Biological Invasions

, Volume 18, Issue 2, pp 445–456 | Cite as

The impact of black wattle encroachment of indigenous grasslands on soil carbon, Eastern Cape, South Africa

  • Myles OelofseEmail author
  • Torben Birch-Thomsen
  • Jakob Magid
  • Andreas de Neergaard
  • Ross van Deventer
  • Sander Bruun
  • Trevor Hill
Original Paper


Black wattle (Acacia mearnsii, De Wild.) is a fast growing tree species introduced into South Africa in the nineteenth century for commercial purposes. While being an important source of timber and firewood for local communities, black wattle is an aggressive invasive species and has pervasive adverse environmental impacts in South Africa. Little is known about the effects of black wattle encroachment on soil carbon, therefore the aim of this study was to investigate the impact of black wattle encroachment of natural grassland on soil carbon stocks and dynamics. Focussing on two sites in the Eastern Cape, South Africa, the study analysed carbon stocks in soil and litter on a chronosequence of black wattle stands of varying ages (up to >50 years) and compared these with adjacent native grassland. The study found that woody encroachment of grassland at one site had an insignificant effect on soil and litter carbon stocks. The second site showed a clear decline in combined soil and litter carbon stocks following wattle encroachment. The lowest stock was in the oldest wattle stand, meaning that carbon stocks are still declining after 50 years of encroachment. The results from the two sites demonstrate the importance of considering changes in soil carbon when evaluating ecosystem effects of invasive species.


Acacia mearnsii Carbon sequestration Invasive alien plants Soil organic matter Biomass 


  1. Archer S, Boutton TW, Hibbard KA (2001) Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulz D, Harrison S, Holland J et al (eds) Global biogeochemical cycles in the climate system. Academic Press, San Diego, pp 115–138CrossRefGoogle Scholar
  2. Bernoux M, Cerri CC, Neill C et al (1998) The use of stable carbon isotopes for estimating soil organic matter turnover rates. Geoderma 82(1–3):43–58CrossRefGoogle Scholar
  3. Birch-Thomsen T, Elberling B, Fog B, Magid J (2007) Temporal and spatial trends in soil organic carbon stocks following maize cultivation in semi-arid Tanzania, East Africa. Nutr Cycl Agroecosyst 79:291–302CrossRefGoogle Scholar
  4. Boutton TW, Liao JD, Filley TR et al (2009) Belowground carbon storage and dynamics accompanying woody plant encroachment in a subtropical Savanna. In: Lal R, Follett RF (eds) Soil carbon sequestration and the greenhouse effect, 2nd edn. SSSA special publications no. 57, Soil Science Society of America, Madison, pp 181–205Google Scholar
  5. Bruun S, Clauson-Kaas S, Bobulska L et al (2014) Carbon dioxide emissions from biochar in soil: role of clay, microorganisms and carbonates. Eur J Soil Sci 65(1):52–59CrossRefGoogle Scholar
  6. Caldeira MVW, Schumacher MV, Barichello LR et al (2003) Determinacao de carbono organico em povoamentos de Acacia mearnsii De Wild. Plantados no Rio Grande do Sul. Rev Acad Cienc Agrar Ambient 1(2):47–54Google Scholar
  7. Davis MR, Condron LM (2002) Impact of grassland afforestation on soil carbon in New Zealand: a review of paired-site studies. Soil Res 40(4):675–690CrossRefGoogle Scholar
  8. De Deyn GB, Cornelissen JHC, Bardgett RD (2008) Plant functional traits and soil carbon sequestration in contrasting biomes. Ecol Lett 11(5):516–531CrossRefPubMedGoogle Scholar
  9. de Neergaard A, Saarnak C, Hill T et al (2005) Australian wattle species in the Drakensberg region of South Africa: an invasive alien or a natural resource? Agric Syst 85(3):216–233CrossRefGoogle Scholar
  10. De Wit MP, Crookes DJ, Van Wilgen BW (2001) Conflicts of interest in environmental management: estimating the costs and benefits of a tree invasion. Biol Invasions 3(2):167–178CrossRefGoogle Scholar
  11. Don A, Schumacher J, Freibauer A (2011) Impact of tropical land-use change on soil organic carbon stocks—a meta-analysis. Glob Chang Biol 17(4):1658–1670CrossRefGoogle Scholar
  12. Egoh BN, Reyers B, Rouget M et al (2011) Identifying priority areas for ecosystem service management in South African grasslands. J Environ Manag 92(6):1642–1650CrossRefGoogle Scholar
  13. Ellert BH, Janzen HH, McConkey BG (2001) Measuring and comparing soil carbon storage. In: Lal R, Kimble JM, Follett RF et al (eds) Assessment methods for soil carbon. CRC Press, Boca Raton, pp 131–146Google Scholar
  14. Forrester DI, Bauhus JA, Khanna PK (2004) Growth dynamics in a mixed-species plantation of Eucalyptus globulus and Acacia mearnsii. For Ecol Manag 193(1):81–95CrossRefGoogle Scholar
  15. Fuller LG, Anderson DW (1993) Changes in soil properties following forest invasion of black soils of the Aspen Parkland. Can J Soil Sci 73(4):613–627CrossRefGoogle Scholar
  16. Hughes RF, Archer SR, Asner GP et al (2006) Changes in aboveground primary production and carbon and nitrogen pools accompanying woody plant encroachment in a temperate Savanna. Glob Chang Biol 12(9):1733–1747CrossRefGoogle Scholar
  17. IBM Corp. (2001) IBM SPSS statistics for windows, version 20.0. IBM Corp., ArmonkGoogle Scholar
  18. Jackson RB, Banner JL, Jobbagy EG et al (2002) Ecosystem carbon loss with woody plant invasion of grasslands. Nature 418(6898):623–626CrossRefPubMedGoogle Scholar
  19. Le Maitre DC, Versfeld DB, Chapman RA (2000) The impact of invading alien plants on surface water resources in South Africa: a preliminary assessment. Water SA 26:397–408Google Scholar
  20. Le Maitre DC, Gaertner M, Marchante E et al (2011) Impacts of invasive Australian acacias: implications for management and restoration. Divers Distrib 17(5):1015–1029CrossRefGoogle Scholar
  21. Lehmann J, Abiven S, Kleber M et al (2015) Persistence of biochar in soil. Earthscan, London, pp 233–280Google Scholar
  22. Li D, Niu S, Luo Y (2012) Global patterns of the dynamics of soil carbon and nitrogen stocks following afforestation: a meta-analysis. New Phytol 195(1):172–181CrossRefPubMedGoogle Scholar
  23. Liao JD, Boutton TW, Jastrow JD (2006) Storage and dynamics of carbon and nitrogen in soil physical fractions following woody plant invasion of grassland. Soil Biol Biochem 38(11):3184–3196CrossRefGoogle Scholar
  24. Mills AJ, O’Connor TG, Donaldson JS et al (2005) Ecosystem carbon storage under different land uses in three semi-arid shrublands and a mesic grassland in South Africa. S Afr J Plant Soil 22(3):183–190CrossRefGoogle Scholar
  25. Morris TL, Esler KJ, Barger NN et al (2011) Ecophysiological traits associated with the competitive ability of invasive Australian acacias. Divers Distrib 17(5):898–910CrossRefGoogle Scholar
  26. Mucina L, Rutherford MC (2006) The vegetation of South Africa, Lesotho and Swaziland. South African National Biodiversity Institute, PretoriaGoogle Scholar
  27. Paul KI, Polglase PJ, Nyakuengama JG et al (2002) Change in soil carbon following afforestation. For Ecol Manag 168(1):241–257CrossRefGoogle Scholar
  28. Pinno BD, Wilson SD (2011) Ecosystem carbon changes with woody encroachment of grassland in the northern Great Plains. Ecoscience 18(2):157–163CrossRefGoogle Scholar
  29. Rangan H, Kull C, Alexander L (2010) Forest plantations, water availability, and regional climate change: controversies surrounding Acacia mearnsii plantations in the upper Palnis Hills, southern India. Reg Environ Chang 10(2):103–117CrossRefGoogle Scholar
  30. Richardson DM, van Wilgen BW (2004) Invasive alien plants in South Africa: how well do we understand the ecological impacts? Working for water. S Afr J Sci 100(1 and 2):45Google Scholar
  31. Scholes RJ, Archer SR (1997) Tree grass interactions in savannahs. Annu Rev Ecol Syst 28(1):517–544CrossRefGoogle Scholar
  32. Shackleton CM, McGarry D, Fourie S et al (2007) Assessing the effects of invasive alien species on rural livelihoods: case examples and a framework from South Africa. Hum Ecol 35(1):113–127CrossRefGoogle Scholar
  33. Smith P, Martino D, Cai Z et al (2008) Greenhouse gas mitigation in agriculture. Philos Trans R Soc B Biol Sci 363(1492):789–813CrossRefGoogle Scholar
  34. Unruh JD (2008) Carbon sequestration in Africa: the land tenure problem. Glob Environ Chang 18(4):700–707CrossRefGoogle Scholar
  35. van Wilgen BW, Dyer C, Hoffmann JH et al (2011) National-scale strategic approaches for managing introduced plants: insights from Australian acacias in South Africa. Divers Distrib 17(5):1060–1075CrossRefGoogle Scholar
  36. Zavaleta ES, Kettley LS (2006) Ecosystem change along a woody invasion chronosequence in a California grassland. J Arid Environ 66(2):290–306CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Myles Oelofse
    • 1
    Email author
  • Torben Birch-Thomsen
    • 2
  • Jakob Magid
    • 1
  • Andreas de Neergaard
    • 1
  • Ross van Deventer
    • 3
  • Sander Bruun
    • 1
  • Trevor Hill
    • 3
  1. 1.Department of Plant and Environmental Sciences, Faculty of ScienceUniversity of CopenhagenFrederiksbergDenmark
  2. 2.Department of Geosciences and Natural Resource ManagementUniversity of CopenhagenCopenhagenDenmark
  3. 3.Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, Pietermaritzburg CampusUniversity of KwaZulu-NatalPietermaritzburgSouth Africa

Personalised recommendations