Articles by Author: Helga Van Der Merwe

Search results for Helga Van Der Merwe

We found 170 results for you
  1. Vegetation dynamics after experimental fire disturbance in the arid Succulent Karoo, South Africa

    Vegetation dynamics after experimental fire disturbance in the arid Succulent Karoo, South Africa

    Item type: Journal Article • Journal: African Journal of Range & Forage Science
    Disturbance by fire in the Succulent Karoo is rare but fire events could increase as a result of an increase in grassiness (alien and indigenous species). This study assessed the effects of fire eight years after an experimentally induced burn...
  2. Long-term vegetation change (&gt;20 years) in the plains habitat on the Goegap Nature Reserve, Succulent Karoo, South Africa<xref ref-type="fn" rid="FN0000"/>

    Long-term vegetation change (&gt;20 years) in the plains habitat on the Goegap Nature Reserve, Succulent Karoo, South Africa<xref ref-type="fn" rid="FN0000"/>

    Item type: Journal Article • Journal: African Journal of Range & Forage Science
    Because vegetation change in arid ecosystems is slow, long-term data are essential to gain an understanding of how the vegetation responds to short-term, inter-annual variation in rainfall; long-term cyclic rainfall patterns; and grazing pressure. The point intercept method was conducted...
  3. Reflections, applications and future directions of Long-Term Ecological Research at Tierberg<xref ref-type="fn" rid="FN0000"/>

    Reflections, applications and future directions of Long-Term Ecological Research at Tierberg<xref ref-type="fn" rid="FN0000"/>

    Item type: Journal Article • Journal: African Journal of Range & Forage Science
    Tierberg-LTER is a research site established in 1987 in the semi-arid Succulent Karoo near Prince Albert in the Western Cape province, South Africa. The original purpose for its establishment was to study ecosystem dynamics and the drivers of vegetation in...
  4. Growth in three Karoo shrub species under various grazing treatments: the tracking of marked individuals over 25 years

    Growth in three Karoo shrub species under various grazing treatments: the tracking of marked individuals over 25 years

    Item type: Journal Article • Journal: African Journal of Range & Forage Science
    Growth studies of long-lived shrubs are uncommon. In semi-arid rangelands, livestock and wildlife grazing influence growth processes and may interact with changing climate. Tierberg-LTER, excluded from livestock since 1987, and two adjacent ranches allowed for a comparative growth study of...
  5. Production Capacity of Softwood Sawmills in the Republic of South Africa, Swaziland and Transkei

    Item type: Journal Article • Journal: South African Forestry Journal
    The technical and practical capacities of softwood sawmills and boxmills in the Republics of South Africa, Transkei and Ciskei and the Kingdom of Swaziland were estimated as at 30 June 1987. These estimates show that sawmills in Southern Africa are...
  6. A Technique for Producing Soil Water Retention Curves

    Item type: Journal Article • Journal: South African Forestry Journal
    Water retention curves compiled for specific soil types are an essential management and research tool in evaluating plant stress. The method of producing water retention curves by means of the 1500 kPa pressure extractor is described.
  7. Storage of <em>Pinus radiata</em> Foliage Prior To Determination of Water Potential

    Item type: Journal Article • Journal: South African Forestry Journal
    A procedure to sample and store foliage of Pinus radiata seedlings prior to determination of the water potential is described. The water potential of P. radiata fascicles sampled at pre-dawn can be maintained for seven hours by storing the foliage...
  8. Water Retention in Cultivated Forest Soils of the Southern Cape Province

    Item type: Journal Article • Journal: South African Forestry Journal
    In South Africa, commercial tree planting is restricted because of limited water resources in the soil. Therfore, it is important to recognise relevant soil characteristics and soil amelioration techniques to optimise water supply for best tree growth. The Gompertz function...