Biomes

Biomes

Some parts of the art have more or less the same kind of abiotic and biotic factors spread over a large are, creating a typical ecosystem over that area. Such major ecosystems are termed as biomes.

               An ecologist recognises a number of large ecological units  called biomes, which are based on the growth forms of the dominant vegetation. The distribution of terrestrial biomes is determined primarily by temperature and precipitation, but is also influenced by soil fertility and fire. Each biome is more or less isolated by oceans, mountain ranges or desert barriers. This geographical isolation tends  to restrict gene flow between these biomes. As a result, each biome maintains a characteristic species of living organisms.

Terrestrial biomes   Seven categories of the earth’s major biomes arranged by distance from equator are listed below.

1.       Tropical rain /evergreen forest  occur near equator, receive an enormous amount of rain year round, temperature ranges between 25° C  - 29° C  year round  and are characterized by the growth of tall tress and lush vegetation. Animal  diversity is highest in trophical forests.

2. Savanna ( hot deserts) alo lie near the equator but experience lesser rain than tropical rain forests and sometimes have prolonged dry spells. Savannas are characterised by open grasslands with scattered tress and shrubs.

3. Deserts (Cold Desert ) are extremely dry biomes; hot deserts are hot yearn round, whereas cold deserts are hot only in the summer. Deserts are great biological interest due to the extreme behavioral , morphological  and physiological adaptations of plants and animals that live there.

4. Temperate grasslands receive less rainfall than savannas but more than  deserts; the soil in temperate grassland is rich, so they are well suited to agriculture. Large grazers and burrowing mammals are native to temperate grasslands.

5. Temperate deciduous/ broad leaf forests receive moderate precipitation that well distributed throughput the year. The climate of temperate deciduous forests differs from tropical forests as they receive les rainfall, are found at higher and cooler latitudes and experience cold winters. The trees in temperate  deciduous forests lose their leaves and remain dormant throughout the winter. I has vertical layers including a closed canopy, one or two strata of under story trees,  a shrub layer and an herbaceous layer. In the northern hemisphere , many mammals in this biome hibernate in the winters, while bird species migrate to warmer climates.

6. Taiga is the coniferous forest of the north. It is the largest terrestrial biome on earth. The taiga consists primarily of cone-bearing  evergreen trees, which are able to survive long cold winters and low levels of precipitation . these forests are home to many birds and mammals. These forests are being logged at a very high   rate and old-growth stands of conifers may soon disappear.

7. Tundra even farther north than the taiga is the tundra, which covers about 20% of the earth’s land surface and consists largely of open grassland, often  boggy in summer, which lies over layer of of permafrost –soil whose water is permanently frozen. Alpine tundra is found on high mountain –top at all latitudes. The  arctic tundra winter is long and cold, while summer is short and mild. The  growing season is very short. Tundra vegetation is mostly herbaceous consisting of mixture of lichens, mosses,  grasses, dwarf shrubs and tress. Migratory birds use artic tundra extensively  during the summer as nesting grounds. Arctic tundra has recently become the focus of significant minerals and oil extraction.