Хэрэглэгч:Tsogo3/Ноорог/Үндсэн өгүүллэгээс/?Ширэнгэн ой-Rainforest
Ширэнгэн ой гэдэг нь жилд 1750-2000 мм-ээс илүү хур тундас (бороо) унадаг бүс нутаг дахь өтгөн ой юм.
Ширэнгэн ойд Дэлхийн нийт амьтан, ургамлын зүйлийн гуравны хоёр нь байх ба эрдэмтэд хэдэн сая зүйлийн ургамал, шавьж, микроорганизм нээгдээгүй байгаа гэж үзэж байна. Хэдийгээр хэрэглэдэг хэмжээнээсээ илүү хүчилтөрөгч ялгаруулдаг эсэх нь тогтоогдоогүй байгаа ч гэсэн, ширэнгэн ойг "Дэлхийн уушиг" гэж нэрлэдэг байна[1].[2]. Мөн ширэнгэн ойг "Дэлхийн хамгийн том эмийн сан" гэж хэлэх нь бий. Учир нь эндээс ихээхэн хэмжээний эмийн ургамлууд нээгдээд байна.
Тархалт засварлах
Тропикийн ширэнгэн ой засварлах
Тропикийн ширэнгэн ой нь экватор орчмийн өргөргийн 20 градусийн бүсэд байрлана. Дэлхийн хамгийн том тропикийн ширэнгэн ой бол Өмнөд Америкийн хойд хэсэгт, Амазон мөрний ай сав дахь Амазоны ширэнгэн ой юм. Үүнээс гадна Төв Америк, Африкт экваторын бүсийн дагуу Камерунаас Конго хүртэл, зүүн өмнөд Азид Мьянмараас Индонез, Папау Шинэ Гвиней хүртэл, мөн хойд ба зүүн Австрали, Хавайн арлууд дээр тархсан байна.
Дунд өргөргийн ширэнгэн ой засварлах
Тропикоос гадна, Хойд Америкийн Номхон далайн эрэг, Европт Ирланд, Шотланд, өмнөд Норвеги, Адиатын тэнгисийн эрэг, Хар тэнгисийн зүүн эрэг, Азид өмнөд Хятад, Тайвань, Япон, Солонгос, Сахалины арал, Оросын зүүн эрэг, Өмнөд Америкт Чили, Аргентин, Өмнөд Африк, Шинэ Зеланд, зүүн өмнөд Австралид ширэнгэн ой ургана. Энэ ширэнгэн ойг дунд өргөргийн ширэнгэн ой гэж нэрлэдэг байна.
Хөрс засварлах
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.
Уур амьсгалд үзүүлэх нөлөө засварлах
Эрдэмтдийн дийлэнхи нь ширэнгэн ойг нүүрстөрөгчийн давхар ислийг шингээгч гэж үзэхгүй байгаа ба бусад ойтой адил нейтраль төвшинд байдаг гэж тооцож байна[3][4]. Өөрөөр хэлбэл ширэнгэн ой нь агаар мандал дахь CO2 агуулгад төдийлөн нөлөөлөхгүй, харин уур амьсгалд хүчтэй нөлөө (жмшээлбэл, үүл үүсэх буюу усны уурын эргэлтэнд) үзүүлнэ. Харин хүний нөлөөгээр сүйтгэгдэж буй ширэнгэн ой (их хэмжээгээр мод огтолж буйгаас болж) нь ихээхэн хэмжээний CO2 ялгаруулж[5], үүнээс улбаалан мөн томоохон хэмжээний ган болж байна[6].
Rainforest layers засварлах
The rainforest is divided into five different parts, each with different plants and animals, adapted for life in that particular area.
Emergent layer засварлах
This layer contains a small number of very large trees which grow above the general canopy, reaching heights of 45-55 m, although on occasion a few species will grow to 60 m or 70 m tall. They need to be able to withstand the hot temperatures and dry winds. Eagles, butterflies, bats and certain monkeys inhabit this layer.
Canopy layer засварлах
The canopy layer contains the majority of the largest trees, typically 30-45 m tall. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops.
The canopy, by some estimates, is home to 40% of all plant species, suggesting that perhaps half of all life on Earth could be found there. The fauna is similar to that found in the emergent layer, but more diverse. A quarter of all insect species are believed to exist in the rainforest canopy.
Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, U.S. naturalist William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles".
True exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Exploration of the canopy is still in its infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor. The science of accessing tropical forest canopy is called dendronautics.[7]
Understorey layer засварлах
There is a space between the canopy and the forest floor, which is known as the understorey . This is home to a number of birds, snakes, and lizards, as well as predators such as jaguars, boa constrictors, and leopards. The leaves are much larger at this level. Insect life is also abundant. Many seedlings that will grow to the canopy level are present in the understorey. Only about 5% of the sunlight shining on the rainforest reaches the understorey. This layer can also be called a shrub layer.
Shrub Layer засварлах
The layer just above the floor, consists of mainly large-leaved plants and small trees able to survive on the meager amount of light let through by the canopy.
Forest floor засварлах
This region receives only 2% of the rainforest's sunlight, thus only specially adapted plants can grow in this region. Away from river banks, swamps and clearings where dense undergrowth is found, the forest floor is relatively clear of vegetation, as little sunlight penetrates to ground level. It also contains decaying plant and animal matter, which disappears quickly due to the warm, humid conditions promoting rapid decay. Many forms of fungi grow here which help decay the animal and plant waste.
Амьтан засварлах
Ширэнгэн ойд хөхтөн, гүрвэл, шувуу, шавьж зэрэг ихээхэн хэмжээний амьтан амьдардаг ба Дэлхийн амьтан ба ургамлын зүйлийн бүрдлийн тэн хагасаас илүү нь буюу 5 сая илүү зүйл байдаг байна[баримт хэрэгтэй].
Хүний хэрэглээ засварлах
Many foods originally came from tropical forests, and are still mostly grown on plantations in regions that were formerly primary forest.[8] Tropical rainforests are also the source of many medicinal drugs, with over half the medications originating from the rainforest. Tropical rainforests also provide timber as well as animal products such as meat and hides. Rainforests also have value as tourism destinations and for the ecosystem services provided.
Ой мод сүйтгэлт засварлах
Tropical and temperate rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is rapidly shrinking. Biologists have estimated that large numbers of species are being driven to extinction (possibly more than 50,000 a year) due to the removal of habitat with destruction of the rainforests Загвар:Waybackdate. Protection and regeneration of the rainforests is a key goal of many environmental charities and organizations. (It is doubtful that this rate will be sustained as the relative cost of logging rises with dwindling resources.)
Another factor causing the loss of rainforest is expanding urban areas. Littoral Rainforest growing along coastal areas of eastern Australia is now rare due to ribbon development to accommodate the demand for seachange lifestyles.
About half of the mature tropical rainforests, between 750 to 800 million hectares of the original 1.5 to 1.6 billion hectares that once graced the planet have already been felled. The devastation is already acute in South East Asia, the second of the world's great biodiversity hot spots. Most of what remains is in the Amazon basin, where the Amazon rainforest covered more than 600 million hectares, an area nearly two thirds the size of the United States. The forests are being destroyed at an ever-quickening pace. Unless significant measures are taken on a world-wide basis to preserve them, by 2030 there will only be 10% remaining with another 10% in a degraded condition. 80% will have been lost and with them the natural diversity they contain will pass away forever.
Many tropical countries, including Indonesia, Thailand, Malaysia, Bangladesh, China, Sri Lanka, Laos, Nigeria, Liberia, Guinea, Ghana and the Cote d'lvoire have already lost large areas of their rainforest. Eighty per cent of the forests of the Philippine archipelago have already been cut down. "In 1960 Central America still had four fifths of its original forest; now it is left with only two fifths of it. Half of the Brazilian state of Rondonia's 24.3 million hectares have been destroyed or severely degraded in recent years. Several countries, notably the Philippines, Thailand and India have declared their deforestation a national emergency.[1][2]
Мөн үзэх засварлах
Ишлэл засварлах
- ↑ Broeker, W.S., 2006 "Breathing easy, Et tu, O2" Columbia University http://www.columbia.edu/cu/21stC/issue-2.1/broecker.htm.
- ↑ Moran, E.F., "Deforestation and Land Use in the Brazilian Amazon", Human Ecology, Vol 21, No. 1, 1993 “It took more than 15 years for the "lungs of the world" myth to be corrected. Rain forests contribute little net oxygen additions to the atmosphere through photosynthesis.”
- ↑ Broeker, W.S. (2006) Breathing easy, Et tu, O2. Columbia University http://www.columbia.edu/cu/21stC/issue-2.1/broecker.htm
- ↑ Pregitzer, K. and Uskirchen, S. (2004) Carbon cycling and storage in world forests: biome patterns related to forest age. Global Change Biology 10: 1–26
- ↑ Malhi, Y and Grace, J. 2000 " Tropical forests and atmospheric carbon dioxide”, Tree 15
- ↑ http://www.theage.com.au/articles/2004/03/06/1078464675256.html?from=storyrhs
- ↑ http://www.dendronautics.org/
- ↑ Myers, N. (1985). The primary source. W. W. Norton and Co., New York, pp. 189-193.
- Richards, P. W. (1996). The tropical rain forest. 2nd ed. Cambridge University Press ISBN 0-521-42194-2
- Whitmore, T. C. (1998) An introduction to tropical rain forests. 2nd ed. Oxford University Press. ISBN 0-19-850147-1
- Butler, R. A. (2005) A Place Out of Time: Tropical Rainforests and the Perils They Face. Published online: rainforests.mongabay.com
Гадаад холбоос засварлах
Commons: Rainforest – Викимедиа дуу дүрсний сан