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Grass competition is more important than seed ingestion by livestock for Acacia recruitment in South Africa

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Abstract

Although grazing livestock may have direct negative effects on woody species through herbivory and trampling, (heavy-)grazing is often associated with woody plant encroachment. Two main mechanisms can explain the positive effects of grazers on woody cover: (1) Grazers reduce the interspecific competition with trees and may reduce fuel load, and (2) gut passage through livestock increases seedling establishment by scarification (increased germination) and fertilization by dung (higher survival and growth of seedlings). We tested the effects of fire, grass, cattle ingestion (transit) and dung on germination, seedling height and survival as well as on recruitment of Acacia sieberiana in a sub-humid grassland of South Africa. About 8,000 seeds were planted in the field in a randomized block design. The removal of grass by grazing and/or fire had the most important effect on Acacia recruitment in savanna. Our findings highlight the hierarchy of the main factors affecting Acacia recruitment, which provides new insights to the understanding of woody plant encroachment.

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References

  • Archer S, Schimel DS, Holland EA (1995) Mechanisms of shrubland expansion: landuse, climate or CO2. Clim Change 29:91–95

    Article  Google Scholar 

  • Bodmer R, Ward D (2006) Frugivory in large mammalian herbivores. In: Danell K, Bergstrom R, Duncan P, Pastor J (eds) Large herbivore ecology, ecosystem dynamics and conservation. Cambridge University Press, Cambridge

    Google Scholar 

  • Bond WJ (2008) What limits trees in C4 grasslands and savannas? Annu Rev Ecol Evol Syst 39:641–659

    Article  Google Scholar 

  • Brown NAC, de Booysen PV (1967) Seed germination and seedling growth of two Acacia species under field conditions in grassveld. S Afr J Agric Sci 10:659–666

    Google Scholar 

  • Brown J, Scholtz CH, Janeau J-L, Grellier S, Podwojewski P (2010) Dung beetles (Coleoptera: Scarabaeidae) can improve soil hydrological properties. Appl Soil Ecol 46:9–16

    Article  Google Scholar 

  • Burkinshaw AM, Bork EW (2009) Shrub encroachment impacts the potential for multiple use conflicts on public land. Environ Manage 44:493–504

    Article  PubMed  Google Scholar 

  • Bush JK, Van Auken OW (1995) Woody plant growth related to planting time and clipping of a C4 grass. Ecology 76:1603–1609

    Article  Google Scholar 

  • Campbell ML, Clarke PJ (2006) Seed dynamics of resprouting shrubs in grassy woodlands: seed rain, predators and seed loss constrain recruitment potential. Aust Ecol 31:1016–1026

    Article  Google Scholar 

  • Casenave A, Valentin C (1992) A runoff capability classification system based on surface features criteria in the arid and semi-arid areas of West Africa. J Hydrol 130:213–249

    Article  Google Scholar 

  • Coe M, Coe C (1987) Large herbivores, acacia trees and bruchid beetles. S Afr J Sci 83:624–635

    Google Scholar 

  • Coffin DP, Lauenroth WK (1990) A gap dynamics simulation model of succession in a semi-arid grassland. Ecol Model 49:229–266

    Article  Google Scholar 

  • Cramer MD, Chimphango SBM, Cauter AV, Waldram MS, Bond WJ (2007) Grass competition induces N2 fixation in some species of African Acacia. J Ecol 95:1123–1133

    Article  CAS  Google Scholar 

  • Edwards PB, Aschenborn HH (1987) Patterns of nesting and dung burial in Onitis dung beetles: implications for pasture productivity and fly control. J Appl Ecol 24:837–852

    Article  Google Scholar 

  • Gignoux J, Lahoreau G, Julliard R, Barot S (2009) Establishment and early persistence of tree seedlings in an annually burned savanna. J Ecol 97:484–495

    Article  Google Scholar 

  • Goheen JR, Keesing F, Allan BF, Ogada D, Ostfeld RS (2004) Net effects of large mammals on Acacia seedling survival in an African savanna. Ecology 85:1555–1561

    Article  Google Scholar 

  • Goheen JR, Palmer TM, Keesing F, Riginos C, Young TP (2010) Large herbivores facilitate savanna tree establishment via diverse and indirect pathways. J Anim Ecol 79:372–382

    Article  PubMed  Google Scholar 

  • Grellier S (2011) Hillslope encroachment by Acacia sieberiana in a deep-gullied grassland of KwaZulu-Natal (South Africa). PhD thesis, University of Pierre and Marie Curie, Paris

  • Guillard P (1967) Coprophagous beetles in pasture ecosystems. J Aust Inst Sci 33:30–34

    Google Scholar 

  • Guy RM, Smith JMB (1995) A land potential classification for KwaZulu-Natal. KwaZulu-Natal Department of Agriculture, Cedara

    Google Scholar 

  • Halevy G (1974) Effects of gazelles and seed beetles (Bruchidae) on germination and establishment of Acacia species. Isr J Bot 23:120–126

    Google Scholar 

  • Hilty JH, Eldridge DJ, Rosentreter R, Wicklow-Howard MC (2003) Burning and seeding influence soil surface morphology in an Artemisia shrubland in southern Idaho. Arid Land Res Manage 17:1–11

    Article  Google Scholar 

  • Jeltsch F, Milton SJ, Dean WRJ, Van Rooyen N (1996) Tree spacing and coexistence in semiarid savannas. J Ecol 84:583–595

    Article  Google Scholar 

  • Kambatuku JR, Cramer MD, Ward D (2011) Intraspecific competition between shrubs in a semi-arid savanna. Plant Ecol 212:701–713

    Article  Google Scholar 

  • Kanz WA (2001) Seed and seedling dynamics of certain Acacia species as affected by herbivory, grass competition, fire and grazing system. MSc thesis, University of KwaZulu-Natal, Pietermaritzburg

  • Kraaij T, Ward D (2006) Effects of rain, nitrogen, fire and grazing on tree recruitment and early survival in bush-encroached savanna, South Africa. Plant Ecol 186:235–246

    Article  Google Scholar 

  • Maclean JE, Goheen JR, Doak DF, Palmer TM, Young TP (2011) Cryptic herbivores mediate the strength and form of ungulate impacts on a long-lived savanna tree. Ecology 92:1626–1636

    Article  PubMed  Google Scholar 

  • Mbatha KR, Ward D (2010) The effects of grazing, fire, nitrogen and water availability on nutritional quality of grass in semi-arid savanna, South Africa. J Arid Environ 74:1294–1301

    Article  Google Scholar 

  • Miller MF, Coe M (1993) Is it advantageous for Acacia seeds to be eaten by ungulates? Oikos 66:364–368

    Article  Google Scholar 

  • Miriti M (2006) Ontogenetic shift from facilitation to competition in a desert shrub. J Ecol 94:973–979

    Article  Google Scholar 

  • Mucina L, Rutherford MC (2006) The vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19. South African National Biodiversity Institute, Pretoria

    Google Scholar 

  • Neave M, Rayburg S (2007) A field investigation into the effects of progressive rainfall-induced soil seal and crust development on runoff and erosion rates: the impact of surface cover. Geomorphology 87:378–390

    Article  Google Scholar 

  • O’Connor TG (1995) Acacia karroo invasion of grassland: environmental and biotic effects influencing seedling emergence and establishment. Oecologia 103:214–223

    Article  Google Scholar 

  • Oluwole FA, Sambo JM, Sikhalazo D (2008) Long-term effects of different burning frequencies on the dry savannah grassland in South Africa. Afr J Agric Res 3:147–153

    Google Scholar 

  • Or K, Ward D (2003) Three-way interactions between acacias, large mammalian herbivores and bruchid beetles—a review. Afr J Ecol 41:257–265

    Article  Google Scholar 

  • Or K, Ward D (2007) Maternal effects on the life histories of bruchid beetles infesting Acacia raddiana in the Negev desert, Israel. Entomol Exp Appl 122:165–170

    Article  Google Scholar 

  • Podwojewski P, Janeau JL, Chaplot V, Grellier S, Lorentz S (2011) Influence of vegetal soil cover on water runoff and soil detachment in a sub-humid South African degraded rangeland. Earth Surf Proc Land 36:911–922

    Article  Google Scholar 

  • Prior LD, Murphy BP, Russell-Smith J (2009) Environmental and demographic correlates of tree recruitment and mortality in north Australian savannas. For Ecol Manage 257:66–74

    Article  Google Scholar 

  • Riginos C (2009) Grass competition suppresses savanna tree growth across multiple demographic stages. Ecology 90:335–340

    Article  PubMed  Google Scholar 

  • Rohner C, Ward D (1999) Large mammalian herbivores and the conservation of arid Acacia stands in the Middle East. Conserv Biol 13:1162–1171

    Article  Google Scholar 

  • Roques KG, O’Connor TG, Watkinson AR (2001) Dynamics of shrub encroachment in an African savanna: relative influences of fire, herbivory, rainfall and density dependence. J Appl Ecol 38:268–280

    Article  Google Scholar 

  • Sankaran M, Ratnam J, Hanan NP (2004) Tree–grass coexistence in savannas revisited—insights from an examination of assumptions and mechanisms invoked in existing models. Ecol Lett 7:480–490

    Article  Google Scholar 

  • Sankaran M, Hanan NP, Scholes RJ, Ratnam J, Augustine DJ, Cade BS, Gignoux J, Higging SI, Roux XL, 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 438:846–849

    Article  PubMed  CAS  Google Scholar 

  • Sankaran M, Ratnam J, Hanan NP (2008) Woody cover in African savannas: the role of resources, fire and herbivory. Glob Ecol Biogeogr 17:236–245

    Article  Google Scholar 

  • Schulze RE (1997) South African atlas of agrohydrology and climatology. Water Research Commission, Pretoria

    Google Scholar 

  • Trollope WSW (1980) Controlling bush encroachment with fire in the savanna areas of South Africa. Proc Grassl Soc S Afr 15:173–177

    Google Scholar 

  • Valentin C, Bresson LM (1992) Morphology, genesis and classification of soil crusts in loamy and sandy soils. Geoderma 55:225–245

    Article  Google Scholar 

  • Van Auken OW (2009) Causes and consequences of woody plant encroachment into western North American grasslands. J Environ Manage 90:2931–2942

    Article  PubMed  Google Scholar 

  • Ward D (2005) Do we understand the causes of bush encroachment in African savannas? Afr J Range Forage Sci 22:101–105

    Article  Google Scholar 

  • Ward D, Esler KJ (2010) What are the effects of substrate and grass removal on recruitment of Acacia mellifera seedlings in a semi-arid environment? Plant Ecol 212:245–250

    Article  Google Scholar 

  • Wiegand K, Saltz D, Ward D (2006) A patch-dynamics approach to savanna dynamics and woody plant encroachment—insights from an arid savanna. Perspect Plant Ecol Evol Syst 7:229–242

    Article  Google Scholar 

  • Wigley BJ, Bond WJ, Hoffman MT (2009) Bush encroachment under three contrasting land-use practices in a mesic South African savanna. Afr J Ecol 47:62–70

    Article  Google Scholar 

  • Wilson JB (1988) Shoot competition and root competition. J Appl Ecol 25:279–296

    Article  Google Scholar 

  • World Reference Base (1998) World reference base for soil resources. In: World Soil Resources Reports, FAO, Rome

Download references

Acknowledgments

We would like to thank Joe Culverwell for the use of his land. Our acknowledgments go to Moses Gichua, Andile Shange, Desale Okubamichael, Kyle Tomlinson, Gary Stafford, Lucas Janeau, Neeta Soni, and all assistants for their help in the field and in the shade house. We further acknowledge the University of KwaZulu-Natal for the facilities provided in the Ukulinga experimental farm. This study was funded by the Institute of Research and Development and by the Water Research Commission. DW acknowledges the financial support from the National Research Foundation of South Africa.

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Authors and Affiliations

  1. IRD BioEMco c/o School of Bioresources Engineering and Environmental Hydrology, University of KwaZulu-Natal, Scottsville, South Africa

    Séraphine Grellier & Jean-Louis Janeau

  2. IRD BioEMco, Ecole Normale Supérieure, Paris, France

    Sébastien Barot

  3. School of Biological & Conservation Sciences, University of KwaZulu-Natal, Scottsville, South Africa

    David Ward

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  1. Séraphine Grellier
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  2. Sébastien Barot
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  3. Jean-Louis Janeau
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  4. David Ward
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Correspondence to Séraphine Grellier.

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Grellier, S., Barot, S., Janeau, JL. et al. Grass competition is more important than seed ingestion by livestock for Acacia recruitment in South Africa. Plant Ecol 213, 899–908 (2012). https://doi.org/10.1007/s11258-012-0051-3

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  • DOI: https://doi.org/10.1007/s11258-012-0051-3

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