Recovery from fire : Observations in the alpine vegetation of western Mt. Kilimanjaro (Tanzania)
Beck, E.; Scheibe, R.; Schulze, E.-D.
In summer and autumn 1981 the afroalpine vegetation on the western side of Mt. Kilimanjaro (including the Shira Mountains and Plateau) was subjected to extraordinary strong bush fires. During the fire and shortly afterwards, the vegetation of this region has been studied (Beck et al. 1983). In spring 1985 the burnt area was reinvestigated in order to obtain an idea of the recovery of plants of the various afroalpine life forms as well as of the different vegetation formations. None of the 5 life forms characteristic of the afroalpine vegetation (Hedberg 1964b) appeared to be inevitably exterminated even by a large fire. Most of the woody species, belonging to the so-called sclerophyllous bush or scrub vegetation are capable to recover sooner or later by suckers or basal shoots. Only the giant rosette trees of the genus Dendrosenecio are not able to rejuvenate in this way. However, specimens having survived the damage, obviously have been stimulated by the fire to bloom; and the seeds could then find suitable germination conditions on the patches of still bare soil in the burnt areas. The other life forms, namely tussock grasses, acaulescent rosette and cushion plants did not suffer very much from the fire and thus could recover within a short time. A similar observation as for the persistence of the different plant life forms was made with respect to the various afroalpine plant communities. In spite of convincing evidence of recurrent burning, an ultimate replacement of a distinct vegetation formation or even plant community by a more fire-resistant one could not be detected. On the contrary, especially with the sclerophyllous bush and scrub species, some features of adaptation to the recurrent loss of their above-ground living matter by fire were observed. Naturally, recovery of the various vegetation formations requires different time spans. Full regeneration was observed in 1985 only with the tussock grassland. However, recovery of the other plant communities was apparent, too. 3 1/2 years after the fire the first stage of the regeneration cycle, which is characterized by a dominance of grasses, had started to become replaced by a second stage in which sclerophyllous species such as Alchemilla and Helichrysum reach dominance in the field layer. This second stage is expected to lead to a higher shrub and bush vegetation. This study does not confirm the idea that recurrent burning triggers and promotes a nonreversible succession from sclerophyllous bush or scrub vegetation to a grass- or moorland type. There is evidence that repeated fires cause a sequence of complete or incomplete succession cycles in which the grasslands are only one component.