Continuum or zonation? Altitudinal gradients in the forest vegetation of Mt. Kilimanjaro

Abstract

Based on the analysis of 600 vegetation plots using the method of Braun-Blanquet (1964) the composition of the whole vascular forest plant flora with about 1220 species was studied in the forests of Mt. Kilimanjaro. The altitudinal distribution of all strata (trees, shrubs, epiphytes, lianas and herbs) along a transect of 2400 m is discussed with respect to altitudinal zonation and ecological factors. With unidimensionally constraint clustering significant discontinuities were revealed that occurred simultaneously in the different strata. Thus even in structurally highly complex, multilayered tropical montane forests distinct community units exist that can be surveyed and classified by the Braun-Blanquet approach. This observed zonation was significantly correlated with altitude, temperature and soil acidity (pH); rainfall was of importance in particular for the zonation of epiphytes. Other key factors were humidity (influenced by stable cloud condensation belts) and minimum temperature (in particular the occurrence of frost at 2700 m altitude upslope). The contrary results of other transect studies in East Africa in respect to continuity of change in floristic composition appear to be caused by different sampling methods and intensities or mixing of data from areas with different climate conditions, whereas species richness did not influence the clarity of floristic discontinuities on Kilimanjaro and other parts of East Africa.

Contribution of mass elevation effect to the altitudinal distribution of global treelines

“…It was generally taken as the average elevation of foothills in isolated mountains in the plain and hilly areas without intra-montane basins or valleys, e.g., Mt. Kilimanjaro (Hemp 2006). For oceanic islands such as Tenerife in the insular Spain, MBE is zero.…”

“…For example, the absolute height of Mt. Kilimanjaro is as high as 5895 m above sea level and it is even close to the equator, but the treeline is at about only 3500 m (Hemp 2006), about 1100~1400 m lower than in the interior Tibetan Plateau (Schickhoff 2005). The reason may be that it's a volcanic cone without intra-mountain plateaus or basins, and that mountain slopes are all completely exposed to the free air, so the temperature difference between the mountain surface and the free air at the same altitude may be very small.…”

Assessing Vulnerability of Food Availability to Climate Change in Hai District, Kilimanjaro Region, Tanzania

“…The cloud forests are of great importance for watersheds in East Africa [15] [18]. In addition to the function of filtering and storing water, the upper montane and subalpine cloud forests have a high potential of collecting cloud water.…”

Regional-scale identification of three-dimensional pattern of vegetation landscapes

“…Mountainous areas are characterized by various types of vegetation which are found at different elevations and mountain flanks (Kitayama, 1992;Hemp, 2006). These different types of vegetation form a three-dimensional pattern in horizontal and altitudinal gradients.…”

“…He found that the vegetation landscape had a similar pattern to that in the latitudinal zone extending from the tropic to the pole (Sachs, 2003). Many studies have investigated vegetation types and patterns along altitudinal gradients in the mountains (Kitayama, 1992;Lovett, 1996;Kessler, 2000;Hemp, 2006). The three-dimensional pattern of vegetation landscapes are usually been related to the species diversity and distribution (Körner, 2000;Kitayama and Aiba, 2002;Wang el al., 2002;Bhattarai and Vetaas, 2003;Wang et al, 2007;Batllori et al, 2009;Sang, 2009 (Daniels and Veblen, 2003;Gian-Reto et al, 2005;Walther et al, 2005;Erschbamer et al, 2009;Odland, 2009;Wang et al, 2009).…”