A preliminary investigation of the phenology of subtropical thicket and karroid shrubland in the lower Sundays River Valley, SE Cape

I studied the phenology of a range of growth forms in four vegetation types along an aridity gradient in the lower Sundays River Valley to test two phenology models for semi-arid ecosystems. As aridity increased along the gradient, phenological activity became concentrated within a shorter period. For the most arid site, in the Central Lower Karoo, the data favour Noy-Meir’s (1973) view of a ‘pulse-activity’ phenological response to unpredictable rainfall. In the subtropical thicket communities, geophytes, lianes and leaf and stem succulents — all growth forms which contain water storage abilities — generally grew independently of seasonal rainfall. Communities with a greater number of species with adaptations for water storage generally showed a higher incidence of species which grew outside of the main rainfall period.