<p class="TBody">Soil erosion on lakeshores due to the fluctuating water levels, waves, and other factors, remain a world-wide problem. Lakeshore vegetation can be helpful in preventing erosion. We investigated the effects of drawdown rate and depth on the growth and reproduction of a keystone lakeshore plant. We hypothesised that plants with access to water for longer would grow better and have higher reproductive output.</p> <p class="TBody">We subjected 108 Spiny Sedge (<em>Cyperus gymnocaulos</em>) plants to six treatments comprising three drawdown rates (static, slow, fast) and two water depths (shallow and deep). We measured plant stem heights and numbers of flowers and bulbils weekly, and the initial and final biomass of the above ground and below ground components.</p> <p class="TBody">Plants in treatments without access to water for long periods had the lowest growth and reproductive output. However, if the final water level was deep but drawdown was done slowly, plants were able to maintain similar growth and reproduction rates to plants with continuous access to water.</p> <p class="TBody">Fluctuating water levels in lakes cause lakeshore plants at lower elevations to be inundated for longer and plants at higher elevations to be deprived of water for longer. Plants located at mid-elevations will thrive if their roots have access to water and their above ground parts are not fully submerged.</p> <p class="TBody">Our findings are useful to water managers and ecologists concerned about preserving lakeshores from erosion by promoting vegetation. Both the rate and depth of drawdown should be considered in managing lake water levels. Where water levels fluctuate over large depths slower rates of drawdown will enable most plants to have access to water for longer, promoting their growth and reproduction, hence, reducing the lakeshore erosion.</p> <p class="TBody"> </p> <p class="TBody"> </p> <p class="TBody">Keywords: lakes, vegetation, drawdown, erosion, sustainability</p>

Background Soil erosion adversely impacts natural and human environments globally. Vegetation is a sustainable approach used in mitigating erosion. Although using vegetation to reduce erosion is a widely accepted concept, how the different traits of vegetation mitigate the different mechanisms of erosion are not well understood. Methods We developed 12 hypotheses on how traits of vegetation (roots, leaves, and stems) act to reduce erosion through different mechanisms (binding soil particles, promoting suspended sediment deposition and reducing the energy of waves, runoff, and wind). We then conducted a rapid evidence assessment of the scientific literature using the Eco-Evidence method. Results We found strong evidence to support our overarching hypothesis – an increase in plant abundance reduces erosion. We also found support for the specific hypotheses that plant roots bind soil particles and that greater plant stem density and leaf area reduce surface run-off and promote sediment deposition. There was insufficient evidence to support the hypotheses that plant roots promote sediment deposition or reduce wave energy, or that stem density and leaf area reduce wave or wind energy. None of our hypotheses were rejected. Conclusion Species with high root and stem densities and greater leaf area will be most effective in mitigating erosion. Our review highlights that there is insufficient evidence regarding some potentially important mechanisms between vegetation and erosion, making these prospective areas for further research. These results should be considered by environmental engineers in designing schemes to reduce erosion and ecologists who are concerned about preserving vegetation in erosion-prone environments.

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The Nachchaduwa sub-catchment (598.74 km 2) of the Malwathu Oya basin is seasonally stressed in the dry during monsoon seasons while the fate and behaviour of excess to agricultural fertilisers used in the upstream areas remain unresolved. This study incorporated the Water and Energy of the catchment concerning water resources and pollutant transport. Results showed that the catchment response to the in fertilisers applied in this catchment exceeded the actual plant requirement. In both wet [Maha cultivation season (October to March)] and dry [Yala cultivation season (April to September)] components-total, dissolved and particulate) in waterways had about 5~7 times the dry season value of the total suspended solids (TSS) in the streams, and in both seasons, the modelled TSS, and were within the ranges of the previously published results. This study will be continued in the future to analyse possible hydrological and material transport related scenarios to identify best water resources management practices and to pragmatically cope with the excess fertiliser usage, an issue commonly found in most of the similar catchments.

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