Can forest transformation help reducing floods in forested watersheds? Certain aspects on soil hydraulics and organic matter properties

Former floodplains in many European countries increasingly suffer from serious floods due to intensified human activity. These floods have caused safety and ecological problems as well as they have resulted in economic losses in agricultural used watersheds. In this context, the influence of the management practice of forest transformation in forested areas on soil hydraulic properties is presented and discussed as a means of preventing such disasters at a reasonable cost and during a foreseeable period. Investigations were carried out in northeastern Germany on forest stands differing in tree populations and stand structure. It was found that infiltration capacity and hydraulic conductivity K exhibit overall low values nevertheless the tree species. This finding appears to be related to water repellency, the predominating texture, and a poor macroporosity. During the different stages of forest transformation, the type and amount of soil organic matter and humus in the litter layer change, leading to a decrease of the water capacity of the litter layer and the uppermost part of the mineral soil. Furthermore, these changes affect soil properties connected with water repellency. It is concluded that for the approximate duration of one century the practice of forest transformation does not contribute to flood prevention through enhanced infiltration capacity or water retention.