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Temperate Rainforest
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Temperate Rain Forest
The Tongass National Forest of Southeast Alaska is part of the largest temperate rainforest on Earth, stretching from Southcentral Alaska to Northern California. And it does rain! Ketchikan receives about 150 inches of rain (and about 40 inches of snow) each year. Juneau sees about 225 rainy days a year. September and October are the wettest months, and April and May are the driest. That rainfall supports a forest of predominantly Sitka spruce and western hemlock trees, which require a lot of moisture.
A walk in the temperate rain forest on a summer day is a rich experience. The shady forest floor is dappled by patches of sunlight, and it seems that every inch of ground, every stump and decaying, fallen tree is covered with moss and vegetation. Enormous leaves of skunk cabbage rise from damp areas. Platter-size devil's club leaves, studded with splinter-like thorns, can rise eight to 12 feet high and spread above blueberry, elderberry and cranberry bushes. Mosses and lichens hang from trees. Ground cover plants such as fern-leaf goldthread, five-leaf bramble and bunchberry thrive and are important and nutritious forage for deer.
Fire is rare in the rain forest, and wind storms take out far more trees than wildland fires. Many trees in the Tongass grow in thin, poorly drained soil and have shallow root systems. Winter storms can set up a chain reaction where falling trees topple their poorly anchored neighbors. This opens up the forest canopy and allows sunlight to pour in, accelerating the growth of adjacent trees and vegetation.
There are trees more than 700 years old and over 200 feet tall on the Tongass. But the biggest trees are not necessarily the oldest; they may just be in extremely productive areas like valley floors and floodplains with rocky, well-drained soil.
Trees such as Alaska yellow cedar and western red cedar are special features of the southern part of Southeast Alaska. Red cedar is prominent in the southern islands but scarce north of Petersburg. Yellow cedar extends farther north. Yellow cedar has droopy, flat sprays of scaly leaves, while red cedar has brighter green, more aromatic branches. Cedar wood is durable and rot-resistant and has been profoundly important to Native people of the coast. Cedar provides wood for totem poles, canoes and houses; and fibrous bark and pliable roots for weaving and basketry. On an Alaska beach covered with battered, bark-stripped driftwood, the red and yellow trunks of cedar logs can be readily distinguished from spruce and hemlock logs.
The Tongass National Forest is not all trees. Largely hidden from view of the water are expansive, boggy meadows called muskegs. These are open, poorly drained areas thickly carpeted with sphagnum moss and lichens. The wet "soil" here is largely the accumulation of dead sphagnum. This creates an acidic environment low in nutrients that few forest plants can tolerate. Some have specially adapted, plants like the tiny, insect-eating sundews, which trap bugs with sticky hairs and digest them to supplement their nutritional needs. Aromatic heathers such as Labrador tea grow as low bushes. Tannins leached from vegetation color the water brown. Small ponds with this tea-colored water dot the muskeg and shelter dragonflies and water beetles amid buckbean and bright yellow pond lilies.
Animals forage in the muskeg, but benefit more from the edge areas where the forest meets the open meadows. The open area provides abundant sunlight that allows plants to flourish, and the trees provide cover and protection from predators.
Few trees can tolerate muskeg conditions. However, these wet meadows are often dotted with a hardy conifer known as the shore pine. The scientific name, Pinus contorta, refers to the twisted and contorted forms this tree can take when subjected to ongoing harsh wind and weather. The shore pine is a variety of lodgepole pine found throughout the Western United States. In the nutrient-poor muskeg, a 20-foot tall shore pine may be 200 years old.
The forests of Southeast Alaska climb from sea level to an elevation of about 2,500 feet. The treeline varies depending on the aspect or direction of slope. At about 1,500 feet, tree species change, and mountain hemlock begins replacing the western hemlock. At about 2,500 feet, trees thin out and become scraggly, and the forest gives way to sub-alpine meadows, and then open alpine tundra. This treeless realm of mountain ridges, rock and ice encompasses millions of acres of the Tongass National Forest.