It is only a matter of minutes, in many rainforests, before dung is discovered and utilized by various insects. Virtually all organic matter is rapidly processed, even fecal matter and perspiration. These organisms take up nutrients, which are released as wastes when organisms die. As organic material decays, it is recycled so quickly that few nutrients ever reach the soil, leaving it nearly sterile.ĭecaying matter (dead wood and leaf litter) is processed so efficiently because of the abundance of decomposers including bacteria, fungi, and termites. In the rainforest, most of the carbon and essential nutrients are locked up in the living vegetation, dead wood, and decaying leaves. The colonial settlers did not realize that they were dealing with an entirely different ecosystem from their temperate forests where most of the nutrients exist in the soil. The answer lies in the rapid nutrient cycling in the rainforest. Settlers wondered why their crops perished and how such poor soil could support the luxuriant growth of tropical rainforest. The cleared land supported vigorous agricultural growth, but only for one to four years, when mysteriously, plant growth declined to a point where copious amounts of fertilizer were required for any growth. Early European settlers in the tropics were convinced (and even assured by scientists at the time) that the lushness of the "jungle" was due to the rich soils, so they cut down large patches of forest to create croplands. Under such conditions, one wonders how these poor soils can appear to support such vigorous growth. Amazonian soils are so weathered that they are largely devoid of minerals like phosphorus, potassium, calcium, and magnesium, which come from "rock" sources, but are rich with aluminum oxide and iron oxide, which give tropical soils their distinctive reddish or yellowish coloration and are toxic in high amounts. ![]() Many tropical forest soils are very old and impoverished, especially in regions-like the Amazon basin-where there has been no recent volcanic activity to bring up new nutrients. Over two-thirds of the world's rainforests, and three-fourths of the Amazonian rainforest can be considered "wet-deserts" in that they grow on red and yellow clay-like laterite soils which are acidic and low in nutrients. ![]() Why there are problems with clearing rainforest lands for agriculture and how soils are an important factor influencing Understanding the basic composition of forest soils helps explain the concept of nutrient cycling in the rainforest Part II: SOILS and NUTRIENT CYCLING IN THE RAINFOREST The ground level is the region of the forest which was first explored and has been the most intensively studied.īamboo fungus (Phallus indusiatus) in Xishuangbanna, Yunnan. It is also home to thousands of plants and animals, and provides support for trees responsible for the formation of the canopy. The forest floor is one of the principal sites of decomposition, a process paramount for the continuance of the forest as a whole. CHARACTERISTICSĭespite its constant shade, the ground floor of the rainforest is the site for important interactions and complex relationships. Vigorous ground growth is only possible where plenty of light is available-where there is a break or thinning in the light-absorbing canopy which screens out all but the 0.5-5 percent of light that reaches the floor in the primary forest. Such "jungle" is characteristic of disturbed forest, usually near the forest edges, in recently opened light gaps, river banks, and areas where the forest is reclaiming previously cleared land. The term "jungle" is frequently applied to forest areas having dense ground growth. ![]() Instead of choking vegetation, a visitor will find large tree trunks, interspersed hanging vines and lianas, and countless seedlings and saplings and a relatively small number of ground plants. In undisturbed primary forests, a flashlight may be more useful than a machete since the subdued lighting limits ground growth. The canopy not only blocks out sunlight, but dampens wind and rain, so much so that a visitor to the rainforest may not immediately know it is raining because raindrops are deflected and collected by various canopy plants. It is actually rather the opposite: the floor is relatively clear of vegetation due to the deep darkness created by perhaps 100 feet (30 m) of canopy vegetation above. The forest floor of primary tropical rainforest is rarely the thick, tangled jungle of movies and adventure stories.
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