NITREX: the timing of response of coniferous forest ecosystems to experimentally-changed nitrogen deposition

Tietema A. 1, Wright R.F. 2, Blanck K. 3, Boxman A.W. 4, Bredemeier M. 5, Emmett B.A. 6, Gundersen P. 7, Hultberg H. 8, Kjønaas O.J. 9, Moldan F. 8, Roelofs J.G.M. 4, Schleppi P. 10, Stuanes A.O. 11, Van Breemen N. 12

1 Dept. Phys. Geogr. Soil Sci., Univ. Amsterdam, NL-1018 VZ Amsterdam
2 Norwegian Inst. Water Res., N-0411 Oslo
3 Inst. Soil Sci. For. Nutr., Univ. Göttingen, D-37077 Göttingen
4 Dept. Ecol., Univ. Nijmegen, NL-6500 GL Nijmegen
5 Res. Ctr. For. Ecosyst., Univ. Göttingen, D-37077 Göttingen
6 Inst. Terr. Ecol., Bangor LL57 2UP, Wales
7 Danish For. Landsc. Res. Inst., DK-2970 Hoersholm
8 Swedish Environm. Res. Inst., S-40285 Gothenburg
9 Norwegian For. Res. Inst., N-1432 Ås
10 Swiss Fed. Inst. For. Snow Landsc. Res., CH-8903 Birmensdorf
11 Inst. Soil Water Sci., Agric. Univ. Norway, N-1432 Ås
12 Dept. Geol. Soil Sci., Wageningen Agric. Univ., NL-6700 Wageningen

Water Air Soil Pollut. 85 (1995): 1623-1628

DOI: 10.1007/BF00477212


In large regions of Europe and eastern North America atmospheric deposition of inorganic nitrogen (N) compounds has greatly increased the natural external supply to forest ecosystems. This leads to N saturation, in which availability of inorganic N is in excess of biological demand and the ecosystem is unable to retain all incoming N. The large-scale experiments of the NITREX project (NITRogen saturation EXperiments) are designed to provide information regarding the patterns and rates of responses of coniferous forest ecosystems to increases in N deposition and the reversibility and recovery of impacted ecosystems following reductions in N deposition.The timing of ecosystem response generally followed a hypothesized ''cascade of response''. In all sites N outputs have responded markedly but to very different degrees within the first three years of treatment. Within this time significant effects on soil processes and on vegetation have only been detected at two sites. This delayed response is explained by the large capacity of the soil system to buffer the increased N supply by microbial immobilization and adsorption. We believe that this concept provides a framework for the evaluation and prediction of the ecosystem response to environmental change.