Responses to warming and low soil moisture provide insights into vulnerability of key plant species of Southern Africa

Abstract The study evaluated whether common bulbous ( Eucomis autumnalis , Bulbine natalensis , Agapanthus praecox ), herbaceous perennial ( Pelargonium sp.), palm ( Dypsis lutescens , Neodypsis decary i), shrub ( Barleria greenii , Carissa macrocarpa ) and succulent ( Portulacaria cafra , Crassula ovata ) functional groups of Southern Africa differed in biomass and physiological stress responses under warmer (2 °C above ambient midday temperature) and drier future climates. We set a species × warming × soil moisture factorial experiment in a completely randomised design, with five replicates of each treatment combination. Warming and soil moisture interacted in influencing plant biomass across different species. Biomass in bulbous plants significantly dropped by 33%. At low soil moisture, total biomass significantly dropped in bulbous and herbaceous plants. Under a warmer microclimate, shrubs and herbaceous plants prioritised their biomass towards belowground organs. The ambient temperatures were close to what the bulbous and herbaceous functional groups could tolerate. Long term field monitoring studies of bulbous and herbaceous functional groups are therefore recommended.