Capim-Gordura (Melinis minutiflora) no Parque Estadual da Serra do Rola-Moça: impactos na comunidade de plantas, alterações do micro-clima,características do fogo e características reprodutivas

Abstract

The end of the Cerrado vegetal formations located outside protected areas is foreseen in 2030, and areas characterized by exotic species will have to be excluded from these 5.5% remaining areas where original Cerrado vegetation was found. The molasses grass is one of the main invasive species in the Cerrado, and is the exotic grass which has caused the greatest impact on the native flora. The species is present in several Cerrado conservation units but there are no reports about efforts to eradicate it from them, even though some studies on howto eradicate it have been done. The effects of this species on the native flora are mainly due to shading (due to its size), possible allelopathy and the accumulation of large quantities of combustible biomass that alters the characteristics of fires. Fire is a natural component of theCerrado ecosystem. However, when its intensity, extension, frequency, seasonality and kind (underground, surface and canopy) differ from the characteristics of a natural Cerrado fire, it can affect ecological relations favouring exotic species over the ones that are favoured by thenatural regime. It can also eliminate species with unique characteristics that give them protection against the natural fire regime but not against the altered fires. Continuing the research done at the Serra do Rola-Moça State Park (PESRM) during 2009 (Rossi, 2009) this work intended to study important characteristics of the molasses grass and its associatedcommunity in order to understand the invasive process and its main effects on the native vegetal communities. Our results indicate that the molasses grass: a) at the study area it produces a mean of 1 billion, 24 million and 110 thousand full florets per hectare (extrapolated data); b) alters the microclimate of invaded areas, increasing air humidity andreducing luminosity on the ground surface, but not changing air temperature at ground level; c) with the increase of the degree of invasion there is a reduction in the biomass of native monocotyledons; d) reduces the number of dicotyledonous individuals as well as the numberof species (richness) present in invaded areas; and e) alters fire characteristics increasing flame length, maximum spreading rate, fire line intensity and heat per area unit. We conclude that the PESRM presents a high degree of invasion, with the production of billions ofmolasses grass seeds that spread all over the Park and that, in already invaded sites reduce the number of native monocotyledonous and dicotyledonous individuals and dicotyledonous species producing fires with more severe characteristics of those natural to the Cerrado.