Master of Science
Peatlands are important wetland systems, but dominant macroarthropod groups endemic to peatlands and the environmental factors that affect them are poorly represented in the literature. I examined the richness, abundance, and community composition of soil and surface dwelling macroarthropods using emergence traps, peat sorting, and pitfall traps in two Ontario fens differing in water table, nutrient level, and vegetation. I found 218 arthropod morphospecies, with each site having a similar richness of emergent arthropods, but patterns of community composition differed between the two sites. The Carex (sedge) dominated site had twice as many emergent individuals, and total abundances declined dramatically over the growing season, whereas the Sphagnum (moss) dominated site had consistent arthropod abundances. Seasonal change in soil moisture was a significant correlate of arthropod abundance. Since Canadian peatlands face increasing climate warming, this study provides baseline information on the resident macroarthropod communities in different peatland types.
Summary for Lay Audience
Soil organisms are hyperdiverse, have high biomass, and play important roles in both below-ground and above-ground food webs as both predators and as food source for other organisms. Yet despite soil arthropods having important ecological roles, they are not well understood because they are difficult to directly observe. Many soil-dwelling species only live in soil for part of their life cycle, emerging when they reach maturity. Along with predatory macroarthropods (mostly spiders) on the soil surface, these emergent macroarthropods (mainly the Nematocera or lower flies) connect the below-ground system to the above-ground food web. Peatlands are important wetland systems, but dominant macroarthropod groups endemic to peatlands lack records in the literature. I examined the diversity of soil and soil-surface dwelling macroarthropods in two adjacent peatlands that differ in water table, nutrient level, and vegetation. I collected these macroarthropods using insect emergence traps, peat sorting, and pitfall traps. Altogether I found 218 morphospecies (groups differentiated based on morphological traits), with each site having the same richness, but twice as many emergent individuals in the Carex (sedge) dominated site compared to a Sphagnum (moss) dominated site. At the Carex site, emergent arthropod abundances declined dramatically over the season, while the Sphagnum site had a much more stable emergent community, with no significant changes in abundance. The abundances of the surface ground-dwelling community were very similar between the two fens, but there was little overlap in the species present at each site. Seasonal changes in soil moisture were an important correlate for the overall abundance of emergent insects collected. Northern peatland ecosystems are expected to undergo significant changes in vegetation and soil moisture under ongoing climate warming with unknown consequences for peatland biodiversity. This study provides baseline information for the emergent insects and their ground-dwelling predators that are important components of peatland biodiversity.
Carscallen, Grace, "Arthropod Diversity in Contrasting Ontario Peatlands" (2019). Electronic Thesis and Dissertation Repository. 6703.