Pinel-Alloul, B. & A. Patoine. (2000). Comparative Impact of Natural Fires and Forest Logging on Zooplankton Communities of Boreal Lakes. Sustainable Forest Management Network Final Report. 39 pp.

508754

10.7939/R30F4V [view]

Pinel-Alloul, B. & A. Patoine

2000

39 pp.

Publication

Available for editors  

The goal of the research project was to determine if natural fires and forest logging have a significant impact on zooplankton biomass, biodiversity, species assemblages, and size spectra in lakes of the Canadian Boreal Shield. Wildfires and logging disturbances occurred in 1995. The research project was carried out from 1996 to 1998 in 38 lakes of the boreal forest in Québec: Twenty (20) lakes, undisturbed since 70 years, served as references; nine (9) lakes had 9-72% of their watershed logged and another 9 lakes had 50-100% of their watershed burnt. Three methodological approaches were used to determine zooplankton attributes: a) taxonomic analysis for zooplankton biomass, species richness and assemblages, b) analysis of size-fractionated limnoplankton ash-free dry weight, and c) determination of crustacean biovolume size spectra using an Optical Particle Counter (OPC). Our study reveals that natural fire and logging disturbances have different impacts on zooplankton community of boreal lakes. Natural fires increase zooplankton and limnoplankton biomass because of higher inputs of mineral nutrients (nitrates and phosphorus) from burnt watersheds. Burnt lakes supported on average 53-64% more biomass of cyclopoids and rotifers (or 59% more biomass of limnoplankton 100-200 µm size fraction) than reference lakes the first 2 years after fire. In contrast, logging does not increase zooplankton biomass because of higher inputs of dissolved organic carbon from watershed which inhibit light transmission and biological production. Cut lakes supported on average 43% fewer biomass of calanoids than reference lakes during the first year after logging. The biomass of cladocerans and copepodite stages did not vary significantly among reference, cut and burnt lakes. The impacts of natural fire and logging on zooplankton biomass were more pronounced 2 years after disturbances. Impacts of wildfire and logging on zooplankton biodiversity and species assemblages, measured the first year following disturbances, are minor. Crustacean biovolumes in large size classes (1200-1500 µm) were higher in perturbed lakes, especially in burnt lakes. Zooplankton biomass and size spectra, as well as limnoplankton biomass are promising tools to monitor the effects of watershed disturbances by natural fire and logging on zooplankton communities in boreal lakes. However among-lake and seasonal changes in watershed and limnological characteristics are more important sources of variability in zooplankton biomass than watershed disturbances, and should be considered when assessing the environmental impacts of watershed disturbances on zooplankton in boreal lakes .

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