Ecophysiology of Vascular Plants on Inselbergs

Abstract

As described in Chapter 4, this Volume (Porembski et al.) in more detail, inselbergs represent by no means uniform ecosystems but rather show clear fragmentation in subhabitats such as exposed rock surfaces, drainage channels, crevices between rocks, humus-filled depressions on top or the slopes of the rocks, or even wet flushes and seasonal rock pools (Barthlott et al. 1996). These habitat types differ largely in the constellation of edaphic and microclimatic factors (see Szarzynski, Chap. 3, this Vol.) and thus in the ecophysiological demands with which the plants colonizing such ecological units have to cope. As a consequence, inselbergs show a high floristic ß-diversity, i. e., they are covered by mosaics of plant communities consisting of species highly adapted to the environmental conditions of the given habitat type. For this reason, inselbergs provide promising models for comparative studies on mechanisms and effectivity of ecological adaptation in plants, but the ecophysiological investigation of inselberg vegetation is still at its beginning (for review see Lüttge 1997). The aim of this chapter is first to analyze some mechanisms of ecophysiological adaptation in vascular plants inhabiting inselbergs.In the second part we will apply these considerations to the vegetation of Mt. Angavokely, an inselberg of the central high plateau of Madagascar. Finally, possible consequences of adaptation for the diversity of life-forms in vascular inselberg plants will be discussed.