Many other plants in these areas are characterized by having a number of adaptations that conserve water, such as deep roots, reduced foliage, and water-storing stems. Seed plants in the desert produce seeds that can remain in dormancy for extended periods between rains. To reduce water loss and conserve energy, many desert animals like the fennec fox are nocturnal and burrow during the day.
Fennec fox : Fennec foxes live in the deserts of Northern Africa and have large ears for heat dissipation during the day. They stay in burrows during the day and are mostly active at night. Desert plants : To reduce water loss, many desert plants have tiny leaves or no leaves at all.
The leaves of ocotillo Fouquieria splendens , shown here in the Sonora Desert near Gila Bend, Arizona, appear only after rainfall and then are shed.
The chaparral, also called the scrub forest, is found in California, along the Mediterranean Sea, and along the southern coast of Australia. The annual rainfall in this biome ranges from 65 cm to 75 cm Due to the very dry summers, many chaparral plants are dormant during that season. The chaparral vegetation is dominated by shrubs and is adapted to periodic fires, with some plants producing seeds that only germinate after a hot fire.
The ashes left behind after a fire are rich in nutrients, such as nitrogen, that fertilize the soil and promote plant regrowth.
Chaparrals : The chaparral, or scrub forest, is dominated by shrubs adapted to periodic fires. Some plants produce seeds that only germinate after a hot fire. Temperate grasslands are areas with low annual precipitation, fluctuating seasonal temperatures, and few trees. Temperate grasslands are found throughout central North America, where they are also known as prairies, and within Eurasia, where they are known as steppes.
Temperate grasslands have pronounced annual fluctuations in temperature, with hot summers and cold winters. The annual temperature variation produces specific growing seasons for plants. Plant growth is possible when temperatures are warm enough and when ample water is available to sustain it, which typically occurs in the spring, summer, and fall.
During much of the winter, temperatures are low and water, which is stored in the form of ice, is not available for plant growth. Temperate grasslands in New Zealand : Temperate tussock grasslands form expansive and distinctive landscapes in the South Island and to a lesser extent in the central plateau region of the North Island of New Zealand. Annual precipitation ranges from 25 cm to 75 cm 9. Because of relatively-lower annual precipitation in temperate grasslands, there are few trees, except for those found growing along rivers or streams.
The dominant vegetation tends to consist of grasses; some prairies sustain populations of grazing animals. The vegetation is very dense and the soils are fertile because the subsurface of the soil is packed with the roots and rhizomes underground stems of these grasses, which anchor plants into the ground and replenish the organic material humus in the soil when they die and decay.
Fires, mainly caused by lightning, are a natural disturbance in temperate grasslands. When fire is suppressed, the vegetation eventually converts to scrub and dense forests.
Often, the restoration or management of temperate grasslands requires the use of controlled burns to suppress the growth of trees and maintain the grasses. Burning causes new grass to grow, which brings back the grazing animals. Mites, insect larvae, nematodes and earthworms inhabit deep soil, which can reach 6 meters 20 ft underground in undisturbed grasslands on the richest soils of the world. These invertebrates, along with symbiotic fungi, extend the root systems, break apart hard soil, enrich it with urea and other natural fertilizers, trap minerals and water, and promote growth.
Some types of fungi make the plants more resistant to insect and microbial attacks. Grasslands also are home to a vast variety of mammals, reptiles, birds, and insects. Grazing animals : The American bison Bison bison , more commonly called the buffalo, is a grazing mammal that once populated American prairies in huge numbers. Temperate forests are characterized by fluctuating seasonal temperatures and constant-but-moderate rainfall. This biome is found throughout mid-latitude regions.
Precipitation is relatively constant throughout the year, ranging between 75 cm and cm Because of the moderate, annual rainfall and temperatures, deciduous trees are the dominant plant in this biome. Deciduous trees lose their leaves each fall, remaining leafless in the winter; thus, no photosynthesis occurs during the dormant winter period. Each spring, new leaves appear as the temperature increases. Because of the dormant period, the net primary productivity of temperate forests is less than that of tropical wet forests.
In addition, temperate forests show less diversity of tree species than do tropical wet forest biomes. Deciduous trees : Deciduous trees, those that lose their leaves seasonally, are the dominant plant in the temperate forest.
The trees of the temperate forests leaf out and shade much of the ground; however, this biome is more open than tropical wet forests because trees in the temperate forests do not grow as tall as the trees in tropical wet forests. The soils of the temperate forests are rich in inorganic and organic nutrients due to the thick layer of leaf litter on forest floors.
As this leaf litter decays, nutrients are returned to the soil. The leaf litter also protects soil from erosion, insulates the ground, and provides habitats for invertebrates such as the pill bug or roly-poly, Armadillidium vulgare and their predators, such as the red-backed salamander Plethodon cinereus. The leaf litter is home to invertebrates such as the pill bug or roly-poly, Armadillidium vulgare and their predators, including the red-backed salamander Plethodon cinereus.
Pileated woodpeckers depend upon dead or dying trees as a source of food and for constructing their nests, and many migratory birds, such as the spring warblers, time their arrival to coincide with the opening of the tree canopy, which provides the insects that are their principal food sources for raising young.
Many well-known animals are found in temperate deciduous forests including squirrels, deer, and bears. The top predators in deciduous forest were once wolves and cougars, but their populations have been in decline.
White-tailed deer : Deer such as the white-tailed deer of North America are common inhabitants of temperate forests. The boreal forest is characterized by coniferous trees, while the arctic tundra is characterized by permanently frozen soils. This biome has cold, dry winters and short, cool, wet summers. The summers, while short, are generally warm and humid. The annual precipitation, from 40 cm cm Little evaporation occurs because of the cold temperatures.
The long and cold winters in the boreal forest have led to the predominance of cold-tolerant, cone-bearing plants. These are evergreen, coniferous trees such as pines, spruces, and firs, which retain their needle-shaped leaves year-round.
Evergreen trees can photosynthesize earlier in the spring than can deciduous trees because less energy from the sun is required to warm a needle-like leaf than a broad leaf. This benefits evergreen trees, which grow faster than deciduous trees in the boreal forest. In addition, soils in boreal forest regions tend to be acidic, with little available nitrogen. Leaves are a nitrogen-rich structure that deciduous trees must produce yearly.
Therefore, coniferous trees that retain nitrogen-rich needles may have a competitive advantage over the broad-leafed deciduous trees. The net primary productivity of boreal forests is lower than that of temperate forests and tropical wet forests. The aboveground biomass of boreal forests is high because these slow-growing tree species are long-lived, accumulating standing biomass over time.
Plant species diversity is less than that seen in temperate forests and tropical wet forests. Boreal forests lack the pronounced elements of the layered forest structure seen in tropical wet forests. The structure of a boreal forest is often only a tree layer and a ground layer. When conifer needles are dropped, they decompose more slowly than do broad leaves; therefore, fewer nutrients are returned to the soil to fuel plant growth.
Plants in the boreal forest : The boreal forest taiga has low-lying plants and conifer trees; it often consists of only a tree layer and a ground layer. In some cases, the annual rainfall can be as low as 2 cm 0. The low species diversity of this biome is closely related to its low and unpredictable precipitation.
Despite the relatively low diversity, desert species exhibit fascinating adaptations to the harshness of their environment. Very dry deserts lack perennial vegetation that lives from one year to the next; instead, many plants are annuals that grow quickly and reproduce when rainfall does occur, then they die. Perennial plants in deserts are characterized by adaptations that conserve water: deep roots, reduced foliage, and water-storing stems Figure 6 below. Seed plants in the desert produce seeds that can lie dormant for extended periods between rains.
Most animal life in subtropical deserts has adapted to a nocturnal life, spending the hot daytime hours beneath the ground. The Namib Desert is the oldest on the planet, and has probably been dry for more than 55 million years.
It supports a number of endemic species species found only there because of this great age. For example, the unusual gymnosperm Welwitschia mirabilis is the only extant species of an entire order of plants. There are also five species of reptiles considered endemic to the Namib. In addition to subtropical deserts there are cold deserts that experience freezing temperatures during the winter and any precipitation is in the form of snowfall. The chaparral is also called scrub forest and is found in California, along the Mediterranean Sea, and along the southern coast of Australia Figure 7 below.
The annual rainfall in this biome ranges from 65 cm to 75 cm Summers are very dry and many chaparral plants are dormant during the summertime. The chaparral vegetation is dominated by shrubs and is adapted to periodic fires, with some plants producing seeds that germinate only after a hot fire.
The ashes left behind after a fire are rich in nutrients like nitrogen and fertilize the soil, promoting plant regrowth. Fire is a natural part of the maintenance of this biome. Temperate grasslands are found throughout central North America, where they are also known as prairies, and in Eurasia, where they are known as steppes Figure 8 below.
Temperate grasslands have pronounced annual fluctuations in temperature with hot summers and cold winters. The annual temperature variation produces specific growing seasons for plants. Plant growth is possible when temperatures are warm enough to sustain plant growth, which occurs in the spring, summer, and fall.
Annual precipitation ranges from Temperate grasslands have few trees except for those found growing along rivers or streams. The dominant vegetation tends to consist of grasses. The treeless condition is maintained by low precipitation, frequent fires, and grazing. The vegetation is very dense and the soils are fertile because the subsurface of the soil is packed with the roots and rhizomes underground stems of these grasses.
The roots and rhizomes act to anchor plants into the ground and replenish the organic material humus in the soil when they die and decay. Fires, which are a natural disturbance in temperate grasslands, can be ignited by lightning strikes. It also appears that the lightning-caused fire regime in North American grasslands was enhanced by intentional burning by humans.
When fire is suppressed in temperate grasslands, the vegetation eventually converts to scrub and dense forests. Often, the restoration or management of temperate grasslands requires the use of controlled burns to suppress the growth of trees and maintain the grasses. This biome is found throughout mid-latitude regions. Temperatures range between —30 o C and 30 o C —22 o F to 86 o F and drop to below freezing on an annual basis.
These temperatures mean that temperate forests have defined growing seasons during the spring, summer, and early fall. Precipitation is relatively constant throughout the year and ranges between 75 cm and cm Deciduous trees are the dominant plant in this biome with fewer evergreen conifers.
Deciduous trees lose their leaves each fall and remain leafless in the winter. Thus, little photosynthesis occurs during the dormant winter period. Each spring, new leaves appear as temperature increases. Because of the dormant period, the net primary productivity of temperate forests is less than that of tropical rainforests. In addition, temperate forests show far less diversity of tree species than tropical rainforest biomes. The trees of the temperate forests leaf out and shade much of the ground.
However, more sunlight reaches the ground in this biome than in tropical rainforests because trees in temperate forests do not grow as tall as the trees in tropical rainforests. The soils of the temperate forests are rich in inorganic and organic nutrients compared to tropical rainforests.
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