Environmental drivers of three neighbouring monodominant stands in Pantanal wetland

Abstract

Questions Inundation is an important feature linked to monodominance in tropical wetlands. The occurrence of neighbouring monodominant species indicates that soil can also have an important role. This study aimed to determine if variations in densities of three neighbouring monodominant species, Byrsonima cydoniifolia, Copernicia alba and Tabebuia aurea, are related primarily to variation of flooding patterns and secondarily to soil physicochemical variations in the Pantanal. Location This study was performed in the southern Pantanal subregion of Miranda. Methods We sampled 74 plots of 25 m × 25 m distributed among 15 patches of these species (five patches of each species). In each plot, we sampled all individuals of all shrub and tree species, checked the water mark left on tree trunks by the last flooding, and collected soil samples. Data were analyzed using canonical correspondence analysis (CCA) and regression trees. Results We found that the main driver splitting these monodominant stands is soil, and that the secondary driver is inundation. The main drivers for Copernicia alba were higher soil pH, higher inundation and soil contents of Mg. For Byrsonima cydoniifolia, the main drivers were low Ca and Mg contents and high content of fine sand. Tabebuia aurea was the only species for which inundation was the main driver. Conclusions We reject the hypothesis that inundation is the main driver splitting these monodominant stands. Differences in flooding levels were not crucial for two of the three species. Except for Tabebuia aurea, which was more influenced by inundation, soils were found to play an essential role in this spatial separation.