Morphology & management of Seriphium plumosum in Bankenveld grassland, South Africa Nkosi, S.E., Brown, L.R. and Barrett, A.S. Applied Behavioural Ecology & Ecosystems Research Unit, UNISA, Private Bag X6, Florida, 1710
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Introduction Seriphium plumosum is an aggressive encroacher dwarf-shrub threatening grasslands in South Africa. It is an indigenous pioneer plant that invades poorly managed grasslands and cultivated areas. In this study we investigate the morphology of S. plumosum at Telperion Nature Reserve (Fig 1), different ways of controlling it, and the costs involved. Findings suggest an integrated approach using 100% removal with follow up foliar herbicide application to remove new young plants. a)
Control measures All control measures instituted resulted in reductions to the number of S. plumosum plants over the shortterm (Fig 4). Figure 4. Error plots comparing initial and final counts for the control and various treatment options.
b) Telperion Nature Reserve.
For the control plot there was a slight decline in numbers of S. plumosum plants, for all control measures declines were noticeable (Table 1). Table 2. Results from Wilcoxon Signed-rank Tests comparing initial plant numbers to plant numbers six months post-treatment.
Figure 1. a) Location of the study site (red dot) in Mpumalanga, South Africa b) Images of S. plumosum.
Methods • Four exclosure plots (25x25m) were randomly placed in areas infested with S. plumosum. • Sixteen sub-plots (4x4m) were placed within each exclosure plot. • Control measures were randomly allocated to the sub-plots. Morphology Wet weight of above and below ground plant structures were examined for three height classes (HC1 0-35cm, HC2 35-70, HC3 >70cm) using Pearson Correlation Tests. Control measures Three control measures were applied to S. plumosum (Fig 2). Pre- and posttreatment differences were assessed using Wilcoxon signed-rank tests. a)
Financial implications The per hectare costs for the different control options using current per hour labour rates are depicted in Table 2. Table 2. Per hectare costs for removing S. plumosum using three control techniques (100% removal, 50% removal, and Foliar Spraying).
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Conclusion & Recommendations
Figure 2. a) 100% removal, b) 50% removal c) Foliar herbicide application. Financial implications Costs of instituting the control measures were calculated in ZAR as at June 2015.
Results Morphology • Height was responsible for 27.9% variation in above ground wet weight for plants in HC1 and 39.1% in HC2 (Fig 3a). • There were no significant relationships for wet root weight across the different height classes (Fig 3b).
Morphology Morphology investigations indicate a positive linear relationship between height and wet weight for plants in HC1 and HC2 (actively growing plants). Control measures To control S. plumosum, our preliminary findings indicate that both herbicide and 100% removal are effective. The 50% removal option is not viable since remaining plants will produce seeds and re-infest cleared areas. Our recommendation is to use an integrated approach: a once off 100% removal followed by annual herbicide treatments at the start of the growing season for new young plants. Annual treatments are to continue until the seed bank in the soil is depleted. Financial implications The combined costs of 100% removal and an annual follow up foliar application for any new young plants is estimated at ZAR7726.38 for the first year and then ZAR420.13 per annum thereafter.
References Snyman, H.A. 2009. Germination potential of Seriphium plumosum (bankrupt bush, slangbos or vaalbos). Grassroots: Newsletter of the Grassland Society of Southern Africa, Vol. 9(1) Wildi, O. 2013. Data Analysis in Vegetation Ecology. 2nd ed. Wiley-Blackwell, Sussex. Pp 301. Wildi, O. 2013. Data Analysis in Vegetation Ecology. 2nd ed. WileyBlackwell, Sussex. Pp 301.
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Figure 3. Box plots summarizing the relationship between a) height and above ground wet weight, b) height and wet root weight.
Zuur, A., E.N. Ieno, Walker, N, Saveliev, A.A. & Smith, G.M. 2009. Mixed Effects Models and Extensions in Ecology with R. Springer, New York. Pp 574.
