PS 50-174 - Impact of forest harvesting on the functioning of boreal lakes

Background/Question/Methods

The boreal forest is the second-largest terrestrial biome in the world and is the largest source of freshwater on Earth, with more than 1.5 million lakes. Forest and freshwater ecosystems are in constant interaction and strongly influence each other's functioning. Forest harvesting is one of the most important economic activities in Canada. However, the impact of forest harvesting on aquatic ecosystems is not well known yet. Our project aims to determine the impact of this anthropogenic disturbance on the functioning of lake ecosystems in Canadian boreal forests. To achieve this objective, we will evaluate the physicochemical changes including the concentration of greenhouse gases. We will also evaluate the consequences of forest harvesting on the structure and functioning of aquatic food webs. Finally, we will study the role and importance of mixotrophy in the lake by observing under fluorescence microscope. Twelve lakes will be sampled three times per year to account for seasonality. Half of these lakes are on the top of eskers i.e. fluvioglacial sandy formations which are poorly influenced by the watershed, and the other six are lakes situated on clay which are at the lower points of the landscape and thus strongly influenced by the watershed.

Results/Conclusions

The samplings before harvesting have been done last year and sampling after harvesting will be done this year and next year. According to preliminary results, the dissolved organic carbon concentration of lakes situated on clay is 3 times higher than lakes on eskers. For the concentration of total nitrogen, clay-situated lakes are 1.5 times greater than esker-situated lakes. These results highlight the strong influence of the geological background on the lakes of the region. The subsequent results of this study will provide a better understanding of the impact of logging on the functioning of aquatic ecosystems and their food webs and will contribute to the creation of a new paradigm in sustainable forest management that includes interactions between terrestrial and aquatic ecosystems