Application of a ‘stem number guide curve\' for sustainable harvest control in the dry woodland savanna of northern Namibia

The savanna woodlands of north-eastern Namibia are a significant source of essential resources for the rural population. Thus far, however, there is little or no growth data available to predict future timber supplies and current yield regulation is limited to the issuing of harvesting permits based on the assessment of available tree sizes, rather than a tree population as a whole. This paper presents the negative exponential function for the development of a guide curve. The curve defines an optimum stand structure based on desired timber yields for specific tree sizes, the intrinsic mortality rates of individual species and the total desirable stocking of a stand. The application of the approach is assessed using the size class distributions of two prominent tree species of the Kanovlei area in north-eastern Namibia. While the function models the development of the populations of the species well, timber and non-timber trees will need to be modelled separately. In the coming years it will be an important priority to establish a system of sample plots to obtain growth data that may support or augment the system.Keywords: Savanna woodlands, stem number, negative exponential function, guide curve Southern African Forestry Journal No. 204 2005: 37-4

Quantified range condition assessment of open Camelthorn savanna along a degradation gradient

Measurements were taken at 20 different sites in a relatively homogenous area of open Camelthorn savanna in eastern Namibia. Ordination of grass species composition did not provide a good degradation gradient, due to domination by different species of annual grasses at many of the sites. However a centred PCA ordination of perennial grass species indicated a degradation gradient. This gradient was used to allocate a range condition score to each site, which was then correlated with other measurements. The range condition score did not correlate well with mulch cover, basal cover, proportion of bare soil, above-ground grass biomass, proportion of moribund grass, proportion of seedlings amongst the perennial grasses, density of woody plants lower than 0.5m and canopy cover of browsable woody plants over 0.5m tall. A weak correlation (r2 = 0.68,