NITROGEN-RETENTION IN FOREST WETLANDS

Forests in southern Sweden are receiving nitrogen depositions that are about twice the critical load. There are indications that nitrogen lo sses from forest land are increasing. Forest wetlands may in this pers pective become important traps for nitrogen, thus, protecting streams, lakes and marine environments from eutrophication. A number of forest wetlands in southwestern Sweden have been investigated with the aim o f assessing their efficiency as nitrogen traps. Nitrogen retention is small in undisturbed upland forest. However, increased nitrate flux fr om a clearcut area was largely retained in one of the studied wetlands . In the spruce, which is the dominating tree in southern Sweden, the large-scale damages due to soil acidification or climatic causes canno t be excluded and it is advocated that forest wetlands should not be s ubject to drainage.