Back
 AS  Vol.12 No.10 , October 2021
Influence of Tree Density on Vegetation Composition and Soil Chemical Properties in Savanna Rangeland of Eastern Cape, South Africa
Abstract: The proliferation of woody species alters the vegetation structure, leading to loss of rangeland productivity. It aimed to assess the influence of tree density on vegetation and soil chemical properties at three levels of encroachment; open, moderate and dense. Each level of encroachment was replicated 3 times, a 5000 m2 plot was marked per replicate. Four belt transects 200 m2 were placed per plot. Woody species within each belt transect per replicate were identified and recorded to evaluate woody species composition. Grass species composition was assessed using a step point method. Soil was sampled per replicate and analysed for chemical properties. Results showed that 71% of grasses were increasers and 29% decreasers. Digitaria eriantha and Eragrostis obtusa were the most dominant species. Vachellia karoo and Aloe ferox were the most dominant woody species. The dense had high nitrogen (1.48%) compared to the moderate (0.23%) and the open (0.17%). Increaser species, soil carbon, soil pH increased with the increase of tree density. It was concluded that the replacement of highly palatable grasses with inferior ones was due to improper rangeland management practices. It was recommended that land users form rangeland management associations and set up conservation agreements for proper management of resources.
Cite this paper: Tokozwayo, S. , Mopipi, K. and Timpong-Jones, E. (2021) Influence of Tree Density on Vegetation Composition and Soil Chemical Properties in Savanna Rangeland of Eastern Cape, South Africa. Agricultural Sciences, 12, 991-1002. doi: 10.4236/as.2021.1210064.
References

[1]   Mokgosi, R.O., Kellner, K. and Malan, P. (2018) Effects of Tree Encroachment Control in a Communal Area in the Taung Region, North West Province, South Africa.

[2]   Mucina, L. and Rutherford, M.C. (2006) The Vegetation of South Africa, Lesotho and Swaziland. South African National Biodiversity Institute, Pretoria, 348-437.

[3]   De Groot, R., Brander, L., Van Der Ploeg, S., Bernard, F., Braat, L., Christie, M., Costanza, R., Ghermand, I.A., Hein, L., Kumar, P., Mcvittie, A., Portela, R., Rodriguez, L. and Ten Brink, P. (2012) Global Estimates of the Value of Ecosystems and Their Services.
https://doi.org/10.1016/j.ecoser.2012.07.005

[4]   Ward, D., Wiegand, K. and Getzin, S. (2013) Walter’s Two-Layer Hypothesis Revisited: Back to the Roots. Oecologia, 172, 617-630.
https://doi.org/10.1007/s00442-012-2538-y

[5]   Scheiter, S. and Higgins, S.I. (2007) Partitioning of Root and Shoot Completion and the Stability of Savannas. Journal of American Naturalist, 170, 587-601.
https://doi.org/10.1086/521317

[6]   Kraaij, T. and Ward, D. (2006) Effects of Rain, Nitrogen, Fire and Grazing on Tree Recruitment and Early Survival in Tree Encroached Savanna. South Africa Plant Ecology, 186, 235-246.
https://doi.org/10.1007/s11258-006-9125-4

[7]   De Klerk, J.N. (2004) Tree Encroachment in Nambia. Report on Phase One of the Tree Encroachment Research, Monitoring Project, Ministry of Environment and Tourism, Windhoek.

[8]   Walker, B., Holling, C.S., Carpenter, S.R. and Kinzing, A. (2004) Resilience, Adaptability and Transformability in Social Ecological Systems. Ecological Social Science, 9, 5-8.
https://doi.org/10.5751/ES-00650-090205

[9]   Moncrieff, G.R., Scheiter, S., Bond, W.J. and Higgins, S.I. (2014) Increasing Atmospheric CO2 Overrides the Historical Legacy of Multiple Stable Biome in Africa. New Phytologists, 201, 908-915.
https://doi.org/10.1111/nph.12551

[10]   Belayneh, A. and Tessema, Z.K. (2011) Mechanisms of Tree Encroachment and Its Interconnection with Rangeland Degradation in Semi-Arid Ecosystem: A Review. Journal of Arid Lands, 9, 299-312.
https://doi.org/10.1007/s40333-016-0023-x

[11]   Vetter, S., Goqwana, W.M., Bond, W.J. and Trollope, W.S.W. (2006) Effects of Land Tenure, Geology and Topography on Vegetation and Soils of Two Grassland Types in South Africa. Journal of Forage and Science, 23, 13-27.
https://doi.org/10.2989/10220110609485883

[12]   Trollope, W.S.W. (1989) Veld Burning as a Veld Management Practices in Livestock Production. In: Danckwerts, J.E. and Teague, W.R., Eds., Veld Management in the Eastern Cape, Government Printer, Pretoria, 67-73.

[13]   Tefera, S., Snyaman, H.A. and Smit, G.N. (2007) Rangeland Dynamics of Southern Ethiopia: (2). Assessments of Woody Vegetation Structure in Relation to Land Use and Distance from Water in Semi-Arid Borana Rangelands. Journal of Environmental Management, 85, 443-452.
https://doi.org/10.1016/j.jenvman.2006.10.008

[14]   ALASA (1998) Handbook of Feeds and Plants Analysis.

[15]   Bremner, J.M. and Breitenbeck, G.A. (1983) A Simple Method of Determination of Ammonium in Semi Micro Kjedahl Analysis of Soil and Plant Material Using a Block Digester. Communication in Soil Science and Plant Analysis, 14, 905-913.
https://doi.org/10.1080/00103628309367418

[16]   Nelson, D.D. and Somers, L.E. (1982) Total Carbon, Organic Carbon and Organic Matter. Methods of Soil Analysis, Part 2. Chemical and Microbiological Properties, 2nd Edition, Madison, 595-579.

[17]   SAS (2009) Institute. Inc. SAS Software. Frame Entry Usage and Reference. Version 8. Cary.

[18]   Ward, D. (2005) Do We Understand the Causes of Tree Encroachment in African Savannas? African Journal of Rangeland and Forage Science, 22, 101-105.
https://doi.org/10.2989/10220110509485867

[19]   Tokozwayo, S. (2016) Evaluating Farmers’ Perceptions and the Impact of Tree Encroachment on Herbaceous Vegetation and Soil Nutrients in Sheshegu Communal Rangelands of the Eastern Cape, South Africa. MSc. Thesis, University of Fort Hare, Alice.

[20]   Kinyamario, J.I., Trlica, M.J. and Njoka, J.T. (1995) Influence of Tree Shade on Water Status, Gas Exchange and Water Use Efficiency of Panicum Maximum and Themeda Triandra in Kenya Savanna. African Journal of Ecology, 33, 114-123.
https://doi.org/10.1111/j.1365-2028.1995.tb00787.x

[21]   Savadogo, P., Sawudogo, L. and Tiveau, D. (2006) Effects of Grazing Intensity and Prescribed Fire on Soil Physical and Hydrological Properties and Pasture Yield in the Savanna Woodlands of Burkina Faso. Agriculture, Ecosystems and Environment, 11, 80-92.
https://doi.org/10.1016/j.agee.2006.05.002

[22]   Tessema, Z.K., De Beor, W.F., Baars, R.M.T. and Prins, H.H.T. (2011) Changes in Soil Nutrients, Vegetation Structure and Herbaceous Biomass in Response to Grazing in a Semi-Arid Savanna of Ethopia. Journal of Arid Environments, 75, 662-670.
https://doi.org/10.1016/j.jaridenv.2011.02.004

[23]   Dangerfield, J.M. and Modukanele, B. (1996) Overcompensation by Acacia Erubescens in Response to Stimulated Browsing. Journal of Tropical Ecology, 12, 905-908.
https://doi.org/10.1017/S0266467400010178

[24]   Smit, G.N. (2004) An Approach to Tree Thinning to Structure Southern African Savannas for Long-Term Restoration from Bush Encroachment. Journal of Environmental Management, 71, 179-191.
https://doi.org/10.1016/j.jenvman.2004.02.005

[25]   Ward, D. and Esler, K.J. (2011) What Are the Effects of Substrate and Grass Removal on Recruitment of Acacia Mellifera Seedlings in a Semi-Arid Environment? African Journal of Plant Ecology, 212, 255-250.
https://doi.org/10.1007/s11258-010-9818-6

[26]   Jourbert, D.F., Rothauge, A. and Smit, G.N. (2008) A Conceptual Model of Vegetation Dynamics in the Semi-Arid Savannah of Namibia, with Particular Reference to Tree Thickening by Acacia Mellifera. Journal of Arid Environments, 72, 2201-2210.
https://doi.org/10.1016/j.jaridenv.2008.07.004

[27]   Wiegand, K., Ward, D. and Saltz, D. (2005) Multi-Scale Patterns and Tree Encroachment in an Arid Savanna with a Shallow Soil Layer. Journal of Vegetation Science, 16, 311-320.
https://doi.org/10.1111/j.1654-1103.2005.tb02369.x

[28]   Mojiri, A., Aziz, H.A. and Ramaji, A. (2012) Potential Decline in Soil Quality Attributes as a Result of Land Use Change in a Hill Slope in Lordgan, Western Iran. Africa Journal of Agricultural Research, 7, 577-582.
https://doi.org/10.5897/AJAR11.1505

[29]   Retallack, G.J. (2001) Cenozoic Expansion of Grasslands and Climatic Cooling. Journal of Geology, 109, 407-426.
https://doi.org/10.1086/320791

[30]   Rutherford, M.C. and Powrie, L.W. (2010) Severely Degraded Rangeland: Implications for Plant Diversity from a Case Study in Succulent Karroo, South Africa. Journal of Arid Environments, 74, 692-701.
https://doi.org/10.1016/j.jaridenv.2009.10.013

[31]   Vitousek, P.M., Cassman, K., Claveland, C., Crews, T., Field, C.B. and Grimm, N.B. (2002) Towards an Ecological Understanding of Biological Nitrogen Fixation. Biogeomechemistry, 57, 1-45.
https://doi.org/10.1007/978-94-017-3405-9_1

[32]   Foth, D.H. (1990) Fundamentals of Soil Science. 8th Edition, John Wiley and Sons Incorporated, Hoboken.

[33]   Zhang, Y., Xu, Z., Jiang, D. and Jiang, Y. (2013) Soil Exchangeable Base Cations along a Chronosequence. Caragana Microphylla Plantation in a Semi-Arid Sandy Land, China. Journal of Arid Lands, 5, 42-50.
https://doi.org/10.1007/s40333-013-0140-8

[34]   Okpamen, S.U., Ilori, E.G., Agho, I., Nkechika, A., Maidoh, F.U. and Okonjo, P.N. (2013) Influence of Depths and Soil PH on Forms of Magnesium in Soils of Four Parent Material (Rhodic Paleudults, Rhodic Tropudalts, Oxic Tropudalts, and Aquatic tropossament). Journal of Soil Science, 4, 71-76.
https://doi.org/10.5897/JSSEM12.082

[35]   Abdallah, F., Noumi, Z., Touzard, B., Belgacem, A.O., Neffati, M. and Chelab, M. (2008). The Influence of Acacia tortilis (Forssk) subsp. Raddiana (savi) and Livestock Grazing on Grass Species Composition, Yield and Soil Nutrients in Arid Environments of South Tunisia. Floro, 203, 116-125.
https://doi.org/10.1016/j.flora.2007.02.002

[36]   Magandana, T.P. (2016) Effect of Acacia Karoo Encroachment on Grass Production in the Semi-Arid Savannas of the Eastern Cape, South Africa. M.Sc. Thesis, University of Fort Hare, Alice.

[37]   Abule, E., Smit, G.N. and Snyman, H.A. (2005) The Influence of Woody Plants and Livestock Grazing on Grass Species Composition, Yield and Soil Nutrients in the Middle Awash Valley of Ethiopia. Journal of Arid Environments, 60, 343-358.
https://doi.org/10.1016/j.jaridenv.2004.04.006

[38]   Hagos, M.G. and Smit, G.T. (2005) Soil Enrichment by Acacia mellifera subsp. Detinens on Nutrient Poor Sandy Soils in a Semi-Arid Southern African Savannah. Journal of Arid Environments, 61, 47-59.
https://doi.org/10.1016/j.jaridenv.2004.08.003

 
 
Top