* What: Hot and wet areas with broadleaved evergreen forest
* Where: Within 5°N and S of the equator
* Climate, limiting factors: High rainfall(2000-5000 mm yr-1), high temperatures( 26-28°) and high insolation, P>E rain washes nutrients out of the soil, so nutrients may limit plant growth
* Structure: amazingly high levels of biodiversity: plants compete for light thus growing tall to absorb it, so there is a multi-storey profile to the forests called stratification. Many niches and habitat for animals and large mammals can get enough food
* Net productivity: produce 40% of NPP of terrestrial ecosystems. Fast rates of decomposition, ...view middle of the document...
Oil has been found under deserts in the Gulf States. Irrigation is possible but evaporation rate is high so as water evaporates it leaves salts behind. Eventually crops will not grow because salt concentration is too high (salinization)
* Issues: desertification – an area becomes a desert through overgrazing/overcultivation/ drought e.g. the Sahel
* Examples: Sahara, Namib in Africa; Gobi in China
* What: fairly flat areas dominated by grasses and herbaceous (non-woody) plants.
* Where: in centres of continents 40-60°N of the equator
* Climate and limiting factors: P=E or P slightly > E. Temperature range high as not near the sea, which moderates temperatures. Clear skies, low rainfall, threat of drought
* Structure: grasses, wide diversity. Grazing animals, grasses die in winter, but roots survive. Decomposed vegetation forms a mat in which high levels of nutrients. Kangaroo, bison, antelope, carnivores e.g. wolves, coyotes. No trees
* Net productivity: not very high
* Human activity: cereal crops, black earth soils of the steppes rich in organic matter ideal for agriculture. Prairies in America less fertile-> have to add fertilizers. World’s “bread basket” wheat, maize. Livestock: cattle, sheep
* Issues: dust bowl in 1930s America: overcropping and drought led to soil being blown away on the Great Plains (ecological disaster). Desertification because of overgrazing
* Examples: North American prairies, Russian steppes, pampas in Argentina
What: mild climate, deciduous forest.
Where: between 40°-60°N and S of the equator.
Climate and limiting factors: P>E. Rainfall is 500-1500 mm per year. Winters freezing in some, milder in Western Europe due to the Gulf Stream. Temp range -30°C to + 30°C. Summers cool.
Structure: fewer species than tropical rainforests. Many woodlands show stratification, are dominated by one species, e.g. beech, oak. Trees have a growing season of 6-8 months. Rapid recycling of nutrients, although some are lost through leeching. Well-developed food chains with many autotrophs, herbivores (rabbits) and carnivores (foxes). Coniferous trees towards polar latitudes. P>E sufficiently to cause some leaching.
Net productivity: 2nd highest NPP after trop....