Terrestrial Biomes
Tropical ForestDistribution: equatorial and subequatorial regions
Precipitation: in tropical rainforests, rainfall is relatively constant (about 200-400 cm) annually. In tropical dry forests, it is highly seasonal (about 150- 200 cm) annually, with a 6-7 month dry season Temperature: high year round, averaging 25°-29°C with little seasonal variation Plants: tropical forests are vertically layerd , and competition for light is intense. Layers in rain forests include emergent trees that grow above a closed canopy, 1 or 2 layers of subcanopy trees, and layers of shrubs and herbs. There are generally fewer layers in torpical dry forests. Broadleaf evergreen trees are doninant in tropical dry forest, whereas many tropical dry forest trees drop their leaves during the dry season. Epiphytes such as bromeliads and orchids generally cover tropical forest trees but are less abundant in dry forests. Thorny shurbs and succulent plants are common in some tropical dry forests Animals: earth's tropical forests are gome to millions of species, including an estimsted 5-30 million still undescribed species of insect, spiders, and other arthropods. Animal diversity is higher in tropical forests than in any other terrestrial biome. The animals include amphibians, birds,and other reptiles, mammals and arthropods, are adapted to the vertically layered environment and are ofter inconspicuous.arthropods Human Impact: |
DesertDistribution: deserts occur in bands near 30° north and south latitude or at other latitudes in the interior of continents
Precipitation: precipitation is low and highly variable, generally less than 30 cm per year Temperature: temperature is variable seasonally and daily. Maximum air temperature in hot deserts may exceed 50°C, in cold deserts air temperature may fall below -30°C Plants: Desert landscapes are dominated by low, widely scattered vegetation. The proportion of bare ground is high compared with other terrestrial biomes. The plants include succulents, deeply rooted shrubs, and herbs that grow during infrequent moist periods. Many of the plants exhibit C4 or CAM photosynthesis. Animals: Common desert animals include snakes and lizards, scorpions, ants, beetles, migratory and resident birds, and seed eating rodents. Many of them are nocturnal. Some species survive solely on water from breaking down carbohydrates and seeds. Human Impact: Long distance transport of water and deep ground water wells have allowed humans to maintain substantial populations in deserts. |
SavannaDistribution: Equatorial and sub-equatorial regions
Precipitation: Seasonal, averages 30-50 cm per year. In dry seasons, it can last 8 to 9 months. Temperature: The savanna is warm year round. 24 to 29 degrees C, but with somewhat more seasonal variation than in tropical forests. Plants: The scattered trees found at different areas of the savanna are often thorny and have small leaves, which is in adaption to the dry seasons. Fires are also common in the dry season, and dominant plant species are fire-adapted and tolerant. Grasses and small, non-woody plants make up most of the ground cover. Animals: Large, plant eating mammals such as wildebeests and zebras, and predators including lions and hyenas are common inhabitants. Dominant herbivores are insects, especially termites. During seasonal drought, grazing mammals often migrate to parts of the savanna with more forage and scattered watering holes. Human Impact: There is evidence that the earliest humans lived in savannas. Fires set by humans may help maintain this biome. Cattle ranching and over hunting led to declines in large mammal populations. |
ChaparralDistribution: This biome occurs in mid-latitude coastal regions on several continents.
Precipitation: Precipitation is highly seasonal, with rainy winters and dry summers. Annual precipitation generally falls within the range of 30-50 cm Temperature: fall, winter, and spring are cool, with average temperatures in the range of 10-12 degrees C. Average summer temperature can reach 30 degrees C and daytime maximum temperature can exceed 0 degrees C Plants: Chaparral is dominated by shrubs and small trees, along with many kinds of grasses and herbs. Plant diversity is high, with many species confined to a specific, relatively small geographic area. Adaptations to drought include the tough evergreen leaves of woody plants, which reduce water loss. Adaptations to fire are also prominent. Some of the shrubs produce seeds that will germinate only after a hot fire; food reserves stored in their fire resistant roots enable them to re sprout quickly and use nutrients released by the fire. Animals: Native mammals include browsers, such as deer and goats, that feed on twigs and buds of woody vegetation, and a high diversity of small mammals. Chaparral areas also support many species of amphibians, birds and other reptiles, and insects Human Impact: Chaparral areas have been heavily settled and reduced through conversion to agriculture and urbanization. Humans contribute to the fires that sweep across the chaparral. |
Temperate GrasslandsDistribution: The Veldts of South Africa, the puszta if Hungary, the pampas of Argentina and Uruguay, the steppes of Russia, and the plains and prairies of central North America are examples of temperate grasslands
Precipitation: Precipitation is often high ly seasonal, with relatively dry summers. Annual precipitation generally averages between 30 and 100 cm. Periodic drought is common Temperature: Winters are generally cold, with average temperatures frequently falling well below -10 degrees C. Summers,with average temperatures often approaching 30 degree C, are hot Plants: The dominant plants are grasses and forbs, which vary in height from a few centimeters to 2 m in tall grass prarie. Many grassland plants have adaptations that help them survive periodic, protracted droughts and fires. Animals: Native mammals include large grazers such such as bison and wild horses. Temperate grasslands are also inhabited by a wide variety of burrowing mammals, such as prairie dogs in North America. Human Impact: Deep, fertile soils make temperate grasslands ideal places for agriculture, especially for growing grains. As a consequence, most grassland in North America and much of Eurasia has been converted to farmland. |
Northern Coniferous ForestDistribution: Across northern North America and Eurasia to the edge of the arctic tundra.
Precipitation: Ranges from 30 to 70 centimeters, with periodic droughts. Some coastal coniferous forests of the U.S. Pacific Northwest are temperate rain forests that may receive over 300 centimeters. Temperature: Winters are cold; summers are hot. Some areas of coniferous forest in Siberia range in temperature from -50 degrees C in winter to over 20 degrees C in summer. Plants: Dominated by cone-bearing trees, such as pine, spruce, fir, and hemlock, some of which depend on fire to regenerate. The conical shape of conifers prevents snow from accumulating and breaking their branches, and their needle- or scale-like leaves reduce water loss. The diversity of plants in shrub and herb parts of these forests is lower than in temperate broadleaf forests. Animals: Migratory birds nest in these forests as well as moose, brown bears, and Siberian tigers. Periodic outbreaks of insects that feed on the dominant trees can kill vast tracts of trees. Human Impact: Although these forests are not heavily populated by humans, northern coniferous forests are being logged at a fast rate, and the old-growth stands of these trees may soon disappear. |
Temperate Broadleaf ForestDistribution: Found mainly at mid latitudes in the Northern Hemisphere, with smaller areas in Chile, South Africa, Australia, and New Zealand
Precipitation: Precipitation can average from about 70- over 200 cm annualy. Significant amounts fall during all seasons, including summer rain and in some forests, winter snow Temperature: Winter temperatures average around 0 degrees C. Summers near 35 degrees C, are hot and humid. Plants: A mature temperate broadleaf forest has distinct vertical layers, including a closed canopy, one or two strata of under story trees, a shrub layer, and an herb layer. The dominant plants in the Northern Hemisphere are deciduous trees, which drop their leaves before winter, when low temperatures would reduce photosynthesis. Animals: In the Northern Hemisphere, many mammals hibernate in winter while many bird species migrate to warmer climates. Mammals, birds, and insects make use of all the vertical layers of the forest. Human Impact: Temperate broadleaf forest has been heavily settled on all continents. Logging and land clearing for agriculture and urban development have destroyed virtually all the original deciduous forests in North America |
TundraDistribution: Tundra covers expansive areas of the Arctic, amounting to 20% of Earth's land surface. High winds and low temperatures produce plant communities, alpine tundra, on mountaintops at all latitudes, including the tropics.
Precipitation: Averages from 20 to 60 centimeters annually in the arctic tundra, but it exceeds 100 centimeters in alpine tundra. Temperature: Winters are cold with averages in some areas below -30 degrees C. Summer temperatures are average less than 10 degrees C. Plants: Vegetation is mostly herbaceous, consisting of a mixture of mosses, grasses, and forbs, along with dwarf shrubs and trees and lichens. A permanently frozen layer of soil called permafrost restricts growth of plant roots. Animals: Large grazing musk oxen (resident), caribou and reindeer(migratory), bears wolves foxes(predators), and many bird species- migrate here for summer. Human Impact: Sparsely settled but has become the focus for mineral and oil extraction. |