Short-term impact of forest harvesting on water quality and zooplankton communities in oligotrophic headwater lakes of the eastern Canadian Boreal Shield

The objective of this study was to investigate the short-term impact of forest harvesting within the first year after perturbation on water quality and zooplankton in oligotrophic lakes of the eastern Canadian Boreal Shield. To achieve this objective a balanced multiple before/after-control-impact (MBACI) experimental design was used including four headwater lakes sampled twice before (July and September 2003) and twice after harvesting (July and September 2004) and four undisturbed control lakes sampled at the same dates. Significant increases in dissolved organic carbon (DOC) and total phosphorus (TP) concentrations were detected after the perturbation but did not result in a bottom-up effect. Differences in pelagic phytoplankton biomass and zooplankton community structure were not related to harvesting activities. Spatial and temporal variability was observed among lakes in logged as well as in control lakes. Therefore natural variability seemed to be more important in determining ecological patterns within the lakes than the short-term impacts of forest harvesting. We hypothesise that novel logging strategies such as careful logging around advanced growth in combination with 20-m buffer strips fringing streams and lakes might be an efficient protection to mitigate short-term effects of additional allochthonous matter input in lake pelagic zones after forestry activities on watersheds.