Effects of rainfall, competition and grazing on flowering of Osteospermum sinuatum (Asteraceae) in arid Karoo rangeland.

Abstract

Reports on the effects of rainfall, grazing and interspecific competition on flowering of Osteospermum sinuatum. The shrub flowered after heavy rain in autumn, winter and spring. The number of flowers produced per bush was positively correlated with basal stem diameter and rainfall in the 12 weeks before anthesis. Illustrates with a diagram, tables and graphs; The shrub Osteospermum sinuatum, an important fodder plant in Karoo rangelands, flowered after heavy rain in autumn, winter and spring. The number of flowers produced per bush was positively correlated with basal stem diameter and rainfall in the 12 weeks before anthesis. Flowering increased when neighbouring plants of all species were removed. Grazing during flowering and seed set, by sheep stocked at recommended densities, reduced potential seed set by as much as 90%. Birds, hares and small antelope consumed 10-50% of the flowers. Size-class distributions indicated that little recent recruitment had taken place on a ranch where palatable plants were scarce and where O. sinuatum flower production was severely depressed by grazing sheep.Language: English

Keywords: Asteraceae; Florivory; Herbivory; Karoo; Osteospermum sinuatum; Phenology; Seeding; flowering; grazing; rainfall; rangeland; seed; sheep; competition; distribution; recruitment; production; arid karoo; fodder; rangelands; flowers; anthesis; seed set; size-class distribution; flower production; south africa; tierberg