In southern humid Chaco forests dominated by Schinopsis balansae, woody plants are clumped and species composition varies spatially over short distances. We examined how these spatial patterns are associated with local environmental heterogeneity for three size classes of woody individuals: adults, saplings, and seedlings. Our study was based on the detailed description of two forest plots (3200 m2 in total) in which we mapped all individuals of woody species, and delimited patches with different microrelief, soil moisture, and ground cover of terrestrial bromeliads. Our results showed that woody-individual distribution is related to local environmental heterogeneity. For all size classes, density of woody individuals was highest on convex patches. These convex patches were dominated by both tree (Acacia praecox and Achatocarpus praecox) and shrub species (Celtis pallida, Capparis retusa and Grabowskia duplicata), while level patches were dominated only by tree species (Schinopsis balansae, Prosopis spp. and Geoffroea decorticans). Drier patches contained all the woody species present in the forest, while wetter patches contained only a subset of them. Within convex patches, trees are likely to occur in places with bromeliad colonies and shrubs in patches without bromeliads. The results suggest forest structure is controlled by environmental heterogeneity associated with microrelief and soil moisture.
Abbreviation: MRPP = Multiple Response Permutation Procedure.