taller trees. In the United States, Sierra Nevada Giant
Sequoia groves, coastal California Redwood groves,
and Pacific Northwest old- growth forests of Sitka
Spruce, Douglas- fir, Western Redcedar, and Western
Hemlock all routinely exceed the height of the majority
of tropical forest trees. So do the temperate bluegum
(Eucalyptus) forests in southeastern Australia. Neither
the tallest, the broadest, nor the oldest trees on Earth
occur in rain forest: the tallest is a California Redwood,
at 115.85 m (380.08 ft); the broadest is a Montezuma
Cypress in subtropical Mexico, with a circumference
of about 36 m (118 ft); and the oldest is a Great Basin
Bristlecone Pine in the White Mountains of eastern
California, about 4,600 years old.
Tropical trees the world over exhibit a distinctive
parasol shape, alluded to earlier, and this distinctive
morphology is most clearly evident when you observe
emergent trees from open areas, as when you traverse
a river (plate 3- 4). Take a moment and look up into
the canopy, observing the spreading, flattened crown.
See how the branches radiate out from one or a few
points, resembling the spokes of an umbrella. Each
of these main radiating branches contributes to the
overall symmetry of the crown, in an architectural
pattern called sympodial construction. The effect of
crowding by neighboring trees can significantly modify
crown shape. Single trees left standing after adjacent
trees have been felled often have irregularly shaped
crowns, a result of earlier competition for light with
neighboring trees. Trees in the understory tend to be
lollipop- shaped. Because they have not yet reached the
canopy, their crowns are composed of lateral branches
emerging from a single main trunk. Lower branches
will eventually drop off through self- shading as the tree
grows and becomes a sympodial canopy tree. Trees
growing in forest gaps, where sunlight is abundant (see
“The Understory and Forest Gaps,” below; and chapter
7), are densely multilayered with leaves, an adaptation
to intercept abundant sunlight.
Buttresses, Prop Roots, and Surface Roots
Many rain forest tree species are buttressed. Indeed,
buttresses are iconic features of trees of tropical forests
the world over. A buttress is a root flaring out from the
trunk aboveground to form a flange- like base (plate 3-
5). Because so many trees have buttressed roots, this
characteristic gives a tropical forest a distinctive look in
comparison with temperate forests. Buttresses radiate
Plate 3- 4. The spreading sympodial crown of this riverside tree
shows the radiating branching pattern and overall parasol
shape characteristic of many tropical tree species.
Photo by John Kricher.Plate 3- 6. Buttressed and spreading surface roots are evident
in many trees that inhabit riverine areas in the tropics.
Photo by John Kricher.Plate 3- 5. Buttressed roots are common throughout the
world’s tropical forests. They occur as growth patterns in
numerous tree species. Photo by John Kricher.42 chapter 3 rain forest: the realm of the plants