Biomes Biology

Biomes

29/11/2012 AD

Taiga or Boreal forest The Taiga is an area of coniferous forest that is the largest land Biome as it makes up 29% of the forest cover of the world. It constitutes most of inland Canada, Alaska and northern US states, most of Sweden, Finland and Norway, lowland and coastal areas of Iceland, Russia: from St. Petersburg to the Pacific ocean including most of Siberia, northern Kazakhstan, northern Mongolia, and northern Japan on the island of Hokkaidō. Being a coniferous area of woodland the main tree species are: pine, larch, birch and spruce. Some of these trees (spruce and pine) are adapted to the climate by having smaller, prickly leaves with waxy cuticles to reduce water loss and do not defoliate in winter. The advantage of this being that the trees may take in all the available sunlight for photosynthesis. The branches on such trees tend to be slightly elastic and bend under the eight of snow causing it to fall off and expose the leaves to the sun. The trees also have very shallow roots due to the continuous permafrost that restricts growth and also slows down the nutritional development of the soil. Temperatures in the Taiga have a huge variation between winter and summer and may vary from −54 °C to 30 °C throughout the whole year. The summers are generally short but are humid, warm and never last more than four months. In much of the taiga, -20 °C would be an average winter day temperature and 18 °C an average summer day temperature with average annual temperatures at 3°C. In some parts of the Taiga such as the Alaska-Yukon area the annual temperatures could be as low as -10°C due to the extended winters. Precipitation is generally low in the Taiga and the majority is summer rain, in all: there is 400mm to 600mm of precipitation per year to the west and eastward it gradually falls to 200mm a year.

Mediterranean The Mediterranean forests, woodlands, and scrub biome can be found around the world in five different locations: Mediterranean Basin, Californian chaparral, Southwest Australia, Chilean Matorral and the Western Cape areas of South Africa. It is named Mediterranean because of the climate shared with that of the general area of the Mediterranean Sea. Mediterranean forests, woodlands, and scrub biome, are characterized by dry summers and rainy winters. Summers are typically hot in low-lying inland locations but can be cool near some seas, as near San Francisco, which have a sea of cool waters. Temperatures will frequently exceed 40°C but normally remain above 30°C. Winters are typically mild to cool in low-lying locations but can be cold in inland and higher locations such as the Appennini in Italy where it often snows in winter. Average temperatures vary between 3 to 5°C in winter but the cold does not last long because of the long summers that give the Mediterranean its characteristic appearance. The rainfall ranges from 100-150mm in winter to around 15-25mm in summer. The vegetation in the Mediterranean biome must withstand the arid soil, prolonged droughts of the summer and long periods of rainfall in winter. Pines, Oaks, Sycamores, Oaks, and Buckeyes, Olives, Figs, Citrus, Walnuts and Grapes are all prime examples of Mediterranean plants because they can survive the long droughts – citrus plants especially because water that would normally be sent to the fruit would instead be carried to the rest of the plant to stay alive. Pines as evergreens do not lose much water in the hot temperatures due to the small leaves and smaller surface area.

Tundra The Tundra is one of the coldest biomes on the planet and occupies the regions: coastal Greenland, very north of Canada and Alaska and Russia, Antarctic islands and subantarctic islands. The main characteristic is that it lacks trees due to the very low annual temperatures, poor nutritional soil, low precipitation levels and short growing seasons. Due to this there occur tree lines that mark the very edge of growth; this may also be seen in high mountainous regions e.g. the Himalayas and the Alps. Low-lying tundra is located in the northern hemisphere, around the North Pole and spreading south to coniferous regions and the outermost extremities of the Antarctic in the southern hemisphere. The arctic tundra is cold with desert-like conditions and the growing season for plants lasting around 50 to 60 days cannot support larger organisms. The soil there is frozen from 25–90 cm which makes it impossible for trees to grow. Instead small mossy organisms and grass may grow but lasting only a matter of weeks before the winter temperatures kills them. Average winter temperatures may be around -34°C but an average summer temperature could be significantly higher: 3°C to 12°C which enables the biome to sustain life. Precipitation is 60% solid and less than 400mm annually. In Alpine Tundra no trees grow because of the limiting factors to photosynthesis and respiration. The temperature is too low and denatures the enzymes; the air at altitude is thinner so there is not enough oxygen for respiration. The growing season is about 180 days long. Unlike the arctic tundra, the soil in the alpine is better drained which means that in the short days of spring and summer more life can exist: mostly grasses, shrubs and flowers. Precipitation in mountainous regions, and other weather patterns, is more unpredictable than with normal weather patterns but normally it is very possible for a metre of snow to fall in winter in the space of just one day.

Savannah The Savannah is a grassland ecosystem consisting of scattered trees and isolated accumulations of vegetation. It is found between the rainforest and desert biomes, either side of the equator. Areas around the world considered as savannah grassland are: half of Africa, regions of Australia, South America, and India. The Savannah has two seasons and the characteristics of both seasons do not vary much in temperature due to their proximity to the equator but the summer/rain season brings disproportionate quantities of precipitation while the winter winter/dry season usually brings prolonged droughts. Savannahs are generally warm and temperate throughout the whole year. In the dry season only an average of 10cm of rain falls. Between December and February no rain falls at all and the dry season is a little cooler but it is still on average 21°C. In the summer the monsoon rains begin in May in which an average of 15 to 25cm of rain falls during this time. In this time the climate is very hot and humid so every day the hot, humid air rises from the ground and collides with cooler air above causing outbreaks of rain. Every year 51cm to 127cm of rain may fall but due to the concentration of this rain for six months of the year the savannah is mostly dry; otherwise the climate could be tropical. Also due to the porous soil the layer of humus is very thin allowing only superficial growth. For this reason the savannah is occasionally classified as a forest. A few of the plant species found in the savannah are: Baobab trees, elephant trees, acacia Senegal and eucalyptus, grasses and many shrubs. The adaptations these plants have to survive in this climate are more for the dry season as the trees have expanded water storage and transpire very slowly to conserve the water. Some trees are Pyrophytic which means that they are resistant to fire as such a dry place often sees bush fires.

Tropical Rainforest The tropical rainforest biomes are found within 30 degrees north and south of the equator – between the tropics of Capricorn and the tropics of Cancer - and its most distinct quality is that year-round the temperature and rainfall remains consistently high. Rainforests can be found in Asia, Australia, Africa, South America, Central America, Mexico and on many of the Pacific, Caribbean, and Indian Ocean islands. The reason why the climate is so stable is because the proximity to the equator means that the changes in seasons are menial so the average annual temperature is always from 20°C to 25°C and remains within this 5°C limit. The rainfall is annually more than 200cm making the rainforest the wettest biome on the planet. The moisture and humidity is trapped by the trees creating a miniature sub-climate with an additionally greater humidity. The high moisture and optimum temperatures mean that the rainforest has the greatest species diversity in the world: one square kilometre may contain as many as 100 different tree species, orchids, bromeliads, vines, ferns, mosses, and palms make up a large percentage to the hugely varied biodiversity. It is predicted that 70% of all biotic species live in the rainforest and this is one of the greatest reasons why deforestation is such a threat to life other than the environmental factor that deforestation reduces the planet’s ability to remove carbon dioxide from the atmosphere. Human ecological interventions in the form of deforestation occur as slash and burn where the land is cleared for agriculture. The biggest problem with this is that rainforest soil is very nutritionally poor so after only a period of a few years the land becomes useless leading to more deforestation and the use of artificial fertilisers.

--------------------------------------------
[ 1 ]. http://www.wilds.mb.ca/taiga/tbsfaq.html
[ 2 ]. http://worldwildlife.org/ecoregions/na0406 from the WWF website.
[ 3 ]. http://worldwildlife.org/ecoregions/na0607 from the WWF website.
[ 4 ]. http://wwf.panda.org/about_our_earth/ecoregions/eastern_siberian_taiga.cfm from the WWF website.
[ 5 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/tundra.php
[ 6 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/tundra.php
[ 7 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/tundra.php
[ 8 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/tundra.php
[ 9 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/grasslands.php
[ 10 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/grasslands.php
[ 11 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/grasslands.php
[ 12 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/forests.php#tropical
[ 13 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/forests.php#tropical
[ 14 ]. http://www.ucmp.berkeley.edu/exhibits/biomes/forests.php#tropical