Montane (Mountain) Forests
When visiting the Neotropics make sure you include
a segment in the magnificent Andes Mountains. Don’t
just settle for lowland rain forest. Do some climbing.
The ecology is different up in the mountains, and the
views are great. The Andes mountain chain extends
from Trinidad and Venezuela all the way down the
western part of the continent of South America to
Tierra del Fuego (plate 13- 1; fig. 13- 1). The mountains
in Central America, as well as those of islands such
as Puerto Rico, are not as tall as the Andes but are
nonetheless rich with cloud forests, and there is much
to be seen in them.
Elevational Changes: An Overview
With increasing elevation up an Andean mountainside,
temperature decreases and condensation and
precipitation both increase, conditions supporting
cooler and humid forests rich with trees often densely
laden with epiphytes. Temperature gradients can
be steep, and it is often surprisingly cool at higher
elevations. In the upper montane forests, trees are
gnarled and small in stature, forming a kind of elfin
forest. In high- elevation Andean zones, conditions
become colder and increasingly windy, too severe
for trees to survive, so only grass and shrubs prevail.
Depending upon conditions, these alpine grassy and
shrubby areas are called either páramo or puna (both
discussed below). Snow is typical at high elevations,
even in equatorial regions (plate 13- 2). Conditions
above tree line are frequently foggy and bog- like, with
extensive areas of soft peat and mossy groundcover.
As airborne moisture from the lowland tropical forest
meets the Andes it rises and cools, and mid- elevation
montane forest becomes enshrouded in dense mist
and fog— a cloud forest— for at least part of each day.
Clear morning skies yield to afternoon fog that persists
through nightfall. Cloud forests look and feel overcast
and damp, because you are literally walking in a cloud
when you traverse such areas.
Alexander von Humboldt, who explored the
Neotropics from 1799 to 1804, first described the
ecological zonation that is evident along tropical
elevation gradients (plate 13- 3). He documented how
lowland moist forests grade into cloud (or fog) forests,
Chapter 13. Scaling the Andes
NORTH
AMERICA
SOUTH
AMERICA Peru
Atacama
Desert
Chile
Pacific
Ocean
Pacific
Ocean
Tierra del Fuego
Strait of Magellan
Cape
Horn
Scotia
Sea
Falkland
Islands (UK)
Argentina
Patagonia
PAMPAS
Uruguay
Bolivia
Paraguay
Brazilian
Shield
Amazon
Basin Brazil
Brazilian Highlands
600 kilometers
600 miles
Galápagos
Islands
(Ecuador)
Colombia
Ecuador
ANDES
ANDE
S
ANDES
Caribbean Sea
Venezuela
Guyana
Suriname AtlanticOcean
Atlantic
Ocean
French
Guiana
(France)
LlanosGuiana
Highlands
Figure 13– 1. General map showing the extensive range of the
Andes Mountains. Reprinted with permission from Kricher,
John. Tropical Ecology. Princeton, NJ: Princeton University
Press, 2011.
Plate 13- 3. Alexander von Humboldt was the first to carefully
document how elevational change in the Andes Mountains
alters plant community structure; we call this the life- zone
concept. Photo by John Kricher.
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