Prospects for sustained harvesting of mopane (Colophospermum mopane) on the Venetia Limpopo Nature Reserve and its implications for browsing ungulates

[摘要] ENGLISH ABSTRACT:Principle objectives of this study were to investigate the ecological feasibility of sustained utilization of mopane, using Venetia Limpopo Nature Reserve as a pilot study area. The study was limited to three different mopane dominated vegetation types on the reserve with most research being conducted in C.mopane woodland.Results can be summarized as follows:1. Colophospermum mopane is ubiquitous on VLNR.2. C.mopane woodland has the deusest mopane growth of the three vegetation types and highest densities are found on soils (OaB, VaB, Du, SwB & VaA) in association with C.mopane woodland. There seems to be a correlation betweenmopane density and soil type.3.Largest mopane trees according to height and circumference were found in C.mopane/C.apiculatum open woodland. There is no significant difference between height and circumference on different soil types.4. Most senility occurs in C.mopane shrubland and there is a significant difference in senility between mopane associated with different soils on which this vegetation type occurs.5. Oldest average ages per tree were fo•.md in C.mopanewoodland while growth rates were fastest inC.moparse!C.apiculatum open woodland.6. There is a significant positive correlation between total and charcoal weights for mopane. Total and charcoul weights per tree were highest for C.mopane/C.apiculatum open woodland, while weights per hectare were highest for C.mopane woodland. Soils could not positively be associated with this trend.7. Mopar.e lends itself to harvesting, especiallyC.mopane ••10odland in the Endora, Lizzulea and Hilda areas. Winter months seem to be most desirable for harvesting activities. Hand felling in elongated patches (increases ecotone boundary) is recommended where labour is cheap. A harvesting strategy of between 25% and 50% would make the operation economically viable and ecologically acceptable. An optimum harvesting rate of 27% is suggested by a harvesting model developed specifically for this mopane data.8. Total herbivore densities, distribution and species proportions can be expected to change following bush clearing. Habitat for grazers should increase due toan increased grass production.Habitat for browsers should not be influenced much.Effect of noise and human disturbance during harvesting, especially for elephants is negligible, as hunting activities already take place on VLNR.9. Grass production would increase but quality shoulddecrease after harvesting, due to an increase in low quality opportunistic species, especially if soil disturbance takes place.Grass quality is best in association with herbaceous species such as Salvadora angustifolia. Carrying capacity for grazers shouldincrease after harvesting as a result of habitat change and grass biomass increase.10. Total browse production would decrease but leaf biomass should increase on remaining trees as theyhave improved water availability due to Q lack of intra­specific competition.Higher seed production and more flowering takes place at lower tree densities. Greatest advantages for browsers after harvesting, is the fact that leaves become senescent later in autumn and that spring leaf flush takes place earlier thus prolonging bro\'se availability.

[发布机构] Stellenbosch University