The impact of cover crop inclusion on the belowground microbiome and root physiology of a perennial woody crop under different nutrient conditions
Restricted (Penn State Only)
- Author:
- Cao, Lily
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 03, 2023
- Committee Members:
- Jason Kaye, Program Head/Chair
Terrence Bell, Thesis Advisor/Co-Advisor
Joshua J Kellogg, Committee Member
Michela Centinari, Thesis Advisor/Co-Advisor - Keywords:
- microbiome
root interactions
metabolomics
cover crop
rhizosphere
agroecology
vineyard
nutrient
competition
metatranscriptomics
amplicon sequencing - Abstract:
- Cover crops increase plant diversity in agroecosystems throughout the year and promote positive ecosystem functioning and crop productivity. While cover crops have been used in combination with various cash crops, there is limited understanding on how cover crops affect perennial crops, such as grapevines. A key difference between annual and perennial systems is that cover crops are typically co-grown with perennials throughout the year, leading to long-term direct root interactions and potential competition between the cover crop and perennial crop. Although aboveground between plant interactions have been studied extensively, belowground interactions are less understood. Belowground interactions are complex and potentially more influential on plant physiology due the impacts from soil microorganisms, root exudates, nutrient dynamics, and neighboring plant roots. The work presented in this thesis will examine how the resulting interspecies root interactions caused by under-vine grass cover crop inclusion in vineyards impact the soil microbiome and root physiology of grapevines under different soil nutrient conditions. This thesis consists of three chapters. Chapter 1 begins with a discussion on under-vine cover crop applications in woody perennial systems, specifically in vineyards, and why there is growing interest in this alternative cover crop application method in regions with high rates of precipitation and soil nutrient resources. Key concepts involving belowground interspecies root interactions and nutrient competition from a soil microbiome and root centric perspective are introduced. Chapters 2 and 3 document studies performed during the Summers of 2021 and 2022 at a Pennsylvania vineyard. We explored under-vine grass cover crop (Festuca rubra) and Noiret (interspecific Vitis sp. hybrid) grapevine interspecies root interactions under different nutrient conditions, and their impacts on the soil and grapevine rhizosphere microbiome, as well as grapevine root morphological and physiological traits. In Chapter 2, we present findings on how interspecies root interactions from cover crop inclusion and the addition of organic nitrogen fertilizer impacted the bulk soil and grapevine rhizosphere microbial composition. Nitrogen amendment had a significant impact on the bacterial and fungal composition in the bulk soil and rhizosphere. Interspecies root interactions from cover crop inclusion also exhibited the potential to shift bulk soil bacterial and fungal composition, but in the rhizosphere, only bacterial composition shifted under more nutrient-limited soils. In Chapter 3, we expand on the Chapter 2 findings from a functional perspective to study changes in soil microbial functioning and the morphological and physiological traits of grapevine roots due to interspecies root interactions and nitrogen amendment. As with Chapter 2, rhizosphere microbial functioning and grapevine morphological and physiological traits shifted due to interspecies root interactions, with root traits impacted more in soils without nitrogen amendment. In summary, we demonstrated that interspecies root interactions from the inclusion of grass under-vine cover crops can influence both the belowground microbiome and grapevine root physiology through changes in soil microbial composition, soil microbial functioning, grapevine root morphological traits, and grapevine root metabolome. Additionally, the impacts of interspecies root interactions were more prominent in soils without the addition of a nitrogen amendment; this indicated that soils with more nitrogen availability made influences from interspecies root interactions minimal or caused them to have no effect on the soil microbiome and grapevine root traits. Overall, this work showcased the importance of belowground interactions and competition caused by increased plant diversity on soil health and plant productivity.