Succession on the Rocky Outcrop Vegetation: A Rupestrian Grassland Scheme

Abstract

We investigated the nature of the temporal processes involved in the formation of vegetation on the heterogeneous landscape of rocky outcrops on ridge tops in rupestrian grasslands (campos rupestres) , Northeastern Brazil. Relationships were established between spatial patterns and gradual processes of succession and their respective species life-forms. The first plants to occupy the isolated rock are mainly chamaephyte monocotyledons (tolerant to desiccation or epilithic) and hemicryptophytes (with or without rosettes). With time, species with other life-forms and eudicotyledons join them, gradually to go from a solitary spatial distribution on the rock to a more continuous distribution. In the initial steps, droughts and storms are the most intense disturbances . In subsequent steps, due to the continuity of the vegetation and high frequency of fires, fire is the predominant factor. The scheme presented here follows the general pattern described for vegetation in other rocky outcrops, with similar taxonomic and/or functional groups. The simultaneous occurrence of several successional steps in the same area increases the probability that part of the vegetation will remain when confronted with disturbances, and constitutes an important diversity factor in rupestrian grasslands.