Nematodes as soil indicators: functional and biodiversity aspects

Since it has become appreciated that soil nematode assemblages are abundant, diverse and contribute to soil nutrient turnover, they have been increasingly used as indicators of soil condition. Use of nematodes as functional indicators relies on the allocation of nematodes to feeding groups and reproductive strategies; in both cases groupings are uncertain. Species within feeding groups vary in their food resources and response to environmental variables, as shown by the difficulties in managing plant-pathogenic nematodes. Therefore species-level discrimination is necessary to permit further advances in understanding the role of nematodes in soil processes and thus in ecosystem resilience. Analysis of published nematode lists shows that among the bacterial-feeding nematodes Cephalobidae are often the most abundant group in soils; Rhabditidae may increase following a resource pulse; in stressed, natural environments Plectidae may be important. To be comparable with other biota, nematode biodiversity assessment requires species-level identification. In many jurisdictions such identification will be difficult due to inadequate systematic knowledge of the nematode fauna.