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Beck, E; Rehder, H; Pongratz, P; Scheibe, R; Senser, M: Ecological Analysis of the Boundary between the Afroalpine Vegetation Types "Dendrosenecio Woodlands" and "Senecio brassica-Lobelia keniensis Community" on Mt. Kenya., Journal of the East African Natural History Society, 172, 1-11 (1981)
Abstract:
Two of the most conspicuqus plant communities of the afroalpine belt of Mt Kenya, namely the Senecio brassica-Lobelia keniensis Community and the Dendrosenecio Woodlands, are separated by a very pronounced boundary. An attempt was made to analyze the formation of this boundary. The S.brassica-L.keniensis Community was found on waterlogged but not flooded ground of the Mountain Wet Gley or Peaty Gley type which was observed on moderate slopes near the valley floor and in gullies of the valley walls. Both character species are rhizome plants which, in addition to the normal roots, develop pneumatophore-like ones in their fibrous root systems. Those specialized roots enable these plants to inhabit the water-soaked and therefore poorly aired soils. The character species of the Dendrosenecio Woodlands vegetation, Senecio keniodendron and Lobelia telekii possess only ordinary tap roots. The soil covered by this vegetation type was ascribed to the Mountain Brown Soil-Gley type. Due to the lack of waterlogging of this soil its temperatures are not as much balanced as they are in the Mountain Wet Gley soils. In particular during the dry season this lack results in lower temperatures of the root bed. The hypothesis is put forward that the lower temperatures combined with the lower water content of the Mountain Brown Soil-Gley ground could make water uptake more difficult for S. brassica and L. keniensis and thus prevent a successful invasion of these species into the area of the Dendrosenecio Woodlands. The sharp boundary between both vegetation types is therefore equivalent to the borderline between waterlogged Wet or Peaty Gley Soils and the drier Mountain Brown Soil-Gley ground.

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