Vegetation succession on Mt. Kenya in relation to glacial fluctuation and global warming

Abstract

AbstractQuestionsHow has the Mt. Kenya plant community responded to recent glacial retreat? Has the recent glacial retreat been affected by increases in temperature? How have number of plant clumps and proportion of vegetation cover changed with distance from the glacier edge (i.e. till age)?LocationFrom Tyndall Tarn to the foot of Tyndall Glacier of Mt. Kenya (0°6′ S, 37°18′ E), Kenya.MethodsThe topography, soils, vegetation and glacial distribution around the Tyndall Glacier of Mt. Kenya were investigated from 1992 to 2011. The effect of glacial retreat on the rate of movement of leading edge (upper distribution limit) of plant species was examined. The distribution of vegetation was examined in a permanent plot that was surveyed in 1996 and 2011. The effects of temperature variation on glacial retreat were assessed with a least squares regression model.ResultsTyndall Glacier retreated at a rate of ~3 m·yr−1 from 1958 to 1997, which increased to 7–15 m·yr−1 between 1997 and 2011. The leading edge of Senecio keniophytum, the first pioneer species to establish after glacial retreat, advanced with glacial recession. It was sparse in 1996; by 2011, the number of clumps and proportion of cover had increased. Clump size was affected by distance from the glacier edge (i.e. till age) in areas of recent deglaciation but not in deglaciated areas >15 yr old. Monthly mean minimum temperature at Mt. Kenya increased by >2 °C from 1963 to 2011, and glacial retreat was related to increase in monthly mean minimum temperature.ConclusionThe glaciers on Mt. Kenya have diminished rapidly in recent years, and pioneer plant species have advanced in response. The movements of some species do not appear to be directly spatially related to glacial retreat but may be related to increases in air temperature, soil development, seed dispersal limitation and interval of masting. Recent unusually high temperatures and precipitation also likely caused the blooming of some species during atypical seasons.