Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Range condition assessment to document the extent of degradation on selected semi-arid rangelands of the Eastern cape, South Africa

Auteur : Akhona Ndandani

Université de soutenance : University of Fort Hare

Grade : Master Science (MS) Pasture Science 2016

Résumé partiel
The assessment of communal rangelands and Nature Reserve capability is crucial in order to prevent resource degradation and facilitate adaptive management practice. This study was conducted to document the extent of land degradation in three selected semi-arid rangelands of the Eastern Cape, South Africa. These comprised the Great Fish River Nature Reserve, Glenmore and Ndwayana communal rangelands. Each rangeland was demarcated into two homogenous vegetation units (HVU’s) toplands, bottomlands and a benchmark site. Botanical composition (woody and herbaceous), aboveground biomass production, soil seed bank composition and density and soil micro nutrients (Cu, Mn, Zn) and macro nutrients (N, P, K, OC, Mg, Ca, Na) were determined. Twenty two (22) perennial grass species and some forbs were recorded in all the HVU’s. In general the grass species composition consisted of 59 percent pioneer (Increaser II) species, 36.4 percent mesophytes (Decreaser) species and the remaining were 4.54 percent sub-climax/climax (Increaser I) species. The grazing value of the grass species was : High 41 percent, Moderate 14 percent and Low45 percent. Six dominant grass species and were recorded, comprising mainly of Increaser species in all the HVU’s, (except for Digitaria eriantha). Biomass production in the benchmark (2700 kg/ha) was significantly higher in summer than all the other HVU’s, but in winter (1715 kg/ha) it was not significantly different from the bottomlands of the Great Fish RNR. There was an increasing trend in mean basal cover from the benchmark to Ndwayana toplands (0.0-15.75cm). The results showed that the benchmark had higher dense cover (0.0 to 1.5cm) than all of the other HVU’s. There were 27 woody species, where 56 percent were acceptable to browsers while 44 percent were not acceptable. Of these woody plants 41 percent had thorns or spines whilst 59 percent had no thorns or spines. Ptaeroxylon obliquum (14 percent) was the most dominant species and the least dominant being Pappea capensis (0.05 percent) respectively.Glenmore had significantly higher bush density (1181.25 and 1337.5Trees/ha) and TE (1069 TE/ha) than all the other HVU’s. Soil samples from each sample plot were collected with an auger from a 20 cm layer with the use of a 0.25m2 quadrat distributed within the four 100 m transects in each sample plot. The samples were analyzed for N, P, K, OC, Na, Ca, Mg, Zn, Cu and Mn and pH using photospectrometer.

Sujets  : Rangelands — South Africa — Eastern Cape. — Land degradation — Soil degradation

Présentation

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