Historical vegetation–environment patterns for assessing the impact of climatic change in the mountains of Lesotho
Climate change will probably profoundly impact the Maloti Mountains in Lesotho, which are likely to have a warmer, wetter and more CO2-enriched (eCO2) atmosphere in the future. Intensive smallstock grazing could exacerbate the effects of climate change on the mountain grasslands. Vegetation composition data collected in ca. 1990 in the eastern and western Maloti provide a baseline for assessing historical and future shifts in the abundance of functional groups such as C3 and C4 grasses and encroaching unpalatable dwarf Karroid shrubs. C3/C4 grasses had a skewed topographic distribution with the 50% floristic crossover from C4 to C3 grasses occurring approximately at 2 900 m above sea level (asl) on northerly slopes and 2 700 m asl and 2 400 m asl on south-facing slopes in the east and west, respectively. Shrubs were restricted to low, warm and dry slopes. C3/C4 grass patterns were most strongly correlated with modelled daily temperatures in early spring (October) and late summer (February), whereas winter temperatures and evaporation appeared important for shrubs. Warming would favour C4 grasses but eCO2 might benefit C3 grasses, whereas unpalatable C3 shrubs would be promoted by warming, eCO2 and grazing and should expand their distribution. Monitoring functional groups by remote sensing is recommended.
Keywords: C3 and C4 grasses, grazing, Karroid shrubs, temperature, topography