Acúmulo de biomassa aérea e concentra??o de nutrientes em Melinis minutiflora P. Beauv. e gramíneas nativas do cerrado

摘要

The African grass, Melinis minutiflora P. Beauv., is causing concern in Brazil since it is replacing native grasses in the cerrado region, even in protected areas. In the present study the accumulation of aerial biomass and concentration of nutrients in M. minutiflora and native grass species were compared to determine whether M. minutiflora was capable of accumulating greater biomass with lower concentration of nutrients. The study was conducted in the National Park of Brasília. Four different sites of cerrado sensu stricto where invasion by M. minutiflora was occurring were selected and at each site two 20 m x 20 m plots were laid out, one with only M. minutiflora and the other with only native grasses. Four aerial biomass samples were collected from each plot every three months for a year, using 25 cm x 25 cm quadrats. Concentrations of nutrients were determined in live and dead biomass. Soil samples from 0-15 and 15-30 cm depths from the same plots were also analyzed. The live aerial biomass of M. minutiflora was greater than that of native grasses during the dry season at the time of flowering of M. minutiflora and at the beginning of the rainy season. There were no differences between M. minutiflora and native grasses in the availability of nutrients in the soil or in the concentrations of nutrients in live biomass. In the case of dead biomass, only nitrogen was present in lower concentrations in M. minutiflora.