MICROBIAL CARBON AND NITROGEN DYNAMICS IN CONIFEROUS FOREST FLOOR MATERIAL COLLECTED ALONG A EUROPEAN NITROGEN DEPOSITION GRADIENT

Microbial carbon (C) and nitrogen (N) cycling was studied in forest fl oor material from five coniferous forests situated along a gradient of N deposition across northwestern Europe. Results from the European NI TREX project, a consortium of eight field-scale manipulation experimen ts with N deposition, indicated that three of these sites could be con sidered as N-saturated, whereas the other two sites were N-limited. Co mpared to the N-saturated sites, microbial C and N cycling in N-limite d sites was characterized by low gross NH4+ transformation rates, low respiration rates, high microbial C efficiencies and high microbial C: N ratios. Microbial NO3- immobilization was not detected in any of the forest floors studied here. (C) 1998 Elsevier Science B.V.