Drought susceptibility in emergent wetland angiosperms: a comparison of water deficit growth in five herbaceous perennials |
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Authors: | B W Touchette A Frank L R Iannacone G Turner |
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Institution: | (1) Center for Environmental Studies, Elon University, Campus Box 2625, Elon, NC 27244, USA |
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Abstract: | Freshwater wetlands often exist as transitional areas between terrestrial uplands and deep open water. Thus they are fundamentally
sensitive to changes in hydrology. Some of the more dramatic changes in wetland water supply occur during extensive droughts,
where both precipitation and soil water table markedly decline. While it is generally understood that herbaceous wetland macrophytes
are more sensitive to decreased water availability than wetland trees, the degree of susceptibility among wetland herbs remains
relatively unexplored. Therefore, the purpose of this study was to evaluate plant growth responses of five herbaceous wetland
species (monocots Carex alata, Juncus effusus, and Peltandra virginica, and dicots Saururus cernuus, and Justicia americana) to simulated drought conditions (up to 6 weeks in a 1-in-25-year precipitation low with receding soil water tables). Of
the five species studied, three (J. americana, S. cernuus, and J. effusus) had no survivors after 6 weeks of simulated drought. J. americana, appeared to be the most sensitive to water deprivation with a 67% decrease in plant phytomass and an 85% decrease in leaf
area with only 2 weeks of drought, and complete mortality after 3 weeks. While P. virginica also had significant decreases in biomass, leaf area, relative growth rate (RGR) and unit leaf rate (ULR), in as little as
2 weeks of drought, no noticeable decreases in survival were observed. In contrast, when J. effusus experienced between 2- and 4-weeks of water deprivation, there were significant increases in RGR, ULR, phytomass, leaf area,
and shoot:root ratios. S. cernuus and C. alata remained relatively unaffected following 4 weeks of drought; however by the fifth week, there were significant declines in
leaf area for both species. In general, this study provides experimental evidence on how herbaceous macrophytes grow under
drought conditions. This basic understanding is fundamental if we are to develop better working models on how wetlands will
respond to changing environmental conditions that lead to decreased water supply. |
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Keywords: | Drought Herbaceous Macrophytes Plant growth Productivity Water deficit Wetlands |
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