Anisotrope Variation der gesättigten Wasserleitfähigkeit einer unterschiedlich beweideten Salzmarsch im Deichvorland

Anisotropic variation of saturated hydraulic conductivity of a variously grazed salt marsh soil Undisturbed core samples were taken in horizontal and vertical direction from a variously grazed salt marsh soil for investigation of the anisotropic variation of saturated hydraulic conductity K_sat, bulk density, and pore size distribution. The results show that saturated hydraulic conductivity varies significantly anisotropically. The average Kv/Kh ratio is 0.38 for the soil profile and 0.44 for the surface soil. This anisotropy of K_sat is mainly attributed to the stratified structure of soil due to the sedimentation conditions in the salt marsh environment and decreases if soil structure development through pedological processes progresses. Furthermore. K_sat decreases significantly if the stocking rate of grazing is larger than 1.0 sheep unit/ha and the effect is more pronounced near the dike. However, both the Kv and Kh are affected by grazing in the same manner, so that the anisotropy of K_sat is independent from grazing. Bulk densitiy and macroporosity are affected by grazing but not by the direction of sampling. There are significant correlations between K_sat and > 50 μm as well as > 10 μm pore volume. The correlation between K_sat and total porosity is however not significant. The anisotropy of K_sat implicates the favouring of the lateral water flux and in the hydrological research and modelling of the salt marsh ecosystem the anisotropy of K_sat should be taken into account.