SIMULATION OF GROUNDWATER FLUCTUATIONS AND WATER STRESS IN NEWLY FORMED SPHAGNUM LAYERS AFTER REWETTING

摘要

In the Fochteloerveen bog relict in the north of the Netherlands, rewetting has started several decades ago. On some sites new Sphagnum layers developed, on most sites Moliniz. is the dominating plant species. Groundwater behaviour at different sites is very different. Soil physical properties were analysed in detail and the SVAT-model SWAP was used to simulate groundwaterfluctuations and soil moisture conditions. The model simulations were used to evaluate the impact of different physical site conditions on groundwaterlevel fluctuations and water stress conditions in Sphagnum layers. The variables were: (ⅰ) coverage and thickness of Sphagnum layer, (ⅱ) microtopography (i.e. presence of open water), (ⅲ) hydrophysical properties of the top soil layer and (ⅳ) rate of downward seepage flux. It was shown that characteristics of the micro-environment (topography) and depth of moss layers are the most relevant variables for groundwater behaviour and risks for water stress.Thin Sphagnum layers (cm's) are more vulnerable for water stress than thicker layers (20 cm). The results underline the close interdependency of Sphagnum development and soil hydrophysical changes during the rewetting stage in bog restoration projects.