. Elements of ecology. Ecology. 178 Temperature the principal biotic formations, or biomes, that will be discussed more fully in Chapter 12. A synoptic view of the life zones of the world could be obtained by chartering a plane at the equator and flying toward the north pole, or toward the south pole. On such a trip, you would observe that the life zone characteristic of the equatorial region is the tropical rain forest. In this zone a wide variety of trees provides continuous shade and humid conditions for the many species of plants and ani- mals that live in and under the forest. North of th
. Elements of ecology. Ecology. 178 Temperature the principal biotic formations, or biomes, that will be discussed more fully in Chapter 12. A synoptic view of the life zones of the world could be obtained by chartering a plane at the equator and flying toward the north pole, or toward the south pole. On such a trip, you would observe that the life zone characteristic of the equatorial region is the tropical rain forest. In this zone a wide variety of trees provides continuous shade and humid conditions for the many species of plants and ani- mals that live in and under the forest. North of the tropical rain forest the flying ecologist comes to a life zone in which dry seasons alternate with rainy seasons. Farther to the north the plane passes over a belt of varying width of desert or grassland and thence over deciduous forests of oak, hickory, beech, and maple. The colder region to the north is heavily forested with spruce and other conifers that form a circumpolar life zone. At the limit of the spruce forest the plane crosses the tree line and reaches the tundra where dwarf birches or willows, scattered grasses or other flowering plants, mosses, and lichens struggle to keep alive on ground that is frozen for much of the year. Eventually all land vegetation is lost to view in a land- scape of universal snow and ice. If the plane trip had been made from the equator southward, the same general sequence of life zones would have been traversed except for the gap caused by the great expanse of the Antarctic Ocean. 13,500 ft. North UINTA MOUNTAINS TAVAPUTS PLATEAU 4,000 m 3,500 3,000 2,500 2,000 1,500 South Fig. Diagrammatic representation of the altitudinal life zones in the Uinta Basin. (Graham, 1937.) Without an airplane you may observe the same general series of life zones on a much smaller scale by climbing a mountain. If the mountain is a high one and located in the tropics, as is Mt. Popo- catepetl in Mexico with an altitude of 5448 m, the basal slopes may.
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