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Solid Cycle....


Recycling in the tropical rainforest. Fungi immediately decompose organic "waste," such as a dead moth. Temperature and humidity don't allow for the creation of humus.

Falter mit Pilzen - organischer Abfall - Recycling

Lichen, moss, alga. The entire forest is a filter that holds onto the minerals that come in rainwater.

The rainy season has begun. Fungi begin their work and decompose organic "waste."

Soil Structure and Nutrient Cycle

In contrast to the forests at northern European latitudes, most rainforests are not dependent on nutrients from the soil. The impoverishment of the soil from millions of years of erosion has forced the organisms to a high level of adaptation. How is it possible that the impressive giants of the tropical rainforest, and with them the most diverse ecosystem on earth, are rooted in the depleted soil of all places? The answer is astonishingly simple. Tropical rainforests don't take their nutrients from the soil, they keep them and replenish themselves. The mineral nutrients circulate in a cycle without ever ending in the soil. In particular the trees have developed the capacity to store nutrients, thus most of the minerals are stored in the living organisms.

Peru Rainforest Amazon Pachitea Llullapichis Panguana Species Diversity : Stoffkreislauf

A falling leaf, a fruit, a branch or a dead animal; all dead organic material is processed within a few days and brought back into the cycle. The threat of starvation from minerals being washed fully away doesn't exist in the rainforest, since its nutrients are kept in the living organisms instead of stored in humus that is easily washed away.

Small Beings - Large effect

Bacteria, fungi, termites and ants are the main actors in the decomposition of organic material for tree roots to take up. Most rainforest trees have shallow roots that don't penetrate deeply into the infertile soil, but rather search for their nourishment directly under the surface. Stilt and buttress roots increase the platform of the trees. Most of the delicately branched root networks are in the top 30 centimeters of the earth, where they find every nook and cranny.

The wonder of Mykorrhiza

The so-called mycorrhiza fungus plays a decisive role in the absorption of nutrients, without which most trees in the tropical forest couldn't live. Their microscopically small threads go all though the roots and enter into a symbiosis (mycorrhiza). The effect of the mycorrhiza fungus is two-fold.

On the one hand they increase the surface area of the thick tangle or roots several times over, and on the other hand they bring the nutrients from decomposed organic substances directly to the trees. This "short circuited" cycle works almost without losing any energy. The soil in tropical rainforests is constantly lacking in phosphates. With the help of radioactively marked phosphate North American scientists were able to follow their path through the Mykorrhizen fungus in the tree roots. In other tests phosphorous and calcium were added to the soil. Over 99 percent of both elements were found later in the roots and other plant parts, which shows an incredibly effective Mykorrhizen symbiosis. The Mykorrhizen fungi make nutrients available to the trees before the next tropical rainstorm washes them away. In return they get carbohydrates for their own food. Even by the nearly complete effectiveness of the fungus, a tiny bit of lost minerals being washed away is unavoidable. One now know that the rainforests compensate for this loss through the minerals that are held in rainwater.

The rain forest is constantly fertilized by way of massive global transportation of substances. Around 500 million tons of Sahara dust are brought annually westward over the Atlantic to the American rainforests on the Northeast trade wind. This brings around 13 kilograms of potassium, three kilograms of phosphate and up to 16 kilograms of calcium per hectare of rainforest. Magnesium, a basic element for chlorophyll and thus a prerequisite for photosynthesis, also comes from the Sahara.

From the crown down to the roots, with its Mykorrhizen fungi, the rainforests acts as a huge nutrient filter. The vital minerals contained in the Sahara dust never reach the soil. They are converted on the way down from Epiphytes (such as bromeliads and orchids) and grabbed up by epiphyllous plants (lichens and moss that grow on leaves). The "rainforest filter" is so effective that the water flowing through the streams and rivers is almost completely absent of minerals and nearly have the values of distilled water.

Text und Fotos © Andreas Schlüter 2003-2004