Soluble N compounds in trees exposed to high loads of N: a comparison between the roots of Norway spruce (Picea abies [L.] Karst) and beech (Fagus sylvatica L.) trees grown under field conditions. - Geßler, ,A.,.; Schneider, ,R.,.; Hanemann, ,U.,.; and Rennenberg, ,H.. (New Phytologist, 1998)