The role of hydraulic strategies in understanding the response of fynbos to drought
This dissertation is an investigation into the relevance of the hydraulic framework (sensu McDowell et al., 2008) in understanding the response of diverse communities to drought. This framework distinguishes species that respond to dehydration by rapidly decreasing stomatal conductance (gs) (isohydric), thereby maintaining relatively constant midday minimum water potential, from those that maintain relatively high gs (anisohydric), thereby maintaining carbon assimilation albeit at the cost of hydraulic dysfunction. However, currently, the importance of the hydraulic framework in explaining drought response in diverse communities is poorly understood. Drought-related plant mortality is of particular concern in South Africa’s fynbos biome, a global biodiversity hotspot. This Mediterranean-type region is predicted to experience an increase in drought, with unknown consequences for the endemic flora. We asked whether drought affected this diverse ecosystem in a predictable manner and if these patterns fit with existing frameworks of plant drought-mortality mechanisms.
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