Semester

Spring

Date of Graduation

2019

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Applied and Environmental Biology

Committee Chair

Zachary Freedman

Committee Co-Chair

Jeffrey Skousen

Committee Member

Edward Brzostek

Abstract

Bioenergy crop production has steadily increased due to growing political support for renewable energy, thus initiating a demand to find alternative agricultural land. An innovative option is the use of marginal soils, such as reclaimed mine lands, to produce bioenergy crops. Switchgrass (Panicum virgatum) is a promising bioenergy crop that can be grown on marginal lands due to its robust growth in various soil types and climates. However, little is known regarding plant-microbe interactions among switchgrass systems within reclaimed mine lands. A study conducted in 2008 grew switchgrass on high- and low- quality reclaimed mine sites (Hampshire and Hobet, respectively) in West Virginia to examine the resilience of switchgrass as a reclamation-friendly bioenergy crop. Switchgrass yields at Hampshire were nearly an order of magnitude higher than Hobet (8.4 Mg ha−1 vs 1.0 Mg ha−1). Within Hampshire, the Cave-in-Rock cultivar yield was approximately 2-fold greater than that of Shawnee (12.9 Mg ha-1 vs. 7.6 Mg ha-1). Here, I sought to illuminate plant-microbial interactions that may account for this drastic shift in cultivar yield by assessing the soil microbial community’s function and composition. I tested two hypotheses: i) that the microbial community’s ability to acquire C, N, and P will be greatest in Hampshire soils compared to that of Hobet and ii) that there will be a cultivar-specific root-associated microbiome that may drive previously observed greater, but differential yields across switchgrass cultivars at Hampshire. I found that reclamation strategy substantially impacts the switchgrass microbiome’s composition as well as its ability to acquire critical nutrients like carbon, nitrogen, and phosphorus. I also found that a functionally, but not necessarily compositionally, unique microbiome exists in the root-associated soils compared to that of the bulk soil. Additionally, there were indicators that organic amendments to the topsoil may induce cultivar-specific soil microbiomes that mediate or facilitate differential yields within Hampshire. Taken together, I suggest that organic amendments to the topsoil during reclamation selects for a cultivar-specific microbiome more adept to acquiring critical nutrients and thus, increases aboveground productivity.

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