In the forested catchments of the Luxembourg Keuper area, deeply-incised valleys have developed in which streambank erosion is a widespread phenomenon. For one of the catchments in this area, the Schrondweilerbaach catchment, a sediment budget was constructed in order to determine the relative contributions of the various channel and valley slope processes to sediment output.Streambanks contributed 53 per cent of the output with bank scour and subsoil fall being the main processes while to a lesser extent bank material was supplied by bank failures, splash erosion, and soil creep. The remaining 47 per cent of the sediment was derived from the valley slopes mainly through the combined action of rainsplash detachment and overland flow transport. During the two years of investigations sediment output from the drainage basin almost equalled sediment input from streambanks and valley slopes. The results of the measurements of the various streambank processes are integrated in a descriptive model for the present-day widening of valley incisions in the study area and used to hypothesize the palaeohydrological development of the basin. Special attention is paid to the (in)direct effects of the forest vegetation on streambank erosion and sediment transport through the stream channel.

ZusammenfassungNutrient deposition in throughfall and stemflow were measured on a two-weekly basis in an oaWbeech forest in the eastern part of the Netherlands. The large number of sampling points (11 throughfall and 8 stemflow collectors) enabled an analysis of the spatial variability in ion deposition.Spatial variability of ion depositions in throughfall revealed wide variation both between dissolved constituents as between seasons for single dissolved constituents. On a two weekly basis coefficients of variation ranged from 20-72 % with highest values generally occurring for ortho-P and H and during spring. In contrast coefficients of variation based upon annual deposition totals ranged from 9-31 %. Ion depositions in stemflow showed a much higher spatial variability with coefficients of variation for annual totals ranging from 46-115 % with highest values again reported for ortho-P and H. The results on the ion-depositions in throughfall are summarized in a scheme in which for a given dissolved constituent and a desired accuracy interval, the needed number of sampling points is indicated. Raumliche Variabditiit der Nahrstoffdeposition in einem Buchen-Eichen-WaldIn einem Buchen-Eichenwald in den Ost-Niederlanden wurde die Deposition von Nahrstoffen in der Kronentraufe und im Stammabfluss auf 2-wochiger Basis gemessen. 11 Sammler fur die Kronentraufe und 8 Stammabfluss-Sammler erlaubten eine Analyse der raumlichen Variabilitat der Ionen-Deposition. In der Kronentraufe wurde eine hohe Variabilitat sowohl hinsichtlich der einzelnen Ionen wie auch bei bestimmten Ionen fur einzelne Jahreszeiten festgestellt . Fur Sammelperioden von 2 Wochen schwankte der Variationskoeffizient zwischen 20 und 72 % mit Maximalwerten fur Orthophosphat und H sowie im Fruhjahr. Fur die Jahressummen ging der Variationskoeffizient auf 9-31 % zuruck. Die Ionen-Deposition im Stammabfluss zeigt mit Variabilitatskoeffizienten zwischen 46 und 115 % bei Maximalwerten fur Orthophosphat und H eine hohere raumliche Variabilitat. Die fur die Kronentraufe erhaltenen Ergebnisse wurden in einem Schema dargestellt, aus dem fur die einzelnen Ionen die erforderliche Anzahl an Sammler zur Erreichung einer vorgegebenen Genauigkeit entnommen werden kann. elements in the precipitation beneath a sessile oak canopy. Journal of Ecology, 54, Duijsings, J . J. H. M . , Bouten, W . and Verstraten, f . M . , (in prep.): Hydrochemical balance of a forest ecosystem and its implications for the protonbudget. Kimmins, J. P. (1973): Some statistical aspects 65-85.