The effect of vineyard ground cover vegetation on soil fungi and plant-soil feedback

Groundcover vegetation is managed in vineyards for many purposes including for soil quality, trafficability, and pest and fertility management. Because plants are major drivers of soil biota, groundcover identity could also cause changes in soil microbial communities that then influences vine health. Using greenhouse and field trials as well as a multi-year survey of Okanagan valley vineyards, I studied the effect of groundcover identity and management on soil fungi known to be important in influencing vine health and growth attributable to these plant-soil feedbacks. Overall, groundcover vegetation influenced abundances of each of the studied guilds of soil fungi in the drive row, with plant effects on the entomopathogenic Beauveria bassiana being the most consistent. Under vine living mulches, however, did not affect these same groups of fungi. When soil trained by different groundcovers from the same field were used as microbial inoculant in the greenhouse, they led to differences in arbuscular mycorrhizal (AM) communities in vine roots, but differences in vine growth were only seen when a pathogen was also included. Taken together, these results suggest that groundcover vegetation does influence soil fungi in drive rows of Okanagan vineyards. Certain groundcovers may provide ecosystem services such as conservation biological control of pest insects through increases in entomopathogenic fungi, improved carbon sequestration and soil structure through increases in AM fungi, and deterrence of soil-borne pathogens. However, feedback effects on vines in this dissertation were limited to abiotic competitive effects in the field and biotic responses in the greenhouse, suggesting a high degree of context-dependency of plant-soil feedbacks in this system.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat