Possible rehabilitation methods of Galenia africana-dominated old lands in the Cederberg Mountains, South Africa

Abstract

Several methods to rehabilitate old cropping lands in the Cederberg Mountains were tested to determine what type of soil disturbance, if any, and which of five indigenous perennial plant species are the most successful and economically feasible. Old lands are dominated by the unpalatable and poisonous, pioneer perennial Galenia africana. A complete randomised block design was followed with eight treatments and four replicates. All treatments, excluding the control, included re-seeding with five palatable species from the region. Soil disturbance was important with best results after three years in the ploughing-and-seeding and rolling-and-seeding treatments, which were also the most cost-effective treatments. Rainfall played a major role, with good germination in year one, but after a dry summer most of the new seedlings died. After three years the grasses Chaetobromus involucratus subsp. dregeanus and Ehrharta calycina, followed by the dwarf shrub Tripteris sinuata, established the best, but less than 1% of the seed sown established. The near-absence of perennial species in the soil seedbank and above ground necessitate the addition of seed. In conjunction with this, applying mechanical soil disturbance using an environmentally-friendly method, such as a knife roller, is advised to rehabilitate old croplands to a more productive state for herbivores.

Keywords: indigenous perennial species, improved forage, re-seeding, soil disturbance, species diversity