A Closer Look at Temperate Rainforests

07 June 2010

In last week's Cast Your Vote, you had the chance to pick a topic to study. Plants of the Temperate Rainforest won by a landslide over Kelp and Plants of the Intertidal Zone. We hope this Notes From the Trail provides you with all the information you would like to know about Temperate Rainforests. For more information, we encourage you to check out Unit 3 of our Curriculum Guide or any of the links provided below the article.

Temperate rainforests of the world are shown in dark green. Image source: http://commons.wikimedia.org/wiki/File:Temperate_rainforest_map.png

What is a Temperate Rainforest?

A temperate rainforest is basically a rainforest found in a temperate climate. In other words, these forests receive a high amount of rainfall, but have a cooler average temperature than tropical rainforests. Did you know that the temperate rainforest of the Pacific Northwest is the largest temperate rainforest in the world? This temperate rainforest extends along the Pacific coast of North America from Alaska south through Canada to California. Temperate rainforests can also be found in South America, Scandinavia, New Zealand, Ireland, and Scotland.

Temperate rainforests get a lot of rain, up to 80 inches (200 cm). In some areas, such as Olympic National Park in Washington, the rainforest receives over 167 inches (425 cm) of rain per year. That’s almost 14 feet (over 4 meters)! Temperate rainforests have heavy fog in the summer time. The fog creates the humid conditions required by epiphytes and other rainforest plants, like ferns.

Epiphytes are plants that have no roots and don't touch the soil in any way. Instead, they actually grow on other plants and draw their water from the moist air of the rainforest and from rainfall!

Temperate rainforests are usually found close to the ocean. There are just a few inland pockets of forests that fit the basic definition of a temperate rainforest. However the majority of these forests are located close to the coast where ocean rains provide the climate necessary to sustain the plants of the rainforest.

Biodiversity and Biomass of Temperate Rainforests

Temperate rainforests have a long growing season. Unlike tropical rainforests, temperate rainforests have a major change of seasons. Temperatures change from 80°F in summer down to near freezing in winter. The cooler temperatures mean that temperate rainforests are not as biodiverse as tropical rainforests. This means they contain fewer different species of plants and animals.

The coniferous temperate rainforests of the U.S. Pacific coast have the highest levels of biomass of any place on earth. Biomass means the total amount of living things in a region. While there may not be as many different species as a tropical rainforest, trees and plants still grow very well here. These are among the most productive forests in the world—producing more biomass than tropical rainforests. Temperate rainforests have fertile soil. This is a result of all the dead materials rotting into the soil. Decomposing matter releases nutrients back into the soil and is good for growing thick stands of fast growing trees. Trees grow tall here – sometimes over 250 feet and their trunks can reach 15 feet across. Some of these trees can live for 500 years!

Layers of the Temperate Rainforest

The temperate rainforest has three layers. They are the canopy, understory, and forest floor.

Canopy: The canopy is the top layer. The canopy is dominated by tall conifers. These conifers grow year-round, so they can get massively tall, up to 300 ft (91 meters)! There are many bird species that depend on the canopy of the temperate rainforest. However, fewer animals can be found in the canopy of temperate rainforests compared to the canopy of tropical rainforests.

Understory: The understory is the middle layer of the temperate rainforest. The understory is composed of small, shade-loving trees.

Forest Floor: The forest floor is the lowest layer of the temperate rainforest. On the forest floor, there is a thick covering of lichens, mosses, and small plants. The forest floor is also covered in decomposing conifer needles, leaves, branches, twigs, and fallen trees. The soil is full of nutrients from all the dead organic material. The cool temperatures mean that material is broken down much more slowly than in the tropical rainforest. Most of the animals of the temperate rainforest live on or near the forest floor.

Plants of the Pacific Northwest

Conifers are the most common type of tree in the Pacific Northwest temperate rainforest. The dominant tree is the Douglas Fir, which grows up to 280 feet (85 meters). It is one of the tallest trees and is considered one of the most important trees to the timber industry. Further south, the great redwoods grow in northern California, reaching over 300 ft (91 meters) tall. Douglas Fir seeds are an extremely important food for small mammals. Mice, voles, shrews, and chipmunks eat the seeds in the cones that drop from the Douglas Firs.

Western Hemlock can grow to be 130 ft (40 meters) tall and live up to 500 or even 1,000 years old. Their trunks can be more than 100 ft (30 meters) around! Western Hemlocks have a shallow root system, which allows them to grow almost anywhere—on decaying wood or raw humus, but this the drawback is that they are susceptible to blow-down. Western Hemlock is an important food source for deer and elk.

Western Red Cedar is also found throughout the Pacific Northwest. It is also a large tree, ranging from 40 to 150 ft (12 to 45 meters) tall and up to 22 ft (7 meters) in trunk diameter! Historically, it has been a very important tree to many First Nations throughout the Pacific Northwest. The cedar wood would be used for constructing housing, totem poles, and crafting objects like masks, utensils, boxes, instruments, and even canoes. Roots and bark would be used for making baskets, ropes, rings, blankets, and clothing.

Other trees that grow in the temperate rainforest include Sitka Spruce, Noble Fir, and Pacific Silver Fir. Smaller trees include Big Leaf Maple, Dogwood, and Vine Maple. The forests are shady and damp, so shade-loving underbrush thrives here. Some of these plants are Pacific Rhododendron, Blackberries, Salmonberries and Thimbleberries, Sword Ferns, Devil’s-Club, Redwood Sorrel, moss and lichens. Many varieties of mushrooms, toadstools and fungi thrive in this shady, moist environment.

To learn more about Temperate Rainforests, check out Unit 3 of our Curriculum Guide or follow the links to any of the resources below.

http://quest.arc.nasa.gov/projects/jason/xv/docs/TempRain.pdf

Temperate rainforest canopy critters

http://academic.evergreen.edu/projects/ican/education/trfwebsite/canopycritters.h
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Great activities for grades 4-12

http://academic.evergreen.edu/projects/ican/education/trfwebsite/curriculum.html

http://biology.suite101.com/article.cfm/the_temperate_rainforest_ecosystem#ixzz
0kqUctVOp

Temperate rainforest description

http://www.worldbuilders.org/lessons/less/biomes/rainforest/temp_rain/temprain.html

Olympic National Park

http://www.nps.gov/olym/naturescience/temperate-rain-forests.htm

http://www.exploringnature.org/db/detail.php?dbID=44&detID=590