Rainforest Info.

Rainforests are forests characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1750 mm and 2000 mm.
The largest tropical rainforests exist in the Amazon Basin (the Amazon Rainforest), in Nicaragua (Los Guatuzos, Bosawás and Indio-Maiz), the southern Yucatán Peninsula-El Peten-Belize contiguous area of Central America (including the Calakmul Biosphere Reserve), in much of equatorial Africa from Cameroon to the Democratic Republic of Congo, in much of southeastern Asia from Myanmar to Indonesia and Papua New Guinea, northern and eastern Australia and in some parts of the United States. Outside of the tropics, temperate rainforests can be found in British Columbia, southeastern Alaska, western Oregon and Washington, the northern coast of California, Scotland and Norway, the western Caucasus (Ajaria region of Georgia), parts of the western Balkans, Japan, southern Chile, New Zealand, Tasmania, and parts of eastern Australia.
Rainforests are home to two-thirds of all the living animal and plant species on the planet. It has been estimated that many hundreds of millions of new species of plants, insects and microorganisms are still undiscovered. Tropical rain forests are called the "jewels of the earth", and the "world's largest pharmacy" because of the large amount of natural medicines discovered there. Tropical rain forests are also often called the "Earth's lungs", however there is no scientific basis for such a claim as tropical rainforests are known to be essentially oxygen neutral, with little or no net oxygen production.[1].[2]
Despite the growth of vegetation in a rainforest, the actual quality of the soil is often quite poor. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red color and sometimes produces minable deposits (e.g. bauxite). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile.
The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level. This makes it possible for people and other animals to walk through the forest. If the leaf canopy is destroyed or thinned for any reason, the ground beneath is soon colonized by a dense tangled growth of vines, shrubs and small trees called jungle.
In contradiction to popular belief rainforests are not major consumers of carbon dioxide and like all mature forests are approximately carbon neutral.[3][4] Recent evidence suggests that the majority of rainforests are in fact net carbon emmiters.[5] However, rainforests do play a major role in the global carbon cycle as stable carbon pools. Clearance of rainforest leads to increased levels of atmospheric carbon dioxide. Rainforests may also play a role in cooling air that passes through them. As such, rainforests are of vital importance within the global climate system.





Contents[hide]

1 Rainforest layers

1.1 Emergent layer
1.2 Canopy layer
1.3 Understory layer
1.4 Shrub Layer
1.5 Forest floor
2 Fauna
3 Human uses
4 Deforestation
5 See also
6 References

6.1 General references
6.2 Specific references
7 External links
雨林是雨量甚多的生物區系。它有「綠色地獄」之稱。雨林依位置的不同分熱帶雨林和溫帶雨林。雨林大多數靠近赤道，在赤道經過的非洲、亞洲和南美洲，都有大片的雨林。濕潤的氣候保證了樹和植物的快速生產。同時，樹和植物也為雨林中的成千上萬種生物提供了食物和庇護所。
雨林曾經覆蓋了14%地球土地表面，但現在只剩下6-8%土地表面，即整體表面的2%。雖然雨林只覆蓋地球的6%的土地，但卻有一半以上的動物和植物的品種在雨林中出現。
雨林有時被稱為「地球肺部」和「世界最大藥廠」，因為大量自然藥物或藥物的原材料都在那兒找到。全球所用的藥物中，幾乎一半來自雨林。科學家相信更多疾病的解藥將來可以在雨林中找到。
雨林地區往往有大河流過，如南美洲的亞馬遜河。許多雨林在一年中有幾個月會暴發洪水。