Untitled

• Eight major terrestrial biomes exist: tropical rainforests, savannas, subtropical deserts, chaparral, temperate grasslands, temperate forests, boreal forests, and Arctic tundra.
• Biomes are distinguished by characteristic temperature ranges and precipitation amounts that affect the vegetation and animal life thriving in those areas.
• The same biome can occur in geographically distinct areas if their climates are similar.

Tropical Rainforests

• Located in equatorial regions and are the most biodiverse terrestrial biome.
• Biodiversity is extraordinarily threatened by logging and deforestation for agriculture.
• Called nature's pharmacy due to its potential for new drugs hidden in diverse organisms,
• Vegetation is characterized by plants having spreading roots and broad leaves that fall throughout the year.
• Temperature ranges from 20°C to 34°C (68°F to 93°F).
• Consistent daily sunlight of 11-12 hours provides high primary productivity due to little temperature seasonality that promotes year-round plant growth.
• Annual rainfall ranges from 125 to 660 cm (50-200 in).
• Distinct habitats are formed for animals via vertical layering of vegetation.
• There is a sparse layer of plants and decaying plant matter on the forest floor.
• Above that is an understory of short, shrubby foliage.
• Above the understory is topped by a closed upper canopy of branches and leaves from a layer of trees.
• Some additional trees emerge through this closed upper canopy, providing diverse habitats for plants, animals, and other organisms.

Savannas

• Grasslands with scattered trees that are located in Africa, South America, and northern Australia.
• Savannas are hot, tropical areas that have temperatures averaging from 24°C -29°C (75°F −84°F) and an annual rainfall of 51–127 cm (20–50 in).
• They have an extensive dry season and consequent fires leading to dominating grasses, and herbaceous flowering plants.
• Plants have evolved well-developed root systems that quickly re-sprout due to fire being an important source of disturbance.

Subtropical Deserts

• Exist between 15° and 30° north and south latitude and are centered on the Tropic of Cancer and the Tropic of Capricorn.
• The deserts are frequently located on the downwind or lee side of mountain ranges, which create a rain shadow.
• Extremely dry due to high-pressure, dry air descending at those latitudes and evaporation exceeding precipitation.
• Daytime soil surface temperatures can rise above 60°C (140°F) and nighttime temperatures approaching 0°C (32°F).
• Characterized by low annual precipitation of less than 30 cm (12 in) with little monthly variation and unpredictable rainfall patterns.
• Low species diversity is related to its low and unpredictable precipitation patterns.
• Desert species have adaptations to the environment such as annuals that grow and reproduce quickly when it rains, and then die.
• Perennial plants have adaptations that conserve water via deep roots, reduced foliage, and water-storing stems.
• Seed plants produce seeds that can lie dormant for extended periods between rains.
• Animal life in subtropical deserts has adapted to a nocturnal life, to which it spends daytime hours beneath the ground.
• Cold deserts experience freezing temperatures during the winter and precipitation occurs as snowfall.

Chaparral

• Also called scrub forest and is found in California, along the Mediterranean Sea, and along the southern coast of Australia.
• Annual rainfall ranges from 65 cm to 75 cm (25.6–29.5 in), with most of the rain falling in the winter.
• Summers are very dry and many chaparral plants are dormant in the summertime.
• Dominated by shrubs and adapted with the vegetation to periodic fires, along with some plants that produce seeds that germinate only post-fire.
• Ashes are rich in nutrients like nitrogen promoting plant regrowth which makes fire a natural part of the biome's maintenance.

Temperate Grasslands

• Found throughout central North America, where they are also known as prairies, and as steppes in Eurasia.
• There are pronounced annual fluctuations in temperature with hot summers and cold winters.
• Temperature variation produces specific growing seasons for plants with growth possible in the spring, summer, and fall.
• Annual precipitation ranges from 25.4 cm to 88.9 cm (10-35 in).
• Consist of few trees with dominant vegetation that consists of grasses.
• Treeless conditions are caused by low precipitation, frequent fires, and grazing.
• Vegetation is dense, soils are fertile, with roots that anchor plants and replenish the organic material (humus) in the soil.
• Fires, a natural disturbance, can be ignited by lightning strikes or enhanced by intentional burning by humans.
• Fire suppression in grasslands leads to scrub and dense forests while restoration or management requires controlled burns to suppress tree growth and maintain grasses.

Temperate Forests

• Are found in eastern North America, Western Europe, Eastern Asia, Chile, and New Zealand.
• Biome is found throughout mid-latitude regions.
• Temperatures range between -30°C and 30°C (−22°F to 86°F) and drop below freezing on an annual basis.
• Defined growing seasons occur during the spring, summer, and early fall due to the varying temperatures
• Precipitation is relatively constant throughout the year and ranges between 75 cm and 150 cm (29.5-59 in).
• Deciduous trees are the dominant plant with fewer evergreen conifers where deciduous trees that lose their leaves each fall and remain leafless in the winter.
• Photosynthesis experiences a dormant winter period and new leaves appear each spring as temperatures increase.
• The net primary productivity is less than that of tropical rainforests because of the dormant period that leads to less diversity of tree species than in the tropical rainforest.
• More sunlight reaches the ground in this biome which has soils richer in inorganic and organic nutrients with a thick layer of leaf litter on forest floors.
• Leaf litter protects soil from erosion, insulates the ground, and provides habitats for invertebrates and their predators.

Boreal Forests

• The forest is found roughly between 50°and 60° north latitude across most of Canada, Alaska, Russia, and northern Europe.
• Above a certain elevation in mountain ranges throughout the Northern Hemisphere.
• Cold, dry winters and short, cool, wet summers are prominent within.
• Annual precipitation is from 40 cm to 100 cm (15.7-39 in) and is usually in the form of snow with relatively little evaporation occurs because of cool temperatures exist.
• Long, cold winters have led to cold-tolerant cone-bearing plants like pines, spruce, and fir, which retain their needle-shaped leaves year-round.
• Evergreen trees can photosynthesize earlier because less energy from the Sun is required to warm a needle-like leaf.
• Soils tend to be acidic with little available nitrogen.
• Coniferous trees retain nitrogen-rich needles given that boreal forests lack the layered forest structure with only a tree layer and a ground layer, meaning that nutrients return to the soil when conifer needles drop.

Arctic Tundra

• Lies north of the subarctic boreal forests and is throughout the Arctic regions of the Northern Hemisphere.
• Exists at high elevations above the tree line on mountains.
• Average winter temperature is -34°C (−29.2°F) and the average summer temperature is 3°C-12°C (37°F -52°F).
• Plants have a short growing season of approximately 50-60 days and experiences of almost 24 hours of daylight.
• Annual precipitation is low (15–25 cm or 6–10 in) with little annual variation and evaporation due to cold temperatures.
• Plants are generally low to the ground and include low shrubs, grasses, lichens, and small flowering plants.
• Consists of little species diversity, low net primary productivity, and low above-ground biomass.
• Soils may remain in a perennially frozen state called permafrost.
• Permafrost makes it for roots to penetrate far into the soil and slows decay of organic matter, which inhibits the release of nutrients.
• Melting of permafrost during the brief summer provides water for a burst of productivity, permitting the ground to be covered with plants or lichens.