THREE types of rain forest can generally be recognized on wet tropical mountains: lowland rain forest, lower Montane rain forest and upper Montane rain forest1-3. These forest types can be defined both by distinctive plant associations1 and by the altitudinal limits within which they lie. These limits, however, vary with the type of mountain. On small, isolated mountains and outlying ridges of major ranges, the upper limit of lowland rain forest is about 700-900 m and that of the lower Montane rain forest about 1,200-1,600 m, whereas on the main ridges of major ranges the limits are higher, approximately 1,200-1,500 m and 1,800-2,300 m, respectively4. This phenomenon is known as the `Massenerhebung' effect.