17 - Plant form and function in alpine New Guinea  pp. 307-318

Plant form and function in alpine New Guinea

By R. J. Hnatiuk

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Introduction

The tropical alpine environment is surprising. Although it is predictable (Troll 1961; Humboldt, in Botting 1973), it is still remarkable to experience cool, misty mountains that rise out of the lowland tropics. These alpine places bear surprising resemblance in vegetation to the arctic, and to the alpine zones of temperate mountains. They also bear climatic and vegetational resemblance to remote islands of the Southern Ocean. The similarities of vegetation derive primarily from the changes in physical climate that occur as altitude increases on humid mountains. As temperatures decline, different plant species replace those adapted to growth in warmer conditions. The conspicuous changes to vegetation are a transition from tall, tree-dominated communities to low, shrub or herb dominated communities. These transitions occur on a grand scale that has been expressed as a three-dimensional model of climate and vegetation of the earth (Troll 1961; Humboldt, in Botting 1973).

There is controversy about the terms that should be applied to the regions. The argument turns on the degree of recognition given to thermal seasonality, which is weak or absent on the high tropical mountains and profound in the temperate alpine and near polar regions. There are many regional names: alpine, páramos, pahonales, mountain grassland, orosubantarctic, gras maunten, ais, etc. Each has its utility for its own zone – none is without misleading connotations when applied outside its region of origin. In this chapter, the phrase ‘tropical alpine’ is being used to conform to the usage of this book.