Ecological characteristics of a nitrogen-saturated coniferous forest in The Netherlands

Abstract

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 mobilization from the organic horizon. The N cycle in this forest has been 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 thought to provide additional NH₄-N, which explains the high NO₃-N output. Together with a reduction in the number and vitality of the pine trees, there is an increase in the number of nitrophilous plants, such as Deschampsia flexuosa and Rumex acetosella. The ectomycorrhizal and litter-decaying fungi are specific, N-resistant species. Soil fauna are classified as common inhabitants of dry, acid, nutrient poor forests.