Environmental Management

, Volume 49, Issue 2, pp 387–402 | Cite as

An Overview of Nitrogen Cycling in a Semiarid Savanna: Some Implications for Management and Conservation in a Large African Park



Nitrogen (N) is a major control on primary productivity and hence on the productivity and diversity of secondary producers and consumers. As such, ecosystem structure and function cannot be understood without a comprehensive understanding of N cycling and dynamics. This overview describes the factors that govern N distribution and dynamics and the consequences that variable N dynamics have for structure, function and thresholds of potential concern (TPCs) for management of a semiarid southern African savanna. We focus on the Kruger National Park (KNP), a relatively intact savanna, noted for its wide array of animal and plant species and a prized tourist destination. KNP’s large size ensures integrity of most ecosystem processes and much can be learned about drivers of ecosystem structure and function using this park as a baseline. Our overview shows that large scale variability in substrates exists, but do not necessarily have predictable consequences for N cycling. The impact of major drivers such as fire is complex; at a landscape scale little differences in stocks and cycling were found, though at a smaller scale changes in woody cover can lead to concomitant changes in total N. Contrasting impacts of browsers and grazers on N turnover has been recorded. Due to the complexity of this ecosystem, we conclude that it will be complicated to draw up TPCs for most transformations and pools involved with the N cycle. However, we highlight in which cases the development of TPCs will be possible.


Ecosystem management Elephants Fire Herbivores Mineralisation Savanna Total soil N 


  1. Abbadie L, Lata J-C (2006) Nitrogen dynamics in the plant–soil systems. In: Abbadie L, Gignoux G, Le Roux X, Lepage M (eds) Lamto: structure, functioning, and dynamics of a savanna ecosystem, ecological studies 179. Springer, New York, pp 277–308Google Scholar
  2. Abbadie L, Mariotti A, Menaut JC (1992) Independence of savanna grasses from soil organic matter for their nitrogen supply. Ecology 73:608–613CrossRefGoogle Scholar
  3. Alard G (2009) A comparison of grass production and utilization in sodic and crest patches on a semi-arid granitic savanna catena in the southern Kruger National Park, South Africa. MSc Thesis, University of the Witwatersrand, JohannesburgGoogle Scholar
  4. Anderson TM, Ritchie ME, Mayemba E, Eby S, Grace JB, McNaughton SJ (2007) Forage nutritive quality in the Serengeti ecosystem: the roles of fire and herbivory. American Naturalist 170:343–357CrossRefGoogle Scholar
  5. Anderson TM, Hopecraft JGC, Eby S, Ritchie M, Grace J, Olff H (2010) Landscape scale analyses suggest both nutrient and antipredator advantages to Serengeti nutrient hotspots. Ecology 91:1519–1529CrossRefGoogle Scholar
  6. Andreae MO (1997) Emissions of trace gases and aerosols from southern African savanna fires. In: van Wilgen BW, Andreae MO, Goldammer JG, Lindesay JA (eds) Fire in the southern African savannas: ecological and environmental perspectives. Witwatersrand University Press, Johannesburg, South Africa, pp 161–183Google Scholar
  7. Aranibar JN, Macko SA, Anderson IC, Potgieter ALF, Sowry R, Shugart HH (2003a) Nutrient cycling responses to fire frequency in the Kruger National Park (South Africa) as indicated by stable isotope analysis. Isotopes in Environmental and Health Studies 39:141–158CrossRefGoogle Scholar
  8. Aranibar JN, Anderson IC, Ringrose S, Macko SA (2003b) The importance of nitrogen fixation in soil crusts of southern African arid ecosystem: acetylene reduction and stable isotope studies. Journal of Arid Environments 54:345–358CrossRefGoogle Scholar
  9. Archer S, Boutton TW, Hibbard KA (2001) Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulze E-D, Harrison SP, Heiman M, Holland EA, Lloyd JL, Prentice C, Schimel D (eds) Global biogeochemical cycles in the climate system. Academic Press, San Diego, pp 115–130Google Scholar
  10. Archibald S (2008) African grazing lawns: how fire, rainfall and grazing numbers interact to effect grass community states. Journal of Wildlife Management 72:492–501CrossRefGoogle Scholar
  11. Archibald S, Bond WJ, Stock WD, Fairbanks DHK (2005) Shaping the landscape: fire-grazing interactions in an African savanna. Ecological Applications 15:96–105CrossRefGoogle Scholar
  12. Asner GP, Levick SR, Kennedy-Bowdoin T, Knapp DE, Emerson R, Jacobsen J, Colgan SM, Martin RE (2009) Large-scale impacts of herbivores on the structural diversity of African savannas. Proceedings of the National Academy of Sciences USA 106:4947–4952CrossRefGoogle Scholar
  13. Augustine DJ (2003) Long-term, livestock-mediated redistribution of nitrogen and phosphorus in an East African savanna. Journal of Ecological Applications 40:137–149CrossRefGoogle Scholar
  14. Augustine DJ, Frank DA (2001) Effects of migratory grazers on spatial heterogeneity of soil nitrogen properties in a grassland ecosystem. Ecology 82:3149–3162CrossRefGoogle Scholar
  15. Augustine DJ, McNaughton S (2006) Interactive effects of ungulate herbivores, soil fertility and variable rainfall on ecosystem processes in a semi-arid savanna. Ecosystems 9:1242–1256CrossRefGoogle Scholar
  16. Augustine DJ, McNaughton SJ, Frank DA (2003) Feedbacks between soil nutrients and large herbivores in a managed savanna ecosystem. Ecological Applications 13:1325–1337CrossRefGoogle Scholar
  17. Barnes RFW (1983) The elephant problem in Ruaha National Park, Tanzania. Biological Conservation 26:127–148Google Scholar
  18. Baxter PWJ, Getz WM (2005) A model-framed evaluation of elephant effects on tree and fire dynamics in African savannas. Ecological Applications 15:1331–1341CrossRefGoogle Scholar
  19. Beater MMT (2002) The rates of potential nitrogen mineralization across a semi-arid granitic catena in the Kruger National Park. B.Sc. dissertation. University of the Witwatersrand, JohannesburgGoogle Scholar
  20. Bechtold JS, Naiman RJ (2006) Soil texture and nitrogen mineralization potential across a riparian toposequence in a semi-arid savanna. Soil Biology and Biochemistry 6:1325–1333CrossRefGoogle Scholar
  21. Belsky AJ (1994) Influences of trees on savanna productivity: tests of shade, nutrients, and tree-grass competition. Ecology 75:922–934CrossRefGoogle Scholar
  22. Bengis RG, Grant R, de Vos V (3002) Wildlife diseases and veterinary controls: a savannah ecosystem perspective. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 349–369Google Scholar
  23. Biggs HC, Rogers KH (2003) An adaptive system to link science, monitoring and management in practice. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, pp 59–80Google Scholar
  24. Biggs R, Biggs HC, Dunne TT, Govender N, Potgieter ALF (2003) Experimental burn plot trial in the Kruger National Park: history, experimental design, and suggestions for data analysis. Koedoe 46:1–15Google Scholar
  25. Blair JM (1997) Fire, N availability, and plant response in grasslands: a test of the transient maxima hypothesis. Ecology 78:2359–2368CrossRefGoogle Scholar
  26. Boko M, Niang I, Nyong A, Vogel C, Githeko A, Medany M, Osman-Elasha B, Tabo R, Yanda P (2007) Africa. In Parry ML, Canziani OF, Palutikof JP, Van der Linden PL, Hanson CE (eds) Climate change 2007: impacts, adaptation and vulnerability. Contribution of working group II to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 433–462Google Scholar
  27. Bond WJ, Midgley GF, Woodward FI (2003) The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannas. Global Change Biology 9:973–982CrossRefGoogle Scholar
  28. Brits J, Van Rooyen MW, Van Rooyen N (2002) Ecological impact of large herbivores on the woody vegetation at selected watering points on the eastern basaltic soils in the Kruger National Park. African Journal of Ecology 40:53–60CrossRefGoogle Scholar
  29. Buis GM, Blair JM, Burkepile DE, Burns CE, Chamberlain AJ, Chapman PL, Collins SL, Fynn RWS, Govender N, Kirkman KP, Smith MD, Knapp AK (2009) Controls of aboveground net primary production in mesic savanna grasslands: an inter-hemisphere comparison. Ecosystems 12:982–995CrossRefGoogle Scholar
  30. Bustamante MC, Medina E, Asner GP, Nardato GB, Garcia-Montiel DC (2006) Nitrogen cycling in tropical and temperate savannas. Biogeochemistry 79:209–237CrossRefGoogle Scholar
  31. Cech PG, Kuster T, Edwards PJ, Venterink HO (2008) Effects of herbivory, fire and N2-fixation on nutrient limitation in a humid African savanna. Ecosystems 11:991–1104CrossRefGoogle Scholar
  32. Chapin FS III, Matson PA, Mooney HA (2002) Principles of terrestrial ecosystem ecology. Springer-Verlag, New York, p 472Google Scholar
  33. Clark CM, Tilman D (2008) Loss of plant species after chronic low-level nitrogen deposition to prairie grasslands. Nature 451:712–715CrossRefGoogle Scholar
  34. Coetsee C (2007) Long-term effects of fire on nitrogen cycling in a broad-leaf savanna, Kruger National Park, South Africa. PhD Thesis, University of Cape Town, Cape TownGoogle Scholar
  35. Coetsee C, February EC, Bond WJ (2008) Nitrogen availability is not affected by frequent fire in a South African savanna. Journal of Tropical Ecology 24:647–654CrossRefGoogle Scholar
  36. Coetsee C, Bond WJ, February EC (2010a) Frequent fire affects soil nitrogen and carbon in an African savanna by changing woody cover. Oecologia 162:1027–1034CrossRefGoogle Scholar
  37. Coetsee C, Stock WD, Craine JM (2010b) Do grazers alter nitrogen dynamics on grazing lawns in a South African savannah? African Journal of Ecology 49:62–69CrossRefGoogle Scholar
  38. Collins NM (1981) Populations, age structure and survivorship of colonies of Macrotermis bellicosus (Isoptera, Termitidae). Journal of Animal Ecology 50:293–310CrossRefGoogle Scholar
  39. Cook GD (2001) Effects of frequent fires and grazing on stable nitrogen isotope ratios of vegetation in northern Australia. Australian Ecology 26:630–636CrossRefGoogle Scholar
  40. Craine J, Ballantyne F, Peel M, Zambatis N, Morrow C, Stock W (2009) Grazing and landscape controls on nitrogen availability across 330 South African savanna sites. Australian Ecology 34:731–740CrossRefGoogle Scholar
  41. Craine JM, Morrow C, Stock WD (2008) Nutrient concentration ratios and co-limitation in South African grasslands. New Phytologist 179:829–836Google Scholar
  42. Cramer MD, Chimphango SBM, Van Cauter A, Waldram MS, Bond WJ (2007) Grass competition induces N2 fixation in some species of African savanna. Journal of Ecology 95:1123–1133CrossRefGoogle Scholar
  43. Cramer MD, Van Cauter A, Bond WJ (2010) Growth of N2 fixing African savanna Acacia species is constrained by below-ground competition with grass. Journal of Ecology 98:156–167CrossRefGoogle Scholar
  44. Crews TE (1999) The presence of nitrogen fixing legumes in terrestrial communities: evolutionary vs ecological considerations. Biogeochemistry 46:233–246Google Scholar
  45. Cumming DHM, Brock FM (1997) Elephants, woodlands and biodiversity in southern Africa. South African Journal of Science 93:25–30Google Scholar
  46. Dublin HT, Sinclair ARE (1990) Elephants and fire as causes of multiple stable states in Serengeti-Mara Woodlands. Journal of Animal Ecology 59:1147–1164Google Scholar
  47. Du Toit JT (2003) Large herbivores and savanna heterogeneity. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 292–309Google Scholar
  48. Du Toit JT, Bryant JP, Frisby K (1990) Regrowth and palatability of Acacia shoots following pruning by African savanna browsers. Ecology 71:149–154CrossRefGoogle Scholar
  49. Eckhardt HC, Van Wilgen BW, Biggs HC (2000) Trends in woody vegetation cover in the Kruger National Park, South Africa, between 1940 and 1998. African Journal of Ecology 38:108–115CrossRefGoogle Scholar
  50. Egunjobi JK (1971) Ecosystem processes in a stand of Ulex europaeus L. II The cycling of chemical elements in the ecosystem. Journal of Ecology 59:669–678CrossRefGoogle Scholar
  51. Feig GT (2004) The effects of fire regime on soil microbial community composition and activity. M.Sc. Thesis, University of the Witwatersrand, JohannesburgGoogle Scholar
  52. Feig GT, Mantimin B, Meixner FX (2008) Soil biogenic emissions of nitric oxide from a semi-arid savanna in South Africa. Biogeoscience Discussion 5:2795–2837CrossRefGoogle Scholar
  53. Ferwerda JG, Siderius W, Van Wieren SW, Grant CC, Peel M, Skidmore AK, Prins HHT (2006) Parent material and fire as principal drivers of foliage quality in woody plants. Forest Ecology and Management 231:178–183CrossRefGoogle Scholar
  54. Fey M (2010) Soils of South Africa. Their distribution, properties, classification, genesis, use and environmental significance. Cambridge University Press, CambridgeGoogle Scholar
  55. Fisher NT (2006) Denitrification in a semi-arid South African savanna: The Kruger National Park. MSc Thesis, University of the Witwatersrand, JohannesburgGoogle Scholar
  56. Fisher NT, Jacobs SM, Scholes M, Naiman RJ (2011) Potential denitrification and N2O emissions along a savanna toposequence in semiarid southern Africa. Kruger National Park, MopaniGoogle Scholar
  57. Fornara DA, Du Toit JT (2007) Browsing lawns? Responses of Acacia nigrescens to ungulate browsing in an African savanna. Ecology 88:200–209Google Scholar
  58. Fornara DA, Du Toit JT (2008) Community-level interactions between ungulate browsers and woody plants in an African savannah dominated by palatable-spinescent Acacia trees. Journal of Arid Environments 72:534–545CrossRefGoogle Scholar
  59. Fox-Dobbs K, Doak DF, Brody AK, Palmer TM (2010) Termites create spatial structure and govern ecosystem function by affecting N2 fixation in an East African savannah. Ecology 91:1296–1307CrossRefGoogle Scholar
  60. Frank DA (1998) Ungulate regulation of ecosystem processes in Yellowstone National Park: direct and feedback effects. Wildlife Society Bulletin 26:410–418Google Scholar
  61. Frank DA, Groffman PM, Evans RD, Tracy BF (2000) Ungulate stimulation of nitrogen cycling and retention in Yellowstone Park grasslands. Oecologia 123:16–121CrossRefGoogle Scholar
  62. Fritz H, Duncan P, Gordon IJ, Illius AW (2002) Megaherbivores influence tropical guilds structure in African ungulate communities. Oecologia 131:620–625Google Scholar
  63. Frost PGH, Edinger SB (1991) Effects of tree canopies on soil characteristics of annual rangeland. The Journal of Range Management 44:286–288CrossRefGoogle Scholar
  64. Furley P (2010) Tropical savannas: Biomass, plant ecology, and the role of fire and soil on vegetation. PPGEO 34:563–585Google Scholar
  65. Giorgiadis NJ (1989) Microhabitat variation in an African savanna: effect of woody cover and herbivores in Kenya. Journal of Tropical Ecology 5:93–108CrossRefGoogle Scholar
  66. Grant CC, Scholes MC (2006) The importance of nutrient hot-spots in the conservation and management of large wild mammalian herbivores in semi-arid savannas. Biological Conservation 130:426–437CrossRefGoogle Scholar
  67. Grant CC, Meissner HH, Schultheiss WA (1995) The nutritive value of veld as indicated by faecal phosphorus and nitrogen and its relations to the condition and movement of prominent ruminants during the 1992–1993 drought in the Kruger National Park. Koedoe 38:17–31Google Scholar
  68. Grant CC, Peel MJS, Van Ryssen JBJ (2000) Nitrogen and phosphorus concentrations in faeces: an indicator of range quality as a practical adjunct to existing range evaluation methods. African Journal of Range and Forest Science 17:81–92CrossRefGoogle Scholar
  69. Hatton JC, Smart NOE (1984) The effect of long-term exclusion of large herbivores on soil nutrient status in Murchison Falls National Park, Uganda. African Journal of Ecology 22:23–30Google Scholar
  70. Hibbard KA, Archer S, Schimel DS, Valentine DV (2001) Biogeochemical changes accompanying woody plant encroachment in a subtropical savanna. Ecology 82:1999–2011CrossRefGoogle Scholar
  71. Higgins SI, Bond WJ, February EC, Bronn A, Euston-Brown DIW, Enslin B, Govender N, Rademan L, O’Regan S, Potgieter ALF, Scheiter S, Sowry R, Trollope L, Trollope WSW (2007) Effects of four decades of fire manipulation on woody vegetation structure in savanna. Ecology 88:1119–1125CrossRefGoogle Scholar
  72. Hobbs NT, Schimel DS, Owensby CE, Ojima DS (1991) Fire and grazing in the tallgrass prairie: Contingent effects on nitrogen budgets. Ecology 72:1374–1382CrossRefGoogle Scholar
  73. Hoffman WA, Jackson RB (2000) Vegetation–climate feedbacks in the conversion of tropical savanna to grassland. Journal of Climate 13:1593–1602Google Scholar
  74. Holdo R, Mack M, Stephen A (2011) Tree canopies explain fire effects on soil nitrogen, phosphorus and carbon in a savanna ecosystem. The Journal of Vegetation Science 24:1149Google Scholar
  75. Holland EA, Detling JK (1990) Plant responses to herbivory and belowground nitrogen cycling. Ecology 71:1040–1049CrossRefGoogle Scholar
  76. Holt JA, Coventry RJ (1990) Nutrient cycling in Australian savannas. Journal of Biogeography 17:427–432CrossRefGoogle Scholar
  77. Hopcraft JC, Olff H, Sinclair ARE (2010) Herbivores, resources and risks: alternating regulation along primary environmental gradients in savannas. Trends in Ecology and Evolution 25:119–128CrossRefGoogle Scholar
  78. Hudak AT, Wessman CA, Seastedt TR (2003) Woody overstory effects on soil carbon and nitrogen pools in South African savanna. Australian Journal of Ecology 28:173–181CrossRefGoogle Scholar
  79. Hughes RF, Archer SR, Asner P, Wessman CA, McMurtry C, Nelson J, Ansley J (2006) Changes in aboveground primary production and carbon and nitrogen pools accompanying woody plant encroachment in a temperate savanna. Global Change Biology 12:1733–1747CrossRefGoogle Scholar
  80. Isichei AO, Muoghalu JI (1992) The effects of tree canopy cover on soil fertility in a Nigerian savanna. Journal of Tropical Ecology 8:329–338CrossRefGoogle Scholar
  81. Jackson RB, Banner JL, Jobbágy E, Pockman WT, Wall DH (2002) Ecosystem carbon loss with woody plant invasion of grasslands. Nature 418:623–626CrossRefGoogle Scholar
  82. Jacobs OS, Biggs R (2002) The impact of the African elephant on marula trees in the Kruger National Park. SAJ Wild Research 32:13–22Google Scholar
  83. Jacobs SM, Pettit NP, Naiman RJ (2007a) Nitrogen fixation by the savannah tree Philenoptera violacea (Klotzsch) Schrire (Apple leaf) of different ages in a semi-arid savannah riparian landscape. SAJ Botany 73:163–167Google Scholar
  84. Jacobs SM, Bechtold JS, Biggs HC, Grimm NB, Lorentz S, McClain ME, Naiman RJ, Perakis SS, Pinay G, Scholes MC (2007b) Nutrient vectors and riparian processing: a review with special reference to African semiarid savanna ecosystems. Ecosystems 10:1432–1440CrossRefGoogle Scholar
  85. Johnson LC, Matchett JR (2001) Fire and grazing regulate below-ground processes in tallgrass prairie. Ecology 82:3377–3389CrossRefGoogle Scholar
  86. Jones CL, Smithers NL, Scholes MC, Scholes RJ (1990) The effect of fire frequency on the organic components of a basaltic soil in the Kruger National Park. SAJ Plant Soil 7:236–238Google Scholar
  87. Kauffman JB, Cummings DL, Ward DE (1994) Relationships of fire, biomass and nutrient dynamics along a vegetation gradient in Brazilian cerrado. Journal of Ecology 82:519–531CrossRefGoogle Scholar
  88. Keretetse MT (2009) Water and available nitrogen as co-determinants of a mesic savanna, Kruger National Park. MSc Thesis, University of Cape Town, Cape TownGoogle Scholar
  89. Kerley GIH, Landman M, Kruger L, Owen-Smith N (2007) Chapter 3: Effects of elephants on ecosystems and biodiversity. In Scholes RJ, Mennell KG (eds) Elephant management: a scientific assessment of South Africa. Witwatersrand University Press, Johannesburg, pp 41–58. http://www.elephantassessment.co.za/files/ch03.draft2.GIHK.pdf
  90. Kgope BS, Bond WJ, Midgley GF (2010) Growth responses of African savanna trees implicate atmospheric CO2 as a driver of past and current changes in savanna tree cover. Australian Journal of Ecology 35:451–463Google Scholar
  91. Khavhagali VP (2008) Forest colonization of savannas: patterns and process. MSc Thesis, University of Cape Town, Cape TownGoogle Scholar
  92. KNP Management Plan (2008) South African National Parks, Scientific Services, Skukuza, p 1350Google Scholar
  93. Lebauer DS, Treseder KK (2008) Nitrogen limitation of primary productivity in terrestrial ecosystems is globally distributed. Ecology 89:371–379Google Scholar
  94. Levick SR, Asner GP, Kennedy-Bowdoin T, Knapp DE (2010) The spatial extent of termite influences on herbivore browsing in an African savanna. Cons Biol 141:489–498Google Scholar
  95. Livesley SJ, Grover S, Huntley LB, Jamali H, Butterbach-Ball K, Fest B, Beringer J, Arndt S (2011) Seasonal variation and fire effects on CH4, N2O and CO2 exchange in savanna soils of northern Australia. Agric Forest Meteor. doi:10.1016/j.agrformet.2011.02.001
  96. Ludwig F (2001) Tree-grass interactions on an East African savanna: The effects of competition, facilitation and hydraulic lift. PhD Thesis, Wageningen, The NetherlandsGoogle Scholar
  97. Marchant R (2010) Understanding complexity in savannas: climate, biodiversity and people. Current Opinion in Environmental Sustainability 2:101–108CrossRefGoogle Scholar
  98. Marom D (2002) The effects of Impala Dung and Buffalo Dung on the Soil Nitrogen Mineralization rate. B.Sc. dissertation. University of the Witwatersrand, JohannesburgGoogle Scholar
  99. McNaughton SJ (1984) Grazing lawns: animals in herds, plant form and coevolution. The American Naturalist 124:863–886CrossRefGoogle Scholar
  100. McNaughton SJ (1985) Ecology of a grazing ecosystem: the Serengeti. Ecological Monographs 55:258–294CrossRefGoogle Scholar
  101. McNaughton SJ (1992) Laboratory-simulated grazing: interactive effects of defoliation and canopy closure on Serengeti grasses. Ecology 73:170–182CrossRefGoogle Scholar
  102. Medina E (1982) Nitrogen balance in the Trachypogon grasslands of Central Venezuela. Plant and Soil 67:305–314CrossRefGoogle Scholar
  103. Menaut J-C, Abbadie L, Vitousek PM (1993) Nutrient and organic matter dynamics in tropical ecosystems. In: Crutzen PJ, Goldammer JG (eds) The ecological, atmospheric and climatic importance of vegetation fires. John Wiley and Sons Ltd, Chichester, UK, pp 215–231Google Scholar
  104. Meyer VW, Crewe RM, Braack LEO (2003) Estimates of food consumption by the fungus-growing termite Macrotermis natalensis in a South African savanna-woodland. SAJ Science 99:207–208Google Scholar
  105. Mills AJ, Fey MV (2003) Declining soil quality in South Africa: effects of land use on soil organic matter and surface crusting. SAJ Science 99:429–436Google Scholar
  106. Moore AW (1960) The influence of annual burning on a soil in the derived savanna zone of Nigeria. Transactions of the 7th International Congress of Soil Science, Medison, Wisconsin 4: 257–264Google Scholar
  107. Mordelet P, Abbadie L, Menaut J-C (1993) Effects of tree clumps on soil characteristics in a humid savanna of West Africa (Lamto, Côte d’Ivoire). Plant and Soil 153:103–111CrossRefGoogle Scholar
  108. Murray MG (1995) Specific nutrient requirements and migration of wildebeest. In: Sinclair ARE, Arcese P (eds) Serengeti II: dynamics, management and conservation of an ecosystem. University of Chicago, Chicago, USA, pp 231–256Google Scholar
  109. Mutanga O, Prins HHT, Skidmore AK, Van Wieren S, Huizing H, Grant R, Peel M, Biggs H (2004) Explaining grass-nutrient patterns in a savanna rangeland of southern Africa. Journal of Biogeography 31:819–829CrossRefGoogle Scholar
  110. Naiman RJ, Rogers KH (1997) Large animals and system-level characteristics in river corridors. BioScience 47:521–529CrossRefGoogle Scholar
  111. Naiman RJ, Braack L, Grant R, Kemp AC, Du Toit J, Venter F (2003) Interactions between species and ecosystem characteristics. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 221–241Google Scholar
  112. Oguntala AB (1980) The effects of fire on some aspects of nitrogen cycling in Olokemeji Forest Reserve, Nigeria. In: Rosswall T (ed) Nitrogen cycling. Royal Swedish Academy of Science, Stockholm, Sweden, pp 317–323Google Scholar
  113. Ojima DS, Schimel DS, Parton WJ, Owensby CE (1994) Long- and short-term effects of fire on nitrogen cycling in tallgrass prairie. Biogeochemistry 24:67–84CrossRefGoogle Scholar
  114. Parsons DAB, Scholes MC, Scholes RJ, Levine JS (1996) Biogenic NO emissions from savanna soils as a function of fire regime, soil type, soil nitrogen, and water status. Journal of Geophysical Research 101:23683–23688CrossRefGoogle Scholar
  115. Pettit NE, Naiman RJ (2005) Flood-deposited wood debris and its contribution to heterogeneity and regeneration in a semi-arid riparian landscape. Oecologia 145:434–444Google Scholar
  116. Pettit NE, Naiman RJ (2007) Fire in the riparian zone: characteristics and ecological consequences. Ecosystems 10:673–687Google Scholar
  117. Pollard S, Shacleton C, Carruthers J (2003) Beyond the fence: people and the Lowveld landscape. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 422–446Google Scholar
  118. Pringle RM, Doak DF, Brody AK, Jocque R, Palmer TM (2010) Spatial pattern enhances ecosystem functioning in an African savanna. PLoS Biology 8:1–12CrossRefGoogle Scholar
  119. Ratnam R, Sankaran M, Hanan NP, Grant RC, Zambatis N (2008) Nutrient resorption patterns of functional plant groups in a tropical savanna: variation and functional significance. Oecologia 157:141–151Google Scholar
  120. Rees RM, Wuta M, Furley PA, Changseng L (2006) Nitrous oxide fluxes from savanna (miombo) woodlands in Zimbabwe. Journal of Biogeography 33:424–437CrossRefGoogle Scholar
  121. Reich PB, Peterson DW, Wedin DA, Wrage K (2001) Fire and vegetation effects on productivity and nitrogen cycling across a forest-grassland continuum. Ecology 82:1703–1719Google Scholar
  122. Ruess RW, McNaughton SJ (1987) Grazing and the dynamics of nutrient and energy regulated microbial processes in the Serengeti grassland. Oikos 49:101–110CrossRefGoogle Scholar
  123. Ruess RW, Seagle SW (1994) Landscape patterns in soil microbial processes in the Serengeti National Park, Tanzania. Ecology 75:892–904CrossRefGoogle Scholar
  124. Sankaran M, Ratman J, Hanan NP (2008) Woody cover in African savannas: the role of resources, fire and herbivory. Global Ecology and Biogeography 17:236–245CrossRefGoogle Scholar
  125. Schmidt S, Stewart GR (2003) δ15N values of tropical savanna and monsoon forest species reflect root specializations and soil nitrogen status. Oecologia 134:569–577Google Scholar
  126. Scholes RJ (1990) The influence of soil fertility on the ecology of southern African dry savannas. Journal of Biogeography 17:415–419CrossRefGoogle Scholar
  127. Scholes RJ, Walker BH (1993) An African savanna, synthesis of the Nylsvley study. Cambridge University Press, Cambridge, UK, p 306CrossRefGoogle Scholar
  128. Scholes MC, Scholes RJ, Otter LB, Woghiren AN (2003) Biogeochemistry: the cycling of elements. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 41–58Google Scholar
  129. Scogings PF, Hjältén J, Skarpe C (2011) Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas. Oecologia. doi:10.1007/s00442-011-2042-9
  130. Seagle SW, McNaughton SJ, Ruess RW (1992) Simulated effects of grazing on soil nitrogen and mineralisation in contrasting Serengeti grasslands. Ecology 73:1105–1123CrossRefGoogle Scholar
  131. Shackleton CM, Scholes RJ (2000) Impact of fire frequency on woody community structure and soil nutrients in the Kruger National Park. Koedoe 43:75–81Google Scholar
  132. Shannon G, Druce DJ, Page BR, Eckhardt HC, Grant R, Slotow R (2008) The utilization of large savanna trees by elephant in southern Kruger National Park. Journal of Tropical Ecology 24:281–289CrossRefGoogle Scholar
  133. Siebert F, Echkardt HC (2008) The vegetation and floristics of the Nkhuhlu exclosures, Kruger National Park. Koedoe 50:126–144Google Scholar
  134. Siebert F, Echkardt HC, Siebert SJ (2010) The vegetation and floristics of the Nkhuhlu exclosures, Kruger National Park, South Africa. Koedoe 52:126–144CrossRefGoogle Scholar
  135. Singh RS (1994) Changes in soil nutrients following burning of dry tropical savanna. International Journal of Wildland Fire 4:187–194CrossRefGoogle Scholar
  136. Skidmore AK, Ferwerda JG, Mutanga O, Van Wieren SE, Peel M, Grant CC, Prins HHT, Balcik FB, Venus V (2010) Forage quality of savannas simultaneously mapping foliar protein and polyphenols for trees and grass using hyperspectral imagery. Remote Sensing of Environment 114:64–72CrossRefGoogle Scholar
  137. Smallie JJ, O’connor TG (2000) Elephant utilization of Colophospermum mopane: possible benefits of hedging. African Journal of Ecology 38:352–359Google Scholar
  138. Smit IPJ, Ferreira SM (2011) Management intervention affects river-bound spatial dynamics of elephants. Biological Conservation 143:2172–2182CrossRefGoogle Scholar
  139. Smit IPJ, Grant CC (2009) Managing surface-water in a large semi-arid savanna park: effects on grazer distribution patterns. Journal for Nature Conservation 17:61–71CrossRefGoogle Scholar
  140. Sterner RW, Elser JJ (2002) Ecological stoichiometry: the biology of elements from molecules to the biosphere. Princeton University Press, UKGoogle Scholar
  141. Stevens CJ, Dise NB, Mountford JO, Gowing DJ (2004) Impact of nitrogen deposition on the species richness of grasslands. Science 303:1876–1879CrossRefGoogle Scholar
  142. Treydte AC, Heitkonig IMA, Prins HHT, Ludwig F (2007) Trees improve grass quality for herbivores in African savannas. Perspectives in Plant Ecology 8:197–205CrossRefGoogle Scholar
  143. Trollope WSW, Trollope LA, Biggs HC, Pienaar D, Potgieter ALF (1998) Long-term changes in the woody vegetation of the Kruger National Park, with special reference to the effects of elephants and fire. Koedoe 41:103–112Google Scholar
  144. Tucker KM (2002) Comparative study of the effects of fire frequency on the carbon and nitrogen dynamics over a decade on two soils in the Kruger National Park. B.Sc. dissertation. University of the Witwatersrand, JohannesburgGoogle Scholar
  145. Uhlmann KL (2006) Variation in leaf traits along a rainfall gradient in the Kruger National Park. Bsc Thesis. The University of New South WalesGoogle Scholar
  146. Van Reenen CH, Visser GJ, Loos MA (1992) In: Van Wilgen BW, Richardson DM, Kruger FJ, Van Hensbergen HJ (eds) Fire in South African mountain fynbos: ecosystem, community and species response of Swartboskloof. Ecological Studies: Analysis and synthesisGoogle Scholar
  147. Van de Vijver CADM, Poot P, Prins HHT (1999) Causes of increase nutrient concentrations in post-fire regrowth in an East African savanna. Plant and Soil 214:173–185CrossRefGoogle Scholar
  148. Van der Waal C, de Kroon H, de Boer WF, Heitkönig IMA, Skidmore AK, de Knegt HJ, Van Langevelde F, Van Wieren SE, Grant CC, Page BR, Slotow R, Kohi EM, Mwakiwa E, Prins HHT (2009) Water and nutrients alter herbaceous competitive effects on tree seedlings in a semi-arid savanna. Journal of Ecology 97:430–439CrossRefGoogle Scholar
  149. Van der Waal C, Kool A, Meijer SS, Kohi EM, Heitkönig IMA, De Boer WF, Van Langevelde F, Grant CC, Peel MJS, Slotow R, de Knegt HJ, Prins HHT, De Kroon H (2011) Large herbivores may alter vegetation structure of semiarid savannas through soil nutrient mediation. Oecologia 165:1095–1107CrossRefGoogle Scholar
  150. Van Voorthuizen EG (1976) The mopane tree. Botswana Notes and Records 8:223–230Google Scholar
  151. Van Wilgen BW, Biggs HC (2011) A critical assessment of adaptive ecosystem management in a large savannah protected area in South Africa. Biological Conservation 144:1179–1187CrossRefGoogle Scholar
  152. Van Wilgen BW, Biggs HC, Potgieter ALF (1998) Fire management and research in the Kruger National Park, with suggestions on the detection of thresholds of potential concern. Koedoe 41:69–87Google Scholar
  153. Van Wilgen B, Govender N, Biggs H (2007) The contribution of fire research to fire management: a critical review of a long-term experiment in the Kruger National Park, South Africa. International Journal of Wildland Fire 16:519–530CrossRefGoogle Scholar
  154. Van Wilgen BW, Govender N, Biggs HC, Ntsala D, Funda XN (2004) Response of savanna fire regimes to changing fire management policies in a large African park. Conservation Biology 18:1533–1540Google Scholar
  155. Venter FJ (1990) A classification of land for management planning in the Kruger National Park. PhD Thesis, University of South Africa, PretoriaGoogle Scholar
  156. Venter FJ, Scholes RJ, Eckhardt H (2003) The abiotic template and its associated vegetation patterns. In: Du Tiot JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 83–129Google Scholar
  157. Venter FJ, Naiman RJ, Biggs HC, Pienaar DJ (2008) The evolution of management philosophy: science, environmental change and social adjustments in Kruger National Park ecosystems 11:173–192Google Scholar
  158. Vitousek PM, Howarth RW (1991) Nitrogen limitation on land and sea: how can it occur? Biogeochemistry 13:87–115Google Scholar
  159. Wan S, Hui D, Luo Y (2001) Fire effects on nitrogen pools and dynamics in terrestrial ecosystems: a meta-analysis. Ecological Applications 11:1349–1365Google Scholar
  160. Whyte IJ, van Aarde R, Pimm SL (2003) Kruger’s elephant population: its size and consequences for ecosystem heterogeneity. In: Du Toit JT, Rogers KH, Biggs HC (eds) The Kruger experience: ecology and management of savanna heterogeneity. Island Press, Washington, USA, pp 332–348Google Scholar
  161. Wigley BJ, Bond WD, Hoffman MT (2009) Thicket expansion in a South African savanna under divergent land use: local vs. global drivers. Global Change Biology 16:964–976CrossRefGoogle Scholar
  162. Williams RJ, Myers BA, Muller WJ, Duff GA, Eamus D (1997) Leaf phenology of woody species in a North Australian tropical savanna. Ecology 78:2542–2558CrossRefGoogle Scholar
  163. Williams RJ, Hutley LB, Cook GD, Russell-Smith J, Edwards A, Chen X (2004) Assessing the carbon sequestration potential of mesic savannas in the Northern Territory, Australia: approaches, uncertainties and impacts of fire. Functional Plant Biology 31:415–422CrossRefGoogle Scholar
  164. Woghiren AJ (2002) Nitrogen characterization of the savanna flux site at Skukuza, Kruger National Park. M.Sc. Thesis. University of the Witwatersrand, JohannesburgGoogle Scholar
  165. Yeaton RI (1988) Porcupines, fires and the dynamics of the tree layer of the Burkea africana savanna. Journal of Ecology 76:1017–1029CrossRefGoogle Scholar
  166. Young KD, Ferreira SM, Van Aarde RJ (2009) The influence of increasing population size and vegetation productivity on elephant distribution in the Kruger National Park. Austral Ecology 34:329–342Google Scholar
  167. Zak DR, Grigal DF (1991) Nitrogen minelization, nitrification and denitrification in upland and wetland ecosystems. Oecologia 88:186–196CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  • Corli Coetsee
    • 1
  • Shayne Jacobs
    • 2
  • Navashni Govender
    • 3
  1. 1.School of Natural Resource ManagementNelson Mandela Metropolitan UniversityGeorgeSouth Africa
  2. 2.Department of Conservation Ecology and EntomologyStellenbosch UniversityStellenboschSouth Africa
  3. 3.Sanparks Scientific ServicesKruger National ParkSkukuzaSouth Africa

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