Historical variability of subfossil chironomids (Diptera: Chironomidae) in three lakes impacted by natural and anthropogenic disturbances

In the eastern boreal forest of Quebec, Canada, harvesting strategies try to mimic the effects of fire on forest ecosystems, assuming that both disturbances have similar impacts. However impacts of both types of perturbations on lacustrine ecosystems, especially on chironomids (non-biting midges), are still poorly understood. The objectives of this study were to determine if logging and fire resulted in chironomid assemblages significantly different than pre-disturbance states and to see if the harvesting strategy (careful logging around advanced growth (CLAAG) and buffer zones) protect lakes from logging effects in the boreal forest. Three statistical tests were used to study the difference between pre- and post-disturbance assemblages: a principal component analysis (PCA), analysis of similarity (ANOSIM) and a non-metric multi-dimensional scaling (MDS) ordination. All statistical analyses suggested that fire did not have any effects on chironomid assemblages. The PCA analysis showed that two logging events in Lac aux Huards created chironomid assemblages slightly outside the pre-disturbance variability. However, ANOSIM showed that these differences were not significant at the 0.5% level of significance. These results suggest that the presence of a buffer zone probably limited the impacts of logging on lakes in this area.