خيارات البحث
النتائج 1 - 10 من 34
Critical loads of sulphur and nitrogen for terrestrial ecosystems in Europe and Northern Asia influenced by different soil chemical criteria.
2008
Reinds, G.J. | Posch, M. | Vries, de, W. | Slootweg, J. | Hettelingh, J.P.
A critical load data base was developed for Europe and Northern Asia using the latest data bases on soils, vegetation, climate and forest growth. Critical loads for acidity and nutrient nitrogen for terrestrial ecosystems were computed with the Simple Mass Balance model. The resulting critical loads are in accordance with critical loads from previous global empirical studies, but have a much higher spatial resolution. Critical loads of acidity are sensitive to both the chemical criterion and the critical limit chosen. Therefore a sensitivity analysis of critical loads was performed by employing different chemical criteria. A critical limit based on an acid neutralizing capacity (ANC) of zero resulted in critical loads that protect ecosystems against toxic concentrations of aluminium and unfavourable Al/Bc ratios, suggesting that ANC could be an alternative to the commonly used Al/Bc ratio. Critical loads of nutrient nitrogen are sensitive to the specified critical nitrate concentration, especially in areas with a high precipitation surplus. If limits of 3¿6 mg N l¿1 are used for Western Europe instead of the widely used 0.2 mg N l¿1, critical loads double on average. In low precipitation areas, the increase is less than 50%. The strong dependence on precipitation surplus is a consequence of the simple modelling approach. Future models should explore other nitrogen parameters (such as nitrogen availability) instead of leaching as the factor influencing vegetation changes in terrestrial ecosystems.
اظهر المزيد [+] اقل [-]Mercury in fish in Swedish lakes - linkages to domestic and European sources of emission
1990
Haakanson, L. (Umeaa Univ. (Sweden). Dept. of Physical Geography) | Andersson, T. | Nilsson, A.
Vegetation, soils and ion transfer through the forest canopy in two Nova Scotia lake basins
1989
Percy, K.E. (Forestry Canada Maritimes Region, Fredericton, N.B. (Canada))
Improved growth in stunted brown trout (Salmo trutta L.) after reliming of Lake Hovvatn, southern Norway
1989
Barlaup, B.T. (Bergen Univ. (Norway). Museum of Zoology) | Aatland, A. | Raddum, G.G. | Kleiven, E.
Facts and fallacies concerning mercury uptake by fish in acid stressed lakes
1988
Richman, L.A. (Toronto Univ., Toronto, Ont. (Canada). Inst. for Environmental Studies) | Wren, C.D. | Stokes, P.M.
The Loch Fleet and other catchment liming programs
1988
Brown, D.J.A.
Loch Fleet - a research watershed liming project
1988
Brown, D.J.A. | Howells, G.D. | Dalziel, T.R.K. | Stewart, B.R.
Effects of lake liming on phytoplankton production in acidic Adirondack lakes
1988
Bukaveckas, P.A.
Changes in the fish community of a limed lake near Sudbury, Ontario: effects of chemical neutralization or reduced atmospheric deposition of acids?
1988
Gunn, J.M. | McMurtry, M.J. | Casselman, J.M. | Keller, W. | Powell, M.J.
Liming acidic waters in Norway: national policy and research and development
1988
Hindar, A. | Rosseland, B.O.
