To determine the extent of bush encroachment with focus on Prosopis species on selected farms in the Vryburg district of North West Province
Mampholo, Ramakgwale Klaas
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The study was undertaken to determine the woody component with the focus on Prosopis species at selected farms in the of Vryburg district, Naledi municipality. The study also tested differences of plant density, size (structure) and bush equivalents between previously controlled and non-controlled plots. The study was conducted on the farms of Orsets, Trent 1, Trent 2, Mimosa, Eensaam, Mooidraai and Werda situated South East of Vryburg in Veld type A16 of Kalahari thornveld and shrub bushveld. A belt transect of 400 m2 was used to carry out the vegetation survey. The woody component was recorded according to species type; height class and bush equivalents were calculated through pre-determined factors for each height class. The results showed that no major differences of bush equivalent exist in previously controlled and non-controlled plots. Species such as Prosopis glandulosa, Acacia mellifera, Ziziphus mucronata, Grewia flava, Diospyros lyciodes and Ehretia rigida were identified. The sampled sites are highly invaded by Prosopis glandulosa with lower abundances of other indigenous species, such as Acacia karroo, Ziziphus mucronata, Diospyros lyciodes, Ehretia rigida and Grewia flava. It is recommended that satellite data should always be verified and complemented by field survey in order to have accurate bush density and species type. The control of Prosopis glandulosa should integrate various options to have long-term good results. It is concluded that the study areas are highly encroached with Prosopis glandulosa. The MODIS satellite remote sensing data are unreliable to study sites on limited scale owing to its reflection of large scale. The use of SPOT images and landsat data provide fair analysis of vegetation growth and extent of bush density. The undertaking of aftercare is mandatory to attain the required control of Prosopis glandulosa in the study sites.