Effect of rotational grazing management on vegetation of floodplain wetlands

In Argentina, the expansion of soybean production has forced the relocation of cattle to marginal sites for agriculture, such as the wetlands of the Parana River floodplain, constituting a threat to the vegetation of these ecosystems. In this context, the aims of this study were (1) to assess the effect of different resting/grazing periods on the composition, richness, diversity and dominance of functional groups of wetlands vegetation assemblages and (2) to analyze the influence of cattle exclusion on these parameters. For these purposes, three wetlands subjected to rotational grazing management included in different paddocks with different resting and grazing periods were selected. Exclosures were established in upland and lowland zones. Samples of vegetation cover were collected in these zones with quadrats of 4m2. Our results demonstrated that vegetation parameters did not differ as grazing and resting time period differed. Both the wetland with short resting/long grazing period as well as the wetland with long resting/short grazing period had lower diversity and richness in comparison with the wetland without cattle grazing. Grazing exclusion favoured the survival of species in upland zones, increasing total richness and diversity and the development of unpalatable non-forage and shrub/subshrub species. Exclosures would be beneficial to the ecological condition of the vegetation of the wetlands, allowing grazing-sensitive species to recover from grazing and trampling.