Figure 1. Each of the world eight major biomes is differentiated by properties temperatures and amount of precipitation. Polar ice caps and mountains are also shown.

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There space eight significant terrestrial biomes: tropic rainforests, savannas, subtropical deserts, chaparral, warm grasslands, warm forests, boreal forests, and also Arctic tundra. Biomes are large-scale environments that are distinguished by properties temperature varieties and amounts of precipitation. These 2 variables affect the types of vegetation and animal life that have the right to exist in those areas. Due to the fact that each biology is characterized by climate, the very same biome can take place in geographically distinct locations with similar climates (Figures 1 and also 2).

Figure 2. Precipitation and temperature are the 2 most vital climatic variables that identify the type of biology in a specific location. Credit: “Climate influence on terrestrial biome” through Navarras is in the general public Domain, CC0

Tropical rainforests are uncovered in equatorial areas (Figure 1) space the most biodiverse terrestrial biome. This biodiversity is under particularly threat primarily through logging and deforestation for agriculture. Tropical rainforests have also been described as nature’s pharmacy because of the potential for new drugs that is largely covert in the chemicals produced by the large diversity the plants, animals, and also other organisms. The vegetation is identified by plants with dispersing roots and wide leaves that autumn off throughout the year, uneven the tree of deciduous woodlands that lose their leaves in one season.

The temperature and also sunlight profiles of dry rainforests are stable in comparison to other terrestrial biomes, with typical temperatures varying from 20oC to 34oC (68oF to 93oF). Month-to-month temperatures space relatively constant in tropical rainforests, in comparison to forests farther from the equator. This absence of temperature seasonality leads to year-round plant development rather than just seasonal growth. In comparison to various other ecosystems, a regular daily amount of sunlight (11–12 hrs per work year-round) provides more solar radiation and also therefore an ext opportunity for main productivity.

The yearly rainfall in tropical rainforests varieties from 125 to 660 cm (50–200 in) with significant seasonal variation. Tropic rainforests have wet month in i m sorry there have the right to be much more than 30 centimeter (11–12 in) that precipitation, as well as dry months in i m sorry there are fewer than 10 centimeter (3.5 in) the rainfall. However, the driest month that a tropic rainforest have the right to still exceed the annual rainfall that some various other biomes, such together deserts.Tropical rainforests have actually high net primary productivity due to the fact that the annual temperatures and precipitation values support rapid plant growth. However, the high amounts of rainfall leaches nutrients from the soils of this forests.

Figure 3. Varieties diversity is really high in tropical wet forests, such as these woodlands of Madre de Dios, Peru, close to the Amazon River. (credit: Roosevelt Garcia)

Tropical rainforests are identified by upright layering that vegetation and also the development of distinctive habitats for pets within each layer. On the woodland floor is a sporadic layer the plants and decaying tree matter. Over that is one understory of short, shrubby foliage. A class of trees rises above this understory and also is topped through a closed top canopy—the uppermost overhead class of branches and leaves. Some added trees arise through this closed upper canopy. This layers provide diverse and complicated habitats because that the selection of plants, animals, and other organisms. Many species of pets use the variety of plants and also the complex structure the the tropic wet woodlands for food and shelter. Some organisms live number of meters above ground, hardly ever descending come the woodland floor.

Figure 4. A MinuteEarth video about exactly how trees produce rainfall, and vice versa.

Savannas room grasslands with scattered trees and are found in Africa, south America, and northern Australia (Figure 4 below). Savannas space hot, tropical locations with temperature averaging native 24oC –29oC (75oF –84oF) and also an yearly rainfall that 51–127 centimeter (20–50 in). Savannas have comprehensive dry season and consequent fires. Together a result, there room relatively couple of trees scattered in the grasses and also forbs (herbaceous flowering plants) that conquer the savanna. Because fire is vital source the disturbance in this biome, tree have progressed well-developed root systems that allow them to conveniently re-sprout after a fire.

Figure 5. Back savannas are overcame by grasses, tiny woodlands, such together this one in mount Archer nationwide Park in Queensland, Australia, might dot the landscape. (credit: “Ethel Aardvark”/Wikimedia Commons)

Subtropical deserts exist in between 15o and 30o north and also south latitude and also are focused on the Tropic that Cancer and also the Tropic the Capricorn (Figure 6 below). Deserts are frequently located on the downwind or lee next of mountain ranges, which create a rain zero after prevailing winds drop your water contents on the mountains. This is typical of the north American deserts, such as the Mohave and Sonoran deserts. Deserts in other regions, such together the Sahara Desert in northern Africa or the Namib Desert in southwestern Africa are dry due to the fact that of the high-pressure, dried air descending at those latitudes. Subtropical deserts are an extremely dry; evaporation frequently exceeds precipitation. Subtropical warm deserts deserve to have daytime soil surface ar temperatures over 60oC (140oF) and nighttime temperature approaching 0oC (32oF). Subtropical deserts are identified by low annual precipitation of fewer than 30 cm (12 in) with tiny monthly variation and lack that predictability in rainfall. Part years might receive tiny amounts of rainfall, when others obtain more. In part cases, the annual rainfall deserve to be as low as 2 cm (0.8 in) in subtropical deserts located in main Australia (“the Outback”) and northern Africa.

Figure 6. A MinuteEarth video about the global climate trends which lead to subtropical deserts.

The low varieties diversity of this biology is closely related to its low and also unpredictable precipitation. Regardless of the relatively low diversity, desert types exhibit fascinating adaptations to the harshness of your environment. An extremely dry deserts absence perennial vegetation that resides from one year come the next; instead, countless plants room annuals that prosper quickly and reproduce as soon as rainfall go occur, climate they die. Perennial tree in deserts are identified by adaptations that conserve water: deep roots, reduced foliage, and also water-storing trunk (Figure 6 below). Seed plants in the desert produce seeds that have the right to lie dormant for extended periods in between rains. Most animal life in subtropical deserts has adjusted to a nocturnal life, security the warm daytime hrs beneath the ground. The Namib Desert is the earliest on the planet, and has most likely been dried for more than 55 million years. It supports a number of endemic types (species discovered only there) because of this an excellent age. Because that example, the unexplained gymnosperm Welwitschia mirabilis is the just extant species of whole order the plants. There are additionally five types of reptiles thought about endemic to the Namib.

In addition to subtropical deserts there space cold deserts that experience freezing temperatures during the winter and also any precipitation is in the kind of snowfall. The largest of these deserts room the Gobi Desert in northern China and southern Mongolia, the Taklimakan Desert in west China, the Turkestan Desert, and the good Basin Desert the the unified States.

Figure 7. Many desert plants have actually tiny leaves or no leaves at all to alleviate water loss. The leaves of ocotillo, presented here in the Chihuahuan Desert in huge Bend nationwide Park, Texas, show up only after rainfall and then are shed. (credit “bare ocotillo”: “Leaflet”/Wikimedia Commons)

The chaparral is also called scrub forest and also is uncovered in California, along the Mediterranean Sea, and along the southern coast of Australia (Figure 7 below). The annual rainfall in this biome varieties from 65 cm to 75 cm (25.6–29.5 in) and also the bulk of the rain drops in the winter. Summers are very dry and many chaparral plants are dormant during the summertime. The chaparral vegetation is conquered by shrubs and also is adjusted to regular fires, through some plants producing seeds that germinate only after a hot fire. The ashes left behind after ~ a fire room rich in nutrients choose nitrogen and also fertilize the soil, cultivating plant regrowth. Fire is a natural part of the maintain of this biome.

Figure 8. The chaparral is overcame by shrubs. (credit: Miguel Vieira)

Temperate grasslands are uncovered throughout main North America, where they are also known together prairies, and in Eurasia, whereby they are well-known as steppes (Figure 8 below). Temperate grasslands have actually pronounced yearly fluctuations in temperature with warm summers and also cold winters. The yearly temperature variation produces certain growing seasons for plants. Plant expansion is feasible when temperatures are warm enough to sustain tree growth, which wake up in the spring, summer, and also fall.

Annual precipitation ranges from 25.4 centimeter to 88.9 cm (10–35 in). Temperate grasslands have few trees except for those found growing along rivers or streams. The leading vegetation has tendency to consist of grasses. The treeless problem is preserved by low precipitation, regular fires, and grazing. The vegetation is really dense and also the soils space fertile due to the fact that the subsurface of the floor is packed with the roots and also rhizomes (underground stems) of these grasses. The roots and rhizomes act to anchor plants into the ground and also replenish the organic product (humus) in the soil as soon as they die and decay.

Figure 9. The American bison (Bison bison), an ext commonly referred to as the buffalo, is a grazing mammal that once lived in American prairies in substantial numbers. (credit: Jack Dykinga, USDA ARS)

Fires, which are a natural disturbance in temperate grasslands, have the right to be ignited by lightning strikes. It also appears that the lightning-caused fire program in north American grasslands was intensified by intentional burning by humans. When fire is suppressed in temperate grasslands, the vegetation ultimately converts come scrub and dense forests. Often, the restoration or monitoring of temperate grasslands calls for the use of controlled burns to suppress the growth of trees and maintain the grasses.

Temperate forests are the most usual biome in eastern North America, western Europe, east Asia, Chile, and new Zealand (Figure 9 below). This biome is discovered throughout mid-latitude regions. Temperatures selection between –30oC and also 30oC (–22oF to 86oF) and also drop to below freezing ~ above an annual basis. These temperatures median that temperate woodlands have defined growing seasons during the spring, summer, and early fall. Precipitation is relatively constant throughout the year and also ranges in between 75 cm and 150 cm (29.5–59 in).

Deciduous trees room the leading plant in this biome with fewer evergreen conifers. Deciduous trees lose their leaves each fall and also remain leafless in the winter. Thus, little photosynthesis occurs during the dormant winter period. Every spring, brand-new leaves show up as temperature increases. Due to the fact that of the dormant period, the net primary productivity of temperate forests is much less than that of dry rainforests. In addition, pleasant forests display far less diversity the tree types than tropical rainforest biomes.

The trees of the temperate forests leaf out and shade lot of the ground. However, much more sunlight get the soil in this biome than in tropic rainforests because trees in temperate forests do not grow as tall together the tree in dry rainforests. The soils of the temperate forests are well-off in inorganic and organic nutrients compared to dry rainforests. This is because of the special layer of sheet litter on woodland floors and reduced leaching of nutrient by rainfall. Together this sheet litter decays, nutrient are went back to the soil. The leaf litter additionally protects soil from erosion, insulates the ground, and also provides habitats for invertebrates and also their predators.

Figure 10. Deciduous trees room the leading plant in the pleasant forest. (credit: Oliver Herold)

The boreal forest, likewise known together taiga or coniferous forest, is found roughly between 50oand 60o north latitude across most that Canada, Alaska, Russia, and northern Europe (Figure 10 below). Boreal woodlands are likewise found above a certain elevation (and listed below high elevations where trees cannot grow) in hill ranges transparent the north Hemisphere. This biome has cold, dry winters and also short, cool, wet summers. The annual precipitation is from 40 cm to 100 cm (15.7–39 in) and usually bring away the type of snow; reasonably little evaporation occurs since of the cool temperatures.

The long and cold winters in the boreal forest have brought about the advantage of cold-tolerant cone-bearing plants. These are evergreen coniferous trees choose pines, spruce, and fir, which retain your needle-shaped leaves year-round. Evergreen trees deserve to photosynthesize earlier in the spring 보다 deciduous trees because less power from the sun is compelled to warmth a needle-like leaf than a vast leaf. Evergreen trees grow much faster than deciduous tree in the boreal forest. In addition, soils in boreal woodland regions have tendency to it is in acidic with small available nitrogen. Leaves room a nitrogen-rich structure and also deciduous trees must create a new set of this nitrogen-rich structures each year. Therefore, coniferous trees the retain nitrogen-rich needles in a nitrogen limiting atmosphere may have had actually a competitive benefit over the broad-leafed deciduous trees.

Figure 11. The boreal woodland (taiga) has low lie plants and also conifer trees. (credit: L.B. Brubaker, NOAA)

The net primary productivity of boreal forests is reduced than the of warm forests and also tropical wet forests. The aboveground biomass of boreal woodlands is high since these slow-growing tree varieties are long-lived and also accumulate stand biomass over time. Types diversity is much less than that checked out in temperate forests and also tropical rainforests. Boreal forests lack the layered woodland structure seen in tropical rainforests or, come a lesser degree, warm forests. The structure of a boreal forest is regularly only a tree layer and also a ground layer. Once conifer needles are dropped, castle decompose an ext slowly than wide leaves; therefore, fewer nutrients are returned to the floor to fuel tree growth.

The Arctic tundra lies north of the subarctic boreal forests and is located throughout the Arctic areas of the north Hemisphere. Tundra additionally exists in ~ elevations above the tree heat on mountains. The median winter temperature is –34°C (–29.2°F) and the average summer temperature is 3°C–12°C (37°F –52°F). Tree in the Arctic tundra have a brief growing season of roughly 50–60 days. However, during this time, there are practically 24 hours of daylight and plant expansion is rapid. The annual precipitation the the Arctic tundra is short (15–25 centimeter or 6–10 in) with little annual variation in precipitation. And, together in the boreal forests, there is tiny evaporation due to the fact that of the cold temperatures.

Figure 12. Low-growing plants together lichen and grasses are typical in tundra. Credit: Nunavut tundra by Flickr: my Nunavut is licensed under CC by 2.0

Plants in the Arctic tundra are typically low come the ground and also include short shrubs, grasses, lichens, and small flowering plants (Figure 11 below). Over there is tiny species diversity, low net main productivity, and also low above-ground biomass. The soils of the Arctic tundra may remain in a perennially frozen state described as permafrost. The permafrost renders it impossible for roots to penetrate much into the soil and also slows the degeneration of organic matter, which inhibits the relax of nutrient from organic matter. The melting of the permafrost in the brief summer offers water for a burst of performance while temperatures and long days permit it. During the growing season, the soil of the Arctic tundra have the right to be fully covered with plants or lichens.

Suggested Supplementary Reading

HHMI. 2018. Biome Viewer. . Howard Hughes medical Institute.


Terrestrial Biomes by OpenStax is licensed under CC by 4.0.

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Environmental biology by Matthew R. Fisher is license is granted under a creative Commons Attribution 4.0 global License, other than where otherwise noted.