9. A Comparative Review of Forest Dynamics
177
The Physical Environment and Broad-Scale Vegetation Patterns
So uth America
The temperate rainforests of South America are associated with the westcoast marine climate of mid- to high-latitude South America (see Lawford,
th is volume) . The west coast of South America south of approximately
37°S is characterized by mild temperature ranges and high annual precipitation, as shown in Figure 9.3 . To the north is the Mediterranean-type
climate, with hot and dry summers. Mediterranean-type precipitation
seasonality is evident in the west -coast maritime climate as far south as
approximately 42°S, where the vegetation is temperate rainforest (refer
to Figure 9.3). The coastal mountains intercept the mid-latitude westerlies
and produce a minor rainshadow effect on the central depression of
south-central Chile, where at approximately 40°S, mean annual precipitation is typ ically less than 2000 mm (A lmeyda & Saez, 1958). In the
Andes at approximately 40°S, mean annual precipitation ranges from
3000 mm to ,more than 5000 mm on the windward slopes of mountains.
Eastward of the Andes, the rainshadow effect becomes extremely pronounced, so that precipitation declines from approximately 3000mm to
less than 800 mm over a west-to-east distance of only 50 krn. Thus, the
rainforests occupy only a narrow be lt on the eastern side of the Andes in
southern Argentina and occur more extensively in southern Chile , South
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Month
Figure 9.3. Mean monthly temperature and precipitation for selected coastal sites
along the coasts of North and South America.