Heterogeneidade de ecossistemas, modelos de desequilíbrio e distúrbios

Abstract

In the past the ecosystem concept as homogeneous units was probably the main reason for fire exclusion in fire prone environments of protected areas through the world. This concept excludes the patterns of natural disturbances what were not understood and still are not understood for management of protected areas. The new paradigm of heterogeneity for ecosystem ecology has required the role of fire as
a factor for spatial and time heterogeneity. This new paradigm would be a search for natural conditions in
fire prone ecosystems such as savannas. However the fire frequency has been high in Brazil´s protected
areas. Therefore, this kind of disturbance has many negative effects for biological conservation. In addition, fire sensitive ecosystems such as forests could experience fire as an extremely negative impact for biological conservation. On the other hand fire exclusion could reduce vegetation heterogeneity and it has been observed in grasslands and savannas. Fire management in fire prone ecosystems inside protected areas should be prescribed after long term monitoring research of fire effects on biodiversity and ecological process. General rules for fire regimes should not be prescribed in fire prone ecosystems since historical data, degree of human impacts, invasive and exotic species, connective patterns of fragments and fauna could influence the fire management results. The protected areas with biogeography island effects and near roads, cities and
intensive agriculture should experience fire management as a more complex challenge since the burnings could have synergistic effects with human impacts.