Watkinson, Autumn

Diversified agroecosystems supporting greater genetic, structural, and functional diversity improve soil health and ecosystem function. However, there is limited understanding of how multiple forms of diversification, such as mixing cover crop species and adding arbuscular mycorrhizal fungi (AMF), alter belowground carbon supply to soil. In a controlled environment experiment using rhizoboxes, I investigated the belowgound response of cover crops – red clover (Trifolium pratense) and barley (Hordeum vulgare) – grown in monoculture or mixture, with and without AMF inoculation. Root morphological and mycorrhizal traits that characterize the hypothesized root economics spectrum (RES) were integrated with novel sampling of dissoved organic carbon fluxes and easily extractable glomlin in rhizosphere soil. Results revealed species-specific shifts on the RES suggesting that diversification through species mixing and AMF additions can alter belowground carbon allocation pathways, with potential implacations for plant performance and soil carbon stabilization in agroecosystems.

Author Keywords: Arbuscular mycorrhizal fungi, carbon sequestration, cover crops

Ecological restoration of grassland ecosystems is increasing in scope in Ontario, as a result the demand for genetically appropriate, high-quality seeds of native plants is also increasing. This mixed methods study characterized fitness and seed quality traits using genetic, demographic and growth trial data for a keystone tallgrass prairie species Big bluestem (Andropogon gerardii). To estimate the ploidy levels in Big bluestem, our flow cytometric results indicated an average of 6.32 picograms of nuclear DNA within sixteen populations surveyed showing that hexaploid (6x) cytotypes are dominant in Southern and Central Ontario populations, aside from one 9x occurrence in Norfolk county, ON. Seed quality, measured through germination and viability testing did not change based on whether a population was remnant or restored. Concerningly, our study shows that remnant populations of Big bluestem are at risk of being lost as high quality seed sources likely because of the absence of stewardship and the resulting loss in population fitness. Workshops with prairie restoration practitioners suggest that there is significant vision behind the future of this work in the province, and that an ecosystem wide seed strategy for keystone tallgrass prairie species is a necessary next step to increase the sustainability of seed-based restoration strategies and preserve remnant site genetics.

Author Keywords: Big bluestem (Andropogon gerardii), Ecological Restoration, fitness, polyploidy, practitioner, seed quality