Mountain Vegetation - Mountain Geography: Physical and Human Dimensions - page 328

CHAPTER SEVEN
Mountain Vegetation
KEITH S. HADLEY, LARRY W. PRICE, and GEORG
GRABHERR
Mountain environments display some of the most striking examples of vegetation trans-
ition on Earth, including such well-known patterns as vegetation zonation, treeline,
and elevation-induced decreases in plant stature and species diversity. These and other
mountain-related vegetation patterns have long intrigued biogeographers and ecologists,
and they continue to provide a contextual background for exploring fundamental biogeo-
graphic patterns such as vegetation boundaries, species diversity gradients, and the geo-
graphical history of plants. This knowledge has further contributed to the development
of such important scientific concepts as natural selection, community succession, and en-
vironmental change.
The goal of this chapter is to summarize the ideas central to the understanding of
mountain vegetation. Although much of this material focuses on the distribution and
characteristics of mountain vegetation, it does so within the context of important biogeo-
graphical and ecological concepts. To achieve this objective, the content of the chapter
is subdivided into several topics. The first section presents a brief overview of vegeta-
tion zones and a comparison of arctic and alpine environments, providing a comparat-
ive context for the remainder of the chapter. The next section examines plant distribu-
tions ( phytogeography ) and the history of mountain plant communities. The main body of
the chapter is then presented in three major sections: (1) mountain forests, (2) timber-
line, and (3) alpine vegetation. The first of these sections examines the characteristics
of mountain forests, primarily using examples from midlatitude and tropical regions. The
second and third sections discuss the positioning, patterns, and causes of treelines and
the characteristics of alpine vegetation. The chapter ends with a brief discussion of the
historical and future human impacts on mountain vegetation.
Vegetation Zones and the Mountain Environment
Vegetation Zones and High-Elevation Climates
The concept of elevation zones is among the oldest and most useful characterizations of
mountain environments (Fig. 7.1). This chapter adheres to this traditional presentation of
vegetation patterns, but does so with a few caveats. The first of these is the recognition
that many of the spatial patterns associated with vegetation are the result of local envir-
onmental differences and ecological processes present at the landscape, community, and