Chapter 9

Notable trees in the montane forests

1) Bristlecone pine The world's longest-lived, single-stemmed tree species is the bristlecone pine The oldest-known individual, at 5,067 years old, is living in the White Mountains in eastern California 2) Giant sequoia The oldest giant sequoias are over 3,000 years old. They are the heaviest single-stemmed trees on the planet. The General Sherman tree, shown here, is 31.3 m (102 ft) in circumference and 83.8 m (275 ft) tall. It weighs almost 2,000 metric tons. 3) Quaking aspen These quaking aspen trees (Populus tremuloides) are found near Utah's Fish Lake. This particular grove of aspen trees is informally known as "Pando" (Latin for "I spread"). It consists of more than 40,000 genetically identical trunks rising from a single root mass that covers 106 acres In total, Pando's root mass (along with its trunks) weighs over 6,000 metric tons and is estimated to be over 80,000 years old.

Botanical terms

1) Broad-leaved Has wide, flat leaves. Usually deciduous (sheds its leaves annually) 2) Coniferous Bears cones; Usually needle-leaved and evergreen 3) Deciduous Loses all leaves in one season, usually winter 4) Evergreen Loses leaves gradually so it always has leaves 5) Herbaceous Lacking woody tissue 6) Needle-leaved Has narrow, needle-like leaves; usually evergreen 7) Sclerophyllous Has hard, leathery, and waxy leaves 8) Woody Grows rigid trunks and stems

Four direct ways saving ecosystems helps humans

1) Ecosystem services Natural ecosystems and the species in them provide humans with clean air and drinking water, fertile soil, filtration of pollutants along coastal zones, buffers against hurricane storm surges, pollination of food crops, and compounds for new medicines. These benefits are services because people need them for their health and sustenance. 2) Climate stabilization Saving ecosystems forestalls climate change. Whereas deforestation releases the carbon stored in trees and the soil to the atmosphere, healthy forests absorb carbon dioxide from the atmosphere and slow the rate at which this greenhouse gas warms the planet 3) Ecotourism revenue Although not without controversy, ecotourism provides important revenue sources for many regions. People travel long distances to see wild places, and in so doing, they create a significant revenue source for people in the places they visit Countries such as Costa Rica, Ecuador, Nepal, and Kenya derive a significant portion of their revenue from their natural places and the people who pay to see them. 4) Aesthetics Without vibrant and healthy nature, the world would be gritty, boring, and monotonous. Ecosystems and their species do more than clean the air and water and fill our stomachs: They feed our spirits. Without the complete Persian rug of life, the world is less interesting and nurturing for people. Humans are connected to and supported by the biosphere. The well-being of our lives matters, and so does the well-being of human societies. Saving species and their habitats preserves ecosystem services, curbs climate change, generates revenue through ecotourism, and preserves a richer and more interesting world. The health and well-being of people are inextricably connected to the health and well-being of the biosphere.

Vegetation structure terms

1) Forest Dominated by trees with a closed canopy 2) Woodland Widely spaced trees with a grass understory 3) Shrubland Continuous cover of shrubs 4) Grassland Continuous cover of grasses 5) Scrubland Widely-spaced, dry-adapted shrubs 6) Desert Sparse plant coverage

The typical sequence of events that cause deforestation in the Amazon rainforest

1) Roads and logging Logging companies or local political bodies build roads into remote, untouched forested regions. Widely spaced valued hardwoods, such as teak and mahogany, are selectively removed from the forest. The remaining forest is left untouched 2) Subsistence slash-and-burn agriculture Logging roads make the forest accessible to poverty-stricken, small-scale, modern subsistence farmers who cut down the forests (slash them), burn the vegetation, and then plant crops. The nutrient-poor soils require farmers to move after 3-4 years to another plot, where they must burn and plant again in a slash-and-burn cycle 3) Commercial ranching and agriculture When subsistence slash-and-burn agriculture is no longer feasible, the lands are used to raise cattle. About 90% of all deforested areas in the Amazon are now being grazed by cattle. Beef and leather are exported mainly to Asian, North American, and European markets. Soybeans and sugarcane are grown for export and for biofuel in Brazil Deforestation in the Amazon rainforest often follows the sequence outlined here. Increasingly, the slash-and-burn step is skipped, as commercial logging is followed directly by forest burning and commercial-scale cattle ranching and agriculture. In 2017, approximately 6,600 km2 (2,550 mi2) of rainforest was lost. The red trend line shows the percentage of remaining original forest compared to its extent in 1970. In 2017, about 81% of the Brazilian forest remained.

Three physical factors that control the vegetation structure of the Mediterranean Biome

1) an extended summer dry season lasting 5 months or longer 2) Frequent wildfires 3) Low soil nutrients and organic matter Many plants in this biome are adapted to a pronounced dry season and fire.

Biome

A biome is an extensive geographic region with relatively uniform vegetation structure. Earth's land surface is covered by biomes. vegetation structure refers to the type of vegetation that dominates a region, such as closed-canopy forest (dense) or open (sparse) grassland Biomes are the second-largest units in the spatial hierarchy; only the biosphere is larger Every human alive lives in a biome. All land surfaces (except where there are ice sheets) are covered by the continuous mantle of biomes Some biomes, such as a forest, are easy to recognize. Other biomes may be less easy to recognize because of how people have changed them. They often exist as small remnants of their former selves, such as natives trees mixed with non-native trees in an urban park. In many places natural biomes are completely gone, replaced by human-built landscapes such as farms and cities A temperate deciduous forest biome once existed in New York City and its environs. The biome has been replaced by the urbanized city, but remnants of it are preserved in Central Park, where native trees are intermixed with non-native trees from around the world. Biome classifications are based on vegetation structure, which is determined mostly by climate

Ecological equivalence

All of Earth's biomes reflect the response of the animal and plant life to regional climate Through evolution, different, unrelated groups of plants and animals within similar climates begin to resemble one another Thus, widely separated but similar climates produce similar plant and animal adaptations. This biome-level resemblance is called ecological equivalence. Although tropical alpine scrublands in different regions are structurally alike, their plant species are genetically unrelated. In this example, different groups of plants share the structure that works best in the Köppen H climate zone in the tropics. Tropical high-elevation settings receive intense ultraviolet radiation. Many tropical alpine plants are adapted to reduce the effects of UV exposure. Many have evolved parabolic rosettes, a growth form in which all the leaves emerge from one location on the plant Reflective silver hairs, also common in tropical alpine plants, reflect UV radiation to protect the plant from its harmful effects Shown here are the Haleakalaā silversword (Argyroxiphium sandwicense) of Hawai'i (A), espeletia (Espeletia pycnophylla) of the Andes in Ecuador (B), and giant lobelia (Lobelia deckenii) on Mount Kilimanjaro in Tanzania (C).

Three prairie types in North America

Before its conversion to agriculture, the temperate grassland of North America was dominated by three prairie types: 1) Tallgrass prairie in the eastern Great Plains 2) Mixed-grass prairie in the central Great Plains 3) Short-grass prairie in the western Great Plains The height of grasses decreases westward, reflecting the increasing aridity in interior North America. The grassland-desert ecotone lies on the western margin of the short-grass prairie.

Three dominant layers in tropical seasonal forests

Canopy, shrubs, and forest floor The canopy is lower and more open than that of the tropical rainforest, so more light reaches the forest floor. The diversity of insects, birds, mammals, reptiles, and amphibians is, in many cases, nearly as high as that of the tropical rainforest.

The Human Footprint in the Montane Forest Biome

Commercial logging is a significant factor in montane forests. Many of these forests have been subjected to clear-cutting: removal of all trees over a large area. Fire is also a powerful force in the montane forest biome and many of its plants are adapted to fire. Anthropogenic fire suppression, and the resulting fuel buildup, can result in catastrophic fires that change the forest structure and species composition Climate change is causing higher temperatures, less snowfall, and greater rates of evapotranspiration in many montane forests. These factors are causing wildfires to increase and become more severe. To combat these trends, forest managers use prescribed burns and selective cutting to reduce accumulations of fuel. Where these techniques are applied, they can be costly but effective.

Temperate Rainforest

Compared with temperate deciduous forest, temperate rainforest is geographically limited, and far fewer people ever see it The temperate rainforest biome occurs where annual precipitation is high and temperatures are mild. It is characterized by large trees that form a dense canopy. A dense understory layer of vegetation lies beneath the trees Epiphytic species, such as ferns, lichens, and bryophytes (mosses and their relatives), thrive in the canopy In the Northern Hemisphere, dominant tree species include western red cedar (Thuja plicata), Sitka spruce (Picea sitchensis), and western hemlock (Tsuga heterophylla). The California redwood (Sequoia sempervirens) dominates the temperate rainforest found in northern California's coast. The California redwood holds the world record as the tallest tree: The Hyperion tree stands 115.9 m (380.3 ft) tall Many temperate rainforests are located along the western coasts of continents, where abundant precipitation, fog, and high humidity occur Evergreen needle-leaved trees dominate this biome in the Northern Hemisphere In the Southern Hemisphere, forests are composed of evergreen broad-leaved trees, such as the southern beech (Nothofagus spp.), podocarps (Podocarpus spp.), and eucalyptus shows, the temperate rainforest receives more precipitation, and has a more moderate maritime climate, than the temperate deciduous forest. This temperate rainforest is near Vancouver, British Columbia, Canada. Because of the abundant precipitation and mild temperatures, immense trees dominate temperate rainforests if they have not been logged This climate diagram for Vancouver, shows that summers are cool, and winters are mild. Average annual temperatures in the temperate rainforest biome range from about 3°C to 20°C Average annual rainfall ranges from 170 to 350 cm (67 to 138 in), and precipitation falls in all months The temperate rainforest biome is scattered throughout midlatitudes where precipitation is sufficient to support it The largest intact temperate rainforests are along the coasts of western North America, southern Chile, and southeastern Australia.

The Human Footprint in the Desert Biome

Deserts are largely off-limits to permanent human settlement because of the lack of available water. As a result, human impacts have been relatively light in this biome. There are places, however, where large populations live in the desert biome. In the United States, for example, Las Vegas, Nevada, and Phoenix, Arizona, are located in deserts. These cities import water, mostly from the Colorado River, and they pump it from the ground. This water use has reduced stream flow and influenced the ecology of many streams and riparian (streamside) areas significantly Other rivers that flow through deserts include the Indus River, which flows through the deserts of eastern Pakistan and western India, and the Nile River, which flows through the easternmost Sahara. These rivers support large desert populations. People have lived sustainably in these desert areas for millennia.

Hot deserts

Located beneath the subtropical high Hot deserts, such as the Namib Desert in Namibia and the Sahara in Northern Africa, exist because of the descending air of the subtropical high in the vicinity of 30 degrees latitude north and south.

Epiphytes

Epiphytes, plants that grow on the surfaces of other plants for access to light but do not take nutrients from those plants, are also common in tropical rainforests

What accounts for a large proportion of human land use?

Food production accounts for a large proportion of human land use. The most widespread human land use is rangelands, where domesticated livestock graze. Rangelands are followed by croplands, the second most widespread human land use.

Unique factors driving rainforest loss

For each geographic region, unique factors drive rainforest loss. As Figure 9.7A illustrates, hardwood logging, cattle ranching, and soybean and sugarcane cultivation are driving rainforest loss in the Amazon In contrast, Indonesia is losing its rainforests largely to palm oil plantations. Orangutans have lost over 80% of their original habitat due to forest clearance for these plantations Orangutans (Pongo pygmaeus and Pongo abelii) are among the most intelligent land animals. Both species of orangutan are listed as "critically endangered," one step away from extinction in the wild. Over 85% of the world's palm oil plantations are in Malaysia and Indonesia. Palm oil has a wide range of uses, from cosmetics to foods to lubricants and, increasingly, biofuels for cars and trucks. The oil is made from the seeds of the African oil palm (Elaeis guineensis).

The Human Footprint in the Tropical Seasonal Forest Biome

Forests burn readily during the relatively dry season, making the tropical seasonal forest extremely vulnerable to fire Increasing pressures from growing human populations, coupled with poverty, force people into the forest for subsistence farming. The soils of the tropical seasonal dry forest are better suited for crops and grazing than are the soils of tropical rainforests

Secondary forests

Forests that have been cleared or disturbed and regrown are called secondary forests. Secondary forests usually have less biodiversity than primary forests. In some areas, the temperate deciduous forest has rebounded after having once been cut. In eastern North America, for example, deciduous forests are more geographically extensive today than they were a century and a half ago because many farmers abandoned their farms and the forest grew back through plant succession In addition, the forests today are less damaged by acid rain than they were a century ago. Legislation such as the Clean Air Act of the 1970s is responsible for this positive change.

Cold deserts

Found at high latitudes and elevations found at the poles and at high elevations Polar regions are deserts because cold air has low water vapor content The McMurdo Dry Valleys of Antarctica, for example, are exceedingly cold and arid Two major cold deserts in Asia are the Taklamakan Desert in China and the Gobi Desert Mongolia.

Habitat fragmentation

Habitat fragmentation is the division and reduction of natural habitat into smaller pieces by human activity. A whole Persian rug functions as a beautiful rug, but if the rug is cut into pieces, it becomes worthless. Our tour of biomes in this chapter has revealed that habitat fragmentation is reducing Earth's natural biomes and ecosystems into ever-smaller pieces that are surrounded by anthropogenic landscapes.

Three broad groups of deserts

Hot deserts (located beneath the subtropical high), rain shadow deserts (on the leeward side of mountain ranges), and cold deserts (found at high latitudes and high elevations)

The Human Footprint in the Tundra Biome

Human impacts in the northern tundra are occurring mostly through road building and resource extraction and transportation Oil and gas exploration in the Prudhoe Bay region on the North Slope of Alaska has had an impact on the tundra there. The Trans-Alaska pipeline transports oil across Alaska from Prudhoe Bay to Valdez. The pipeline blocks the movement of migrating animals and also has been involved in oil spills. The Trans-Alaska pipeline carries oil from Prudhoe Bay on the North Slope of Alaska south to the port city of Valdez. From Valdez it is transferred onto oil tankers and brought to oil refineries in the United States. The oil is heated so that it will flow through the pipeline. Because the oil is heated, the pipeline must be elevated above the tundra so that it does not thaw the permafrost, which would result in a buckled, broken, and leaky pipeline. Climate change is having a growing impact on tundra permafrost soils as well. The Arctic is the fastest-warming region on Earth, and tundra ecosystems are rapidly changing as their permafrost soils thaw. Permafrost soils are rich in carbon from organic remains. As they thaw, they emit methane and carbon to the atmosphere, contributing to the greenhouse effect

Geoglyphs

Human-built trench systems previously hidden by the rainforest in Brazil Some of the oldest geoglyphs were built as early as 2,000 years ago, and it is not clear why they were built. They indicate that large permanent settlements, or "lost cities," once existed in the rainforest Most scientists in the past had assumed that there were few permanent human settlements in the Amazon. But now, based on the widespread occurrence of geoglyphs, some scientists think that at its peak, the Amazon lowland human population numbered as many as 10 million people Amazon rainforest soils are typically nutrient-poor and reddish in color. However, in many of the geoglyph locations, the soil, called terra preta, or "black earth," is uncharacteristically rich with organic matter and dark in color The inhabitants of these ancient settlements built up the soil with charcoal, their own waste, animal bones, and food scraps. These modifications would have made the soil more suitable for growing crops to feed large populations

Causes of aridity in deserts

In many deserts, a combination of factors together cause aridity. For example, the Atacama Desert of Chile averages 0.4 cm (0.15 in) of precipitation per year and is among the driest locations on Earth. It lies in the rain shadow of the Andes and is under the influence of the subtropical high. In addition, a cold offshore current inhibits evaporation and rainfall from the Pacific Ocean. In all deserts, plants and animals exhibit a wide range of physiological and behavioral responses to the scarcity of water, including nocturnal activity in animals, deep roots to reach water, and germination from seeds in plants.

The Human Footprint in the Temperate Deciduous Forest Biome

In the temperate deciduous forest biome, nearly all of the primary forest—forest that has never been significantly altered by people—has been lost to agriculture and human settlement. The soils of the temperate deciduous forest are fertile and well suited for farming once the forest has been cleared. Logging for hardwood lumber has also reduced the extent of temperate deciduous forests Today, little of this biome remains in the British Isles, much of Europe, and eastern China Instead, these regions support extensive agricultural systems. The forests in these areas were cleared beginning some 8,000 years ago. Human activities keep the land under agricultural production even though the climate is suitable for the return of forest Ireland, like most of the rest of northern Europe, has a climate that supports temperate deciduous forest. Throughout Europe, forests were cleared several thousand years ago for farming and livestock grazing. This entirely anthropogenic landscape is maintained by people. If left alone, it would develop into oak and pine forest through ecological succession over many centuries.

Biome loss in India, China, and the Himalayas

India, Java, and much of eastern China are bright blue and purple in Figure 9.28, indicating the presence of villages with large human populations engaged in irrigated and rain-fed agriculture. The seasonal tropical forest and tropical savanna biomes that would occur naturally in India are completely gone, as are China's temperate deciduous forests. The slopes of the Himalayas, once montane forest, are now rice-growing agricultural settlements and dense mixed settlements.

Montane forest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Cold mountain climates, h Vegetation: Needle-leaved trees in the Northern Hemisphere, broad-leaved trees in the Southern Hemisphere Notable features: Cool temperatures; cold winters at the midlatitudes; low seasonality in the tropics Human footprint: Logging, fire suppression, climate change, and fire

Temperate deciduous forest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Humid subtropical, Cfa, Cwa, Cwb; Humid continental, Dfa, Dwa, Dwb, Dfb Vegetation: Broad-leaved deciduous trees Notable features: Winter storms caused by the subpolar low and summer thunderstorms; cold winters, warm summers; fall colors Human footprint: Extensively converted to agriculture and urbanized development in China and Europe

Boreal forest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Subarctic, Dfc, Dwc, Dfd, Dwd Vegetation: needle-leaved evergreen trees Notable features: cold winters and a short summer growing season; found only in the Northern Hemisphere Human footprint: Logging, oil and mineral extraction, climate change and fire

Desert - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Subtropical desert, BWh; midlatitude desert, BWk; ice sheet: EF Vegetation: Xerophytes Notable features: Severe moisture deficits in most or all months; low biomass Human footprint: water diversion from rivers; off-road vehicles; solar power facilities; livestock grazing

Temperate grassland - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Subtropical steppe: Bsh; Midlatitude steppe: Bsk Vegetation: Continuous cover of grasses and forbs Notable features: Aridity caused by interior locations and the subtropical high; strongly continental climate; moisture deficits in most or all months; too dry for forest development; frequent fires Human footprint: Mostly converted to agriculture or farmland Average annual temperatures vary from 18°C (64°F) in South Africa to 2°C (35°F) or less in Canada and Eurasia Precipitation in grasslands ranges from 30 to 100 cm Temperate grasslands occur extensively in interior North America, Eurasia, southern South America, and southern Africa There are also scattered temperate grasslands in Madagascar, New Zealand, California, and Australia. About 90% of the plant biomass in temperate grasslands is grasses, but grasses comprise only about 20% of the species diversity. Forbs (non-grass herbs) such as milkweed (Asclepias spp.), purple coneflower (Echinacea purpurea), and black-eyed Susan (Rudbeckia spp.) greatly increase the plant biodiversity in grasslands in North America Most of the living portions of grassland vegetation is found in the roots of grasses, which may have a biomass some three times greater than the aboveground portions of the plant.

Tropical seasonal forest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Tropical monsoon, Am Vegetation: Broad-leaved deciduous trees, shrubs Notable features: ITCZ dominated, some water stress in winter; vulnerable to winter fire; high biodiversity Human footprint: Burning, mostly converted to agriculture

Tropical savanna - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Tropical savanna, Aw; Tropical steppe, Bsh Vegetation: Broad-leaved deciduous trees, woody and thorny shrubs, grass and forb understory Notable features: Water stress in winter, summer precipitation from the ITCZ; frequent fires; plant adaptations to dry seasons and fire; large grazing animals (in Africa) Human footprint: Overgrazing by livestock leading to desertification; hunting and poaching of large animals

Tundra - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zone: Tundra and cold mountain climates, ET, H Vegetation: Small shrubs and herbs, no trees Notable features: very cold winters, short summer growing season; too cold for trees; occurs at high latitudes and elevations; soils often permanently frozen Human footprint: Mineral extraction, ecosystem shifts, and permafrost thawing due to climate change

Temperate rainforest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zones: Marine west coast, Cfb, Cfc Vegetation: needle-leaved and broad-leaved evergreen trees and layered forest structure; epiphytes, bryophytes, and ferns Notable features: Coastal locations and orographic precipitation; abundant precipitation brought by the subpolar low; mild winters and cool summers Human footprint: Logging

The Mediterranean Biome - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate zones: Mediterranean, Csa, Csb Vegetation: Few trees, sclerophyllous shrubs, adapted to fire Notable features: Aridity caused by subtropical high and cold offshore ocean currents; mild winters, extended summer dry season; frequent fires; high biodiversity Human footprint: Agriculture, non-native species, human development, fire suppression

Tropical rainforest - Köppen climate zone/vegetation/notable features/Human footprint

Köppen climate: Tropical wet, Af Vegetation: Broad-leaved evergreen trees, lianas, epiphytes Notable features: ITCZ dominated, no dry or cold season; layered forest structure and intense competition for light; very high biodiversity Human footprint: Deforestation due to agriculture and livestock ranching, burning and urbanization

Biomes at all latitudes

Mountains, northern tundra, desert, ice

Low-latitude biomes are found where?

Low-latitude biomes are found almost entirely between 30 degrees north and south latitude. Except for high mountainous areas, low-latitude biomes do not experience any significant cold period.

Buttress roots

Many canopy and canopy-emergent trees feature buttress roots have a tripod-like structure that stabilizes and supports tall growth to reach the light.

Northern tundra soils

Many northern tundra soils are permafrost soils, which are frozen just below the surface year-round The vegetation structure of all tundra consists of a single layer of small shrubs and low herbs Plants remain low to the ground, where it is warmer and where they can be protected by an insulating layer of snow in winter. There are few annual plants in the tundra because the growing season is too short and cold for most plants to complete their life cycle and set seed The biomass of standing tundra vegetation is low, as is the diversity of species. Many of the same species grow throughout the tundra across broad geographic regions

Mutualism

Mutualism between plants and animals is common in the tropical rainforest biome At midlatitudes, many plants rely on the persistent westerlies to disperse their pollen, seeds, and fruits. In contrast, equatorial tropical rainforests are dominated by the windless doldrums, and bats, birds, fish, and mammals carry out the work of pollinating flowers and dispersing seeds and fruit This is why many tropical plants produce large, brightly colored flowers and nutritious seeds and fruits In some tropical rainforests, up to 90% of plant species are pollinated and dispersed by animals.

The Human Footprint in the Tropical Rainforest Biome

Natural resources are like the contents of full bank accounts: Spend all the money in one shopping spree, and it disappears. Carefully manage it, live off the interest, and it can last generations Rainforests and other natural resources can be similarly spent or carefully managed. Today, undisturbed tropical rainforest is quickly being lost through deforestation Encouragingly, the rate of loss of the Brazilian forest has decreased in recent years, due mostly to national and international pressure to save the Amazon rainforest

Three trillion trees

Nobody knows the exact number of trees on Earth, but recent research published in the journal Nature perhaps comes close to the mark: 3,040,000,000,000 (more than 3 trillion) trees. By using satellite remote sensing technology and surveys on the ground (called ground-truthing), scientists estimated the total number of trees and where the forests are densest. They found that about 43% (or 1.3 trillion) of all trees on Earth are in tropical rainforests and subtropical forests (the tropical seasonal forests) They also found that the greatest tree densities occur in the northern forests (the boreal forest) that grow across northern North America and Eurasia. About 25% of all trees (750 billion) were found in these northern forests. Most of the rest of the trees grow in the mountains of the world (the montane forests). In the same study, the researchers found that prior to the beginning of the Agricultural Revolution that began 10,000 years ago, there were perhaps 6 trillion trees on Earth. Since that time people have cut almost half of Earth's trees in the process of converting forests to farmland. Today about 15 billion trees are cut each year and not replaced. Forests are critical elements of Earth's biosphere. They produce oxygen and transfer moisture from the soil to the air. Forests also prevent dangerous landslides by stabilizing slopes in mountainous regions. They cycle nutrients and filter and clean air and water, and they absorb carbon dioxide from the atmosphere and help check the pace of anthropogenic climate change.

Rain shadow deserts

On the leeward side of mountain ranges form on the leeward sides of mountain ranges due to adiabatic heating The Gobi Desert, for example, is found throughout Mongolia in the rain shadow of the Himalayas, the Pamirs, and the Altai Mountains Its location in the continental interior and its high elevation and resulting low temperatures also contribute to the Gobi's aridity.

The Human Footprint in the Tropical Savanna Biome

One prevalent threat to the tropical savanna biome is overgrazing by livestock, particularly cattle, sheep, and goats Increased burning by people to stimulate grass growth for livestock is also degrading savanna woodlands and threatening the habitat of native grazing ungulates In addition, populations of these native animals have declined greatly as a result of hunting for trophies, elephant ivory, and rhinoceros horn Many large game preserves and parks have been established throughout Africa to protect large animals. These parks also generate revenue from ecotourists, travelers who seek to visit natural places Hunting pressures have reduced the once-widespread populations of the black rhino (Diceros bicornis) in Kenya. In 2011, a subspecies of the black rhino, called the western black rhino, was officially declared extinct. The remaining black rhino populations are critically endangered. Wildlife wardens are armed to protect animals from poachers. Increasingly, conflicts between African elephants and people have arisen in parts of Africa as the human population has increased and expanded into elephant territory. Today, most African elephant populations are in steep decline as a result of poaching and habitat loss

Wettest region in the US

Pacific northwest is the wettest region in the US, and therefore there are rainforests (especially along the coastlines)

Biggest threats to African elephants

Poaching and habitat loss Based on genetic evidence, scientists recognize two species of African elephant, the African savanna elephant (Loxodonta africana) and the smaller African forest elephant (Loxodonta cyclotis). Both species are considered vulnerable to extinction in the wild, according to the International Union for Conservation of Nature (IUCN). There were originally about 27 million African elephants living throughout the continent (inset map). The period 2014-2016 saw the most severe decline in African elephant populations in the past quarter century: In 2014, there were 700,000 African elephants in the wild, and by 2017, the numbers had dropped to roughly 415,000, a 40% decline from 2014.

Alpine tree line

Similarly, the upper limit of the montane forest is the alpine tree line (or timberline) Harsh conditions stunt tree growth and prevent trees from growing above this elevation.

Temperate Deciduous Forest

Temperate forests are the result of the precipitation caused by the subpolar low at midlatitudes There are two kinds of temperate forest: temperate deciduous forest and temperate rainforest. The temperate deciduous forest biome is dominated by trees that shed their leaves in winter in response to low temperatures. Examples of such trees include oak (Quercus), maple (Acer), elm (Ulmus), and beech (Fagus) This biome occurs at midlatitudes where the annual temperature range is large and winters bring below-freezing temperatures this biome is located mainly in the Northern Hemisphere because there is more land at midlatitudes there than in the Southern Hemisphere This temperate deciduous forest is in Cherokee National Forest, near Chattanooga, Tennessee. This climate diagram for Chattanooga shows an average annual temperatures in the temperate deciduous forest biome vary from 2°C to 20°C (35°F to 68°F). Average annual precipitation ranges from 50 to 250 cm (20 to 98 in) Temperate deciduous forest is or was located mainly in eastern North America and western Europe, and it was also formerly found in eastern Asia To a lesser extent, it is found at midlatitudes in South America, Australia, and New Zealand The deciduous trees in these forests lose their leaves through abscission, a process triggered by changes in light and moisture conditions in the fall Leaves often turn bright colors as they lose their green chlorophyll, revealing brighter-colored anthocyanin pigments beneath.

mid- and high-latitude biomes

Temperate grassland, Mediterranean, temperate deciduous forest, temperate rainforest, boreal forest

"Crowded jungle"

The "crowded jungle" perception of the tropical rainforest is misleading. A walk through the deeply shaded floor of a healthy tropical rainforest is largely unobstructed by plants in many places Crowded plant growth occurs only where there are high light levels, such as in the canopy above, in light gaps created where large trees have fallen, and along stream banks

The Mediterranean Biome

The Mediterranean biome is the smallest of the biomes. It is characterized by hot, dry summers and winter rainfall About half the area of this biome is found in the Mediterranean region of southern Europe and northern Africa This photo taken near Tunis, Tunisia, shows the shrubland vegetation structure of the Mediterranean biome. The trees seen here are drought- and fire-adapted Aleppo pine This climate diagram for Tunis illustrates an average annual temperatures in the Mediterranean biome range from 5°C to 20°C (41°F to 68°F), and annual precipitation totals average 50 to 120 cm The Mediterranean biome is centered at about 35 degrees latitude, and it is geographically isolated on the western margins of five different continents With the exception of the Mediterranean region itself, all of these locations have cold ocean currents offshore that inhibit evaporation of seawater and increase aridity Local names of the Mediterranean region: chaparral, matorral, Maquis and garrigue, Fynbos, Mallee The Mediterranean biome has high biodiversity and high endemism, meaning that many species are geographically restricted to it and found nowhere else The fynbos of South Africa and the chaparral of California, for example, each have about 6,000 different plant species, many of them unique to those areas. The Mediterranean region has more than 7,000 About half of all plant species in the Mediterranen biome are annuals (plants that live for a year or less and perpetuate themselves by seeds) A few perennials (plants that live longer than a year) are summer deciduous Many plants of this biome have sclerophyllous (pronounced skler-AH-fuhlis) leaves-hard, leathery, waxy leaves adapted to reduce water loss and herbivory. Many plants of the Mediterranean biome display fire-adapted traits, such as serotinous (fire-adapted) cones, crown sprouting, and thick bark The ecological health of the Mediterranean biome is dependent on fires. It germinates seeds and vegetation regrowth, cycles nutrients back into the soil

Boreal Forest

The boreal forest (called taiga in Eurasia) is a cold coniferous forest biome found at high latitudes in the Northern Hemisphere The boreal forest is among the largest biomes, comprising about one-fourth of all forested land on Earth. This biome occurs in continental interiors where low winter temperatures and a short summer growing season are typical the boreal forest is not found in the Southern Hemisphere due to the lack of interior continental climates at high latitudes there Boreal forest vegetation is dominated by coniferous, or cone-bearing, trees, most of which are needle-leaved and evergreen. Dominant coniferous trees of this biome include pine (Pinus), spruce (Picea), fir (Abies), and larch (Larix). An understory of mosses, lichens, and herbaceous plants lies beneath the canopy. Conifers and tall and columnar to maximize exposure to sunlight, which is always near the horizon This boreal forest is near Fort Smith, Northwest Territories, Canada. Conifers are tall and columnar to maximize the sunlight, which is always near the horizon, regardless of the time of day. This climate diagram for Fort Smith shows an average annual temperatures in the boreal forest biome range from -5°C to 3°C (23°F to 37°F). Annual precipitation averages 40 to 200 cm (16 to 79 in). The boreal forest extends across North America and Eurasia. It is centered at about 60 degrees north latitude. Fire can be an important factor in the boreal forest during the summer. The fire-return interval ranges from a few decades in the southern portions of the boreal forest to over 1,000 years at the northern edge of the forest.

The Human Footprint in the Boreal Forest Biome

The boreal forest is the most sparsely human populated forested region on Earth. Vast tracts through Eurasia and North America have remained mostly unaltered by people. This is quickly changing, however, as world demand grows for forest products, such as paper and lumber, and minerals, such as petroleum. Recent open-pit mining in Alberta's tar sand deposits has generated considerable conflict between the energy industry's political representatives and those seeking cleaner fuels with fewer environmental impacts in the United States and Canada. The boreal forest is also one of the fastest-warming biomes due to anthropogenic climate change. On top of that, the warmer atmosphere has decreased snowfall and increased fire activity and intensity in the boreal forest as well.

Layered structure of tropical rainforests

The tropical rainforest biome develops a layered structure, with each layer adapted to the light conditions found there The topmost layer, called the emergent canopy, consists of trees that protrude above the canopy into full sunlight. The shaded forest floor, in contrast, may receive as little as 1% of the sunlight found in the upper canopy. As a result, the forest floor is dark and damp. Fungi (mushrooms and molds) are common, and they rapidly decompose and recycle fallen plant material and dead organisms.

The Human Footprint in the Temperate Rainforest Biome

The future of the temperate rainforest biome has become a divisive political issue, as different sides fight either to use it for profit or to preserve it. California redwoods, for example, make prized outdoor decking and furniture because of the rot-resistant qualities of the wood Logging that began in the late 1800s and continued through much of the twentieth century cleared large expanses of old-growth groves of redwoods Today, only about 5% of the original temperate rainforest in California, Oregon, and Washington has remained unlogged In British Columbia, about 50% remains, and Alaska has about 90% of its original temperate rainforest, most of it in the Tongass National Forest, which has largely been protected from logging. Worldwide, about half of the temperate rainforest has been cut. In many areas, temperate rainforest is actively managed as a timber resource.

The Human Footprint in the Temperate Grassland Biome

The geographic extent of the temperate grassland biome has been greatly reduced. This biome is a desirable place for people to live, farm, and raise livestock. Roughly 80% of the original North American prairie is now either developed or being used for commercial agriculture and cattle ranching Many animal species populations collapsed with the loss of these grasslands in the North American grassland ecosystem during the early twentieth century. Prairie dogs were important keystone species 1) Bison Prefer to forage near prairie dog colonies or towns, where the prairie dogs' activities improve plant growth. Bison keep the grass height around prairie dog colonies short, which gives prairie dogs a clear view of approaching predators such as birds of prey, foxes, and and ferrets Conservation status: Between 10-75 million bison occupied the temperate grasslands of North America. By 1884 the bison was almost extinct due to exploitation by European immigrants. Due to conservation efforts, there are about 15,000 wild-ranging bison in North America today. About 500,000 are raised in captivity for food Mutualism with prairie dogs 2) Prairie dogs There are five species of prairie dogs in NA. All of them provide habitats or food for other species, including: black-footed ferrets, burrowing owls, Ferruginous hawks, golden eagles, swift foxes, and grasshopper mice Conservation status: There were originally several billion prairie dogs in NA. Farming and intentional extermination reduced their numbers. 3) Pronghorn Prairie dogs are keystone species in North American temperate grasslands. They are mutualistic partners of many grassland organisms, including bison and pronghorn. Prairie dog burrowing improves plant growth in grasslands by aerating the soil and allowing water to better infiltrate the ground. The animals also add nitrogen to the soil with their fecal pellets. In areas where temperate grassland has not been cultivated for crops, extensive grazing by cattle has altered this biome Cattle grazing has changed nearly all of the North American short-grass prairie by allowing non-native plant species to establish themselves and become dominant Where cattle are grazed intensively, some 90% of the plant species are non-native Light to moderate cattle grazing, however, can simulate the effects of grazing by the now-scarce bison, to which grasses are adapted, and may therefore be beneficial for the prairie ecosystem Grassland restoration ecologists are increasingly seeing the value of managed cattle grazing as a stand-in for native grazers

Desert

The largest of the biomes in area, desert covers nearly 30% of Earth's land surface and is found on every continent The desert biome features chronic moisture deficits and sparse, dry-adapted vegetation Most deserts receive less than 25 cm (10 in) of annual precipitation The single largest desert is the Sahara of northern Africa, covering almost 10 million km2 The Hoggar Mountains near Salah, Algeria are located in the Sahara The largest and driest deserts are found beneath the subtropical high, centered at about 30 degrees latitude north and south, but deserts are found at other latitudes as well.

The Human Footprint in the Mediterranean Biome

The main anthropogenic agents of change in the Mediterranean biome are agriculture and urban development, overgrazing of livestock (particularly by sheep and goats around the Mediterranean Sea), fire suppression, and non-native plants. California has been particularly affected in this last regard, as more than 1,000 non-native plants have established populations there. The native perennial grasses of California have been almost completely replaced by agriculture and non-native annual species, mostly from the Mediterranean region. Many plants in the Mediterranean region, in turn, are from California.

Habitat and Species Loss

The materials that surround us—homes, phones, books, clothes, the materials used to make our roads and buildings—without exception, were at one point resources found in nature. Like any other species, people require resources and food and space. The needs of the 7.6 billion people who are alive in the world lead to the transformation of Earth's surface from natural biomes to mosaics of human land uses. Habitat loss is now the most significant factor causing species endangerment and extinction One-third of the species threatened with extinction today are threatened because their habitat is being degraded or is disappearing altogether The materials people use and the foods people eat come to us through a global network of trade. Many of the goods and materials North Americans and Europeans enjoy originate overseas, where their extraction or production often takes an environmental toll. Coffee, for example, comes from Brazil, beef from Argentina, cacao (chocolate) from Central America, and palm oil from Indonesia Unless they are locally produced or responsibly produced in the host country, many of the goods we use are connected through global trade to habitat degradation and species endangerment far away. The Geoffrey's spider monkey in Central America (Mexico) is threatened by the spread of coffee and cacao plantations

Midlatitudes (temperate latitudes)

The midlatitudes, or temperate latitudes, are the transitional regions between warm subtropical air and cold polar air. Temperate biomes experience a large annual temperature range if they are far from the moderating effects of the oceans they have a smaller annual temperature range if they are near the coast

Where are the world's oldest trees found?

The montane biome High elevations at midlatitudes have low temperatures for much of the year. These low temperatures and the short growing season cause many tree species to grow slowly and allow them live for millennia

Montane Forest

The montane forest biome occurs where orographic lifting increases precipitation on the windward side of a mountain range The vegetation of the montane forest biome is needle-leaved in the Northern Hemisphere and broad-leaved in the Southern Hemisphere. Because it is found at a wide range of latitudes and elevations, the montane forest is one of the most climatologically diverse biomes This montane forest is near Creel, Chihuahua, Mexico. This climate diagram for Creel shows that the average annual temperatures vary greatly within the montane forest biome, depending on elevation and latitude. Average annual precipitation also varies significantly by latitude, with some areas receiving over 250 cm As a rule, precipitation is always sufficient to support trees. Montane forest is found in North America from the highlands of Mexico to southern Alaska. Other significant montane forests are found in the Andes in South America, the eastern African highlands, the European Alps, and the mountains of Asia. The montane forests of the Northern Hemisphere are dominated by species in the pine family, such as spruce, larch, pine, and fir. The pines do not occur in the Southern Hemisphere, and montane forests there are dominated by different tree species, depending on the location. Evergreen broad-leaved eucalyptus trees, for example, dominate Australia's montane forests. New Zealand's montane forests are dominated by evergreen broad-leaved southern beeches, and podocarps, as are Patagonia's in southern South America.

Northern tree line

The northern limit of the boreal forest is called the northern tree line

Temperature ranges of northern and alpine tundra

The northern tundra and alpine tundra at midlatitudes have large annual temperature ranges. In contrast, alpine tundra within the tropics, called tropical alpine scrubland, experience little annual temperature variation Instead, these areas experience diurnal temperature swings: Days are cool, and nights are below freezing every day of the year Tropical alpine scrubland occurs above 3,300 m (10,560 ft) elevation and is found in Hawai'i, the Andes of South America, the mountains of East Africa, and the New Guinea highlands It is dominated by herbaceous perennials with rosette growth forms

Prominent grass species in North America

The prominent grass species found in North America were buffalo grass (Buchloe dactyloides), little bluestem (Schizachyrium scoparium), and switchgrass (Panicum virgatum).

African savanna grazing sequence

Throughout Africa's savanna biome, different herbivorous mammals eat different parts of plants at different times. This variation allows large populations of many species to coexist in the same region without exhausting the resources As the summer rains diminish and the vegetation dries, the animals migrate to a different area with new growth Time -> Weeks and months 1) Water buffalo After monsoon rains, water buffalo arrive first, eat leaves and tall river grasses, and then move on to areas where there new growth 2) Zebras The plains zebra follow the water buffalo. Zebras eat the shortened grasses and new grass growth stimulated by the grazing and stomping of the water buffalo 3) Wildebeests Eat taller grasses that zebra do not eat 4) Topi Topi, eland, and Thompson's gazelles eat herb as grass growth stimulated by earlier animal activity

Temperate grassland

The temperate grassland biome is largely dominated by grasses It is characterized by significant moisture deficits for most of the year, natural fires, and grazing herbivores—all factors that keep trees from becoming established in most temperate grasslands. Temperate grasslands are found mostly between 30 and 60 degrees latitude in continental interiors They go by several local names: prairie in North America, pampas in South America, steppe in Eurasia, and veldt in South Africa The pampas grassland biome near Córdoba, Argentina, is vast. This climate diagram for Córdoba indicates that most temperate grassland regions have a large annual temperature range, with warm summers and cold winters. (Note that Córdoba is in the Southern Hemisphere, so the temperature is coolest in June through August.)

Global extinction rate

The tropical rainforest biome is home to approximately 40% of all species on Earth, making this biome central to efforts to estimate the global extinction rate. The global extinction rate is in large part a reflection of the rate of deforestation in this biome There are anywhere from 5 million to 8 million species worldwide. About 1% to 5% of those species are lost each decade, mostly because of habitat loss—and mostly in tropical rainforests. Consumers of many of the products that are driving rainforest loss—such as palm oil, soybeans, beef, and hardwood lumber—are becoming increasingly aware of the connection between these products and the forests from which they come To help consumers make informed choices, the European Union, for example, passed a law in 2014 requiring food products containing palm oil to be labeled as "palm oil" rather than something misleading, such as "vegetable oil." Likewise, a growing number of companies require that imports of palm oil be sourced from growers that meet stringent sustainability requirements, including the use of farming methods that do not cause deforestation. This allows them to label their palm oil product as "sustainably grown" in order to cater to consumers who are aware of and concerned about this problem Roughly 45 million metric tons of palm oil are produced each year, and about 13% (6 million metric tons) is certified as sustainable. This percentage is small but growing.

Three factors influencing the vegetation structures of tropical savannas

The tropical savanna has low biomass and relatively low biodiversity compared to the tropical rainforest 1) Seasonally intense rainfall The rainfall arrives with the ITCZ in summer, all within a few months, and often in the form of thunderstorms that produce heavy downpours. Deciduous plants grow during the rainy season and are dormant during the dry season 2) Fire During the warm winter dry season, abundant fuel and dry conditions favor frequent wildfires. Many savanna plants are adapted to survive fire. 3) Grazing pressure More than 90 species of grazing ungulates (hoofed mammals) roam the African tropical savanna. Although the tropical savanna has low overall biomass, it is able to support the world's largest and densest grazing animal community because the animals do not all graze at the same time

Tropical seasonal forest biome

The tropical seasonal forest biome is often mistaken for tropical rainforest, but the tropical seasonal forest is distinguished from the rainforest biome by its winter season of reduced precipitation The tropical seasonal forest is sometimes considered an ecotone (a transition between two biomes) for the tropical rainforest and the tropical savanna The tropical seasonal forest biome is found in the warm lowland tropics bordering the tropical rainforest Many trees in this biome are broad-leaved and deciduous A deciduous tree or shrub sheds its leaves, leaving bare branches In the tropical seasonal forest biome, many trees shed their leaves in response to the winter dry season This tropical seasonal forest at the Mayan archaeological site Tikal in eastern Guatemala, is located near Belmopan, Belize. the average annual temperatures in this biome are similar to those of the tropical rainforest biome, never dropping below 18°C (64°F). Precipitation averages roughly 150 to 275 cm (60 to 108 in) per year Most tropical seasonal forest lies within the tropics (23.5 n/s of the equator). In India, however, it was once found as far north as 30 degrees latitude (but has been converted to agriculture)

Tundra

The tundra biome occurs at any elevation or latitude where it is too cold for trees to grow. There are three types of tundra: alpine tundra, found at high elevations; northern tundra, found at high latitudes in the Northern Hemisphere; Antarctic tundra, found only in limited coastal areas in Antarctica. Purple saxifrage (Saxifraga oppositifolia) is typical of the low-growing herbaceous plants in the tundra biome. This plant is in full bloom near Resolute, Nunavut, Canada This climate diagram for Resolute shows that the average annual temperatures in tundra range from -15°C to -5°C (-5°F to 23°F). Average annual precipitation varies considerably with latitude but is generally less than 100 cm (39 in). This map shows the extent of the northern tundra (in purple) and mountainous areas with potential alpine tundra (in gray). The Antarctic tundra is too geographically limited to be visible on this map.

Three fundamental physical limiting factors

The type of native vegetation found in any given area, whether it is forest or desert, reflects three fundamental physical limiting factors: temperature, water, and light. At the local level, other factors may be important, too, such as soil types and biological limiting factors like herbivory and nutrient supplies. In mountain ranges, slope steepness, slope aspect (the direction the slope is facing), and microclimates (the distinct climates of restricted areas) also determine the types of organisms that are found there.

Amazon rainforest layered structure

There are four layers of vegetation in many tropical rainforests: the forest floor, the understory, the canopy, and the emergent canopy. 1) Emergent Canopy (40+ m) Only the tallest trees, like the Brazil nut, reach about the emergent canopy, as high as 60m above the forest floor. Harpy eagles 2) Canopy (24+ m) The branches and leaves of trees are found mostly in the well-lit canopy. Fruits and nuts and concentrated in the canopy, attracted insects and animals. Red and green macaw, maned sloth, and blue morpho (butterflies) Heliophytes dominate in the intense light of the upper canopy 3) Understory (6+ m) A dimly lit area that includes everything between the canopy and forest floor. Vegetation is far less dense in the understory compared to the canopy. Jaguars Lianas climb tree trunks of canopy trees reach the sunlight of the canopy. Light gaps form when a canopy tree falls. Other plants exploit the newly exposed sunlight and quickly fill the gap Epiphytes gain nutrients from water and organic material that falls in their cup-like leaves 4) Forest floor (below 6m) As little as 1% of sunlight reaches the forest floor. The forest floor is a dark, humid, and windless environment where sciophytes dominate. Buttress roots stabilize tall, top-heavy trees. Brazilian tapir Indigenous peoples live in the rainforest, gathering foods like Brazil nuts

Three types of low-latitude biomes

There are three low-latitude biomes: tropical rainforest, tropical seasonal forest, and tropical savanna.

Köppen (pronounced KUHR-pen) climate classification system

There is a spatial correspondence between climates and biomes. For this reason, classifying and categorizing climate types is useful when we are discussing biomes. first published by Wladimir Köppen in 1884. The Köppen system categorizes climates based on the temperature and precipitation characteristics of a region Because of the strong correspondence between vegetation structure and climate, the Köppen climate categories were originally based on the type of natural vegetation growing in an area. There are six major Köppen climate groups containing 25 climate zones. --- A: Tropical climates Af - Tropical wet Am - Tropical monsoon Aw - Tropical savanna B: Dry climates BWh - Subtropical desert BWk - Midlatitude desert BSh - Subtropical steppe BSk - Midlatitude steppe C: Mild midlatitude climates Cfa, Cwa, Cwb - Humid subtropical Cfb, Cfc - Marine west coast Csa, Csb - Mediterranean D: Severe midlatitude climates Dfa, Dwa, Dfb, Dwb - Humid continental Dfc, Dwc, Dfd, Dwd - Subarctic E: Polar climates ET - Tundra EF - Ice sheet H: Highlands H - Cold mountain climates Extreme events such as droughts and disturbances such as fire also determine the spatial distribution of vegetation. For this reason, biomes and Köppen climate zones do not overlap precisely.

Biomes found at all latitudes

Three biomes occur across a wide range of latitudes We cover the biomes in this section using a moisture gradient, from wet to dry, rather than organizing according to latitude. montane forest biome, relatively dry tundra, and the desert biome

Low-latitude biomes

Tropical rainforest, tropical seasonal forest, and tropical savanna

Tropical Savanna

Tropical seasonal forest transitions into tropical savanna, which is centered at about 25 degrees north and south latitude a woodland biome, featuring widely spaced trees with a continuous cover of grass, is characterized by wet summers and dry winters The winter dry period is much drier and lasts much longer in tropical savanna than in tropical seasonal forest—as long as 7 months in some locations In the drier portions of tropical savanna, where the winter dry season lasts 6 months or more, a type of tropical savanna called thorn woodland is found In thorn woodland, which differs from more common tropical savanna, there are more shrubs than trees, and vegetation is tough and thorny in response to frequent fires, grazing pressure by animals, and the prolonged dry season. This climate diagram for Gaborone, Botswana indicates that in tropical savanna, average annual temperatures range from 15°C to 30°C (59°F to 86°F). (Note that Gaborone is in the Southern Hemisphere, so the summer rainy season occurs mainly in November through March.) Winters are warm. Annual average rainfall ranges from 40 to 175 cm Thorn woodland may receive as little as 30 cm (12 in) of rainfall per year. Half of all tropical savanna is found in Africa, where the biome covers about 65% of the continent. Local names for tropical savanna: Llanos, Cerrado, Bushveld and mopane, Brigalow

How can we portray biomes graphically?

We can portray biomes graphically by plotting temperature and precipitation each biome occupies a different climatological space on a graph. This diagram portrays the relationship between biomes and climates graphically. Tropical rainforests occupy the climates with the highest precipitation and temperature, represented by the ecological space at the top left. Tundra occupies the climates with the lowest precipitation and temperature, at the lower right subtropical desert occupies warm and dry climates, at the lower left.

Tropical rainforests soils

Where there is volcanic activity, such as throughout Indonesia, tropical rainforest soils are young and nutrient-rich because they are continually replenished by volcanic ash However, most tropical rainforest soils (called oxisols) in South America and Africa are poor in nutrients Soil weathering (chemical disintegration) in the warm, humid climate and leaching by heavy rainfall move nutrients deep into the soil, out of the reach of plant roots For this reason, decaying organic material is quickly taken up by the shallow root systems of the forest vegetation rather than entering the soils Soils in the Amazon rainforest are particularly nutrient-poor due to leaching. People living in the Amazon long ago modified the soils to support farming. Those modified soils are still being discovered today

Why Should We Save Species?

Why should we lament the fragmentation and loss of a biome? Why should anyone care about the loss of a spider monkey in Central America or orangutans in Borneo? It is unfortunate that we lose roughly 7,000 km2 (2,700 mi2) of Amazon rainforest each year, along with an unknown number of species never before seen by people But does it matter in a practical sense? Even though most people will never see a spider monkey or an orangutan outside a zoo and will never visit a tropical rainforest, saving a single species matters. To save a species, we must save the ecosystem in which it lives, and saving ecosystems helps humans in four direct ways

Anthropogenic biomes

With the aid of remote sensing technology and the powerful tool of GIS, detailed maps of human land use across Earth's surface and the resulting anthropogenic biomes have been made These maps illustrate how natural biomes have been changed by human activity and highlight areas where natural biomes remain In some regions, such as in India and eastern China, the original natural biomes no longer exist. In other regions, such as northern Canada, the natural biomes are intact.

Plant growth forms (largest to smallest)

Within each biome, plants take on a variety of growth forms. In addition to the names of these plant growth forms, this chapter includes a number of botanical (plant-related) terms that describe characteristics of plant growth and plant adaptations 1) Tree Tall, upright woody growth 2) Liana Woody, climbing vine 3) Shrub Many woody stems 4) Forb Low, nonwoody plant other than grass 5) Epiphyte Grows on the surface of trees, not parasitic 6) Bryophyte Member of the division that includes mosses

Alpine tundra

a cold, treeless high-elevation biome whose vegetation consists mainly of shrubs and herbaceous perennials Alpine tundra occurs in high mountainous areas, including the Canadian Rockies, the Andes, and the Himalayas

Northern tundra

a cold, treeless high-latitude biome also dominated by herbaceous perennials found north of the boreal forest throughout northern Eurasia and North America

Tropical alpine scrubland

alpine tundra within the tropics, called tropical alpine scrubland, experience little annual temperature variation Instead, these areas experience diurnal temperature swings: Days are cool, and nights are below freezing every day of the year Tropical alpine scrubland occurs above 3,300 m elevation found in Hawai'i, the Andes of South America, the mountains of East Africa, and the New Guinea highlands It is dominated by herbaceous perennials with rosette growth forms The similarity of the plants in these widely separated locations is an example of ecological equivalence

Primary forest

forest that has never been significantly altered by people

Tropical rainforest

found in the humid lowland tropics has the highest primary productivity the highest biomass (weight of dried vegetation) highest biodiversity of any biome It occupies around 13% of Earth's land surface and accounts for about 40% of the world's biodiversity A great variety of organisms in many different groups, including insects, birds, mammals, and amphibians, live in this biome Worldwide, for example, this biome is home to about 250 species of primates, such as humans, gorillas, lemurs, and monkeys All primates are mammals, and all have nails instead of claws, flexible hands and feet, good eyesight, and high intelligence With the exception of humans and the Japanese macaque (Macaca fuscata), also known as the snow monkey, all primates live in tropical or subtropical areas. Most of them live in the tropical rainforests. in tropical rainforests, the average annual temperature does not drop below 18°C (64°F), and an average of at least 250 cm (98 in) of precipitation falls each year Although tropical rainforest can occur within about 25 degrees north and south of the equator, this biome is found mainly within 10 degrees of the equator. About half of all tropical rainforest is in the Amazon Basin in South America. In the tropical rainforest biome, water is available in every month, and competition for light is a major limiting factor

Five biomes found at the middle and high latitudes

temperate grassland, the Mediterranean biome, temperate deciduous forest, temperate rainforest, and boreal forest

Important feature of the northern tundra

the number of migratory animals it receives each summer. Although its summers are brief, they have an abundance of food resources because the daylight hours are very long North of the Arctic Circle, the Sun does not set, and biological productivity experiences a brief burst during this time. Many bird species use the northern tundra for summer breeding because of the relatively small number of predators found there and the plentiful food supply for their nestlings

Lianas

woody climbing vines that are well adapted to tropical rainforest habitat, grow quickly up trees to reach light in the canopy Lianas also provide routes of travel for arboreal (tree-dwelling) animals such as reptiles and primates, like monkeys and tamarin