Describe major biome types and their typical climate.
Explain the function of each type of biome.
Identify the adaptation of organisms in each biome.
Biomes
Large-scale environments distinguished by characteristic temperature ranges and amounts of precipitation with a specific set of biotic and abiotic features.
Biome Concept
Alexander van Humboldt: Pioneering work on plant geography showed a close relationship between climate and vegetation in geographically disjunct regions, exhibiting climatic similarity in similar regions.
Schimper (1903): Developed the idea that similar climates select for similar plant forms independent of differences in history.
Biomes and Climate
Land biomes of the world are controlled by climate.
Climate: The characteristic condition of the atmosphere near the earth’s surface at a certain place. It is the long-term weather of that area (at least 30 years).
Two most important factors determining an area’s climate are air temperature and precipitation.
Whittaker's Biome Types
Diagram showing the relationship between annual precipitation (cm) and average temperature (°C) for various biomes, including:
Tropical rainforest
Temperate rainforest
Tropical seasonal forest/savanna
Temperate seasonal forest
Boreal forest
Woodland/shrubland
Subtropical desert
Temperate grassland/desert
Tundra
1. Tropical Rain Forests
Most biodiverse terrestrial biome.
High net primary productivity.
Cover about 6-7% of the earth’s land surface.
Found in regions close to the equator.
Climate
Warm and humid all year long.
Always moist and lacking temperature seasonality.
Average temperatures ranging from 20∘C to 34∘C.
Annual rainfall ranges from 125-660 cm (50–200 in) with considerable seasonal variation.
Soil
Highly acidic.
The type of clay particles present has a poor ability to trap nutrients and stop them from washing away.
Lacks minerals and contains little remains of dead plants and animals.
Decomposition is rapid on warm wet soil.
Less than 1 cm of topsoil; not very fertile.
Mycorrhizae help gather nutrients.
Vegetation
Characterized by vertical layering of vegetation and the formation of distinct habitats for animals within each layer.
Dominated by a continuous canopy of tall evergreen trees rising to 30–40 m.
Occasional emergent trees rise above the canopy to heights of 55 m or so.
Climbing lianas, or woody vines, and epiphytes (plants that grow on the branches of other plants and are not rooted in soil) are prominent in the forest canopy itself.
Layers
The Emergent Layer
The Canopy
The Understory
The Forest Floor
Plant Adaptations
Sunlight is a major limiting factor.
Shallow, wide roots since soil is so thin and poor in nutrients.
Little sun reaches the floor.
Plants grow in layers (canopy receives most light).
Examples: Bougainvillea, Bangul Bamboo
Animal Life
Dominant wildlife includes herbivores (sloths, tapirs, and capybaras); predators (jaguars); anteaters; monkeys; birds (toucans, parrots, and parakeets); insects (butterflies, ants, and beetles); piranhas and other freshwater fishes; and reptiles (frogs, Caymans, boa constrictors, and anacondas).
Many animals are specialists and require special habitat components to survive. Camouflage is common.
Heavily settled by humans with extensive clearing for agriculture.
Climate
Climate more seasonal (with a pronounced dry season during part of the year) than tropical rainforest.
Responds to the rhythms of the annual solar cycle which drive the oscillation between wet and dry seasons.
Characterized by little change in temperature.
Soil
Soils generally less acidic and richer in nutrients than tropical rainforests.
The annual pulses of torrential rain make the soil highly vulnerable to erosion, particularly when deforested and converted to agriculture.
Vegetation
Height of trees is correlated with average precipitation. Tallest trees are found in wettest areas.
Over 50% of trees are evergreen in wetter areas.
Have deciduous species of trees that lose their leaves at the onset of the dry season.
Many plants produce animal-dispersed seeds.
Animal Life
Many birds, mammals, and even insects make seasonal migrations to wetter habitats along rivers or to the nearest rainforest.
Many animals reduce their need for water by entering long periods of inactivity called estivation.
3. Savanna
Found in parts of the tropics where there is not enough rainfall throughout the year to create a rainforest.
Transitional between tropical rain forest and desert.
Located closer to the equator than prairies.
Grasslands with scattered trees and are found in Africa, South America, and northern Australia.
Climate
Rainy and dry season.
With Seasonal drought.
Rain comes in summer accompanied by intense lightning starting fire.
Soil
Soil layer with low water permeability.
Impermeable subsoil keeps surface soil waterlogged during the wet season.
Nutrients in soil are present mainly due to a thin layer of humus.
Vegetation
Grasses with few scattered trees.
Fire and grazing undoubtedly play important roles in maintaining the character of the savanna biome. The woody trees are very limited and usually do not get very tall.
Plant Adaptations
Grows in Tufts
Resistance to drought
Many plants have thorns and sharp leaves to protect against predation.
Adapt for short rainy season—migrate as necessary.
Reproduce during rainy season—ensures more young survive.
Examples: Zebras, Chacma Baboon
4. Temperate Grassland
Largest biome in North America.
The major manifestations are veldts of South Africa, the puszta of Hungary, the pampas of Argentina, the steppes of the former Soviet Union and the prairies of Central America.
Climate
Hot summers and cold winters.
Rainfall is moderate (300-1000mm). The amount of annual rainfall influences the height of the grass land vegetation with taller grasses in other regions.
Maximum precipitation occurs in summer.
Soil
The soil is deep and dark with fertile upper layers.
It is nutrient –rich from the growth and decay and many branched grass roots. The rotted roots hold the soil together. The soil is fertile because of the remains of plants and animals and dried leaves of plant fell on the ground.
Soils are fertile because the subsurface of the soil is packed with the roots and rhizomes (underground stems) of these grasses.
The roots and rhizomes act to anchor plants into the ground and replenish the organic material (humus) in the soil when they die and decay.
Vegetation
The dominant vegetation tends to consist of grasses.
The treeless condition is maintained by low precipitation, frequent fires, and grazing. The vegetation is very dense due to fertile soil.
Most abundant are plants called Bunch grasses, fine bladed grasses that grow in clumps to preserve water.
Sod-forming grasses that won’t dry out or blow away in wind.
Many adaptations to survive in extremes temperature and precipitation.
5. Desert
Occupy 20% of land surface.
Low species diversity.
Low water vapor content.
Evaporation and transpiration exceed precipitation.
Climate
Very hot and dry.
Receive less than 25 cm of rain per year while some receive NO precipitation at all during one year.
Receive more than twice as much incoming solar radiation as humid regions.
Often undergo large shifts in temperature during the course of a day.
Soil
Sandy, dry and loose; contains minerals like calcite.
Course-textured, shallow, rocky or gravely with good drainage and have no subsurface water.
Little to no topsoil due to high winds.
Minerals not deep in soil.
Too dry for decay (little OM).
Plant Adaptations
Spines
Succulents
Thick, waxy cuticle
Shallow, broad roots
Examples: Joshua Tree, Barrel Cactus, Ocotollio
Animal Adaptations
Get water from food
Thick outer coat
Burrow during day
Large ears
Smaller animals = less surface area
Examples: Javelina, Bob Cat, Armadillo Lizard
4 Major Types of Desert
Hot and dry desert
Semiarid desert
Cold desert
Coastal desert
Hot and Dry Desert
The seasons are generally warm throughout the year and very hot in the summer. The winters usually bring little rainfall.
The 4 major North American deserts of this type are the Chihuahuan, Sonoran, Mojave and Great Basin.
Vegetation is very rare. Plants are almost all ground-hugging shrubs and short woody trees. All of the leaves store nutrients. Some of the adaptations in this case are the ability to store water for long periods of time and the ability to stand the hot weather.
Animals include small nocturnal carnivores. The dominant animals are burrowers. The animals stay inactive in protected hideaways during the hot day and come out to forage at dusk, dawn or at night, when the desert is cooler.
Cold Desert
Characterized by cold winters with snowfall and high overall rainfall throughout the winter and occasionally over the summer.
Have a short, moist and moderately warm summers with fairly long, cold cactus winters. Usually occur in Antarctic, Greenland and Nearctic realm.
There are no trees and shrubs present at all. The only vegetation able to survive are liverworts, lichens and mosses.
Few amphibians, reptiles or mammals are native to cold deserts, but humans have introduced some animals, such as rats and mice. Native fauna includes spiders, earthworms, beetles and the Arctic fox.
Semiarid Desert
Summers are moderately long and dry and like hot deserts.
Winters normally bring low concentration of rainfall
Summer temperatures usually average between 21−27∘C; does not go above 38∘C and evening temperatures are cool at around 10∘C.
Major deserts of this type include the sage brush of Utah, Montana and Great Basin.
Coastal Desert
The cool winter’s coastal deserts are followed by moderately long, warm summers.
The average summer temperature ranges from 13−24∘C; winter temperatures are 5∘C or below.
The maximum annual temperatures are about 35∘C and the minimum is about −4∘C.
These deserts occur in moderately cool to warm areas such as the Nearctic and Neotrophical realm. A good example of this is Atacam and Chile.
6. Mediterranean Shrubland and Woodland
Occur in all continents except Antarctica.
Most extensive around Mediterranean Sea; extend from California into northern Mexico; also found central Chile, southern Australia, and southern Africa.
Chaparral (western North America); matoral (Mediterranean); fynbos (South Africa); mallee (Australia)
Climate
Cool and moist during fall, winter, and spring.
Summers are hot and dry.
Usually get more rain than deserts and grasslands but less than forested areas.
The combination of dry summers and dense vegetation, rich in essential oils, creates ideal conditions for frequent and intense fires.
Soil
Generally low to moderate fertility and fragile.
Soil erosion can be severe following fire.
Fire coupled with overgrazing has stripped the soil from some Mediterranean woodland and shrubland landscapes.
Vegetation
Dense low plants that contain flammable oils make fire a constant threat.
Trees and shrubs are evergreen and have small, tough leaves, which conserve both water and nutrients.
Sclerophyllous (“hard-leaved”) vegetation
Most herbaceous plants grow during the cool, moist season and die back in summer, avoiding both drought and fire.
Animal Life
Animals tend to be browsers.
Some prominent wildlife are coyotes, wild goats, mule deer, and the Mediterranean gecko.
Camouflage is common in exposed shrubland.
7. Temperate Forest
Found mid-latitude regions.
Harbor ancient trees.
The second largest terrestrial biome.
Most of the human population lives in this biome.
Climate
Temperatures are not extreme.
Annual precipitation averages from 650-3000 mm.
Receive more winter precipitation.
Soil
Soils are usually fertile.
Most fertile develops in deciduous forests with generally neutral or slightly acidic and rich in OM and inorganic nutrients.
Vegetation
Lower diversity of trees compared to tropical forests.
Vertically, stratified (herb layer, shrub layer, shade-tolerant understory trees and canopy.
More sunlight reaches the ground compared compared to a rainforest so more ground dwelling plants are found on the floor.
May either be deciduous (more dominant) or coniferous
Animal Life
Birds, mammals, and insects make use of all the forest strata.
Fungi, bacteria, microscopic invertebrates consume large quantities of wood stored on the floor of old-growth temperate forest.
The activities of these organisms recycle nutrients.
8. Boreal Forest (Taiga)
Found only in Northern Hemisphere (Northern parts of Alaska, Canada, Asia and Europe).
The NPP is lower than that of temperate forests and tropical wet forests.
The above-ground biomass is high because these slow-growing tree species are long-lived and accumulate a large standing biomass over time.
Climate
Warm and rainy summers.
Very long and cold winter lasting to about half a year; precipitation is in the form of snow about 60 cm.
Below -20 °C in winter and about 15°C in summer.
Soil
Soil is not fertile. It takes very long for needlelike leaves to decompose and decomposition is very slow in cold weather.
A layer of snow covers the ground during much of the year.
Soil beneath the snow is grayish on top and brown below and lacks minerals needed by plants to grow.
Vegetation
Mostly contains evergreen coniferous trees like pines, spruce, and fir, which retain their needle shaped leaves year-round.
Evergreen trees can photosynthesize earlier in the spring than deciduous trees because less energy from the sun is required to warm a needle-like leaf than a broad leaf.
Coniferous (needle-bearing) trees are abundant
Roots long to anchor trees
Needles long, thin and waxy
Low sunlight and poor soil keeps plants from growing on forest floor
Usually receives NO more precipitation than a desert biome (<25 in/year)
Short growing season
Limited sunlight
Average temperature is 23°F or 5 °C.
Soil
Ground covered with little snow.
Below the surface soil is permanently frozen (permafrost).
During summer, the top layer of soil thaws, but the rest remains frozen.
Decomposition is very slow because of the extreme cold.
Vegetation
Biodiversity of plant is very low.
Lichens, mosses, and short shrubs are dominant.
Plants are dwarf, prostrate woody shrubs grow low to the ground to gain protection under the winter blanket of snow and ice.
Growing close to the ground
Having shallow roots to absorb the limited water resources.
Trees grow less than 1 m high.
Examples: cottongrass, Reindeer lichen
Animal Life
Many birds that occur in Arctic tundra are migratory (summer).
The main animal population in the Arctic Tundra consists of reindeer, polar bears, arctic fox, arctic hare, snowy owls, lemmings and musk ox.
Animals living in the alpine tundra are pikas, marmots, mountain goats, sheep, elk, grouselike birds, springtails, beetles, grasshoppers,and butterflies.
Animal Adaptations
Many visitors, migration
Few predators
Little Competition
Small ears Insulation, thick coat
Examples: Arctic fox, snowy owl, Grizzly Bear
Types of Tundra
Arctic Tundra
Alpine Tundra
Arctic Tundra
Located between the North Pole and Coniferous Forest or Taiga region. It is extremely cold temperatures and land that remains frozen year-round. A layer of permanently frozen subsoil (permafrost) exists consisting mostly of gravel and finer material. The growing season ranges from 50-60 days.
North America- Northern Alaska, Canada, Greenland
Northern Europe- Scandinavia
Northern Asia- Siberia.
Alpine Tundra
Located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days. Very windy. Typically covered in snow for most of the year.
North America- Alaska, Canada, U.S.A. and Mexico
Northern Europe- Finland, Norway, Russia, and Sweden
Asia- Southern Asia( Mt. Himalayan ) and Japan (Mt. Fuji)
Africa- Mt. Kilimanjava
South America- Andes Mountains
Conclusion
Biomes as "the world's major communities”, are classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment".
The importance of biomes cannot be overestimated.
Thus, conservation and preservation of biomes should be a major concern to all. Because we share the world with many other species of plants and animals, we must consider the consequences of our actions. It is important to preserve all types of biomes as each houses many unique forms of life.