Research projects
H A Snyman
1. Dynamics of the encroacher shrub Serihium plumosum
Seriphium plumosum encroachment in wide-ranging parts across South Africa has converted extensive areas of productive grassland into lower-potential shrubland-grassland. Dense stands of this shrub can suppress grass production by up to 75%. In the study we investigate the distribution, spread, habitat preferences and seed germination of this unpalatable plant. This information can be used in controlling measures of this shrub. Millions of Rands are yearly spent in its control, which is not always successful. Different control measurements are also evaluated.
2. Seed bank studies in semi-arid grassland
The soil seed bank plays an important role in the composition of different plant communities and thus their conservation. In arid and semi-arid grasslands, seed rain events are primarily driven by episodic events and secondarily by continuous trigger events such as rainfall and fire. The effects of grassland degradation on the size and species composition of the soil seed bank and seedling establishment in the field are quantified in a semi-arid climate.
3. Root and water-use efficiency studies on Cactus pear
There is a lack of knowledge on water utilization of cactus pear at community level under field conditions for a full growing season. Therefore the water-use efficiency (cladode dry-mass production per unit of evapotranspiration) is quantified for one to four-year-old Opuntia ficus-indica (cultivar Morado) and O. robusta (cultivar Monterey) plants, in a semi-arid climate.
4. Aboveground and root studies on a semi-arid grassland
For sound grassland management and the debate on global climate change it is essential to develop a better understanding of patterns of plant growth, production and how they relate to the driving influences of water and ecosystem degradation. Therefore the seasonal trend in root distribution and root/shoot ratio are quantified with depth and degradation along a soil-water gradient. The production potential under different veld conditions is also evaluated in terms of water-use efficiency.
5. Response of semi-arid grassland to fire
In arid and semi-arid grasslands of southern Africa, herbage production is determined by unexpected or unplanned fires, which could result in risk management practices in both agricultural and conservation areas. The short-term impact of fire on the dynamics of the grassland ecosystem in a semi-arid climate is investigated in terms of productivity, water-use efficiency, soil loss, soil seed bank, soil compaction and soil temperature.