Effects of Flooding on Connecticut River Plant Species



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Due to dam construction and other human influences, patterns of river water flow, including the timing and duration of flooding, have become increasingly stable in wetlands. Flooding is a natural disturbance event that changes the physical structure and nutrient availability of habitats. The prevention of natural flooding can change species composition in floodplains and assist colonization by non-native species. The presumed mechanism for this pattern is that species differ in their tolerance to flood duration, yet there are few experimental studies that have examined flood tolerances experimentally. The purpose of this study was to quantify differences in flood tolerance among 25 woody plant species found along the Connecticut River, and to determine the degree to which flood tolerance predicts species distributions along flooding gradients. I additionally analyzed the roles of height, non-native status, growth form, and evolutionary history on flood tolerance. Seedlings were subjected to flood treatments of four different durations, with and without suspended clay sediment. The flood tolerance of each species was calculated by comparing individual species’ survival relative to the average survival across all replicates. The flood and sediment treatments had a significant effect on seedling survival, and the distribution of species on flooding gradients was predicted by the experimentally determined flood tolerance. There was significant variation in height between species, and seedlings submerged more deeply were less healthy than those closer to the surface. Native species had overall better health than non- native species with increasing flood stress. Analysis of growth forms showed that shrubs were significantly healthier than vines with increasing flood stress. There were no significant differences between trees and other growth forms. Higher flood tolerance did not map cleanly onto plant families. The most flood tolerant and least flood tolerant species were both in the genus Acer (maples).



flood tolerance, biology, ecology, flooding, sediment, Connecticut, invasive species, flood control, species distribution