Linking Plant and Soil Microbial Diversity via Plant Functional Trait Ecology
dc.contributor.author | Agarwal, Prashasti | en |
dc.contributor.committeechair | Badgley, Brian Douglas | en |
dc.contributor.committeechair | Barney, Jacob | en |
dc.contributor.committeemember | Strahm, Brian | en |
dc.contributor.committeemember | Flessner, Michael L. | en |
dc.contributor.department | Crop and Soil Environmental Sciences | en |
dc.date.accessioned | 2025-06-05T08:02:19Z | en |
dc.date.available | 2025-06-05T08:02:19Z | en |
dc.date.issued | 2025-06-04 | en |
dc.description.abstract | Plant–microbe interactions are central to ecosystem functioning, yet our understanding of how plant diversity relates to soil microbial diversity remains rudimentary. Cover crops are increasingly promoted for their potential to enhance soil health and microbial diversity in agroecosystems, but variability in their effects highlights the need for a more mechanistic, trait-based understanding. This dissertation examines how various attributes of plant diversity influence microbial diversity, and if the patterns observed at species scale can be extended to mixed communities. Using a combination of monocultures and intentionally designed plant mixtures, I evaluated the relationships between microbial diversity and both taxonomic and functional plant diversity using greenhouse mesocosms and field-based studies. In Chapter 2, I quantified plant functional traits (PFTs) for 29 agriculturally relevant species and assessed their relationships with soil microbial community structure. While plant functional traits such as biomass, root diameter, and root tissue nutrients explained variation in bacterial communities, PFTs did not relate to differences in fungal communities. However, specific bacterial and fungal taxa showed strong associations with particular PFTs. Chapter 3 extended these analyses to plant mixtures designed to test either PFT diversity or expected soil microbial diversity. My results showed that the mixtures designed to exhibit distinct PFT composition based on their species-level traits, did indeed vary in their community-level PFT composition. Furthermore, the same mixtures also harbored distinct soil bacterial and fungal communities. However, I could not identify specific traits driving these relationships, suggesting the overall trait diversity is more important than any individual trait for relating PFTs to soil microbial diversity. In Chapter 4, I evaluated whether plant species or trait diversity relates to corresponding soil microbial diversity in semi-natural herbaceous mixed plant communities in a conventionally managed agricultural field over a typical winter cover crop growing period. Variation in PFT composition was positively related to the differences in plant species composition. Although bacterial alpha diversity showed some associations with root traits like %N and C:N ratio, microbial beta-diversity was not well explained by PFT or species diversity. Together, these findings underscore the importance of specific plant traits in structuring microbial communities, while highlighting the complexity of predicting microbial outcomes from plant community composition and diversity, especially across different spatial and temporal scales. This work supports the integration of trait-based frameworks into designing plant mixtures such as cover crop polycultures and points toward future research linking PFTs to microbial functional potential and agroecosystem services. | en |
dc.description.abstractgeneral | Plants and soil microorganisms such as bacteria and fungi influence each other and, together, carry out a multitude of valuable ecological functions such as recycling soil nutrients and improving plant and soil health. These interactions play a huge role in maintaining healthy, productive, and resilient agricultural systems. Even though we know that certain crops can affect microbes living in the soil, we don't fully understand which plant characteristics affect soil microbes in certain ways. This dissertation explores how different types of plant diversity — including which species are present, and how their traits vary — influence the communities of soil microbes growing with them. This research was conducted in the context of cover cropping in agricultural systems — plants that are grown during otherwise fallow period for their benefits to overall ecosystem health and not harvested for yield. I looked at 29 common cover crop species and measured a wide range of plant traits, such as root structure, biomass, and nutrient content. First, I studied how these traits influence the bacteria and fungi living in the soil when plants are grown individually. Based on this information, I next designed specific mixtures of cover crop species to test whether information on traits or expected microbial communities associated with individual plant species could help us predict what happens when we plant multiple species together in mixtures. Lastly, I evaluated how mixed plant communities differing in their plant species and trait composition alter soil microbial communities under field conditions over a short time frame of 6 months – a typical winter cover crop growing period. Overall, I show that while certain plant traits like biomass, leaf area, root and leaf tissue nutrients are important in shaping soil microbial communities, and differences in traits could also predict changes in soil microbes in plant mixtures, these relationships do not readily translate to field systems. This suggests that plant traits can be incorporated for designing diverse plant communities— but we must understand how these plant-microbe interactions present themselves over various range of space and time. Ultimately, this work helps us move toward farming strategies based on ecological principles — ones that use plant diversity not just to grow crops, but to build healthier soils too. | en |
dc.description.degree | Doctor of Philosophy | en |
dc.format.medium | ETD | en |
dc.identifier.other | vt_gsexam:43833 | en |
dc.identifier.uri | https://hdl.handle.net/10919/135065 | en |
dc.language.iso | en | en |
dc.publisher | Virginia Tech | en |
dc.rights | In Copyright | en |
dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
dc.subject | Plant diversity | en |
dc.subject | plant-microbe relationships | en |
dc.subject | soil microbial diversity | en |
dc.title | Linking Plant and Soil Microbial Diversity via Plant Functional Trait Ecology | en |
dc.type | Dissertation | en |
thesis.degree.discipline | Crop and Soil Environmental Sciences | en |
thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
thesis.degree.level | doctoral | en |
thesis.degree.name | Doctor of Philosophy | en |
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