Advertisement

Oecologia

, Volume 88, Issue 3, pp 451–455 | Cite as

Estimates of nitrogen fixation by trees on an aridity gradient in Namibia

  • E.-D. Schulze
  • G. Gebauer
  • H. Ziegler
  • O. L. Lange
Short Communication

Summary

Nitrogen (N2) fixation was estimated along an aridity gradient in Namibia from the natural abundance of 15N (δ15N value) in 11 woody species of the Mimosacease which were compared with the δ15N values in 11 woody non-Mimosaceae. Averaging all species and habitats the calculated contribution of N2 fixation (N f ) to leaf nitrogen (N) concentration of Mimosaceae averaged about 30%, with large variation between and within species. While in Acacia albida N f was only 2%, it was 49% in Acacia hereroensis and Dichrostachys cinerea, and reached 71% in Acacia melifera. In the majority of species N f was 10–30%. There was a marked variation in background δ15N values along the aridity gradient, with the highest δ15N values in the lowland savanna. The difference between δ15N values of Mimosaceae and non-Mimosaceae, which is assumed to result mainly from N2 fixation, was also largest in the lowland savanna. Variations in δ15N of Mimosaceae did not affect N concentrations, but higher δ15N-values of Mimosaeae are associated with lower carbon isotope ratios (δ13C value). N2 fixation was associated with reduced intrinsic water use efficiency. The opposite trends were found in non-Mimosaceae, in which N-concentration increased with δ15N, but δ13C was unaffected. The large variation among species and sites is discussed.

Key words

Nitrogen fixation Carbon isotope ratio Nitrogen isotope ratio Acacia Namibia 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Besler H (1972) Klimaverhältnisse und klimageomorphologische Zonierung der zentralen Namib (Südwestafrika). Stuttg Geogr Stud 83:1–209Google Scholar
  2. Farquhar DG, Hubick KT, Condon AG, Richards RA (1989) Carbon isotope fractionation and plant water-use efficiency. Ecol Stud 68:21–40Google Scholar
  3. Gebauer G (1991) Natural nitrogen isotope ratios in different compartments of Norway spruce from a healthy and a declining stand. Proceedings of the International Symposium on the use of stable isotopes in plant nutrition, soil fertility and environmental studies, IAEA Vienna 1990, in pressGoogle Scholar
  4. Gebauer G, Schulze E-D (1991) Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge, NE Bavaria. Oecologia 87:198–207Google Scholar
  5. Giess W (1971) A prelininary vegetation map of South West Africa. Dinteria 4:1–114Google Scholar
  6. Högberg P (1986a) Soil nutrient availability, root symbiosis and tree species composition in tropical Africa: a review. J Trop Ecol 2:359–372Google Scholar
  7. Högberg P (1986b) Nitrogen-fixation and nutrient relations in Savanna woodland trees (Tanzania). J Appl Ecol 23:675–688Google Scholar
  8. Högberg P (1990) 15N natural abundance as a possible marker of the ectomycorrhizal habit of trees in mixed African woodlands. New Phytol 115:483–486Google Scholar
  9. Merxmüller H (1972) Prodromus einer Flora von Südwestafrika. J Cramer, LehreGoogle Scholar
  10. Osmond CB, Ziegler H, Stichler W, Trimborn P (1975) Carbon isotope discrimination in alpine succulent plants supposed to be capable of Crassulacean Acid Metabolism (CAM). Oecologia 28:323–328Google Scholar
  11. Palgrave KC (1983) Trees of South Africa. C. Struck Publishers, Cape TownGoogle Scholar
  12. Rundel PW, Ehleringer JR, Nagy KA (1988) Stable isotopes in ecological research. (Ecological Studies, vol 68) Springer, Berlin Heidelberg New YorkGoogle Scholar
  13. Schulze E-D, Hall AE (1982) Stomatal responses, water loss and CO2 assimilation rates of plants in contrasting environments. Encyclopedia Plant Physiol 12B:181–230Google Scholar
  14. Schulze E-D, Schulze I (1976) Distribution and control of photosynthetic pathways in plants growing in the Namib desert, with special regard to Welwitschia mirabilis Hook. fil. Madoqua 9:5–13Google Scholar
  15. Schulze E-D, Ziegler H, Stichler W (1976) Environmental control of crassulacean acid metabolism in Welwitschia mirabilis Hook. Fil. in its range of natural distribution in the Namib desert. Oecologia 24:323–334Google Scholar
  16. Shearer G, Kohl DH (1989) Estimates of N2 fixation in ecosystems: The need for and basis of the 15N abundance method. Ecol Stud 68:342–374Google Scholar
  17. Shearer G, Kohl DH, Virginia RA, Bryan BA, Skeeters JL, Nilsen ET, Sharifi MR, Rundel RW (1983) Estimates of N2-Fixation from the natural abundance of 15N in Sonoran Desert Ecosystems. Oecologia 56:365–373Google Scholar
  18. Virginia RA, Jarrell WM, Rundel PW, Shearer G, Kohl DH (1989) The use of variation in the natural abundance of 15N to assess symbiotic nitrogen fixation by woody plants. Ecol Stud 68:375–394Google Scholar
  19. Walter H (1964) Die Vegetation der Erde in ökophysiologischer Betrachtung. Bd. I. Gustav Fischer Verlag, StuttgartGoogle Scholar

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • E.-D. Schulze
    • 1
  • G. Gebauer
    • 1
  • H. Ziegler
    • 2
  • O. L. Lange
    • 3
  1. 1.Lehrstuhl PflanzenökologieUniversität BayreuthBayreuthFederal Republic of Germany
  2. 2.Institut für Botanik und MikrobiologieTU MünchenMünchenFederal Republic of Germany
  3. 3.Lehrstuhl Botanik IIUniversität WürzburgWürzburgFederal Republic of Germany

Personalised recommendations