquatic macrophytas in a natural pond, Trevo pond (N 02º49`01,1 W 060º48`27,7), of a savanna ecosystem in Boa Vista City/Roraima State. Flora survey was undertaken in eight excursions between September, 2006 and May, 2007, and comprised seven collection seasons in three zones (coastal, intermediate and limnetic). For the coastal region, it was followed the species temporal (succession) distribution pattern in a 20 m transept (margin/center). Water collection for physical-chemical analysis was undertaken between September, 2006 and January, 2007. Soil analysis indicated yellow clay on the northwest face and vegetation of a savanna park type. On west and southwest faces, the soil was characterized as hydromorphic quartzarine neosoil, and the vegetal covering as wooded grassland savanna. Physical variables analysis indicated variation on temperature (27,6°C Dec/06 a 32,2°C Oct/06), pH (7,1 Sep/06 a 7,4 Dec/06), OD (2,57mg/L Oct/06 a 5,7 mg/L Dec/06) and murkiness/turbidness (1,16 NTU Dec/07 a 16,16 NTU Jan/07). Nutrient analysis (total nitrogen, ammonia, nitrite, nitrate and phosphorous) did not reveal organic pollution traces for that environment. Flora survey revealed 31 taxons belonging to 17 botanical families, with predominance of the following ones: Cyperaceae (19%), Eriocaulaceae (13%) and Melastomataceae (10%). Among life forms, the amphibians (53%) and emergents (32%) were most prominent. It was observed a species distribution influenced by depth. Out of the 17 families, 16 showed representatives in coastal region.