Erica excelsa as a fire-tolerating component of Mt. Kilimanjaro's forests
Hemp, Andreas; Beck, Erwin
The altitudinal and ecological distribution of Erica excelsa on the southern slopes of Mt. Kilimanjaro was studied at 407 sampling plots, using the method of Braun-Blanquet (1964). Erica excelsa occurs in the altitudinal range between 1600 and 3500 m where it was found on dry ridges as well as in riverine and even swampy forests. On Mt. Kilimanjaro the upper tree line is represented by pure stands of Erica excelsa, which cover large areas of the subalpine zone. However, this tree is also a component of the montane mixed forests with a preference of the upper, and to a lesser degree of the lower montane zone. However, in the central montane zone Erica excelsa is very rare. The boundary between the Podocarpus latifolius-dominated montane forests and the Erica excelsa-dominated subalpine forests is very sharp and presumably a result of fire. After a fire, Erica excelsa regenerates regularly by resprouting rather than from seeds. Whether and where the Podocarpus forests of the upper montane zone are thus replaced by an Erica forest is mainly a question of intensity and frequency of fire. The life strategy and competitive strength of the light-demanding Erica excelsa is thus obviously based on its tolerance of fire. The location of the upper forest line on the south slopes of Mt. Kilimanjaro therefore appears as a result of fire rather than of climatic factors. Unusually disastrous fires during the last years pushed the extant upper forest line downhill by approximately 300 m and recovery of the former tree line would require several decades of undisturbed growth.