Soil fauna communities in cedar-hemlock and hemlock-amabalis fir forest types on northern Vancouver Island, British Columbia

Soil fauna play an important role in regulating decomposition and nutrient cycling. They are able to process a portion of the annual litter input thus decreasing forest litter, increasing microbial activity and increasing mineralization of nutrients. The faunal composition of most Canadian soils has not been investigated. The purpose of this study is to determine and compare the composition of major soil fauna groups in Cedar-Hemlock and Hemlock-Amabalis fir forest types and to examine seasonal changes in vertical distribution within and between the forest types. Four methods were used to extract soil fauna: hand sorting, Lussenhop high gradient extractor, modified Baermann funnel and the Formalin method. Samplingoccurred five times between August 1989 and March 1991. Forty one groups were identified in both forest types. Results indicate that the Hemlock-Amabalis fir forest type maintains a higher abundance and biomass of soil fauna than the Cedar-Hemlock forest type. Nematoda are numerically dominant inboth forest types followed by Acari (in toto), Collembola (in toto) and Copepoda. Diplopoda, Enchytraeidae, Diptera larvae and Acari (in toto) are the dominant groups in both forest types when considering biomass. Similarity indices indicate that the forest types have similar group diversity. Biomass is slightly different between both forest types in October 1990. Analysis of variance performed on mean depth values for twenty groups indicate that mean depth was not significantly different between the two forest types (p > 0.05). Variation in mean depth was significantly different between sampling times for Prostigmata,Isotomidae, Onychiuridae and Nematoda (p > 0.05). Soil moisture content did not significantly affect mean depths. Distribution through the organic horizons showed a decrease in percent abundance of microarthropods in the upper organic layer in the summer with higher abundances in the spring and fall. Enchytraeidae showed a similar pattern in both forest types. Soil moisture content in the mat complex also exhibited this pattern with high moisture contents relating to higher abundances. Nematoda maintained a constant abundance in the upper organic layer throughout the study. This suggests that soil moisture may not be solely responsible for the observed shifts in vertical distribution of the groups examined. Overall, the soil fauna communities are similar between the Cedar-Hemlock and Hemlock-Amabalis fir forest types. Further work is required to increase the level of taxonomy to genus or species, which may identify tax a unique to either forest type. At the very least, this could provide a higher resolution of the distributional trends that might also be observed in species within the organic horizons and possibly relate information on their biological activity within these horizons.Land and Food Systems, Faculty ofGraduat