Biogeochemical modelling is largely concerned with the cycling of carbon, nitrogen, phosphorus and sulphur in the biosphere. It offers a robust approach to modelling many aspects of ecosystem function at the regional scale, since it is not highly dependent on a detailed know ledge of species or organism-level processes. In southern Africa biogeochemical modelling has been used to provide new insight into the geographical distribution and underlying mechanisms of palatable (sweetveld) and unpalatable (sourveld) grasslands and high-herbivory and low- herbivory savannas. It has also been applied to the problem of estimating the emissions of trace gases and smoke particles from vegetation fires in the region, and suggests that the emissions are much lower than previously believed. Work in progress relates to the modelling of tropospheric ozone precursors produced by the soil and plants. Biogeochemical modelling has the potential to be an integrating tool, drawing together data collected at widely different scales in a way that allows hypotheses about the working of the biosphere to be rigorously tested.
Andreae, M.O., Fishman, J., Garstang, M., Goldammer, J.G., Justice, C.O., Levine, J.S., Scholes, R.S., Stocks, B.J., Thompson, A.M. and van Wilgen, B.1994: First results from the IGAC/ BIBEX field campaign STARE/TRACE-A/ SAFARI-92. In Global atmospheric biospheric chemistry, (the first IGAC scientific conference), New York: Plenum Press, 83-101.
2.
Bell, R.H.V.1982: The effect of soil nutrient availability on community structure in African ecosystems. In Huntley, B.J. and Walker, B.H., editors, The ecology of tropical savannas. Ecological Studies42, Berlin: Springer-Verlag , 193-216.
3.
Blackmore, A.C., Mentis, M.T. and Scholes, R.J.1990: The origin and extent of nutrient-rich patches in a nutrient-poor savanna in South Africa. Journal of Biogeography17, 463-70.
4.
Bolin, B.1986: How much CO2 will remain in the atmosphere: the carbon cycle and projections for the future. In Bolin, B., Doos, R., Jager, J. and Warrick, R.A. , editors, The greenhouse effect, climatic change, and ecosystems, (SCOPE), Chichester: Wiley, 93-155.
5.
Bryant, J.P., Kuropat, P.J., Cooper, S.M., Frisby, K. and Owen-Smith, N.1989: Resource availability hypothesis of plant antiherbivore defence tested in a South African savanna ecosystem. Nature340, 227-29.
6.
Cougenhour, M.B.1991: Spatial components of plant interactions in pastoral, ranching and native ungulate ecosystems. Journal of RangeManagement44,530-42.
7.
Cowling, R.M., editor, 1992: The ecology of fynbos: nutrients, fire and diversity. Cape Town: Oxford University Press.
8.
Crutzen, P.J. and Andreae, M.O.1990: Biomass burning in the tropics: impact on atmospheric chemistry and biogeochemical cycles. Science250, 1669-78.
9.
Delmas, R., Lacaux, J.P. and Brocard, D.1995: Determination of biomass burning emission factors: methods and results. Environmental Monitoring and Assessment38, 181-204.
10.
Donaldson, C.H., Rootman, G. and Grossman, D.1984: Long-term nitrogen and phosphorus application to veld . Journal of the Grassland Society of Southern Africa1, 27-32.
11.
East, R.1984: Rainfall, soil nutrient status and biomass of large African savanna animals. African Journal of Ecology22, 245-70.
12.
Ellery, W.N., Scholes, R.J. and Mentis, M.T.1991: An initial approach to predicting the sensitivity of the South African grassland biome to climate change. South AfricanJournal of Science87, 499-503.
13.
Ellery, W.N., Scholes, R.J. and Scholes, M.C.1995: The distribution of sweetveld and sourveld in South Africa's grassland biome in relation to environmental factors. African Journal of Range and ForageScience12, 38-45.
14.
Fishman, J.P., Minnis, P. and Taylor, M.1985: Ozone emissions from tropical forest and savannah fires deduced from satellite observations. In Eighth conference on fire and forest meteorology (Society of American Foresters), 73-80.
15.
Fumiss, P.R., Ferrar, P., Morris, J.W. and Bezuidenhout, J.J.1982: A model of savanna litter decomposition. Ecological Modelling17, 33-51.
16.
Guenther, A., Hewitt, C., Erickson, D., Fall, R., Geron, C., Graedel, T., Harley, P., Klinger, L., Lerdau, M., McKay, B., Middleton, P., Pierce, T., Scholes, R., Steinbrecher, R., Tallamraju, R., Taylor, L. and Zimmerman, P.1995: A global model of natural volatile organic compound emissions . Journal of Geophysical Research100, 8873-92.
17.
Guenther, A., Otter, L., Zimmerman, P., Green-berg, J., Scholes, R.J. and Scholes, M.C.1996: Biogenic hydrocarbon emissions from southern African savannas . Journal of Geophysical Research101, 25859-65.
18.
Hao, W.M., Liu, M.-H. and Crutzen, P.J.1990: Estimates of annual and regional releases of CO 2 and other trace gases to the atmosphere from fires in the tropics, based on the FAO statistics for the period 1975-1980. In Goldammer, J.G., editor, Fire in the tropical biota: ecosystem processes and global challenges. Ecological Studies84, Berlin: Springer-Verlag, 440-62.
19.
Huntley, B.J.1982: Southern African savannas. In Huntley, B.J. and Walker, B.H., editors, The ecology of tropical savannas. Ecological Studies42, Berlin : Springer-Verlag, 101-19.
Kemp, D.D.1994: Global environmental issues (2nd edn). London: Routledge.
22.
Kunz, R.P., Schulze, R.E. and Scholes, R.J.1995: An approach to modelling spatial changes of plant carbon:nitrogen ratios in southern Africa in relation to anticipated global climate change . Journal of Biogeography22, 401-408.
23.
Lacaux, J.P., Cachier, H. and Delmas, R.1993: Biomass burning in Africa: an overview of its impact on atmospheric chemistry. In Crutzen, P.J. and Goldammer, J.G., editors, Fire in the environment: the ecological atmospheric and climatic importance of vegetation fires. Environmental Science Research Report 13, New York: Wiley, 159-91.
24.
Liebig, J.1840: Chemistry and its applications to physiology and agriculture . London: Taylor & Walton.
25.
Likens, G.E., Bormann, F.H., Pierce, R.S., Eaton, J.S. and Johnson, N.M.1977: Biogeochemistry of a forested ecosystem. New York: Springer-Verlag.
26.
Lindeman, R.1942: The trophic-dynamic aspect of ecology. Ecology23, 399-418.
27.
Lovegrove, B.G. and Siegfried, W.R.1989: Spacing and origin(s) of Mima-like earth mounds in the Cape Province of South Africa. South AfricanJournal of Science85, 108-12.
28.
Melillo, J.M., McGuire, A.D., Kicklighter, D.W., Moore, B. Iii, Vorosmarty, C.J. and Schloss, A.L.1993: Global climate change and terrestrial net primary production . Nature363, 234-40.
29.
Miller, R.W. and Donahue, R.L.1995: Soils in our environment (7th edn). London: Maxwell Macmillan .
30.
Odum, H.T.1957: Trophic structure and productivity of Silver Springs, Florida. Ecological Monographs27, 55-112.
31.
Olbrich, K., van Tienhoven, M., Skoroszewski, R., Zunckel, M. and Taljaard, J.1995: A prototype atmospheric deposition risk advisory system for the Eastern Transvaal Province. Report For-I-547. Nelspruit: Division of Forest Science and Technology, CSIR.
32.
O'Neill, R.V., De Angelis, D.L., Waide, J.B. and Allen, T.F.H.1986: A hierarchical concept of ecosystems. Princeton, NJ: Princeton University Press.
33.
Otter, L.B.1995: Non-methane hydrocarbon emissions from selected South African savanna tree species. MSc dissertation, Faculty of Science, University of the Witwatersrand.
34.
Parsons, D.A.B., Scholes, M.C., Scholes, R.J. and Levine, J.S.1996: Biogenic NO emissions from savanna soils as a function of fire regime, soil type, soil nitrogen and water status. Journal of Geophysical Research101, 23683-88.
35.
Parton, W.J., Stewart, J.W.B. and Cole, C.V.1988: Dynamics of C, N, P and S in grassland soils: a model . Biogeochemistry5, 109-31.
36.
Penning deVries, F.W.T., Brunsting, A.H.M. and van Laar, H.M.1974: Products requirements and efficiency of biosynthesis: a quantitative approach. Journal of Theoretical Biology45, 358-77.
37.
Redfield, A.C.1958: The biological control of chemical factors in the environment . American Scientist46, 205-21.
38.
Reynolds, C.S.1978: Phosphorus and the eutrophication of lakes - a personal view. In Phosphorus in the environment: its chemistry and biochemistry . Ciba Foundation Symposium 57 (new series), Amsterdam : Elsevier, 201-28.
39.
Rutherford, M.C. and Westfall, R.H.1986: Biomes of southern Africa: an objective classification. Memoirs of the Botanical Survey of South Africa 63. Pretoria : National Botanical Institute.
40.
Schimel, D.S.1995: Terrestrial ecosystems and the global carbon cycle . Global Change Biology1, 77-91.
41.
Schlesinger, W.H.1991: Biogeochemistry: an analysis of global change. San Diego, CA: Academic.
42.
Scholes, M.C., Martin, R., Scholes, R.J., Parsons, D. and Winstead, E.1997: NO and N2O emissions from savanna soils following the first simulated rains of the season. Nutrient Cycling in Agroecosystems, 7, 17-24.
43.
Scholes, R.J.1990: The influence of soil fertility on the ecology of southern African savannas. Journal of Biogeography17, 417-19.
44.
Scholes, R.J., Kendall, J. and Justice, C.O.1996a: The quantity of biomass burned in southern Africa . Journal of Geophysical Research101, 23667-76.
45.
Scholes, R.J. and Walker, B.H.1993: An African savanna: synthesis of the Nylsvley study . Cambridge: Cambridge University Press.
46.
Scholes, R.J., Ward, D.E. and Justice, C.O.1996b: Emissions of trace gases and aerosol particles due to vegetation burning in southern Africa. Journal of Geophysical Research101, 23677-82.
47.
Sharkey, T.D., Loreto, F. and Delwiche, C.F.1991: The biochemistry of isoprene emission from leaves during photosynthesis. In Sharkey, T.D., Holland, E.A. and Mooney, H.A., editors, Trace gas emissions by plants, New York: Academic Press, 153-84.
48.
Tiessen, H. and Frossard, E.1992: Phosphorus cycles in terrestrial and aquatic ecosystems. Regional workshop 4: Africa. Proceedings of a workshop arranged by SCOPE and UNEP. Saskatoon: The Saskatchewan Institute of Pedology, University of Saskatchewan.
49.
Thompson, A.M., Pickering, K.E., McNamara, D.P., Schoeberl, M.R., Hudson, R.D., Kim, J.K., Browell, E.V., Fishman, J., Kirchhoff, V.W.J.H. and Nganga, D.1996: Where did tropospheric ozone over southern Africa and the tropical Atlantic come from in October 1992? Insights from TOMS, GTE/TRACE-A and SAFARI-92. Journal of Geophysical Research101, 24251-78.
50.
Tyson, P.D., Garstang, M., Swap, R.J., Kalberg, P. and Edwards, M.1996: An air transport climatology for subtropical southern Africa. International Journal of Climatology16, 265-91.
51.
van Wilgen, B.W., Andreae, M.O., Goldammer, J.G. and Lindesay, J.A.1997: Fire in southern African savannas: ecological and atmospheric perspective. Johannesburg: Witwatersrand University Press.
52.
Vitousek, P.1982: Nutrient cycling and nutrient use efficiency. American Naturalist119, 553-72.
53.
White, F.1980: The vegetation of Africa. Natural Resources ResearchXX. Paris : Unesco.
54.
Woomer, P.1993: The impact of cultivation on carbon fluxes in woody savannas of southern Africa. Water, Air and Soil Pollution70, 403-12.
55.
Zaccharias, P.J.K.1990: The seasonal patterns in plant quality in various ecological zones in Natal. MSc (Agric) thesis, University of Natal , Pietermaritzburg.
56.
Zepp, R.G., Miller, W.L., Burke, R.A., Parsons, D.A.B. and Scholes, M.C.1996a: Effects of moisture and burning in soil-atmosphere exchange of trace carbon gases in a southern African savanna. Journal of Geophysical Research101, 23699-706.
57.
Zepp, R.G., Miller, W.L., Tarr, M.A., Burke, R.G., Parsons, D.A.B. and Scholes, M.C.1996b: Dynamics of carbon monoxide emissions from soil and vegetation in a southern African savanna. In: Proceedings of the Chapman conference on biomass burning.
