Spatial distance, not environmental heterogeneity, explains fine-scale
patterns of ß-diversity in multiple life stages of logged tropical
Selective logging of tropical forests substantially alters the
composition and spatial arrangement of plant communities. Previous
studies examining logged-forest tree assemblages have focused primarily
on adult communities, leaving major knowledge gaps regarding the
diversity patterns of earlier life stages. A key question is to
elucidate the temporal dynamics of community assembly in human-modified
forests. Sampling 8,664 sapling, juvenile, and adult trees from a
heavily logged forest in Sabah, Malaysian Borneo, we tested whether
compositional variation and the relative importance of different
environmental and spatial factors explaining patterns of ß-diversity
differed between life stages, and whether dissimilarity was driven by
species turnover or nestedness. We found positive ß-deviations in all
communities, consistent with a strong influence of assembly processes
that result in aggregated spatial distributions of individual species.
Across life stages, ß-diversity was largely explained by spatial
distance, rather than measures of environmental heterogeneity.
Dissimilarity was driven by species turnover not nestedness, with
compositional variation in early life stages strongly correlated with
turnover in adult communities. Collectively, our findings indicate that
despite increased spatial heterogeneity in forest structure, liana
infestation, and canopy openness post-logging, these factors do not
sufficiently explain fine-scale patterns of tree composition.
Alternatively, diversity patterns of earlier life stages more closely
reflect potential assembly processes related to aggregated adult
distributions and associated dispersal limitations resulting from
spatial variation in logging activity.