Der Beitrag des Bergwaldes zum Schutz gegen Oberflächenabfluß und Bodenabtrag

Six forested watersheds, 5 to 16 hectares in size, were chosen as test sites in the Bavarian Alps, close to lake Tegernsee. Geologically, they belong to the formations Flysch and Kalkalpin (Hauptdolomit). The research was directed at finding and quantifying interrelations between forest conditions, soil conditions, runoff and erosion. Therefore, different stages of forest decline were simulated by forest cuts. In autumn of 1992 about 40% and 30% of the growing stock on the Flysch Sonnseite 1 and Flysch Schattseite test sites respectively were cut while Flysch Sonnseite 2 was maintained unchanged as control plot. With the installation of hydrologic and climatic measuring stations 4 to 5 years' data series have become available. Studies prior to cutting show that in particular the catchment areas in the Flysch zone are very similar as regards natural fastors such as geology, soil, precipitation and forest stands. After cutting, the output of solid matter on the Flysch Sonnseite 1 test site was twice as large as that on the control plot. On account of a lesser portion of steep areas the sediment yield of Flysch Schattseite is below that of the control, even after cutting. In the very wet year of 1993 the output of solid matter, amounting to about 9 t/hectare on the clear-cut area of Flysch Sonnseite 1, was clearly not tolerable, while in the arid summer of 1994 only about a fifth of this amount was recorded. Solid matter output occurs predominantly in summertime with the largest portions attibuted to merely a small number of events.