共有的特征是什么?store food in their bodies
有关具体操作步骤。记得的答案有light, attention, leaves, nutrients, holes.
What is Inga alley cropping?
Alley cropping is the growing of crops between rows of trees. Inga alley cropping consists of growing crops between rows of Inga trees. This has been found to increase yields. It is sustainable as it enables the same plot to be cultivated over and over, thus eliminating the need for the continual burning of the rainforest to get new fertile plots (slash and burn or shifting cultivation). Rainforest Saver is supporting Inga projects in Honduras and Cameroon.
The inga tree is native to many parts of Central and South America, but has been found to grow well in other parts of the world in the tropical rainforest belt.
The Inga is suitable because
it grows well on the acid soils of the tropical rainforest and former rainforest soils,
is a leguminous tree that fixes nitrogen (converts nitrogen into a form usable by plants),
has mycorrhizae (special fungi that grow with its roots) that take up phosphorus allowing it to be recycled instead of being washed out from the soil,
has thick leaves that when left on the ground after pruning form a thick cover that protects both soil and roots from the sun and heavy rain,
branches out to a thick canopy so as to cut off light from the weeds below, and
withstands careful pruning year after year.
For Inga alley cropping the trees are planted in rows (hedges) close together, with a gap, the alley, of say 4m between the rows.
When the trees have grown, usually in about two years, the canopies close over the alley and cut off the light and so smother the weeds.
The trees are then carefully pruned. The larger branches are used for firewood. The smaller branches and leaves are left on the ground in the alleys. These rot down into a good mulch (compost). If any weeds haven't been killed off by lack of light the mulch smothers them.
The farmer then pokes holes into the mulch and plants his crops into the holes.
The crops grow, fed by the mulch. The crops feed on the lower layers while the latest prunings form a protective layer over the soil and roots, shielding them from both the hot sun and heavy rain. This makes it possible for the roots of both the crops and the trees to stay to a considerable extent in the top layer of soil and the mulch, thus benefiting from the food in the mulch, and escaping soil pests and toxic minerals lower down. Pruning the Inga also makes its roots die back, thus reducing competition with the crops.
Research found that the main reason for the soil losing its fertility with slash and burn farming was that the rain was washing out phosphorus. The special fungi that grow with the Inga roots take up spare phosphorus, which then goes to the roots and into the tree. As the crops grow, so does the Inga. When the crops are harvested the Inga is allowed to grow back. Once more it closes the canopy, is pruned, and the cycle is repeated, time and again. When the tree is pruned the leaves fall on the ground and rot down and phosphorus is released for the crops. The fungi again take up spare phosphorus. Thus the cycle is repeated time and again. An initial application of rock phosphate has kept the system going for many years.
Not only do the farmers grow their basic crops of maize and beans, but also they now grow cash crops with this system. Previously this was not possible because when the plot was a good distance from the farmer's home he would not have been able to guard it, or give the crops all the attention they might need. But with the same plot being used continuously it can be near his home, thus allowing his family to help to tend and guard it, even when there are young children.
A bovid (family Bovidae) is any of almost 140 species of cloven-hoofed, ruminant mammals with characteristic unbranching horns covered in a permanent sheath of keratin in at least the males.
The family is widespread, being native to Asia, Africa, Europe and North America, and diverse: members include bison, African buffalo, water buffalo, antelopes, gazelles, sheep, goats, muskoxen, and domestic cattle.
The largest bovid, the gaur, weighs well over a ton and stands 2.2 m (7.2 ft) high at the shoulder; the smallest, the royal antelope, weighs about 3 kg and stands no taller than a large domestic cat. Some are thick-set and muscular; others are lightly built, with small frames and long legs. Many species congregate into large groups with complex social structures, but others are mostly solitary. Within their extensive range, they occupy a wide variety of habitat types, from desert to tundra and from thick tropical forest to high mountains.
Most members of the family are herbivorous, except most duikers, which are omnivorous. Like other ruminants, bovids have four-chambered stomachs, which allow them to digest plant material, such as grass, that cannot be used by many other animals. Such plant material includes much cellulose, and no higher animal can digest this directly. However, ruminants (and some others like kangaroos, rabbits and termites) are able to use micro-organisms living in their guts to break down cellulose by fermentation.
Because of the size and weight of their complex digestive systems, many bovids have solid, stocky builds. However, the more gracile species tend to have more selective diets, and be browsers rather than grazers. Their upper canine teeth and incisors are missing, and are replaced with a hard, horny pad that the lower teeth grind against to cut grass or other foliage. The outer pair of teeth in the front of the lower jaw are either considered to be canines, or to be incisors, with the canines missing. The cheek teeth are low-crowned and selenodont, and are separated from the forward teeth by a wide gap, or diastema. The dental formula for bovids is similar to that of other ruminants
All bovids have four toes on each foot – they walk on the central two (the hooves), while the outer two (the dew-claws) are much smaller and rarely if ever touch the ground. Apart from some domesticated forms, the males in all species have horns, and in many the females do, too. The size and shape of the horns vary greatly, but the basic structure is always a pair of simple bony protrusions without branches, often having a spiral, twisted or fluted form, each covered in a permanent sheath of keratin. The unique horn structure is the only unambiguous morphological feature of bovids that distinguish them from other pecorans. Male horn development has been linked to sexual selection, while the presence of horns in females is likely due to natural selection. The horns of females are usually smaller than those of males, and are sometimes of a different shape. The horns of female bovids are thought to have evolved for defense against predators or to express territoriality, as nonterritorial females, which are able to use crypsis for predator defense, often do not have horns
The bovid family is known through fossils from the early Miocene, around 20 million years ago. The earliest bovids, such as Eotragus, were small animals, somewhat similar to modern gazelles, and probably lived in woodland environments. The bovids rapidly diversified and, by the late Miocene, the number of bovid species had greatly expanded. This late Miocene radiation was partly because many bovids became adapted to more open, grassland habitat. About 78 genera are known from the Miocene (compared to 50 today).
Early in their evolutionary history, the bovids split into two main clades: Boodontia and Aegodontia. This early split between Boodontia (of Eurasian origin) and Aegodontia (of African origin) has been attributed to the continental divide between these land masses. When these continents were later rejoined, this barrier was removed, and both groups expanded into each other's territory.
The largest number of modern bovids is found in Africa, while substantial but less diverse populations are in Asia and North America. Many bovid species that evolved in Asia possibly could not survive predation by humans arriving from Africa in the late Pleistocene. By contrast, African species had many thousands or a few million years to adapt to the gradual development of human hunting skills, yet many of the commonly domesticated bovid species (goats, sheep, water buffalo and yak) originated in Asia. This may be because Asian bovids had less fear of humans and were more docile.
The small number of modern American bovids are relatively recent arrivals over the Bering land bridge, but they long predate human arrival.