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Nature Gallery (Eco Regions

Temperate and Sub-Tropical Evergreen Forests

In the middle latitudes, the prevailing winds carry moisture-laden air masses over the west coasts of the continents, which receive substantial rainfall in consequence. In much the same manner, the subtropical east coasts of the continents are kept wet by the trade winds. In these regions, the combination of ample precipitation and comparatively mild temperatures produces dense forests in which evergreen species, both broadleaf and coniferous, preponderate.

Some of these forests are sufficiently wet to be called rainforests. As in the more familiar rainforests of the tropics, many of the trees reach enormous size, and epiphytes are common. Because more light penetrates the canopy, however, the vegetation of the understorey and forest floor is better developed than in the tropics.

In the temperate evergreen forests of the west coasts, rainfall is concentrated in the cool winter months. The mild summers are comparatively dry. These forests line the coast of North America from central California north to southeastern Alaska. The largest trees are all conifers, but broadleaf trees and shrubs are important components of the understorey. The famous redwoods that dominate the forests of the foggy coast of California are replaced further north by spruces, hemlock firs, and other giant conifers. Despite its similar climate, the much-interrupted coast of northwestern Europe lacks this type of evergreen forest, which was eliminated during the last period of glaciation. In the southern hemisphere, temperate rainforests of southern beeches, podocarps, and other species are well developed in central Chile and on Tasmania and the South Island of New Zealand.

The most extensive region of subtropical evergreen forests is in East Asia, where rain falls throughout the year and summers are hot. These forests occupy a large transitional zone between the deciduous forests of northern China and Japan and the tropical evergreen forests of Southeast Asia. The corresponding forests in North America are confined to the Atlantic coastal plain of the southeastern United States, where evergreen oaks and magnolias flourish in the maritime climate. Far to the south of the Equator, significant subtropical evergreen forests grow in southeastern Australia, New Zealand, and the coast and highlands of southern Brazil.