Understanding wetland plant dynamics in response to water table changes through ecohydrological modelling

Abstract

Vulnerability of wetland vegetation to water table changes is a widely studied topic in the field of ecology. Extreme flood or drought conditions imposed on wetlands cause disappearance of plants or shift in the vegetation regime. The recovery of such plant compositions is of particular importance when the wetland is subjected to frequent water table fluctuations resulting from land use changes and requires knowledge of mechanisms underlying evolution of plant growth to changing hydrologic conditions. We used a spatially varying, coupled groundwater-vegetation growth model to investigate the survival mechanism of wetland herbaceous plants. The plants were subjected to long-term water table drainage because of land use changes that caused the disappearance of one of the species composition. In an effort to revive the disappeared species, hypothetical soil saturation was introduced onto the study domain through elevated water table level. Even though the system had returned to hydrologically favourable environment, the disappeared species was unable to recover, which in turn led to the evaluation of factors that determine the re-emergence of the species through sensitivity analysis. The results of the sensitivity analysis showed that the disappeared species recovered during scenarios of reduced duration of drawdown, increased assimilation rates and increased competitiveness. The analysis also showed that the competitiveness of the plants, which was modelled by the classic Lotka-Volterra algorithm, supersedes any of the unfavourable plant growth characteristics. The results of this study demonstrated the ability of the groundwater-vegetation response model to facilitate an understanding of plant development and a hierarchy of important factors that promote their growth in altered hydrologic conditions. © 2012 John Wiley & Sons, Ltd.