RESUMO
The Brazilian savanna (Cerrado) is considered the most floristically diverse savanna in the world, home to more than seven thousand species. The region is a mosaic of savannas, grasslands and forests whose unique biophysical and landscape attributes are on the basis of a recent ecoregional map, paving the way to improved region-based strategies for land management actions. However, as a fire-prone ecosystem, Cerrado owes much of its distribution and ecological properties to the fire regime and contributes to an important parcel of South America burned area. Accordingly, any attempt to use ecoregion geography as a guide for management strategies should take fire into account, as an essential variable. The main aim of this study is to complement the ecoregional map of the Cerrado with information related to the fire component. Using remotely sensed information, we identify patterns and trends of fire frequency, intensity, seasonality, extent and scar size, and combine this information for each ecoregion, relying on a simple classification that summarizes the main fire characteristics over the last two decades. Results show a marked north-south fire activity gradient, with increased contributions from MATOPIBA, the latest agricultural frontier. Five ecoregions alone account for two thirds of yearly burned area. More intense fires are found in the Arc of Deforestation and eastern ecoregions, while ecoregions in MATOPIBA display decreasing fire intensity. An innovative analysis of fire scars stratified by size class shows that infrequent large fires are responsible for the majority of burned area. These large fires display positive trends over many ecoregions, whereas smaller fires, albeit more frequent, have been decreasing in number. The final fire classification scheme shows well defined spatially-aggregated groups, where trends are found to be the key factor to evaluate fire within their regional contexts. Results presented here provide new insights to improve fire management strategies under a changing climate.
Assuntos
Ecossistema , Incêndios , Brasil , Florestas , PradariaRESUMO
Covering almost a quarter of Brazil, the Cerrado is the world's most biologically rich tropical savanna. Fire is an integral part of the Cerrado but current land use and agricultural practices have been changing fire regimes, with undesirable consequences for the preservation of biodiversity. In this study, fire frequency and fire return intervals were modelled over a 12-year time series (1997-2008) for the Jalapão State Park, a protected area in the north of the Cerrado, based on burned area maps derived from Landsat imagery. Burned areas were classified using object based image analysis. Fire data were modelled with the discrete lognormal model and the estimated parameters were used to calculate fire interval, fire survival and hazard of burning distributions, for seven major land cover types. Over the study period, an area equivalent to four times the size of Jalapão State Park burned and the mean annual area burned was 34%. Median fire intervals were generally short, ranging from three to six years. Shrub savannas had the shortest fire intervals, and dense woodlands the longest. Because fires in the Cerrado are strongly responsive to fuel age in the first three to four years following a fire, early dry season patch mosaic burning may be used to reduce the extent of area burned and the severity of fire effects.
Assuntos
Conservação dos Recursos Naturais/métodos , Incêndios , Pradaria , Modelos Teóricos , Algoritmos , Brasil , Desastres , Ecossistema , Geografia , Humanos , Estações do Ano , Fatores de Tempo , Árvores/crescimento & desenvolvimentoRESUMO
Lepidoptera pest species from eucalyptus were collected in Eucalyptus urophylla plantations in the region of TrÛs Marias, State of Minas Gerais, Brazil, every 15 days from June 1989 to June 1994 with five light traps. Twelve primary and 15 secondary pest species were collected in the period with an average of 13,387 and 812 individuals per light trap, respectively. Most collected primary pest species were Stenalcidia grosica (Geometridae), Iridopsis subferaria (Geometridae), Eupseudosoma aberrans (Arctiidae) and Psorocampa denticulata (Notodontidae), totalizing for the study period an average of 5,450, 2,162, 2,436 and 1,458 individuals per light trap, respectively. Idalus admirabilis (Arctiidae) was the most collected secondary pest species, averaging 652 individuals/trap. Most primary pest species were collected during the dry season, from April to July, whereas most secondary pest species were collected during the rainy season, from January to March. These differences on seasonal occurrence between the two groups could be due to the fact that many secondary pest species of Eucalyptus in Brazil pupate in the soil, and they need humidity to complete its pupal stage.
Assuntos
Animais , Eucalyptus , Lepidópteros/classificação , Brasil , Umidade , Densidade Demográfica , Estações do AnoRESUMO
Descriçäo de dois irmäos, com endurecimento da pele nas regiöes dorsolombar e glútea, bem como no terço proximal da coxa, sintomas que apareceram muito precocemente. Isot levou a restriçöes de obilidade nos seus joelhos e quadris. este quadro, mais a ausência de distúrbio no metabolismo dos muscopolissacarídios ou processos inflamatórios, sugerem serem eles afetados pela distrofia congênita da fascia. Os seus genitores säo normais e consanguíneos (F=0.2%). Uma revisäo de literatura indica a possibilidade da existência de heranças autossomica dominante e recessiva nesta doença, os casos aqui descritos fornecendo evidências em favor das últimas