Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Biology

Collaborative Specialization

Environment and Sustainability

Supervisor

Lindo, Zoë

Abstract

Aboveground plants provide resources to the belowground microbial community via plant litter and, in turn, the belowground microbial community provides nutrients for plant uptake, linking the two systems. My aim was to characterize and describe differences in plant community composition, plant litter quality and microbial community composition between two boreal peatlands in northern Ontario. These peatlands have contrasting plant and microbial communities, the Sphagnum moss-dominated peatland harboring a higher fungi to bacteria ratio compared to the Carex sedge-dominated peatland. Clear open top chambers were installed at both sites to simulate warming. Higher temperatures decreased Sphagnum moss in the Sphagnum-dominated peatland, increased aboveground biomass in the Carex sedge dominated peatland, and increased the heterogeneity in plant community composition at both sites. Shifts in aboveground plant community and subsequent plant litter quality inputs to the microbial community has potential implications for peatland carbon storage.

Summary for Lay Audience

Dead plant material that enters the soil system is an important source of nutrients for soil microorganisms who, in turn, recycle nutrients and make them available for plant uptake. Peatlands are a type of wetland with a large organic soil layer composed of partially decomposed plant material called peat. Peat is rich in carbon, making peatlands an important global carbon store. Plants and microorganisms can be described along a spectrum of fast growing with high nutrient demands to slow growing with low nutrient demands, and plants are thought to be paired with microorganisms with similar traits. My thesis describes both the aboveground plant community and the belowground microbial community in two contrasting boreal peatlands located in northern Ontario. The two peatland sites I have characterized are: 1) a Sphagnum moss-dominated peatland with nutrient poor plants that is dominated by fungi, a slow nutrient cycler; and 2) a Carex sedge-dominated peatland with nutrient rich plants, dominated by bacteria, a fast nutrient cycler. The contrasting plant and soil microorganism communities have implications on carbon storage, with the Sphagnum-dominated peatland having the potential to store more carbon. I also explored the impacts of warming on the aboveground plant communities at both of these peatland sites using clear open top chambers that act as a greenhouse, warming the air. At both sites, under higher temperatures, plant community composition was more variable: in the Sphagnum-dominated peatland I saw a decrease in moss abundance, and in the Carex-dominated peatland I saw an increase in aboveground biomass. Sphagnum is important in maintaining the carbon sequestration ability of peatlands, so a reduction in Sphagnum moss could reduce the amount of carbon stored in boreal peatlands. Greater aboveground biomass in the Carex-dominated peatland under warming increases the amount of nutrient rich plant litter. This could increase the activity and also the amount of carbon cycled by the soil microorganisms, again reducing the carbon storage potential of boreal peatlands.

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