Drought stress responses in wild and cultivated Aspalathus linearis of the Suid Bokkeveld, Northern Cape Province of South Africa : linkages between local knowledge and empirical evidence

[摘要] ENGLISH ABSTRACT: The north-western region of the Western Cape forms part of the Fynbos biome and is home to the indigenous plant, A. linearis (rooibos). Rooibos cultivation is restricted to a small geographic area with wild rooibos plants being more at risk as a result of climate change. This research contributes to a growing body of evidence of the impacts observed and experienced by small-scale farmers, by adding much-needed analysis of empirical data on rooibos under low precipitation conditions to the body of science. The overall aim of this study was to examine the physiological response, using xylem hydraulic conductivity, to drought stress of wild and cultivated A. linearis plants in the Suid Bokkeveld and to determine the effects of organic mulch on cultivated rooibos' susceptibility to xylem cavitation in response to drought stress. The information was used to compare farmer perceptions of rooibos drought responses and to spotlight the variations and similarities between the two information systems (scientific and local ecological knowledge) with the hope of providing guidelines for effective climate change adaptation strategies. A. linearis appears to respond to soil moisture gradients but showed little differences within sites according to the reseeder-resprouter dichotomy. On the other hand, the use of mulch did not have an impact on the cultivated rooibos' hydraulic characteristics. Cultivated (reseeding) and wild (resprouting) rooibos ecotypes may differ in terms of their physiology, however, when the effects of drought exceed levels of tolerance in the two ecotypes, according to responses from the questionnaire survey, both may exhibit similar strategies (branch sacrifice and red leaf discoloration) to cope with prolonged precipitation deficits. The quarterly climate change workshops have proven to be a helpful tool when it comes to incorporating local climate issues with that of seasonal forecasts and ultimately provides a platform for adapting new methods in addressing the impacts of drought and climate change. Results from the traditional scientific methods and the survey questionnaire on local knowledge show that there may exist important disparities between these two methodologies, however, each prove invaluable for understanding certain phenomena exhibited, in this case, by wild and cultivated rooibos ecotypes. Local knowledge should be used to emphasize problem areas and detect possible solutions whereas conventional scientific methodologies may often assist in converting potential problems into a broader range of appropriate hypothesis testing.

[发布机构] Stellenbosch University