Abundance and diversity of soil nematodes in chronosequences of coastal Douglas-fir forests on Vancouver Island, British Columbia

Abstract

Summary Soil nematodes were used as indicators of possible differences in biodiversity in seral stages of Douglas-fir forests at three chronosequence sites on southern Vancouver Island, British Columbia. At each site, the seral stages were represented by regeneration, immature, mature and old-growth stands. Average ages of these stands were 8, 42, 93 and 286 years, respectively. The surveys to obtain soil and nematode data were conducted in summer and winter of 1993. Old-growth stands served as control forests. The nematode parameters used were their abundance, taxonomic composition and trophic structure. Abundance was lowest in the regeneration stands and highest in old-growth stands. Intermediate densities were found in the immature and the mature stands, but were generally higher in the former than in the latter stands. This trend is interpreted as indicating that nematode population levels in the three earlier seral stages would be restored to old-growth levels as they attain old-growth features with time. Forty nematode genera/species were found across these sites. Percent distributions of these taxa were generally similar across the seral stages. Measures of diversity and maturity indices, based on relative abundances of the individual genera, were also very similar for all seral stages. Correspondence analysis separated the genera clearly by layer of soil horizons (organic versus mineral), but less clearly by seral stage. Abundance of the genera by trophic habit ranked as: bacteriovores (38%) > omnivores (30%) > predators (25%) > fungivores (5% > plant-parasites (2%), but their relative distributions across seral stages were very similar and closely matched these percentages. These results pertaining to nematode taxa and their trophic habit indicated that the soil nematode community was essentially similar across the four seral stages.