The immediate effects of the 1964/66 drought on the vegetation of specific study areas in the Vryburg district

Abstract

During 1964/66 the Molopo and adjacent semi‐arid ranching areas experienced the most severe drought in living memory. The effects of the drought on the more important grass species in particular, were investigated on three farms in the Vryburg district (namely Buttermere, Seruruble and Fontein). A highly significant decrease in the three dominant grass species (Stipagrostis uniplumis, Schmidtia bulbosa and Eragrostis lehmanniana) was recorded in camps with a moderate stand of woody plant species at the Buttermere and Seruruble sites. Overall mean losses of 82 per cent and 80 per cent of. the three major grass species were recorded at these respective sites. No significant differences in the mortality of these grass species were dectected on plots from which all woody plant species had been eradicated immediately before the drought. The mean hay yields recorded (1965/66 season) from bushed and debushed camps at the Buttermere site were 96 lb and 998 lb respectively. The botanical analysis data of four “dolomite” grassveld camps of the Fontein site revealed significant decreases in the total percentage basal cover and the basal cover of the major grass plant species.

UITTREKSEL

Gedurende 1964/66 het die Molopo en aangrensende semi‐droë gebiede die strsfste droogte in menseheuge‐nis belerf. Die uitwerking van, die droogte op veral die meer belangrike grasspesies is op drie plase in die Vryburg distrik (naamlik Buttermere, Seruruble en Fontein), ondersoek. ‘n Hoogs beduidende verminde‐ring van die dominante grassoorte (Stipagros uniplumis, Schmidtia bulbosa en Eragrostis lehmanniana) in kampe met ‘n matige stand hontagtige plantsoorte, is te Buttermere en Seruruble aungeteken. ‘n Totale gemiddelde verlies van 82% en 80% van genoemde drie soorte, is aangeteken. Op persele waar egter alle houtagtige plante onmiddelik voor die. droogte uitgeroei is, kon geen beduidende verskille in die vrektes van die grassoorte waargeneem word nie. Die gemiddelde hooiopbrengs van die beboste en onbeboste kampe te Buttermere (1965/66 seisoen) was 96 lb en 998 lb onderskeidelik. Die gegewens van ‘n botaniese analise van vier ,,dolomiet” grasveld kampe te fontein, het ‘n beduidende vermindering van die totale persentasie basale bedekking en ook die basale bedekking van die drie genoemde grasspesies aan die lig gebring.