Effects of rising groundwater tables on root condition and tree vitality : Forest Ecosystem Restoration. Ecological and Economical Impacts of Restoration Processes in Secondary Coniferous Forests

2000

S. 194-199

3 Abb., 1 Tab., 4 Lit. Ang.

Unselbständiges Werk

200072936

The groundwater table has been lowered in large parts of the forest area in the Netherlands. To increase the nature value, local forest managers try to retain the water inside the forest. This might have negative effects on tree growth and tree vitality, because of a decreased rooting volume. Two field sites with mature forest were selected to study the effect of raised groundwater tables on root mortality and tree vitality in a range of depths of the groundwater table, focussing on indigenous tree species. To study roots, the profile wall method was used. Oak and Douglas-fire show a near linear reaction to differences in groundwater depth, more pronounced for Douglas-fir. The reaction of beech roots to differences in groundwater depth is not understood yet. Oak decline in one of the sites is associated with the bark beetle Agrilus biguttatus. Nearly always, Oak decline in the interaction between groundwater changes and the bark beetle is not clear yet. At this moment it is not possible to derive conclusions on a regime to change groundwater level that avoids risks for trees. It might be advisable to keep open small ditches, while putting effort in stopping natural or artifical deep drainage.