Temperate rainforest
Temperate rainforests develop under climatic regimes characterized by mild winters and an
abundance of precipitation. Because these systems are too moist to support regular, catastrophic
wildfires, they often develop into old-growth forests, dominated by coniferous trees of mixed
age and species composition. Individual trees can be extremely large, and in extreme cases can
be more than 1,000 years old. Common trees of this biome are species of Douglas fir, hemlock,
cedar, redwood, spruce, and yellow cypress. In North America, temperate rainforests are best
developed on the humid west coast.
deciduous forest
Forests dominated by species-rich mixtures of broad-leaved trees occur in relatively moist,
temperate climates. Because these forests occur in places where the winters can be cold, the
foliage of most species is seasonally deciduous, meaning that all leaves are shed each autumn
and re-grown in the springtime. Common trees of this forest biome in North America are
species of ash, basswood, birch, cherry, chestnut, dogwood, elm, hickory, magnolia, maple,
oak, tulip-tree, and walnut, among others. These various tree species segregate into intergrading
communities on the basis of site variations of soil moisture, fertility, and air temperature.
Tundra
Tundra is a treeless biome occurring in areas with cold climates and a short growing season.
Alpine tundra occurs at high altitudes on mountains, while arctic tundra occurs at high
latitudes. Most tundras receive very small inputs of water as precipitation, but nevertheless
their soil may be moist or wet because there is little evaporation in such cold climates, and
deep drainage may be prevented by frozen soil. The coldest, most northern, high-arctic tundras
are very unproductive and dominated by long-lived but short-statured plants, typically less than
1.97-3.94 in (5-10 cm) tall. Low-arctic tundras are dominated by shrubs as tall as 3.28 ft (1 m),
while wet sites develop relatively productive meadows of sedge, cotton-grass, and grass. In
North America, arctic tundras can support small densities of mammalian herbivores such
as caribou and muskox (although during migration these animals can occur in locally large
densities), and even smaller numbers of their predators, such as wolves.
savanna
Savannas are dominated by grasses and other herbaceous plants, but they also have scattered
shrub and tree-sized woody plants, which form a very open canopy. Tropical grasslands and
savannas can support a great seasonal abundance of large, migratory mammals, as well as
substantial populations of resident animals. This is especially true of savannas in Africa, where
this biome supports a very diverse assemblage of large mammals, including gazelles and other
antelopes, rhinos, elephant, hippopotamus, and buffalo, and some of their predators, such as
lion, cheetah, wild dog, and hyena.
Desert
Desert is a temperate or tropical biome, commonly occurring in the center of continents, and in
the rain shadows of mountains. The distribution of this biome is determined by the availability
of water, generally occurring where there is less than 9.9 in (25 cm) of precipitation per year.
Not surprisingly, the productivity of desert ecosystems is strongly influenced by the availability
of water. The driest deserts support almost no plant productivity, while less-dry situations may
support communities of herbaceous, succulent, and annual plants, and somewhat moister places
will allow a shrub-dominated ecosystem to develop.
tropical rainforest
This biome occurs under tropical climates with abundant precipitation and no seasonal drought.
Because wildfire and other types of catastrophic disturbance are uncommon in this sort of
climate regime, tropical rainforests usually develop into old-growth forests. As such, they
contain a diverse size range of trees, a great richness of species of trees and other plants, as well
as an extraordinary diversity of animals and microorganisms. Many ecologists consider this
biome to represent the epitome of ecosystem development on land, because of the enormous
variety of species that are supported under relatively benign climatic conditions in old-growth
tropical rainforests.
Estuaries
Estuaries are a complex group of coastal ecosystems that are semi-enclosed, but open to the sea.
Estuaries display characteristics of both marine and freshwater biomes, because they typically
have substantial inflows of fresh water from the nearby land, along with large fluctuations
of salt water resulting from tidal cycles. Examples of estuaries include coastal bays, sounds,
river mouths, salt marshes, and tropical mangrove forests. Because their large water-borne
inputs of terrestrial nutrients are partially retained by their semi-enclosed water circulation,
estuaries are highly productive ecosystems. Estuaries provide important habitat for juvenile
stages of many commercially important species of fish, shellfish, and crustaceans, and they are
often characterized as "nursery" habitat for these species.
Taiga, is an extensive northern biome occurring in moist climates with cold winters. The boreal
forest is dominated by coniferous trees, especially species of fir, larch, pine, and spruce. Some
broad-leaved, angiosperm trees are also important in the boreal forest, especially species of
aspen, birch, poplar, and willow. Usually, particular stands of boreal forest are dominated by
only one or several species of trees. Most regions of boreal forest are subject to periodic events
of catastrophic disturbance, most commonly caused by wildfire and sometimes by insects, such
as spruce budworm, that kill trees through intensive defoliation. Montane forests, also
dominated by conifers and similar in structure to the boreal forest, can occur at sub-alpine
altitudes on mountains in southerly latitudes
Grassland
These grasslands occur under temperate climatic regimes that are intermediate to those that
support forest and desert. In the temperate zones, grasslands typically occur where rainfall is 9.924 in (25-60 cm) per year. Grasslands in North America are called prairie (they are often called
steppe in Eurasia), and this biome occupies vast regions in the interior. The prairie is often divided
into three types according to height of the dominant vegetation—tall-grass, mixed-grass, and shortgrass. The once extensive tall-grass prairie is dominated by various Biomes along 87 degrees west
longitude and along 0 degrees longitude. Illustration by Hans & Cassidy. Courtesy of Gale
Group. species of grasses and herbaceous broad leaved plants such as sunflowers and blazing stars,
some as tall as 9.8-13.1 ft (3-4 m). Fire was an important natural factor that prevented much of the
tall-grass prairie from developing into an open forest. The tall-grass prairie is now an endangered
natural ecosystem, because it has been almost entirely converted to agriculture. The mixed-grass
prairie occurs where rainfall is less, and it supports shorter species of grasses and other herbaceous
plants. The short-grass prairie has even less precipitation, and is subject to unpredictable years of
severe drought