ECOLOGICAL CHARACTERISTICS OF A NITROGEN-SATURATED CONIFEROUS FOREST IN THE NETHERLANDS

Wekerom forest shows a high nitrogen (N) load, and the first signs of N saturation. This characterization is based on the high N content of the needles, the high nitrate-N (NO3-N) mobilization and low cation mo bilization from the organic horizon. The N cycle in this forest has be en transformed into an ''open flow'' system, in which the ammonium-N, deposited in large quantities from the atmosphere, is transformed into NO3-N, which is leached into the groundwater. Decomposition of deeper organic layers, such as the fragmented litter and humus layers, is th ought to provide additional NH4-N, which explains the high NO3-N outpu t. Together with a reduction in the number and vitality of the pine tr ees, there is an increase in the number of nitrophilous plants, such a s Deschampsia flexuosa and Rumex acetosella. The ectomycorrhizal and l itter-decaying fungi are specific, N-resistant species. Soil fauna are classified as common inhabitants of dry, acid, nutrient poor forests.