Sucesión ecológica temprana en un deslizamiento de ladera de grandes dimensiones en ambiente tropical seco (Volcán Casita, Nicaragua)

Resumo

This study documents ecological succession on a large landslide located in a highly humanized area that have a tropical dry climate, during the first four years after disturbance (1999-2002). Our aim was to analyze the effects of abiotic heterogeneity, landscape context and the incidence of disturbances and/or stochastic events on succession. We studied the relationships between spatial changes in environmental factors and the spatial distribution of vegetation in the landslide and in the adjacent forest. We determined the main pathways and causes of change for several community features, studied the spatial patterns of colonization of the dominant pioneer species, and analyzed the existence of intra- and inter-specific interactions between them. Pathways of early succession on richness, biomass, species composition and abundance of plant traits differed significantly between different areas or “sectors” within the landslide defined in terms of abiotic heterogeneity (stability and fertility of substrates) and landscape context. Abiotic factors associated with fertility of sites and the incidence of human disturbances were the main causes of change. The general spatial pattern of colonization was determined by the patterns of the most dominant pioneer species, and evidences of intra- and inter-specific interactions between the individuals of Trema micrantha, Muntingia calabura and Wigandia urens appeared. Besides, in the case of T. micrantha, the existence of plastic responses to one-sided competition for light was detected. The results obtained indicate that environmental heterogeneity and human disturbances play an important role in succession on large landslides located in areas with tropical dry climate. This suggest that, rather than focusing research only on largescale disturbances, the study of succession in this type of landslides must consider the response of ecosystems to a hierarchical set of processes that act and generate heterogeneity at different scales. This concurs with the results of recent studies that emphasize the importance of interactions between landslides and other disturbances, and is relevant for the development of suitable restoration strategies in the study area.