Mountain Vegetation - Mountain Geography: Physical and Human Dimensions - page 339

ance of lianas (hanging vines), and the profusion of elaborate flowering plants also
decreases, while lichens and mosses increase on upper slopes (Richards 1966; Grubb
1977).
Temperate-latitude genera also occur in tropical forests above 1,000 m (3,300 ft),
contributing to a far greater number of species than found in forests at higher latitudes.
For example, the tropical montane forests of Mexico harbor over 40 species of pine
( Pinus spp.) and 200 species of oak ( Quercus spp.) (Perry et al. 1998). Comparable di-
versity trends are observed in Malaysia (Troll 1960). Similar to mid- and high-latitude
areas, the number of woody species found in tropical forests declines with increasing
elevation (Grabherr 2000).
Tropical forests generally show a well-developed zonation among the major plant
communities (Fig. 7.1), with a typical progression that includes lowland tropical, sub-
montane, montane, subalpine forest, and alpine grasses and shrubs. One of the more
distinctive subzones is the mossy forest, cloud forest, or elfin woodland located at
1,000-3,000 m (3,300-10,000 ft) within the broader montane or subalpine zones. This
subzone also occurs in subtropical climates where adiabatic cooling and higher precip-
itation are capped by the subtropical trade wind inversion, creating more moist condi-
tions than at higher elevations (Leuschner 1996; Martin et al. 2007). These woodlands
are a form of cloud forest adapted to low light levels and saturated atmospheric condi-
tions. The trees in these forests and woodlands occur in a single layer of stunted and
gnarled individuals about 6 m (20 ft) in height, covered with epiphytic mosses and liv-
erworts; they are found at approximately the same elevations in Malaysia, Africa, and
South America. Although species differ in these widely separated regions, the general
appearance of the forests is similar (Grubb 1974). Areas above cloud forests often show
a temporary increase in tree stature (lower latitudes) or shrubland or grassland veget-
ation types (subtropics) in response to higher light levels and drier conditions.