Page 688 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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20.1
VERTICAL STRUCTURE OF A RAIN FOREST
Trees create the distinctive “architecture” of the rain forest, made up of overstory, canopy, and understory, shown below. Long vines called lianas, rooted in the soil, connect these layers, while dead leaves form litter on the deeply shaded forest floor.
60 m
50 m
40 m
20 m 15 m
5m
Overstory:
The high-level canopy is made up of the tops of huge trees that jut up above the surrounding forest.
Middle canopy:
Heaviest of the three layers. Formed of the interlocking crowns of mature trees, the middle canopy is home to many kinds of animals and plants. The latter include epiphytes, such as orchids.
Understory:
The lower-level canopy is made up of broad-leaved plants that block almost all direct sunlight.
20.1a
20.1b
Rainforest soil:
20.1c
Visit the Study Area in MasteringGeographyTM to explore rain forests.
Visualize: Study a video of plant productivity Assess: Demonstrate understanding of in a warming world. rain forests (if assigned by instructor).
Earth’s rain forests are the natural vegetation of tropical regions with abundant precipitation. Rain forests are also a vast reservoir of biodiversity. The rain forest’s layered structure reflects intense competition for sunlight and
Rain forest in the mountains of Costa Rica [Ivalin/Shutterstock.]
space among numerous species of trees and other plants (GIA 20.1). For several decades, humans have cleared rain forests for agriculture, cattle
ranching, timber export, and palm oil production. (GIA 20.2).
Describe: What are the characteristics of the three main layers of the rain forest?
Lianas, here shown in the middle canopy, drape over branches and trunks to the forest floor.
Leaf litter covers the rainforest floor, seen here with a typical buttressed tree trunk, and lianas in the background.
[Bobbé Christopherson.]
Rainforest soil is poor in nutrients. Most soil nutrients have been taken up to help form the biomass of trees and other rainforest organisms. These nutrients are recycled rapidly as plant and animal remains decay on the forest floor and are reabsorbed by tree roots.
[Bobbé Christopherson.]
geosystems in action 20 TROPICAL RAIN FORESTS AND AMAZON DEFORESTATION