Nematodes normally get a bad reputation. Indeed, some of these minuscule creatures can cause harm in plants and animals. But little is known about the non-parasitic nematodes, which have many beneficial roles. Ashley Shaw from the University of Oregon explores this topic in this article.
Soil nematodes represent eighty percent of animal life by number and live in nearly every habitat. They are hard-working and important organisms. Indeed, some of the best-known nematodes are parasites. There are different nematode parasites of plants and animals. That means they live in or on the plant or animal, cannot survive without them, and sometimes kill their host (and then move on). But many more nematodes are free-living. In soils, nematodes live in water films that surround soil particles. Both plant root parasitic and free-living nematodes play an important role in plant health and plant feedback to soil carbon.
An incredible variety of soil nematodes exist at all levels of the soil food web. At the base of the food web, some feed on plants and algae, others graze on microbes (bacteria and fungi). At higher levels in the food web, nematodes that are predators and omnivores eat other invertebrates, protists, and even other nematodes. In some cases, “predatory” nematodes are the “good guys,” keeping populations of parasitic nematodes in check.
This food web is important to plant health and soil carbon storage. For example, by feeding on bacteria and fungi, microbial grazing nematodes help return nitrogen to the soil through their waste. This makes the nitrogen available again for plant use, improving plant growth.
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