Table 1.
Published studies of vegetation change on Mount Kenya.
Fig 1.
Study location and other published studies mentioned in text.
Location map in eastern Africa (upper left inset) and Mount Kenya (lower left inset) showing: 1) Oblong Tarn (this study, red circle), 2) Hobley Valley mire [63], 3) Small Hall Tarn [47], 4) Rumuiku swamp [41], 5) Lake Rutundu [61], 6) Sacred Lake [35, 61], 7) Lake Nkunga [36], 8) Kiluli Swamp [38]. Lower left inset: Landsat true colour image showing Mount Kenya (scene LC81680602014258LGN00; 15 September, 2014; Data available from the U.S. Geological Survey) with 400 m elevation contours (black lines) and summarised vegetation zones: mixed savanna, mixed cultivations and lower montane forest (LMF), moist montane forest (MMF), upper montane forest (UMF), ericaceous zone (Er) and alpine (vegetation zone boundaries are diffuse and not delimited here). Main figure showing headwater lakes (white outlines) of the Hausburg Valley with Oblong Tarn study site near the recessional tills (dashed outlines) of Josef and César Glaciers. (Image date 14 January 2015; Google Earth/DigitalGlobe, 2015).
Fig 2.
Photograph of Oblong Tarn from the west shore facing east to till deposits from the retreat of Josef Glacier and showing the local patchy alpine vegetation. Photograph credit: Hilde Eggermont (Ghent University) taken 25 August 2010.
Fig 3.
Radiocarbon dates and age-depth models for Oblong Tarn sediment cores.
Age-depth models (red dotted line), random walks (greyscale), and 95% CI (dotted grey lines) of IntCal13 [55] calibrated radiocarbon dates (distributions in blue) with parameter settings (top right red font) for each of the Oblong Tarn sediment cores (Table 2; [53–54]). Ages reported as calibrated year BP (before present, 1950 CE). Pollen samples were taken from both the 1983 core [44] and the 1986 core [45] to create a composite stratigraphy.
Table 2.
Radiocarbon dates from Oblong Tarn sediment core.
Fig 4.
Pollen assemblages from the Oblong Tarn sediment cores.
Pollen diagram of Oblong Tarn, Mount Kenya. Black circles show taxa with <1% relative abundances. LOI organic content (% dry sediment weight) estimated from the 1983 core [44]. At right, open black circles designate pollen samples from the 1983 core and open grey circles designate 1985 core subsamples. CONISS dendrogram shows that the entire record is contained within a single pollen assemblage zone with no statistically significant assemblage changes.
Table 3.
Pollen taxa observed in Oblong Tarn sediments.
Fig 5.
Pollen taxa groups and other palaeoenvironmental records for comparison.
Taxonomic grouping of pollen relative abundances by biome. Alpine, ericaceous and woodland-savannah taxa groups shown with 10x exaggeration (dark black line). LOI and PAR derived from the 1983 core [44]. Rate of Change (RoC) analysis index values [74] and principal component axis one scores (19.5% variance explained) of square-root transformed pollen percentages. PCA scores are reversed for comparison with temperature reconstructions of mean annual air temperatures (MAAT) [103] from Rutundu Lake (in the lower ericaceous vegetation) [82] and Sacred Lake (within montane forest) [82, 105, 106] on Mount Kenya (elevation of the lake sites shown in m asl; shaded grey envelope shows 95% confidence interval).