Drivers of elemental storage and cycling in boreal forests: evaluating the effects of forest disturbances and an introduced ungulate

Moran, Rachael (2024) Drivers of elemental storage and cycling in boreal forests: evaluating the effects of forest disturbances and an introduced ungulate. Masters thesis, Memorial University of Newfoundland.

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Abstract

Selective browsing by ungulates alters forest structure and composition with the potential to suppress forest regeneration. Research suggests that ungulate impacts may be stronger in recently disturbed forests and in novel environments (i.e., introduced ungulates). In this thesis, we used observational and experimental (i.e., paired exclosure-controls) data to test the hypothesis that non-native moose and forest disturbances (i.e., fires and insect outbreaks) have negative impacts on carbon storage (i.e., total, aboveground, and belowground carbon) and plantavailable nitrogen in Newfoundland’s boreal forests. Using our observational data, we found that forest disturbances were a key driver of carbon storage dynamics, but we did not find a relationship between moose densities and carbon storage. We also found that supply rate of ammonium was negatively correlated with soil temperature and positively correlated with moose density. Using our experimental data, we did not detect any effect of disturbance history or moose presence on carbon storage or ammonium supply rates after 24-27 years of moose exclusion. This work demonstrates the impacts of natural disturbances and herbivory on forest ecosystem functions, such as carbon sequestration. Our findings will help natural resource managers consider the effects of moose and disturbances when developing nature-based solutions to climate change.

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