mortiz085

Earthworms are thought to be the most ancient soil animals having started colonizing terrestrial environments about 600 million years ago (Spain and Lavelle 2001). They are the most predominant soil fauna except in dry and cold climates. Earthworms are semiaquatic animals which extract water continuously from the surrounding soil inorder to maintain their cuticle in a moist state to facilitate gas exchange. Thus moisture status is a major limitation to earthworm activities and distribution. Spain and Lavelle (2001) reported that since earthworms live in direct and continuous contact with the soil matrix and the soil solution, their presistence, propagation and activity are greatly affected by the chemical (pH, dissolved ions) characteristics of the soil. Based on their sensitivity to soil pH, earthworms are grouped into acidophilic species (able to thrive below pH 6 such as in organic forest litter), neutrophilic species (they prefer soil pH 6 to 7) and basophi lic species (prefer b

Mycorrhiza is the association between fungi and the roots of higher plants. The term was introduced by the German scientist A.B. Frank in 1885 (Mengel and Kirkby, 2001). Mycorrhiza is considered as the most widespread association between microorganisms and higher plants. On a global scale, between 86% and 94% of plants are mycorrhizal (Brundrett 2009). All Gymnosperms as well as 83% and 79% of dicotyledonous and monocotyledonous plants, respectively, are mychorrhizal (Marschner 1995). Nonmycorrhizal plants can be found in stressed soil environments (very dry or saline, waterlogged, severely disturbed as in mining areas, infertile) or even in very fertile soils. Mycorrhizas (or mycorrhizae) are absent under all environmental conditions in the Cruciferae and Chenopodiaceae (Marschner, 1995). Generally, in root-fungus association the fungus is strongly or wholly dependent on the higher plant, whereas the plant may or may not benefit from the association. It is not also essential for pla