Structure of nematode communities in forest soils of southern British Columbia: relationships to nitrogen mineralization and effects of clearcut harvesting and fertilization

The effects of clearcut harvesting and fertilization of clearcuts on the structure of nematode communities were assessed at three sites in the southern interior of British Columbia. The Shannon-Weaver and Simpson indices of diversity were greater in clearcuts than in forests. The diversity of the bacterivorous and fungivorous trophic groups were not significantly different between clearcuts and forests, whereas the diversity of omnivorous and predacious nematodes was lower in clearcuts than in forests. The nematode maturity index (MI) was lower in clearcuts than in forests. Several ratios describing the prevalence of enrichment opportunists (the absolute abundance of Rhabditida, the relative abundance of Rhabditida, and the ratio of Aphelenchida/fungivorous nematodes) were greater in clearcuts than in forests. Nematode diversity tended to be lower in fertilizer treatments than in controls within clearcuts, but the effects were not consistent across sample dates. The MI was lower in fertilizer treatments than in controls. All ratios representing the relative abundance of enrichment opportunists were greater in fertilizer treatments than in controls. The MI was negatively correlated with N mineralization in data sets representing forests and fertilized and non-fertilized plots within clearcuts. None of the diversity indices were correlated with N mineralization. The absolute abundance of Rhabditida and the relative abundance of Rhabditida were both consistently positively correlated with N mineralization in the data set representing fertilized and non-fertilized plots within clearcuts, and the absolute abundance of Rhabditida was positively correlated with N mineralization in forests.