Impact of Flood Duration on Germination Success of Paraná River Delta (Argentina) Plants

The hydrological regime determines the structure and diversity of wetland vegetation, and it has been considered as the most relevant determinant for the plant communities in the Paraná River Delta. However, experimental validations explaining the causes of the distribution patterns are scarce. The objective of this article is to determine the effect of flood duration on wetland species germination. For that purpose, the seeds of four species from contrasting hydrogeomorphological environments, three ligneous species and one herbaceous species, were sowed. The 24 germination trays were watered weekly, and undergone four flood duration treatments: zero, one, seven and 13-day flood period every two weeks. We found that the longer the flood duration, the greater the reduction on germination for ligneous species, and the opposite was observed for the herbaceous species. The odds of germination in the longer duration treatment, versus control treatment, can be reduced up to 99% for ligneous species, and can be increased 900% for herbaceous species. Germination in the studied species performed as expected in their natural environments, although the ligneous species showed a broader niche, indicating that other mechanisms are also necessary to understand the distribution of these species. The results provide experimental evidence that flood duration impacts on germination and species composition of wetland species and provide tools for the prediction of anthropic impacts and the ecological restoration of wetlands.