What They Are and A Few Interesting Facts
Nematodes are tiny roundworms that are common in soils everywhere, from the freezing Arctic to dry, hot deserts. They are particularly abundant in grassland ecosystems. To give you an idea of exactly how common nematodes are, consider this: one cubic foot of soil can contain millions.
Nematodes can be most easily classified according to their feeding habits. Some graze on bacteria and fungi. Some like plant roots; others prey on other tiny animals. Some aren't fussy at all and will eat any of the above mentioned food items.
Nematodes can't move through the soil unless a film of moisture surrounds the soil particles. Under hot, dry conditions, nematodes can become dormant, allowing them to survive long periods of drought. As soon as water becomes available, they quickly spring back to life.
Why They Are Important
Among the thousands of species that have been identified, many are considered beneficial because they boost the nutritional status of the soil. Nematodes feed on decaying plant material, along with organisms that assist in the decomposition of organic matter (bacteria and fungi). This helps disperse both the organic matter and the decomposers in the soil. Increased organic matter concentration and decomposition boost nitrogen and phosphorus levels.
Because some nematodes prey on other animals, they can be useful for control of pest insects. Nematodes are also being investigated for their potential as biological controls for noxious weeds.
Nematodes aren't all good guys. Some damage the roots of domestic crops, costing U.S. farmers an estimated $8 billion a year. Nematode infestations can be identified by yellowing, stunted plants that grow in sparse stands. Research is underway to develop plants that can resist nematode predation.
Freckman, Diana W., ed. 1982. Nematodes in Soil Ecosystems. Austin, Tx., University of Texas Press. 206 pp.
Freckman, Diana W. 1988. Bacterivorous nematodes and organic-matter decomposition. Agric. Ecosystems Environ., 24: 195-217.
Ingham, Elaine. 1998. The soil biology primer, soil nematodes. USDA, Natural Resources Conservation Service, Soil Quality Institute.
Zak, John C. and Diana W. Freckman. 1991. Soil communities in deserts: microarthopods and nematodes. in Polis, Gary A., ed. The Ecology of Desert Communities. Desert Ecology Series. pp. 55-88.
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