The effects of nutrient deposition and ecological restoration on the structure and functioning of arbuscular mycorrhizal fungal communities


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University of Guelph


The composition and ecological functions of the soil microbiome are sensitive to human-driven environmental change and land use. Protecting the soil microbiome through conservation will require understanding how microbial functional groups respond to environmental change and ecological restoration. Arbuscular mycorrhizal (AM) fungi are a highly abundant microbial functional group that promote numerous ecological processes, including nutrient cycling and primary productivity, by forming nutrient-exchange mutualisms with most plant species. In this thesis, I investigated how AM fungal community composition and functions are altered by human-driven environmental change and land use, and how AM fungal communities can be protected through restoration. In my first chapter, I conducted a meta-analysis of studies that quantified nutrient deposition effects on AM fungal community composition. Nutrient deposition had a relatively small but statistically significant negative effect on AM fungal species richness, but the magnitude of this effect increased with higher nutrient dosages. In contrast, nutrient deposition had a large and highly significant effect on AM fungal community composition at the species level. In my second chapter, I described patterns in AM fungal response to restoration of intensively managed agricultural fields across Southern Ontario. Restoration stimulated significant increases in AM fungal abundance and species richness as species from disturbance-sensitive families replaced species from one disturbance-tolerant family. In my third chapter, I investigated if restoration returns AM fungal communities to a pre-disturbance condition by contrasting restored sites with a variety of different grasslands. AM fungal communities at restored sites were similar in abundance and species richness to less disturbed grasslands, but were compositionally distinct from all grasslands apart from a selection of low-intensity managed grasslands. In my fourth chapter, I determined if restoration can improve the mutualistic services that AM fungi provide to plants. Restored and agriculturally-degraded AM fungi had similar effects on plant productivity, but differed in their ability to deliver phosphorus to plant functional groups. Together, my thesis highlights the sensitivity of soil microbial composition to environmental change and land use, that restoration can be effective in restoring microbial abundance and diversity, but may not fully restore composition and functions to levels that resemble pre-disturbance conditions.



High-throughput sequencing, Microbial community, Mycorrhizal fungi, Nutrient deposition, Plant-microbial interactions, Restoration