Deciduous Forest is characterized by a dense foliage of thin, grass-green leaves which fall and leave bare branches with heavy bark and scale-covered buds during a long, cold rest period. Oak, birch, beech, maple and ash dominate this forest. There are two distinct climatic seasons : a warm, moist season or growth period, and a cold, moist season, or rest period. Precipitation varies from 3o to 7o inches. The soils are either light coloured or grey-brown podsols. Under natural conditions this forest supports a fauna and fruits and nuts for primitive man. It produced much of the wood and hardwood lumber, and has given way to fields of temperate crops and deciduous fruits. There are three great areas of this forest: Eastern United States, western Europe, and eastern Asia. The total area was about 6,5oo,000 square miles.
Coniferous Forest presents a uniform stand of similar evergreen trees, and consists chiefly of pine, spruce and fir. The winter climate is rigorous; rainfall varies from 15 to ioo in. annually; the soil is young but the land is of little agricultural value. This forest is the source of much of the lumber used in commerce. It extends across America and Eurasia south of the tundra and pushes down over the highland as far as north Africa and Mexico. It covers about 7,600,000 sq.m. of which 5,5oo,000 are true forest, and 2,100,000 are woodlands. About i,000,000 sq.m. are suitable for grazing, 40,000 sq.m. suitable for cool-weather crops and 30,00o sq.m. suitable for warm-weather crops.
Dry Forests are deciduous forests in the tropics and are often called monsoon forests. Leafless during the dry period, they have no cold rest period as does the deciduous forest of the temperate regions. These forests are usually composed of leguminous trees. The temperature is high and rainfall 3o to 4o in. during the growth period. Teak and quebracho are valuable forests of this type. The soil produces good crops of warm-weather cereals, vegetables and fruits. This forest is chiefly in Africa, South America, Australia, south-eastern Asia and Oceania, and occupies about 2,000,000 square miles.
Thorn Forest is composed of small thorn trees, vines and suc culents. The trees are leafless during the long drought periods and are found in tropical or sub-tropical regions where the annual rain fall is from ro to 20 in. Legumes, cacti, euphorbias and lilies are important. This area is unfavourable to primitive man and to ani mals, but produces gums, fruits, rubber and tanbark. It has no value agriculturally without irrigation, and covers about 330,000 sq.m. in Africa, South America, Mexico, Australia and the dryer portions of Asia.
Sclerophyll Brushland is a forest of small trees or a brushland with evergreen sclerophylls ranging from minute ericas to tree-like proteas, oaks and cherries. Botanically it is extremely variable.
The temperature seldom falls below 26° F; rainfall is from 20 to 35 in. annually, and there is a drought period of three to five months. It is an unfavourable habitat for man and animals under natural conditions, but under cultivation it is most. favourable for the production of citrus and deciduous fruits and cereals, alfalfa and vegetables. This forest covered about i,foo,000 sq.m. chiefly in the Mediterranean region, Cape Province, south-western Aus tralia, central Chile and California.
The Tall Grass Savanna, known as Low Veld or Tree Steppe, consists of grasses from three to five ft. high with trees i o to 3o ft. high scattered through. The grasses are chiefly andropogons and the trees legumes. The temperature is tropical or sub tropical with rainfall of 3o to 8o in. It is excellent grazing land. It is a favourable home for primitive man and for civilized man, with rich agricultural lands producing cattle and cool or warm weather cereals and vegetables. It covers a world area of about 3,900,00o sq.m. in South America, Africa, India and Australia.
Tall Grass, the prairie of North America, the pampas of South America, and the high veld of South Africa, are luxuriant, pure grasslands of blue-stems (Andropogon), spear-grass (Stipa) and wheat-grass (Agropyron). The climate is temperate; rainfall is from 20 to 4o in. annually, and the soil is unusually deep and rich, forming a true chernozyom in the dryer portion. There is a short drought rest period, followed by a long, cold rest period. It is excel lent grazing land ; it supported great herds of wild game, and later cattle and horses, which have given way to its utilization as the richest grain fields of the world. It occupied about i,58o,000 sq.m. in the United States (chiefly east of the tooth meridian), Uruguay and the Argentine, south Russia and Siberia, Rumania and Hun gary, South Africa and Australia.