Mountain Vegetation - Mountain Geography: Physical and Human Dimensions - page 331

FIGURE 7.2 Latitudinal variation of environmental factors influencing arctic and alpine vegetation.
(Billings 2000.)
Finally, we seek to clarify the common misconception that arctic and alpine environ-
ments are climatically similar (e.g., Löve 1970; Billings 1979; Walker et al. 1999). These
environments share few climatic similarities beyond their low average annual temper-
atures (Fig. 7.2; Table 7.1). Consequently, beyond the general purposes of broad gen-
eralizations, environmental comparisons between arctic and mountain locations are too
variable to be directly compared.
Phytogeography of Mountain Areas
Mountains have played a profound role in the evolution and distribution of terrestrial
plants through their dual capacity as migration corridors and barriers. Mountains serve
as corridors by extending the geographic range of environmental conditions into areas
of dissimilar regional climate, allowing alpine and other mountain-adapted plants to
move freely along mountain axes. For example, north-south-oriented cordilleras con-
sisting of several mountain ranges, such as the Andes, Rockies, Cascades, and Sierra
Nevada of California, play an important role in facilitating the interchange of species
from different latitudes (Van der Hammen 1968; Troll 1968; Lauer 1973; Taylor 1977;
Hadley 1987). Under cooler climate conditions, these corridors have also expanded lon-
gitudinally to include arctic tundra areas in Asia and North America (Major and Bam-
berg 1967a), the Altai Mountains (Weber 1965), and Changaishan area in China (Qi-
an et al. 1999). Many Afroalpine plants are related to temperate-latitude species des-