Nematode diversity in agroecosystems

The diversity of nematode faunae in agroecosystems and their relationships to soil processes suggests that they are potential bioindicators. However, the effects of plants, soil types and nematode biogeography mean a ‘functional group’ may be a better indicator than particular nematodes. Traditionally plant-feeding nematodes (e.g., Heteroderidae, Longidoridae) have been used as indicators. Sampling strategies and methods for extracting, identifying, and indexing nematode assemblages are given. Permanent grassland may be regarded as providing a baseline for nematode diversity in a given soil. Current work suggests that the relative abundance of fungal-feeding and bacterial-feeding nematodes may be a sensitive indicator of management changes. Changes in nematode diversity shown by values of the Shannon–Wiener index (H′) often reflect environmental differences. The nematode ‘maturity index’ can provide useful information on the direction of change within a particular soil, and there are prospects that the abundance or proportion of c–p Groups 1 and 2 may have value as a transferable index. Trends following disturbance events can be shown in c–p triangles. Morphologically distinct groups (e.g., Criconematidae, Longidoridae, Mononchoidea) may be useful within regions or soil types but fail to provide a universal indicator.