Terrestrial ecosystem nitrogen deposition

Impacts of Nitrogen Deposition on Terrestrial Ecosystems, Report of the United Kingdom Review Group on Impacts of Atmospheric Nitrogen, Department of the Environment, London, 1994. Report of the AERC Institute of Arable Crops Research for 1991, AERC, London, 1992, p. 36. 

INDITE, Impacts of Nitrogen Deposition in Terrestrial Ecosystems in the United Kingdom,... 

Historically, nitrogen deposition has not been considered a serious threat to the integrity of aquatic systems. Most terrestrial systems have been assumed to retain N strongly. In such cases there is a small probability that deposited N would make its way to the surface waters that drain these terrestrial systems. Nitrogen within aquatic ecosystems can arise from a... 

Nitrogen is the most commonly limiting nutrient in North American forest ecosystems (20, 21). The form of N used by terrestrial ecosystems strongly affects the acidifying potential of N deposition (Figure 1). Ammonium uptake is an acidifying process (i.e., uptake of NH4+ releases 1 mole of H per mole of N assimilated). 

As a result of their geographical circumstances and these various historical developments, many estuaries appear to be among the most heavily loaded ecosystems in the world in terms of the amount of nitrogen and phosphorus received per unit area (Fig. 5). Even the farm fields of the American corn belt do not receive the fertilization common to many estuaries, and the nutrient inputs to natural terrestrial systems and fresh waters appear to be orders of magnitude lower. There are fewer data available on the inputs of metals and other pollutants to estuaries, but the evidence at hand suggests that the delivery of heavy metals to estuaries may equal or exceed that deposited from the atmosphere on heavily industrialized urban areas and exceed that deposited on rural terrestrial ecosystems by orders of magnitude (Fig. 6). 

Aerts R. and Bobbink R. (1999) The impact of atmospheric nitrogen deposition on vegetation processes in terrestrial non-forest ecosystems. In The Impact of Nitrogen Deposition on Natural and Semi-natural Ecosystems (ed. S. Langan). Kluwer, Dordrecht, pp. 85-122. 

Holland E. A., Braswell B. H., Lamarque J.-F., Townsend A., Sulzman J., Muller J.-F., Dentener F., Brasseur G., Levy H., Penner J. E., and Roelots G.-J. (1997) Variations in the predicted spatial distribution of atmospheric nitrogen deposition and their impact on carbon uptake by terrestrial ecosystems. J. Geophys. Res. 102, 15849-15866. 

Asner G. P., Townsend A. R., Riley W. J., Matson P. A., Neff J. C., and Cleveland C. C. (2001) Physical and biogeochem-ical controls over terrestrial ecosystem responses to nitrogen deposition. Biogeochemistry 54, 1-39. 

Figure 8. Exceedances of critical loads of sulfur and nitrogen Jor terrestrial ecosystems of Ukraine in 1992 deposition.

The SCOPE project constructed a mass balance for reactive nitrogen under anthropogenic influence on the regional scale (Howarth, 1996). For inputs, for the terrestrial ecosystems the SCOPE N analysis considered application of N fertilizers, N fixation by agricultural crops, if any, NOy depositions, and import or export of N in food and animal feedstocks. Output items considered crop uptake, denitrification and volatilization and river discharge. For marine ecosystems, this analysis includes also seawater exchange. 

The rates of precipitation deposition are mapped today and allow a comparison to be made with the results of the forest decline inquiry. To get below the critical load limit for the acid input under the present conditions of reduced input of alkaline dust, it is necessary to reduce not only the S02-emission but also the emission of NO and NHj. The reduction of the nitrogen compounds is also necessary in view of a reduction of the possible eutrophication of terrestrial ecosystems, the nitrate load of the groundwater and surface waters, as well as a reduction of the ozone load. 

Figure 5.4. The Nitrogen Saturation Hypothesis (from Aber et al. 1989 1998, reprinted with permission, copyright American Institute of Biological Sciences), a conceptual model of terrestrial ecosystem responses to chronically elevated nitrogen (N) deposition. This model identifies four stages of ecosystem response to N loading. Soil responses are shown in the upper panel, and plant responses in the lower panel. See text for discussion...

Matson, R, Lohse, K.A. and Hall, S.J. (2002). The globalization of nitrogen deposition Consequences for terrestrial ecosystems. Ambio, 31, 113-119. 

What became popularly known as acid rain is a complex set of physical and chemical phenomena by which gases—especially sulfur dioxide (SO2) and nitrogen oxides (NOJ—are created and emitted, mostly by industrial processes, transported through the atmosphere, transformed into acidic compounds, and deposited onto land and water surfaces, often with serious negative effects for aquatic and terrestrial ecosystems. Acidification of lakes... 

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