Effects of forest harvesting on leaf litter dynamics across the aquatic-terrestrial ecotone of boreal lakes

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Bojarski, Lilly D.
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University of Guelph

The flux of nutrients and biomass associated with leaf litter across the terrestrial-aquatic interface of a suite of small boreal lakes in northeastern Ontario was investigated in relation to the impacts of forest harvesting. The oligotrophic lakes were categorized as 'clear' or 'boggy' based on water chemistry. Litter biomass varied little across lakes and years, but was typically an order of magnitude less for boggy lakes. Pre and post-harvest comparisons indicated little evidence for impacts of forest harvesting on litter biomass deposition in catchments with up to 19% clear-cut harvesting. Similarly, few significant differences in nutrient fluxes were detected between lakes or years. The relative concentrations of elements were ranked as N>Ca>K>Mg>P>Na. The highest concentrations of N were found in alder ('Alnus incana spp. Rugosa') leaves, which represented approximately 30% of all litter collected. Shoreline alder stands may therefore be an important source of N to nearshore aquatic communities. Harvesting practices impacting alder may be detrimental to littoral shoreline communities.

Boreal lakes, Forest harvesting, Leaf litter, Nutrient fluxes, Alders