woodland

Wytham Woods, near Oxford, England. In early spring the forest floor was covered in bluebells, but as new leaves grow and cast more shade, less sunlight reaches the flowers, and they die back. Deciduous woodlands thus have pronounced seasonal differences in flower and vegetation growth, to make use of the available light.

Area in which trees grow more or less thickly; generally smaller than a forest. Temperate climates, with four distinct seasons a year, tend to support a mixed woodland habitat, with some conifers but mostly broad-leaved and deciduous trees, shedding their leaves in autumn and regrowing them in spring. In the Mediterranean region and parts of the southern hemisphere, the trees are mostly evergreen.

Temperate woodlands grow in the zone between the cold coniferous forests and the tropical forests of the hotter climates near the Equator. They develop in areas where the closeness of the sea keeps the climate mild and moist.

Old woodland can rival tropical rainforest in the number of species it supports, but most of the species are hidden in the soil. A study in Oregon, USA, in 1991 found that the soil in a single woodland location contained 8,000 arthropod species (such as insects, mites, centipedes, and millipedes), compared with only 143 species of reptile, bird, and mammal in the woodland above.

The trees determine the character of the wood. Sometimes a single species dominates, as in a pine or beech wood, but there is often a mixture of two or more co-dominants, as in a mixed oak and ash wood. Beneath the tree canopy there is frequently a layer of shrubs and beneath these the herbs. Woodland herbs grow in shady conditions and are adapted in various ways to make the best possible use of the available sunlight. The woodland floor provides moist conditions in which mosses and liverworts thrive and many fungi grow in the soil or on rotting wood. The trees themselves provide habitats for another group including climbing plants, mosses, liverworts, lichens, fungi, and microscopic algae.

A European Commission report, published in October 2000, looked at approximately 129,000 trees from woodlands in 30 countries and concluded that only 36% of European trees (broadleaf and conifer) are healthy. Air pollution, climate change, and soil degradation are among the causes for the decline in tree health, with trees in Mediterranean countries being worst affected.

Woodland

Town and administrative headquarters of Yolo County, north-central California; population (1990) 39,800. It is located 29 km/18 mi northwest of Sacramento. Settled in the 1850s, it is the trade and processing centre of a Sacramento Valley region producing rice, tomatoes, olives, fruit, alfalfa, and sugar beets. Plastics and mobile homes are manufactured in the town.