The general term ‘tropical alpine’ refers to regions within the tropics occurring between the upper limit of continuous, closed-canopy forest (often around 3500–3900 m) and the upper limit of plant life (often around 4600–4900 m: Hedberg 1951, 1964; Beaman 1962; Troll 1969; Wade & McVean 1969; Wardle 1971; Van der Hammen & Ruiz 1984; Vuilleumier & Monasterio 1986; see Figure 1.1) and is used in preference to regional terms such as ‘páramo’ and ‘jalca’ in the moist Andes from Venezuela to Northern Peru, ‘puna’ in the drier central Andes, and ‘Afroalpine’ and ‘moorland’ in Africa. No clear lower boundary can be defined where natural timberline has been eliminated by man, as in many areas of the Andes and Papua New Guinea (Wade & McVean 1969; Hope 1976; Ellenberg 1979; Ruthsatz 1983), or where the forest is patchy or absent due to low rainfall, as on the north slope of Mount Kenya (Coe 1967; Figure 1.2) and the western slopes of the Peruvian Andes (Weberbauer 1911). In these cases alpine species merge gradually with species of montane pasture, savanna or desert.

Physiognomy of tropical alpine vegetation varies greatly with climatic and edaphic factors; however, certain trends are held in common by many New and Old World tropical alpine areas (see, for example, Hedberg 1964; Coe 1967; Cuatrecasas 1968; Wade & McVean 1969; J. Smith 1977, 1980; Cleef 1978), suggesting convergent evolution (Hedberg & Hedberg 1979; Halloy 1983; Smith & Young 1987).