Saturday, 15 July 2006

Pedobiological Action of Soil Fauna.

Angela PINZON PINTO, Corporación tecnológica de Bogotá, Transversal 42 No. 106A-05 Apto. 504,, Transversal 15A 130-80, int.5 apto 202., BOGOTA, Colombia and Maria ROMERO PINTO, Universidad de Bogotá Jorge Tadeo Lozano, Transversal 15A No. 130-80 Int.5 Apto 202, Bogotá - Colombia, Colombia.

The composition and activity of the communities of organisms that live on the soil depends on the properties of this as the humidity, the temperature, the porosity, the organic matter, the pH, among others; the organisms exert an action on the mineral and organic components, like also on the physical properties as the formation of stable aggregates, increase the porosity, aeration and water holding capacity. Each organism has their specific edaphic environment to be developed thus: the Lumbricidos need a rich middle in organic matter and adequate humidity; the Himenoptera prefer clear-sandy soils or sandy-franks; on the contrary the Isoptera need clear-clayey and clayey soils; the Coleoptera develop better their activity in franks soils and the Gasteropoda live specifically in soils loamy rich in calcium. Earthworms: The works carried out with Eisenia fetida indicate that the diets supplied favor in a very wide degree development of the worms. The haeces present high structural stability, retention of humidity, forms pores percentage and so great different as well as high contents of total bases, organic carbon, total nitrogen, available phosphorus and specific behaviors against the accumulation of the heavy metals such as cadmium, copper, leads and zinc. The micromorphological analysis of the earthworm feces showing microagregates of organic matter, isotubules, with large amount of calcium carbonate and quartz absorbed in an organic matrix and another ironess, and a very high percentage of interconnected pores of different shape and size. Ants: The pedoturbation caused by these organisms especially in the landscape of Savannahs is very marked due to the construction of nests or ant hills (figure 2). The most important process carried out by these organism is the translocation of materials from one part of the profile, causing changes in the texture of the horizons and consequently on the physical characteristics. The incorporation of organic materials by the ants increases the contents of organic carbon and total nitrogen; the C/N ratio is high due to the incorporation carbonaceous organic rich comprounds. Termites: These organisms form structures in the shape of mounds (figure 3), which are the result of the accumulation ordinate and continuous of feces produced by the laborers of the colony. These ejections are the final product of the consumption of materials of the soil and of remainders of vegetables, transformed by the termites in their alimentary canal. The same as the ants, the termites also transport material of soil since the depth to the surface, altering completely their physical and chemical properties. To compare the chemical composition of the surrounding soil with the soil of the termiteros, was found that the magnesium, calcium, potassium, phosphorus and the carbon were in higher amount in that structures that on the soil without altering for the termites. Scrawl: Studies carried out to these soil organisms, very abundant in our country, show that the type of soil is very important for their development. The larva and the adult modify it opening channels and tunnels allowing that the water, the air and the nutritional solutions move with greater facility. To analyze the materials excreted by the larvae, is seen how do they enlarge the nutrients especially the phosphorus which reaches levels even in 223 ppm., in comparison with the soil that is 39.9 ppm.; equal forms same way the potassium is 60 times higher in the excrement than on the soil. The construction of crotovinas (figure 4) elaborated by the adults, increase the organic matter. Terrestrial snails: The populations of terrestrial snails are not found evenly distributed in a specific space, due to microclimatic and microtopographic factors, as also the source of food. Terrestrial snails are organisms that cause so much transformations chemical and physical, due to the mucoproteins and cellulose that produce so much in its wastes like to be displaced, which induces to the particles of the soil to be united and to form stronger aggregates. According to the results of chemical analyses made to the heces of the terrestrial snails an increase was found of the contents of calcium, phosphorus, magnesium, potassium and sodium.

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