Can brush-cutting of Pteronia paniculata improve the composition and productivity of veld in the Succulent Karoo, South Africa?

  • N Saayman
  • CD Morris
  • MB Hardy
  • JC Botha

Abstract

Pteronia paniculata is an indigenous, unpalatable shrub that invades mismanaged Karooveld, resulting in degraded rangelands with low species diversity and grazing potential. We conducted a series of trials in the Succulent Karoo Randteveld near Barrydale to determine if the uniform defoliation of P. paniculata dominated vegetation at two heights (0.05 m and 0.20 m above ground level) using a brush-cutter and, in one trial, application of a second cut will improve the plant species composition, productivity and grazing capacity of the veld. Brush-cutting treatments and the uncut control all resulted in a change in species composition towards greater species diversity and more palatable species and an average increase of 540 kg ha–1 (28%) in above-ground biomass over four years. It appears that there was a pervasive improvement in species composition associated with a general decline in the cover and abundance of P. paniculata over the time-scale of the present study that was not influenced by the defoliation treatments, except for the 1996-cut treatment where the cover of P. paniculata increased. The absence of propagules of palatable species in the soil seed bank and competition from P. paniculata (a long-lived, perennial shrub) are assumed to be among the main reasons for the lack of response of the vegetation community to the defoliation treatments. Brush-cutting (in the absence of reseeding), aimed at reducing the dominance of unpalatable karoo shrubs, was more costly but not significantly better than long-term resting in improving veld composition or forage production.

Keywords: competition; defoliation; grazing capacity; palatability; rehabilitation

African Journal of Range & Forage Science 2009, 26(3): 181–190

Author Biographies

N Saayman
Institute for Plant Production, Department of Agriculture: Western Cape, Private Bag X1, Elsenburg 7607, South Africa
CD Morris
Agricultural Research Council, c/o University of KwaZulu-Natal, Private Bag X01, Scottsville 2309, South Africa
MB Hardy
Institute for Plant Production, Department of Agriculture: Western Cape, Private Bag X1, Elsenburg 7607, South Africa
JC Botha
Institute for Plant Production, Department of Agriculture: Western Cape, Private Bag X1, Elsenburg 7607, South Africa
Section
Articles

Journal Identifiers


eISSN: 1727-9380
print ISSN: 1022-0119