Population Ecology and Harvesting of Rooibos (Aspalathus linearis) and Its Ecotypes in the Wild, South Africa.

Abstract

Aspalathus linearis ('rooibos') is a polymorphic perennial shrub native to the drier, northwestern part of the Fynbos Biome in the Cape Floristic Region. It is cultivated on a large scale and wild-harvested on a small scale to produce rooibos tea, a traditional herbal drink. Rooibos is a post-fire pioneer germinating from fire-stimulated soil-stored seed, while some ecotypes also resprout post-fire. We aimed to improve understanding of the ecology and utilization of the species and its ecotypes in the wild. We surveyed 45 populations of wild rooibos across the species' range, distinguishing four ecotypes, and assessing their environmental preferences, density, demographics, extent, and effects of harvesting and fire on population health. Populations appeared demographically healthy with low incidences (average 5%) of mortality and stressed plants (9%). Reseeder and resprouters recruited equally from seed (seedlings comprised 4% of populations) and both exhibited wide-ranging population densities (25 to 30,000 plants.ha^-1). Population densities were higher where fires were more frequent and in younger post-fire vegetation. Seedlings occurred in vegetation of all ages, implying some inter-fire recruitment. The mean fire return period in surveyed populations was long (26 years) by fynbos standards (10-20 years), but rooibos persisted well in old vegetation suggesting that fires at high or low frequency do not pose significant threats to the species. Generally, harvesting levels were low at landscape and population scales; < 45% of sites on private land were subject to harvesting and there < 50% of plants showed evidence of harvesting. Illegal and overharvesting were uncommon (< 3% of sites). Population health and plant vigor were mostly unaffected by harvesting, suggesting that harvesting does not presently have large-scale detrimental effects on wild rooibos.