Journal of Conference Abstracts

Using Biogeochemical Approaches for an Assessment
of Ecosystem Sensitivity to Acidic Deposition
in Developing Countries

Vladimir N. Bashkin (Bashkin@issp.serpukhov.su)

Institute of Soil Science and Photosynthesis, Russian Academy of Sciences,
Pushchino, Moscow Region 142292, Russia.

At present, at least three methods to determine critical load values and ecosystem sensitivity to acidic deposition are available:

1. Steady-state mass balance equations including a quantitative assessment of relevant parameters of pollutant turnover within a specific, defined area (i.e., a watershed). This approach is most applicable in comparatively small areas that have a high degree of information support for calculation of various parameters and constants of balanced equations. Critical loads for many European countries are calculated in this manner.

2. The use of various combinations of expert approaches and geoinformation systems include different modern methods of expert modeling (Bashkin et al. 1994). These systems can operate using data bases and knowledge bases relative to areas of great spatial data uncertainty. As a rule, the given systems include analyses of biogeochemical cycles of various elements in the key plots, a choice of algorithms describing these cycles, and corresponding interpretation of the data. This approach requires numerous cartographic materials (e.g., maps of soil cover, geochemical and biogeochemical structure, self-purification capacity of soil, water, atmosphere, etc). It is the most applicable approach for Russia, as well as China, India, Thailand, Indonesia, Brazil, Argentina, Nigeria, and other Asian, Latin American, African, and Pacific countries, to present adequate information regarding the great spatial variability of natural and anthropogenic factors.

3. The use of factors that indicate potential ecosystem response to acidic deposition (SEI method; Kuylenstierna et al. 1995). Selection of environmental controlling variable has shown that ecosystems susceptible to acid deposition can be successfully mapped on the basis of three parameters: soil buffering ability, land use, and the ratio of precipitation to potential evapotranspiration. This method combines the advantages of above mentioned methods and can be used both for a preliminary outlook and the stability and/or sensitivity of ecosystems to acid forming compounds. The output is intended to be used to indicate ecosystems at risk to acidic deposition. Due to the data used and the criteria employed, the sensitivity of areas can be exaggerated or underestimated. So that these results can be applied for scientists and policy makers, uncertainties associated with these models require investigation. Semi-quantitative assessments of uncertainty are made on the input data, method, and division of classes and categories. Quantitative estimates are made using critical loads.

Validation of the last two methods, for assessment of ecosystem sensitivity to acidic deposition in developing countries of Asia, Africa, Latin and South America, has been made using biogeochemical approaches. The SEI method can be applied successfully for assessment of this sensitivity to the global scale using data characterizing soil buffering ability, ecosystem type, and the precipitation:evapotranspiration ratio. No additional parameters should be used for ecosystems conjugated with neutral and alkaline soils and having "insensitive" buffering ability to acidic precipitation New information layers characterizing the intensity of biogeochemical cycling and period of active temperature duration should be additionally applied for assessing ecosystems having different ranges of sensitivity to acidic deposition, especially for Arctic tundra, boreal taiga forest, sub-boreal forest, monsoon forest, and wet equatorial tropic forest ecosystems. The corresponding values of active temperature and relative biogeochemical coefficients for worldwide ecosystems create new information levels, and aid in the correction of SEI map sensitivity range legends. The comparison of SEI data has been carried out with the corresponding results of quantitative assessment and mapping of critical loads for acid forming N and S compounds in terrestrial ecosystems of northern Asia (Russia) and island Pinos (Cuba). Additional information layers, connected with biogeochemical cycling intensity, and duration of active temperature period, should be of real usefulness for defining ecosystems. The expert-modeling geoinformation system can facilitate the application of soil-ecosystem biogeochemical parameters for users in developing countries.

References

Bashkin, V.N., Kozlov, M.Ya., Priputina, I.V. & Abramychev, A.Yu., Proc. InterCarto: GIS for Environmental Studies and Mapping Conference, 23-25 May 1994; GIS World, Fort Collins, USA, 99-104 (1994).

Kuylenstierna, J.C.I., Cambridge, H., Cinderby, S. & Chadwick, M.J., Water, Air and Soil Poll. 85, 2319-2324 (1995).