The physiography and plant communities of the Jakkalsrivier catchment

Kruger, Frederick John (1974-07)

Thesis (MScFor)--University of Stellenbosch, 1974.


ENGLISH ABSTRACT: The Jakkalsrivier catchment is one of several mountain drainage basins selected for research on the effects of treatment on vegetation, stream flow and erosion in the fynbos ecosystems of the south-western Cape Province of South Africa. This study comprises a report on the physiography and plant communities there. Jakkalsrivier is situated on poor sandstones and quartzites, and soils are characterized by acidity, low base status and wide variation in moisture (seasonal and spatial) and organic content. The land is steep, gently dissected and faces south. The climate may be described as of the moist transitional Mediterranean type. The catchment, which receives about lOOOrnrn of rain per annum and where ambient temperature averages 13,6°C, is cooler, moister and windier than the surrounding lowlands. Altitudinal gradients are marked by increasing precipitation (at a rate of 50 mm per 100 m) and decreasing solar radiation with increasing elevation. Community classification is based on association-analysis and group analysis of a qualitative floristic data set collected from a systematic sample of 367 fifteen-square-metre quadrats. - Eleven communities are distinguished, most of which are essentially of the microphyllous evergreen dwarf scrub formation class, with some microphyllous and some sclerophyll evergreen scrub. Community variation is associated chiefly with major soil type differences and gradients of relative solar insolation and of soil moisture. The sampling system used is felt to be inefficient. A well - designed suite of computer programmes would greatly assist work of this nature.

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