Functional diversity of soil bacterial communities in the tabonuco forest: Interaction of anthropogenic and natural disturbance

Anthropogenic and natural disturbances play critical roles in affecting the structure and function of Caribbean ecosystems, where hurricanes represent important disturbances superimposed on a landscape modified by human agricultural and forestry practices. Based on the differential catabolism of a suite of 128 carbon sources by soil bacterial communities, we focus on four aspects of functional diversity (total substrate activity, substrate richness, substrate evenness, substrate diversity) in the tabonuco forest of Puerto Rico, and assess the degree to which their spatial variability is a consequence of historical landuse or impacts of Hurricane Hugo. Considerable microspatial heterogeneity characterizes the functional diversity of forest soil communities, but the degree of hurricane damage to above-ground plant communities is positively related to all four indexes of functional diversity 5yr after the hurricane. No differences in functional diversity were detected with respect to historical landuse, after controlling for the effects of hurricane damage. However, this lack of significance may be an artifact because the spatial distribution of hurricane damage is not independent of historical landuse. As a consequence, contemporary studies of spatial heterogeneity that do not account for historical patterns of anthropogenic or natural disturbance may yield spurious or incorrect conclusions. Long-term studies help to rectify this problem and are especially important within the context of evaluating the impacts of increasing human demands on natural ecosystems.