A terrestrial ecosystem is an ecosystem found only on landforms. Six primary terrestrial ecosystems exist: tundra, taiga, temperate deciduous forest, tropical rain forest, grassland and desert.
Taigas are cold-climate forests found in the northern latitudes.
Taigas are the world’s largest terrestrial ecosystem and account for about 29% of the Earth’s forests. The largest taiga ecosystems are found in Canada and Russia.
Taigas are known for their sub-arctic climate with extremely cold winters and mild summers.
They primarily consist of coniferous trees, such as pines, although there are some other deciduous trees, such as spruce and elm, that have adapted to live in these areas that receive little direct sunlight for much of the year.
Taigas are home to large herbivores, such as moose, elk, and bison, as well as omnivores, such as bears.
The tundra ecosystems of the world are found primarily north of the Arctic Circle.
They consist of short vegetation and essentially no trees.
The soil is frozen and covered with permafrost for a large portion of the year.
Caribou, polar bears, and musk ox are some of the notable species who call the tundra home.
Temperate forests are the regions which have seasonal variation in climate i.e., the climate changes a lot from summer to winter.
The annual rain fall is about 750- 2000 mm and soil is rich. Such types of forests are found in western and central Europe, Eastern Asia and eastern North America.
These forests have deciduous trees (oaks, maples etc.) and coniferous trees (pines).
These forests contain abundant micro-organ- isms, mammals (hares, deer, fares, coyotesetc). Birds (warblers, wood peckers, owls etc.) snakes, frogs, salamanders etc.
• Tropical Rain forests:
Tropical rain forests are special ecosystems which accommodate thousands of species of animals and plants.
These are usually densely packed tall trees those form a ceiling from the sun above. The filing prevents the growth of smaller plants.
The temperature remains almost same throughout the year.
Such types of forests are found in Brazil of South America (Neotropic) and Central and West Africa. The area is always warm and muggy.
Grasslands are areas dominated by grasses. They occupy about 20% of the land on the earth surface.
Grasslands occur in both in tropical and temperate regions where rainfall is not enough to support the growth of trees.
Grasslands are found in areas having well defined hot and dry, warm and rainy seasons.
Desert are hot and low rain areas suffering from water shortage and high wind velocity.
They show extremes of temperature. Globally deserts occupy about 1/7th of the earth’s surface.
Desert animals include shrew, fox, wood rats, rabbits, camels and goat are common mammals in desert.
Other prominent desert animals are, reptiles, and burrowing rodents insects.
They adapt themselves to the dry weather conditions of desert area as stated in Adaptation topic
MAN MADE CHANGES
All natural environments and ecosystems now have an unprecedented problem to deal with humanity. Humans have brought about profound changes in a few centuries which would otherwise be expected over thousands or millions of years. The full impact of these remains to be accurately estimated. Major human impacts on ecosystems include the following:
1. Habitat Destruction and Fragmentation
The most direct impact of humans on ecosystems is in their destruction or conversion. Clear-cutting (the cutting of all trees within a given forest area) will, obviously, destroy a forest ecosystem. Selective logging may also alter forest ecosystems in important ways. Fragmentation- the division of a once continuous ecosystem into a number of smaller patches- may disrupt ecological processes so that the remaining areas can no longer function as they once did.
2. Climate Change
It is now widely accepted that human activities are contributing to global warming, chiefly through the accumulation of “greenhouse” gases in the atmosphere. The impact of this is likely to increase in the future. As noted above, climate change is a natural feature of the Earth. Previously, however, its effects were mitigated as ecosystems could effectively “migrate” by moving latitude or altitude as the climate changed. Today, so much of the world’s land surface has been appropriated by people that in many cases there is no such place for the remaining natural or semi-natural ecosystems to migrate to.
Contamination of the natural environment through a range of pollutants- herbicides, pesticides, fertilizers, industrial effluents, and human waste products- is one of the most pernicious forms of impact on the natural environment. Pollutants are often invisible, and the effects of air pollution and water pollution may not be immediately obvious, although they can be devastating in the long run.
4. Introduced Species
Human beings have been responsible either deliberately or accidentally for altering the distribution of a vast range of animal and plant species. This includes not only domesticated animals and cultivated plants but pests such as rats, mice, and many insects and fungi. Species which become naturalized may have a devastating impact, through predation and competition, on natural ecosystems, particularly on islands where native species have evolved in isolation. For instance, foxes, rabbits, cane toads, feral cats, and even buffaloes and camels have wreaked havoc in many ecosystems in Australia. Plants such as the South American shrub Lantana have invaded natural forests in many tropical and subtropical islands, causing major changes to these ecosystems, while the African water hyacinth Eichhornia has similarly disrupted freshwater ecosystems in many of the warmer parts of the world.
Removal of excessive numbers of animals or plants from a system can cause major ecological changes. The most important example of this at present is the over-fishing of the world’s oceans. Depletion of the great majority of accessible fish stocks is undoubtedly a cause of major change, although its long-term impact is difficult to assess.
Aquatic ecosystems are water-based ecosystems. Lakes, ponds, estuaries, saltwater marshes, oceans, and thermal vents are all examples of aquatic ecosystems, but each has different characteristics
• Fresh water ecosystem
Water on land which is continuously cycling and has low salt content is known as fresh water and its study is called limnology.
(i) Static or still water (Lentic) e.g. pond, lake, bogs and swamps.
(ii) Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
Physical characteristics: Fresh waters have a low concentration of dissolved salts. The temperature shows diurnal and seasonal variations. In tropical lakes, surface temperature never goes below 40 degreeC, in temperate fresh waters, never goes above or below 4 degree C and in polar lakes never above 4 degreeC.
Lakes and ponds are inland depressions containing standing water.
Three main zones can be differentiated in a lake:-
• Peripheral zone (littoral zone) with shallow water.
• Open water beyond the littoral zone where water is quite deep.
• Bentic zone (bottom) or the floor of the lake.
Ponds are small bodies of freshwater that are surrounded by land. Ponds are smaller and shallower than lakes, which means that the temperature of the water usually stays the same from top to bottom.
Wetlands are areas that periodically get inundated with water and support a flourishing community of aquatic organisms including frog and other amphibians. Swamps, marshes and mangroves are examples of wetlands.
• Marine ecosystem
Marine ecosystems cover approximately 71% of the Earth’s surface and contain approximately 97% of the planet’s water. They generate 32% of the world’s net primary production.
They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among different marine ecosystems.
Marine ecosystems can be divided into many zones depending upon water depth and shoreline features.
a) The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live.
b) The benthic zone consists of substrates below water where many invertebrates live.
c) The intertidal zone is the area between high and low tides; in this figure it is termed the littoral zone.
d) Other near-shore (neritic) zones can include estuaries, salt marshes, coral reefs, lagoons and mangrove swamps.
e) In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.
Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, attenuate floods, recharge ground water and provide habitats for wildlife.