► Seedlings and juveniles of Limonium girardianum were experimentally submersed during eleven weeks. ► Comparison of survival, growth and biomass showed that seedlings are less resistant to flood ...stress. ► Differential response of a plant species to flood may explain species distribution and would be helpful to enhance conservation measure of this threatened species.
In order to define the flooding tolerance capacity of Limonium girardianum according to growth development stage, we submerged 200 seedlings and 200 four-month-old juveniles in fresh water. During the eleven weeks of the experiment, we recorded the survival, growth and dry biomass of both seedlings and juveniles. Every week, we removed a group of ten seedlings and ten juveniles from submerged conditions and put them in drained conditions. We measured the leaf production rate and variation in total leaf area of both seedlings and juveniles. We measured the final above and below-ground dry biomass for both seedlings and juveniles. The seedlings started to die from week-2, while juveniles started to die from week-7. Fifty percent of seedlings died over a six weeks period, while fifty percent of juveniles died over a ten-week period. Beyond seven weeks and nine weeks for seedlings and juveniles respectively, total submersion stopped growth, and delayed leaf production and the increase of the total leaf area. Above-ground dry biomass significantly decreased from 30g to 10g for seedlings and from 30g to 25g for juveniles, according to flood duration. Below-ground dry biomass percentage increased from 60% to 80% between week-4 and week-7 for seedlings. Below-ground dry biomass of juveniles decreased from 80% to 50% between week-4 and week-9. Our study showed that flood-prone plant species have a different response to flood conditions according to the developmental stage. The higher sensitivity to submersion of seedlings is due to its lower survivorship, lower leaf production, lower growth and more important dry biomass decrease than juveniles. This statement can be seen as a threat for population viability in the long term since human activities, such as construction of heavy industrial infrastructures and roads, induces too long flood duration that would compromise the persistence of L. girardianum populations.
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The aim of this research paper is to develop a statistical model that provides a more complete description of a basin's flood regime. The approach adopted in this paper is based on the ...flood-duration-frequency (QdF) analysis which takes into account the temporal variability of floods. This approach is analogous to the intensity-duration-frequency (IdF) model commonly used for rainfall analysis. The proposed model allows QdF curves for a given basin to be estimated while using a minimum number of parameters. This model is called 'converging' model because of the observed convergence of distributions towards small return periods. A local (at-site) model and a regional approach are developed. The regional approach uses classical concepts of regional hydrologic frequency analysis (index-flood (IF) method) and can be used for basins where no streamflow data is available. Results from 158 catchments located in the provinces of Quebec and Ontario (Canada) are used to illustrate the method.
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Riparian wetlands are under heavy pressure from hydrological changes produced by dam construction and water diversion projects. There has been ample documentation of the relationship between the ...extent of flooding and the composition of shoreline plant communities, yet we have few models that allow us to predict the impact of altered flooding regimes on riparian wetlands. In the humid temperate zone, river regulation commonly affects the distribution of two major vegetation types: wooded wetland and herbaceous wetland. The practice of reducing peak floods and augmenting minimum river flows is often followed by the succession of herbaceous to wooded wetland. We used logistic regression models to describe the distribution of wooded wetland as a function of all possible combinations of seven hydrological variables. The variables were chosen to reflect the depth, duration, and time of flooding and were calculated for four different time intervals (3, 7, 12, and 18 growing seasons). Our best model was a combination of two variables: the last day of the first flood and the time of the second flood. For three of the four time intervals, the vegetation type was correctly identified as herbaceous or wooded for >80% of the sample points. Our results suggest that models based on a few key environmental variables can be valuable tools in the conservation management of the vegetation of temperate and boreal zone wetlands.
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Restoration of species-rich flood meadows impoverished by agricultural intensification is an important challenge. The relationships between flooding regime and soil seed bank were compared in three ...successive meadow communities (hygrophilic, mesohygrophilic and mesophilic) distinguished along a topographic and hydric gradient. Differences in flood duration and frequency between the three associations allowed the study of the contribution of floods to soil seed bank richness and density. No significant difference was found in species richness among the three soil seed banks, whereas the densities were significantly higher in the wettest community. The three seed bank compositions were clearly distinguished along the hydric gradient. In fact, the three seed bank types constituted a species poor version of the meadow communities to which they belong. Flood contributions appear to play a minor role in seed bank enrichment. Thus, seed dispersal by flood water would probably be insufficient to enable the restoration of alluvial meadows.
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In the present paper a procedure for the construction of Synthetic Design Hydrographs (SDH) for ungauged sites is proposed, based on the regional estimation of Flood Duration Frequency (FDF) and ...Peak-Duration (PD) curves.
The basic hypothesis is that the reduction ratio between the quantiles of maximum average discharge in given duration and peak discharge is independent of the return period, which in practice occurs for medium-large catchments. Under this assumption the regional estimation of FDF curves reduces to the estimation of peak discharge quantiles and reduction ratio.
The procedure has been applied to the Po river in Italy, employing for the calibration the historical flood waves recorded at eight gauging stations along the river.
The regional estimates of SDHs have been compared with the local ones obtained at the gauging stations. At two consecutive upstream stations, the comparison reveals and partly rectifies some clear data inconsistencies due to uncertainties in stage-discharge relationships.
The proposed model provides an operational tool for hydrologic risk assessment and flood protection planning along the entire course of the Po river. Moreover, the regionalisation procedure is quite simple and its validity is not restricted to the specific case presented in this paper
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Turloughs are seasonal wetlands in Ireland and are priority habitats under the EU Habitats Directive. A number of previously described turlough plant communities were surveyed and, using objective ...floristic analysis, nine communities identified. Within these nine communities, there was gradation from one community to the next. Overall, there was a broad division between sedge-dominated and grass/forb-dominated communities that is recognised by other authors. The variants in these communities differ, however, between the various authors indicating that there may be gradation from one community to the next in relation to subtle differences in environmental variables. A number of environmental variables that may affect these communities were investigated and depth of deposits over bedrock, soil moisture, date of emptying of the turlough, and water phosphorus and nitrogen were found to correlate with the turlough plant communities in this study.
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This study quantified relationships between forest composition and flooding gradients on the Roanoke River floodplain, North Carolina. Because flooding is highly variable in time and space, the ...research was designed to determine the specific hydrological parameters that control woody species abundance on the landscape scale. I specifically tested the importance of spring vs. yearly flood duration, as well as flood duration during hydrologically wet vs. dry years. Field vegetation samples of woody species composition were integrated with spatial data from a Landsat Thematic Mapper (TM) classification and a flood simulation model derived in part from synthetic aperture radar (SAR) imagery. Flood simulations were output and summarized for the periods 1912-1950 (before dams were constructed on the river) and 1965-1996 (after all of the dams were completed). Tenth percentile (dry), median, and 90th percentile (wet) hydroperiod (flood duration) regimes were generated for the spring and year, both pre- and post-dam. Detrended correspondence analysis (DCA) was used to ordinate the plot data, and correlation/regression between ordination axis scores and the flood variables were used to explore the relationships between flooding and species composition. Nineteenth percentile hydroperiod (i.e., wet conditions) correlated most strongly with DCA axis 1 (r > 0.9), indicating that inundation during extremely wet years strongly controls species composition on the floodplain. The results were used to quantitatively determine the niche width for both species and mapped vegetation classes in terms of number of days flooded annually and during the spring growth period. The results suggest that spring hydroperiod is an important mechanism that may drive competitive sorting along the flooding gradient, especially during the early years of succession (i.e., pre-dam, which represents the period during which most of the forests sampled were established), and that annual hydroperiod affects the relative dominance of species as the forests mature.
Extending duration of moderately used 1-day preharvest floods in sugarcane (Saccharum spp.) could improve Florida sugarcane insect control, freeze protection, and soil conservation, and reduce ...unwanted P discharge. The purpose of this study was to compare the effects of flood duration and month of flood application on theoretical recoverable sucrose (TRS), cane yield, and sucrose yield of four sugarcane cultivars. During the plant-cane and first-ratoon crop cycles, 0-, 10-, or 20-day floods were applied in November or to lysimeters planted with cultivars CP 72-2086, CP 80-1827, CP 89-2143, and CP 92-1666. Cane and sucrose yields of flooded treatments were at least as much as those of non-flooded controls. These results warrant research to quantify the profitability of preharvest flooding of sugarcane, recognizing that these 10-20 day floods had minimal impact on yields while offering potential economic returns from other agronomic and ecologic benefits.
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