, 11:991 | Cite as

Effects of Herbivory, Fire and N2-fixation on Nutrient Limitation in a Humid African Savanna

  • Patrick G. Cech
  • Thomas Kuster
  • Peter J. Edwards
  • Harry Olde Venterink


The quantities and spatial distribution of nutrients in savanna ecosystems are affected by many factors, of which fire, herbivory and symbiotic N2-fixation are particularly important. We measured soil nitrogen (N) pools and the relative abundance of N and phosphorus (P) in herbaceous vegetation in five vegetation types in a humid savanna in Tanzania. We also performed a factorial fertilization experiment to investigate which nutrients most limit herbaceous production. N pools in the top 10 cm of soil were low at sites where fires were frequent, and higher in areas with woody legume encroachment, or high herbivore excretion. Biomass production was co-limited by N and P at sites that were frequently burnt or heavily grazed by native herbivores. In contrast, aboveground production was limited by N in areas receiving large amounts of excreta from livestock. N2-fixation by woody legumes did not lead to P-limitation, but did increase the availability of N relative to P. We conclude that the effects of fire, herbivory and N2-fixation upon soil N pools and N:P-stoichiometry in savanna ecosystems are, to a large extent, predictable.


Acacia woodland cattle grassland grazing N:P ratios nitrogen fixation phosphorus stoichiometry tallgrass 

Supplementary material


  1. Aranibar JN, Otter L, Macko SA, Feral CJW, Epstein HE, Dowty PR, Eckardt F, Shugart HH, Swap RJ. 2004. Nitrogen cycling in the soil-plant system along a precipitation gradient in the Kalahari sands. Glob Change Biol 10:359–73.CrossRefGoogle Scholar
  2. Archer S. 1995. Tree-grass dynamics in a Prosopis-thornscrub savanna parkland: reconstructing the past and predicting the future. Ecoscience 2:83–99.Google Scholar
  3. Archer S. 2001. Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulze E-D, Harrison SP, Heimann M, Holland EA, Lloyd J, Prentice IC, Schimel D, Eds. Global biogeochemical cycles in the climate system. San Diego: Academic Press. pp 115–37.CrossRefGoogle Scholar
  4. Archibald S, Bond WJ, Stock WD, Fairbanks DHK. 2005. Shaping the landscape: fire-grazer interactions in an African savanna. Ecol Appl 15:96–109.CrossRefGoogle Scholar
  5. Augustine DJ. 2003. Long-term, livestock-mediated redistribution of nitrogen and phosphorus in an East African savanna. J Appl Ecol 40:137–49.CrossRefGoogle Scholar
  6. Augustine DJ, McNaughton SJ, Frank DA. 2003. Feedbacks between soil nutrients and large herbivores in a managed savanna ecosystem. Ecol Appl 13:1325–37.CrossRefGoogle Scholar
  7. Barger NN, D’Antonio CM, Ghneim T, Brink K, Cuevas E. 2002. Nutrient limitation to primary productivity in a secondary savanna in Venezuela. Biotropica 34:493–501.Google Scholar
  8. Bell RHV. 1982. The effect of soil nutrient availability on community structure in African ecosystems. In: Huntley BJ, Walker BH, Eds. Ecology of tropical savannas. Berlin: Springer. pp 192–216.Google Scholar
  9. Binkley D. 1997. Bioassays of the influence of Eucalyptus saligna and Albizia falcataria on soil nutrient supply and limitation. For Ecol Manage 91:229–34.CrossRefGoogle Scholar
  10. Binkley D, Senock R, Cromack K. 2003. Phosphorus limitation on nitrogen fixation by Facaltaria seedlings. For Ecol Manage 186:171–6.CrossRefGoogle Scholar
  11. Bond WJ, Woodward FI, Midgley GF. 2005. The global distribution of ecosystems in a world without fire. New Phytol 165:525–37.PubMedCrossRefGoogle Scholar
  12. Bourliere F, Hadley M. 1983. Present day savannas: an overview. In: Bourliere F, Ed. Tropical savannas. Amsterdam: Elsevier. pp 1–18.Google Scholar
  13. Bray RH, Kurtz LT. 1945. Determination of total, organic and available forms of phosphorus in soils. Soil Sci 59:39–45.CrossRefGoogle Scholar
  14. Brockington NR. 1961. Studies of the growth of a Hyparrhenia-dominant grassland in Northern Rhodesia. II. Fertilizer responses. III. The effect of fire. Grass Forage Sci 16:54–65.CrossRefGoogle Scholar
  15. Brown JR, Archer S. 1989. Woody plant invasion of grasslands: establishment of honey mesquite (Prosopis glandulosa var. glandulosa) on sites differing in herbaceous biomass and grazing history. Oecologia 80:19–26.CrossRefGoogle Scholar
  16. Bustamante MMC, Medina E, Asner GP, Nardoto GB, Garcia-Montiel DC. 2006. Nitrogen cycling in tropical and temperate savannas. Biogeochemistry 79:209–37.CrossRefGoogle Scholar
  17. Carter MR. 1993. Soil sampling and methods of analysis. Boca Raton: Lewis.Google Scholar
  18. Cech PG. 2008. Impact of fire, large herbivores and N2-fixation on nutrient cycling in humid savanna, Tanzania. PhD thesis, Zurich, Switzerland: Federal Institute of Technology (ETH).Google Scholar
  19. Cook GD. 1994. The fate of nutrients during fires in a tropical savanna. Aust J Ecol 19:359–65.CrossRefGoogle Scholar
  20. Cramer MD, Chimphango SBM, Van Cauter A, Waldram MS, Bond W. 2007. Grass competition induces N2 fixation in some species of African Acacia. J Ecol 95:1123–33.CrossRefGoogle Scholar
  21. Crews TE. 1993. Phosphorus regulation of nitrogen fixation in a traditional Mexican agroecosystem. Biogeochemistry 21:141–66.CrossRefGoogle Scholar
  22. Edwards PJ, Hollis S. 1982. The distribution of excreta on New Forest grassland used by cattle, ponies and deer. J Appl Ecol 19:953–64.CrossRefGoogle Scholar
  23. Elser JJ, Bracken MES, Cleland EE, Gruner DS, Harpole WS, Hillebrand H, Ngai JT, Seabloom EW, Shurin JB, Smith JE. 2007. Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems. Ecol Lett 10:1135–42.PubMedCrossRefGoogle Scholar
  24. Frank DA, Zhang YM. 1997. Ammonia volatilization from a seasonally and spatially variable grazed grassland: Yellowstone National Park. Biogeochemistry 36:189–203.CrossRefGoogle Scholar
  25. Frost PGH, Robertson F. 1987. The ecological effects of fire in savannas. In: Walker BH, Ed. Determinants of tropical savannas. Oxford: IRL Press. pp 93–140.Google Scholar
  26. Fynn RWS, Haynes RJ, O’Connor TG. 2003. Burning causes long-term changes in soil organic matter content of a South African grassland. Soil Biol Biochem 35:677–87.CrossRefGoogle Scholar
  27. Geesing D, Felker P, Bingham RL. 2000. Influence of mesquite (Prosopis glandulosa) on soil nitrogen and carbon development: implications for global carbon sequestration. J Arid Environ 46:157–80.CrossRefGoogle Scholar
  28. Güsewell S. 2004. N:P ratios in terrestrial plants: variation and functional significance. New Phytol 164:243–66.CrossRefGoogle Scholar
  29. Güsewell S, Koerselman W. 2002. Variation in nitrogen and phosphorus concentrations of wetland plants. Perspect Plant Ecol Evol Syst 5:37–61.CrossRefGoogle Scholar
  30. Hagos MG, Smit GN. 2005. Soil enrichment by Acacia mellifera subsp. detinens on nutrient poor sandy soil in a semi-arid southern African savanna. J Arid Environ 61:47–59.CrossRefGoogle Scholar
  31. Hobbs NT, Schimel DS, Owensby CE, Ojima DS. 1991. Fire and grazing in the tallgrass prairie: contingent effects on nitrogen budgets. Ecology 72:1374–82.CrossRefGoogle Scholar
  32. Högberg P. 1986. Nitrogen-fixation and nutrient relations in savanna woodland trees (Tanzania). J Appl Ecol 23:675–88.CrossRefGoogle Scholar
  33. Holdo RM, Holt RD, Coughenour MB, Ritchie ME. 2007. Plant productivity and soil nitrogen as a function of grazing, migration and fire in an African savanna. J Ecol 95:115–28.CrossRefGoogle Scholar
  34. Hudak AT. 1999. Rangeland mismanagement in South Africa: failure to apply ecological knowledge. Hum Ecol 27:55–78.CrossRefGoogle Scholar
  35. Hudak AT, Wessman CA, Seastedt TR. 2003. Woody overstorey effects on soil carbon and nitrogen pools in South African savanna. Aust Ecol 28:173–81.CrossRefGoogle Scholar
  36. Hunt J. 1982. Dilute hydrochloric acid extraction of plant material for routine cation analysis. Commun Soil Sci Plan 13:49–55.Google Scholar
  37. Huntley BJ. 1982. Southern African savannas. In: Huntley BJ, Walker BH, Eds. Ecology of tropical savannas. Berlin: Springer. pp 101–19.Google Scholar
  38. Israel DW. 1987. Investigation of the role of phosphorus in symbiotic dinitrogen fixation. Plant Physiol 84:835–40.PubMedCrossRefGoogle Scholar
  39. Jewell PL, Kauferle D, Gusewell S, Berry NR, Kreuzer M, Edwards PJ. 2007. Redistribution of phosphorus by mountain pasture in cattle on a traditional the Alps. Agr Ecosyst Environ 122:377–86.CrossRefGoogle Scholar
  40. Kauffman JB, Cummings DL, Ward DE, Babbitt R. 1995. Fire in the Brazilian Amazon: 1. Biomass, nutrient pools, and losses in slashed primary forests. Oecologia 104:397–408.CrossRefGoogle Scholar
  41. Klötzli F. 1980. Analysis of species oscillations in tropical grasslands in Tanzania due to management and weather conditions. Phytocoenologia 8:13–33.Google Scholar
  42. Koerselman W, Meuleman AFM. 1996. The vegetation N:P ratio: a new tool to detect the nature of nutrient limitation. J Appl Ecol 33:1441–50.CrossRefGoogle Scholar
  43. Laclau JP, Sama-Poumba W, Nzila JD, Bouillet JP, Ranger J. 2002. Biomass and nutrient dynamics in a littoral savanna subjected to annual fires in Congo. Acta Oecol 23:41–50.CrossRefGoogle Scholar
  44. Lambers H, Raven JA, Shaver GR, Smith SE. 2008. Plant nutrient-acquisition strategies change with soil age. Trends Ecol Evol 23:95–103.PubMedCrossRefGoogle Scholar
  45. Lamoot I, Callebaut J, Degezelle T, Demeulnaere E, Laquière J, Vandenberghe C, Hoffmann M. 2004. Eliminative behaviour of free-ranging horses: do they show latrine behaviour or do they defecate where they graze? Appl Anim Behav Sci 86:105–21.CrossRefGoogle Scholar
  46. Le Roux X, Mordelet P. 1995. Leaf and canopy CO2 assimilation in a West African humid savanna during the early growing season. J Trop Ecol 11:529–45.Google Scholar
  47. Ludwig F, de Kroon H, Prins HHT, Berendse F. 2001. Effects of nutrients and shade on tree-grass interactions in an East African savanna. J Veg Sci 12:579–88.CrossRefGoogle Scholar
  48. McIvor JG, McIntyre S, Saeli I, Hodgkinson JJ. 2005. Patch dynamics in grazed subtropical native pastures in south-east Queensland. Aust Ecol 30:445–64.CrossRefGoogle Scholar
  49. McNaugthon SJ. 1984. Grazing lawns: animals in herds, plant form and coevolution. Am Nat 124:863–86.CrossRefGoogle Scholar
  50. McNaughton SJ. 1988. Mineral nutrition and spatial concentrations of African ungulates. Nature 334:343–5.PubMedCrossRefGoogle Scholar
  51. McNaughton SJ. 1990. Mineral nutrition and seasonal movements of African migratory ungulates. Nature 345:613–5.CrossRefGoogle Scholar
  52. Medina E. 1987. Nutrients: requirements, conservation and cycles in the herbaceous layer. In: Walker BH, Ed. Determinants of tropical savannas. Oxford: IRL Press. pp 39–65.Google Scholar
  53. Norman MJT. 1966. Katherine research station 1956–64: a review of published work. Melbourne: CSIRO.Google Scholar
  54. Ojima DS, Schimel DS, Parton WJ, Owensby CE. 1994. Long-term and short-term effects of fire on nitrogen cycling in tallgrass prairie. Biogeochemistry 24:67–84.CrossRefGoogle Scholar
  55. Olde Venterink H, Wassen MJ, Verkroost AWM, de Ruiter PC. 2003. Species richness-productivity patterns differ between N-, P-, and K-limited wetlands. Ecology 84:2191–9.CrossRefGoogle Scholar
  56. Pate JS. 1986. Economy of symbiotic nitrogen fixation. In: Givinish TJ, Ed. On the economy of plant form and function. Cambridge: Cambridge University Press. pp 299–325.Google Scholar
  57. Penning de Vries FWT, Krul JM, Van Keulen H. 1980. Productivity of Sahelian rangelands in relation to the availability of nitrogen and phosphorus from the soil. In: Rosswall T, Ed. Nitrogen cycling in West African ecosystems. Stockholm: Royal Swedish Academy of Sciences. pp 95–113.Google Scholar
  58. Perreijn K. 2002. Symbiotic nitrogen fixation by leguminous trees in tropical rain forest in Guyana. Tropenbos-Guyana Series 11. Wageningen: TropenbosGoogle Scholar
  59. Ruess RW, McNaughton SJ. 1988. Ammonia volatilization and the effects of large grazing mammals on nutrient loss from East African grasslands. Oecologia 77:382–6.CrossRefGoogle Scholar
  60. Sage RF, Pearcy RW. 1987. The nitrogen use efficiency of C3 and C4 plants. 2. Leaf nitrogen effects on the gas-exchange characteristics of Chenopodium album (L.) and Amaranthus retroflexus (L.). Plant Physiol 84:959–63.PubMedGoogle Scholar
  61. Sanchez PA. 1976. Properties and management of soils in the tropics. New York: Wiley.Google Scholar
  62. Sankaran M, Hanan NP, Scholes RJ, Ratnam J, Augustine DJ, Cade BS, Gignoux J, Higgins SI, Le Roux X, Ludwig F, Ardo J, Banyikwa F, Bronn A, Bucini G, Caylor KK, Coughenour MB, Diouf A, Ekaya W, Feral CJ, February EC, Frost PGH, Hiernaux P, Hrabar H, Metzger KL, Prins HHT, Ringrose S, Sea W, Tews J, Worden J, Zambatis N. 2005. Determinants of woody cover in African savannas. Nature 438:846–9.PubMedCrossRefGoogle Scholar
  63. Scherer-Lorenzen M, Olde Venterink H, Buschmann H. 2007. Nitrogen enrichment and plant invasions: the importance of nitrogen fixing plants and anthropogenic eutrophication. In: Nentwig W, Ed. Biological invasions, Ecological studies. Berlin: Springer. pp 163–80.CrossRefGoogle Scholar
  64. Snyman HA. 2002. Short-term response of rangeland botanical composition and productivity to fertilization (N and P) in a semi-arid climate of South Africa. J Arid Environ 50:167–83.CrossRefGoogle Scholar
  65. Stock WD, Wienand KT, Baker AC. 1995. Impacts of invading N2-fixing Acacia species on patterns of nutrient cycling in 2 Cape ecosystems: evidence from soil incubation studies and 15N natural abundance values. Oecologia 101:375–82.CrossRefGoogle Scholar
  66. Tobler MW, Cochard R, Edwards PJ. 2003. The impact of cattle ranching on large-scale vegetation patterns in a coastal savanna in Tanzania. J Appl Ecol 40:430–44.CrossRefGoogle Scholar
  67. Treydte AC, Edwards PJ, Suter W. 2005. Shifts in native ungulate communities on a former cattle ranch in Tanzania. Afr J Ecol 43:302–11.CrossRefGoogle Scholar
  68. Van de Vijver CADM, Poot P, Prins HHT. 1999. Causes of increased nutrient concentrations in post-fire regrowth in an East African savanna. Plant Soil 214:173–85.CrossRefGoogle Scholar
  69. Verweij RJT, Verrelst J, Loth PE, Heitkonig IMA, Brunsting AMH. 2006. Grazing lawns contribute to the subsistence of mesoherbivores on dystrophic savannas. Oikos 114:108–16.CrossRefGoogle Scholar
  70. Vitousek PM. 1984. Litterfall, nutrient cycling, and nutrient limitation in tropical forests. Ecology 65:285–98.CrossRefGoogle Scholar
  71. Weinmann H. 1938. Effect of fertiliser treatment on Transvaal highveld. S Afr J Sci 35:246–9.Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Patrick G. Cech
    • 1
    • 2
  • Thomas Kuster
    • 1
  • Peter J. Edwards
    • 1
  • Harry Olde Venterink
    • 1
  1. 1.Institute of Integrative BiologyETH ZurichZurichSwitzerland
  2. 2.Swiss Tropical InstituteBaselSwitzerland

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