Biogeography of the Earth

Midlatitude Forests

Mediterranean Woodland 

The Mediterranean woodland is a sclerophyll forest consisting of low branching trees with small hard leaves and gnarled thick bark. The Mediterranean Woodland is found on west coast of continents in the midlatitudes and bordering the Mediterranean Sea, in close association with the Mediterranean (Dry Summer Subtropical) climate. Mediterranean woodland in North America is found along much of coastal southern California. Thick bark and small, waxy leaves are two adaptations to prevent excessive loss of moisture during the severe summer drought experienced in the dry summer subtropical climate. Chaparral vegetation grows to a height of 1 to 3 meters and has leathery leaves to prevent moisture loss. Chaparral is adapted to wildfires common in this environment (see below). Canopy of the typically hardwood, evergreen vegetation covers about 25 to 60 % of the terrain. The sparseness of the vegetative cover is due to the severe summer moisture stress and human disturbance.

Figure BE.23  Chaparral of the North American  (U.S.A.). (Source: U.S. Forest Service )

Figure BE.24 Wildflowers, grasses, and shrubs regenerate after fire in the chaparral. (U.S.A.) (Source: U.S. Forest Service )

Midlatitude Broadleaf Deciduous and Mixed Forest

The Midlatitude Broadleaf Deciduous and Mixed Forest of the humid midlatitudes contains evergreen and/or deciduous trees reaching heights of 15 to 25 meters. The broadleaf forest dominates equatorward, while toward the north, conifers intermingle to create a mixed forest. Needle leaf trees are well adapted to the cool to cold temperatures which occur on the poleward limits on the humid latitude climate. Cold sensitive broadleaf trees enter a period of vegetative dormancy, reducing moisture content and shedding their leaves. Oak, maple, hickory, chestnut and beech are common tree types found in the broadleaf deciduous forest. In most cases the forest is an open forest with little under story growth, though some shade tolerant annual species occupy the ground. The dense canopy inhibits significant amounts of light to penetrate to the forest floor inhibiting growth at ground level.

Figure BE.25 Broadleaf deciduous forest in France*. (Source: A. Vorontzoff. FAO.)

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