Die Rolle des Schilfs im standörtlichen Wasserhaushalt eines norddeutschen Sees
Herbst, Mathias; Kappen, Ludger
This study deals with the water turn-over of Phragmites australis in a reed bank in northern Central Europe (Belau Lake, Schleswig-Holstein). Diurnal courses of transpiration of leaves and leaf sheaths were regularly measured by means of a steady-state porometer during the growing season. During this period microclimatic variables such as irradiance, temperature and air humidity were recorded continuously in the reed bank. Leaf area index (LAI) of the canopy was estimated every third week. Transpiration essentially depends on patterns of attachment and developmental stage of the leaves and on external factors such as irradiance (PAR) and water vapour pressure difference between leaf and air (VPD). A model was established that calculates the transpiratory rate of the leaf area of Phragmites at different phenological stages as a function of PAR and VPD. The water turn-over rate of this reed bank in the cool-temperate climate of northern Germany is in the same order of magnitude as that hitherto observed in more southern regions of Central Europe. One square metre of reed in the open lake loses nearly twice the amount of water that evaporates from the same area of the open lake surface. This figure is equivalent to the annual total of precipitation in our region. In the shaded reed bank the transpiratory rate was much lower.