Indirect impacts of a non-native ungulate browser on soil ecosystem function is variable across soil horizons in the boreal forests of Newfoundland, Canada

Swain, Makayla (2021) Indirect impacts of a non-native ungulate browser on soil ecosystem function is variable across soil horizons in the boreal forests of Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

Herbivores are key players in ecosystem function and connect nutrient cycling across animal and plant trophic levels. Herbivore impacts on ecosystems can be direct or indirect and it is necessary to study both paths to understand herbivore impacts on above-ground and below-ground ecosystem functioning. We conducted an experiment to test the hypothesis that non-native moose on the island of Newfoundland have negative impacts on plant communities, nutrient cycling, soil composition, and soil organism communities. We collected data on plant and invertebrate communities, climate, and soils in 11 paired exclosure-control plots in eastern and central Newfoundland that provide insight into 22-25 years of moose herbivory. Structural equations models revealed that moose had direct negative impacts on palatable tree height and abundance and an indirect negative impact on soil microbial C:N ratios. We found that moose had a direct negative impact on soil horizon depth and plant material and a positive impact on soil temperature and moisture, particularly in the first soil horizon. We detected no significant impact of moose on soil total C and N, net nitrogen mineralization, or macro-invertebrate communities. Overall, we unearthed evidence of indirect cascading impacts of moose on soil functions although these impacts are relatively weak.

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