BiomesWhat is a biome?

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Biotic

Examples: Plants, animals, fungi, bacteriaAbiotic

Examples: Sunlight, soil, air, temperature, light, wind, water

Climate

Precipitation

In the boxes below, write one phrase to summarize and give a definition for your biome. Then, draw a picture to help you remember the defining characteristics of that biome.

Biome Definition Drawing

Tropical Rainfores

t

Temperate

Rainforest

Deciduous Forest

Taiga

Desert

Tundra

Grasslands

Savanna

Tropical Rainforests

Tropical rain forests occur in a belt around the Earth near the equator in South America, parts of Africa and Southeast Asia. They are always heavy with humidity and are characterized by heavy rainfall (250-700cm a year). Because they are near the equator, tropical rainforests maintain a constant warm climate of about 30°C (85°F) year around, making it an ideal climate for growing plants. Tropical rainforests have the greatest amount of biological diversity (number of different species) out of any other biome.

Although the climate is ideal for plant life, the soil is usually thin and devoid (lacking in) of nutrients due to the large amount of rainfall washing away the few nutrients left in the soil after the plants have taken up the majority. Because there are many organisms, there is rapid decay which returns nutrients of the soil but these nutrients are quickly taken up by the plants. Many of the trees adapt to the poor soil conditions by having aboveground roots that grow sideways (stilt roots) from the trees to provide extra support.

Many of the plants in tropical rainforests grow in layers, forming a dense canopy which absorbs about 95% of the sunlight. Little light reaches the understory under the canopy, leaving only shrubs and small trees well adapted to living in shade. Many of the plants grow up the side of large trees to reach the sunlight. Many plants also have drip tips- special leaf shapes which enable the massive amount of rainfall to quickly run off the plant. Common plants include orchids, ferns, bromeliads, banyan trees, pitcher plants, palm trees and bamboo trees.

Because of the incredible diversity of organisms in the rainforest, the animals found there are adapted to exploit specific resources to avoid competition. For example, there are several birds that eat insects but each bird species eats insects only in a certain layer of the vegetation. Insects, bats and birds only pollinate one species of plant, reducing competition for food. Common animals

include the chimpanzee, capybara, orangutan, slow loris, macaws, flying dragons, jaguars, howler monkeys, anacondas, piranhas, toucans and many others.

Tropical rainforests are rapidly disappearing due to deforestation- destroyed by logging or cleared for ranches or farms. Many of the plants

and animals become extinct and native peoples are often displaced. Every year an area of the tropical rainforest the size of North and South Carolina combined is destroyed. Tropical rainforests used to cover about 20% of the Earth’s surfaced- now they cover about 7%.

Temperate Rainforests

Temperate rainforests are found mostly in North America, although some are found in South America and Australia. In North America, temperate rainforests can be found in the Pacific Northwest (Washington, Oregon, Northern California). Temperate rainforests have great diversity, although they contain much fewer species than Tropical Rainforests. They are cool, humid forests which receive a large amount of rainfall and the temperatures rarely fall below freezing.

Temperate Rainforests generally experience rainfall of about 200-400cm a year and experience a cooler climate than tropical rainforests, ranging anywhere from 25°C to 5°C (75°-30°F). Precipitation can take the form of either rain or snow, depending on the season. Temperate rainforests experience four distinct seasons, unlike the tropical rainforest, which maintains a warm climate year around. There are dry summers and colder wet winters.

Temperate rainforests do not have many broadleaf plant like the tropical rainforest. Most of the trees found here are coniferous or evergreens. The decay rate in temperature rainforests is much slower than in tropical rainforests due to the slow decay of needle leaves compared to broad leaves and the cooler temperatures (warm temperatures increase decay). Due to a slower decay, as well as a lack of the wide root systems found in tropical rainforests, the soil in temperate rainforests is much richer than tropical rainforests. There are often “nurse” logs which have fallen and now provide habitats and nutrients for the organisms in the rainforest as they decay.

A canopy and understory is also present in temperature rainforests. Many of the trees are ancient, huge, and have stilts (pitchfork like extensions to allow them to root in the soil). Common plants include incredibly old large coniferous (needle-like) trees such as red cedars, redwoods, Douglas firs and hemlocks, as well as mosses, fungi and lichens growing on decaying logs and as epiphytes (growing on other trees but not acting as parasites).

Many animals live on the forest floor and have adapted to eating the tough conifer needles. Animals in the temperate rainforest camouflage themselves by having brown, gray or green colorings.

Common animals include a variety of slugs, black and brown bears, raccoons, skunks, cougars, elk, owls, chipmunks, moose and rabbits.

Threats to the temperate rainforest include deforestation, clearing the forest for farming, the logging industry cutting down trees and pollution.

Deciduous Forests

Deciduous forests are found throughout eastern North America, Europe and parts of Asia. Deciduous forests are characterized by their deciduous plants, which shed their broad leaves every autumn (unlike coniferous plants who do not shed their leaves). They experience extreme weather changes throughout the year.

Deciduous forests experience the four seasons, which be vary from 35°C (95°F) in the summer to well below freezing in the winter. Deciduous forests receive about 50-250cm of precipitation annually, which allows for the decomposition of dead organic matter by bacteria and a variety of fungi. This leads to a very rich and deep soil which is full of nutrients.

Plants of deciduous forests grow in layers and include a canopy and forest floor. The forest floor receives more light than in rainforests and a larger number of plants grow on the forest floor as a result. Deciduous forest plants have adapted to the seasonal changes by shedding their leaves every fall to conserve moisture and sugar in the tree trunk, as well as to survive heavy snowstorms without risking the breaking of their branches. Rhizomes (underground stems) are present and become dormant during the winter. Rhizomes survive in the cold ground because they are somewhat insulated by the fallen leaves and snow. The trees often grow thick bark to protect themselves from the cold winter temperatures and parasitic fungi. Common plants include maple, oak, sycamore, walnut, ash and birch trees, as well many wildflowers, small shrubs and bushes.

Animals blend into their environment by having less colorful fur due to the lack of tree cover in the winter. Due to the colder temperatures, animals in the deciduous forest have adapted to survive the winters through hibernation. They eat a tremendous amount of food before the winter to store as fat and sleep through the winter to avoid battling for limited food supplies during the snowy winter months. Many species of bird migrate during the winter to warmer climates. Many of the organisms have developed thicker coats to survive the winter. Deer and elk have developed smaller antlers to allow

them to move easily through the underbrush. Common animals include deer, black and brown bears, wolves, raccoons, turkeys, owls, chipmunks, moose and rabbits.

Threats to deciduous forests lie mostly in destroying the forests for agriculture and development of towns/house, as well as logging.

Taiga

The taiga is the northern coniferous forest which stretches across the northern hemisphere through below the Arctic Circle in countries such as Canada, Sweden, Iceland, Finland, Russia and the U.S. (Alaska). The taiga is the largest continuous biome in the world and is often prone to wildfires. There is constant daylight during the summer and very little diversity in species.

The taiga consists of coniferous trees with needle like leaves that contain acidic substances. When the leaves die and fall to the ground, the soil becomes acidified, which is one reason there are very few plants on the forest floor, save for a few ferns and mosses. The soil is thin and lacking in nutrients due to the climate (cold leads to slow decomposition) and acidity.

Taiga is extremely cold and have long winters (6-10 months out of a year). During the winter, the average temperature is often below freezing and can plummet to -54°C (-65°F). The summer months range anywhere from -7°C to 15°C (19.4°F - 59°F). The growing season without frost can be as short as 50 days. The taiga receives little precipitation (30-90cm) and often falls as snow, with some rainfall during the summer months.

Coniferous plants do not shed their needle-like leaves to help them maintain water in their leaves during the harsh winter months. The cone-like shape also helps the tree shed snow stuck on its branches. The plants in the taiga often have thick bark to protect the trees from wildfires. The trees’ waxy needle-like leaves help to preserve water and the tough cones protect the seeds inside. The trees also have shallow roots systems to allow them to use water quickly when the snow melts in the spring. Common plant species include pine, hemlock, spruce and fir trees.

The lakes and swamps attract birds that feed on insects and fish. These birds migrate south for the winter. Year round residents burrow underground or hibernate and remain insulated by the deep snow cover. Many animals have white or brown coloring to camouflage them from predators, as well as thick fur to keep them warm in the winter. Hares that are brown in the summer shed their fur and grow white fur to camouflage them in the winter. Common animals include lynxes, wolves, caribou, foxes, hares, and moose.

The taiga is being destroyed by mining, trapping animals for their fur, pollution in the lakes or rivers and finally by the logging industry, which is cutting down large sections of the taiga’s trees for pulp and paper.

Desert

Deserts are defined as areas that receive less than 25cm of precipitation each year. Deserts are extremely hot and extremely dry. There are only a few periods of heavy rainfall per year. They are generally found between 30° latitude north and 30° latitude south. Deserts are found in northern & southern Africa (Sahara, Kalahari), parts of Australia, North & South America (Mojave desert in CA, NV & AZ) and in Mongolia (Gobi desert).

Deserts receive less than 25cm of precipitation each year. Due to the small amount of rainfall, few nutrients get washed away from the soil. The dryness hinders decay of dead organic matter, leading to soil that is rich in nutrients but poor in organic matter.

Temperatures during the day often exceed 40°C (100°F) and drop to 5°C (41°F) at night. The temperatures drop so drastically at night due to a lack of humidity or trees to retain heat and provide insulation. Deserts cool down rapidly at night and heat up quickly after the sun rises.

All desert plants are characterized by adaptations which allow them to get and conserve water. Succulents and cacti have thick fleshy stems and leave which store water and have a waxy coating to prevent water loss. Cactus spines stop thirsty animals from devouring the plants. Some plants store water in underground bulbs which spread out under the surface to catch as much rain as possible. Others contain toxins which prevents other plants from growing nearby. Common plants include saguaro cacti, barrel cacti, prickly pear cacti, dragon trees, aloe plants and yucca plants.

Animals in the desert must survive the intense heat, searing sun and a lack of water. Some animals get their water from seeds and plants. Others are nocturnal to avoid the hot sun during the day. Many animals stay in the cool underground. Reptiles have dry scaly skin to prevent water loss. Common animals include gila monsters, camels, sidewinder snakes, thorny devils, spadefoot toads, coyotes, rattlesnakes, vultures, scorpions and small rodents.

Global warming is increasing droughts, which lead to the drying up of water holes and a larger number of wildfires. Agriculture and farming leads to the destruction of plants and the soil.

Tundra

The tundra is a biome found north of the Arctic Circle, near the North Pole. Areas of northern Russia and Canada, as well as Greenland and Alaska are considered part of the tundra biome. The tundra is a very cold, windy, rocky biome without trees and with very little precipitation, where grasses and tough shrubs grow in the frozen soil. There are nomadic tribes who survive here in the tundra. There is very low biological diversity found in the tundra.

During winter, it is very cold and dark with the average temperature around -28°C (-18°F), sometimes dropping as low as -50°C (-58°F). During the warm summer months (12°C) when the sun is shining 24 hours a day, the tundra is covered in marshes, lakes and bogs created by the thawing of the top layer of soil. The tundra is similar to deserts in terms of precipitation- it receives between 15-25cm of rainfall per year.

The tundra experiences very short summers causing only the first few inches of soil to thaw. Underneath this lies permafrost, which is the term for permanently frozen soil. Permafrost is impenetrable (impossible to break through). Where soil does exist, it is very thin.

The tundra does not have any trees and the plants found in this biome grow low to the ground due to the arctic winds. Mosses and lichens cover acres of rocks due to their ability to grow without soil. Lichens are organisms which are composed of a fungus and an algae living and growing together. Plants have wide shallow roots to anchor them in the thin soil against the arctic winds. Many plants in the tundra are dark red, which allows them to absorb more heat from the sun in the cold climate. Common plants include lichens, dwarf shrubs, cotton grass and mosses.

Animals in the tundra are adapted to live in the freezing conditions. Most tundra organisms are migratory to avoid the cold winter months, although some do hibernate. Millions of birds feed on the insects and plants in the summer and migrate south during the winter. Rodents burrow underground during the winter and many animals have white fur or feathers to blend into the abundant snow. Animals that do not migrate during the

winter have thick coat to keep them warm and well insulated. Common animals include caribou, wolves, moose, musk ox, arctic foxes, polar bears, and snowy owls.

The tundra is a very fragile biome and is being destroyed by global warming (melting the permafrost) and pollution of lakes and land from the extraction of oil.

Grasslands

Grasslands (prairies/steppes) are big open spaces primarily found throughout Midwestern North America and parts of Asia but they can be seen all over the world. The world’s grasslands once covered about 42% of the total land surface- today grasslands occupy only 12% of the Earth’s surface due to the clearing of the plains for agriculture. Grasslands are found in the inland of continents where there is too little rainfall for trees to grow.

Grasslands receive 25-90cm of precipitation annually. Average temperatures range from -5°C to 20°C (23°F - 68°F) , although many grasslands are found in colder (-20°C/ -4°F) and hotter (30°C/86°F) climates. Depending on where the grasslands are found in the world, they might be hot all year around (close to equator) or experience both hot summers and cold winters (U.S. prairies). Grasslands often experience wildfires which maintains the grass height and also allows some grasses to re-seed. Grasslands have the most fertile soil of all biomes. Because of the fertile soil, many of the grasslands are destroyed to make room for crops.

The hot grasslands near the equator in Africa are called savannas, while the plains found in the U.S. are called prairies. In Europe, they are called steppes and in South America, they are known as pampas.

Grasslands contain many species of grasses with dense root systems which form mat-like structures to survive drought, fire and hold the soil in place. Root depth and grass height vary with the amount of rainfall. There are tall, short and mixed grass prairies based on the amount of rainfall. Trees cannot survive on the prairie due to drought, fire and constant wind.

Common plants other than grasses include milkweed plants, wildflowers and stinging nettles. Prairie

Young grasses are nutritious food for the grazing animals found in the grasslands, such as bison and pronghorns. The bison’s thick coats allow them to survive the cold winters on the plains. Small animals such as badgers, prairie dogs and owls live in underground burrows, which shield them from fires and predators. Common animals include bison, prairie dogs, pronghorns, owls, ferrets, snakes

and many insects.

Steppe

Savanna

Savannas are found in the West African plains, as well as in some areas of South America and India. Savannas are considered a type of grassland found in particularly warm environments. They are found near the equator and occur inland, which causes them to receive too little rain to allow many trees to grow.

Savannas are warmer than most grasslands and have a very long dry season with a very short wet season. Temperatures range from 20°-30°C (68°-86°F) and the Savannah receives anywhere from 50-120 cm (20-50 in) of rainfall annually, most of which occurs during the wet season. Grass fires often sweep across the Savanna during the dry season, which returns nutrients from the ash back into the soil, making it more fertile. Overall, the soil found in

Savannas is infertile and lack nutrients.

Plants in the Savanna must have adaptations present to survive wildfires and preserve water during the dry seasons. Many of the grasses have large underground root systems and thick bark

to allow them to survive fires, obtain as much water as possible and allow plants to quickly regrow after a fire. Many plants also have vertical leaves to help them to conserve water. The shrubs often have thorns or a bitter taste to stop herbivores from eating them. Common plants include different types of grasses, acacia trees, candelabra tree, eucalyptus trees, kangaroo paws and baobabs.

Savannas are home to many herbivores which graze on the grasses. The grazing herbivores have a migratory way of life and follow the rains, allowing them to survive during the hot dry season. Many animals burrow underground to avoid predators and the heat. The animals often give birth only during the rainy season when food is abundant. They avoid competition for food by eating vegetation at different heights (gazelles on grass, rhinos on shrubs, and giraffes on trees). Common animals include lions, ostriches, giraffes, warthogs, elephants, rhinoceros and hyenas.

Many savannas have been used as grazing areas for farmers’ cattle and goats. The farmers do not move their herds often enough and soon the grasses are completely eaten away. Without any vegetation, the savanna turns into a desert. Huge areas of savanna are lost to the Sahara desert every year due to overgrazing and farming.