Field and laboratory experiments on net uptake of nitrate and ammonium by the roots of spruce (Picea abies) and beech (Fagus sylvatica) trees. - Gessler,A..; Schneider,S..; Von Sengbusch,D..; Weber,P..; Hanemann,U..; Huber,C..; Rothe,A..; Kreutzer,K..; Rennenberg,H.. (New Phytologist, 1998)