Research on the impact of forest stand structure on atmospheric deposition.

Dry and wet deposition onto thirty forest stands in relation to stand structure is studied by sampling throughfall and bulk precipitation. Nine measurement sites are situated in Pseudotsuga menziesii stands, ten in Pinus sylvestris and eleven in Quercus robur stands. All stands are situated within a radius of 1.2 km to assure a more or less equal air pollution load. In each stand, detailed forest structure inventories are made to determine aerodynamic roughness, collecting efficiency and surface area parameters. Measurements to data cover a four month period (April-July 1990). First results show relatively high throughfall deposition in Pseudotsuga menziesii stands. Lowest throughfall fluxes are recorded for Quercus robur and intermediate values for Pinus sylvestris stands. There are indications of a relatively strong canopy exchange in Quercus robur stands during the measurement period. Many results from forest stand structure inventories are not available yet. However, a strong relation is observed between throughfall deposition in Pseudotsuga menziesii stands and total crown volume.