Effects of earthworms on soil
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. They combine bilateral symmetry and corresponding external and internal segmentation. This phylum consists of more than 17,000 modern species of worms including earthworms, ragworms, and leeches. They are found in marine environments from tidal zones to hydrothermal vents, in fresh water, and in most terrestrial environments. They generally do not occur in deserts and arid grasslands or in extreme alpine or boreal habitats. Earthworms are often absent from strongly acidic forest soils with poor litter quality and have been identified, with termites and ants, as the most important soil engineering animals. As the heart of the soil engineering concept it is their job to move through the soil and to build mineral structures with specific physical, chemical and microbiological properties. Doing so, earthworms have been described as being one of the main groups of soil engineers in tropical and temperate ecosystems because changing the structural properties of soil influences soil microorganisms and plant growth by improving aeration, water intake and water transmission. Furthermore they are able to consume and incorporate large amounts of organic matter into soil. Such mixing is largely responsible for the formation of mull soils in which surface organic horizons are thoroughly mixed with underlying mineral soil. Despite the documented beneficial effects of earthworms on nutrient dynamics, soil structure and fertility, some aspects of earthworm activities are considered undesirable. These include removing and burying surfaces from erosion; dispersing weed seeds in gardens and agri- cultural fields; transmitting plant or animal pathogens. Is this the net outcome of their positive and negative effects that determines whether earthworms are to be considered pests or benefactors in any given situation, they are...
Please join StudyMode to read the full document