Master of Science, The Ohio State University, 2020, Environment and Natural Resources

Research on dedicated biofuel crops has typically focused on increasing yields and soil carbon sequestration. What is seldom studied is how biofuel crops affect the soil they are grown on. Soil is responsible for influencing important ecosystem services such as carbon sequestration, erosion control, and root development. Three biofuel crops, no-till corn (Zea mays), switchgrass (Panicum virgatum), and miscanthus (Miscanthus giganteus), were selected to examine their influence on soil physical and hydrological properties at three different depths (0 – 10 cm, 10 – 20 cm, and 20 – 40 cm). The goal of our study was to determine whether biofuel crops could improve soil physical and hydrological properties. The field study was conducted in Columbus, OH, on a biofuel research plot 7 years after establishment. A total of 36 bulk samples and 36 soil cores were collected. Miscanthus produced significantly higher yields (16.0 Mg ha-1) than both switchgrass (10.1 Mg ha-1) and corn (4.54 Mg ha-1) following a mid-season harvest. No-till corn produced the lowest yields because of the late seeding and poor crop stand. However, corn did not grow to maturity so the field was left to fallow. Significant differences in soil physical properties only occurred within the top 10 cm. Bulk density under miscanthus (1.39 Mg m-3) was significantly lower compared to both switchgrass (1.51 Mg m-3) and no-till corn (1.53 Mg m-3). There were no significant differences in calculated porosity and % water-stable aggregates. Mean weight diameter and geometric mean diameter were significantly higher under no-till corn (4.77 mm & 1.71 mm) and switchgrass (5.00 mm & 1.79 mm) compared to miscanthus (3.39 mm & 1.32 mm). The aggregate distribution revealed the same trend after wet-sieving, miscanthus retained significantly fewer aggregates larger than 4.75 mm compared to the other crops. When compared to a previous study conducted on the same plots in 2013, bulk density decreased under miscanthus at depth 0 (open full item for complete abstract)

Committee: Rattan Lal PhD (Advisor); Christine Sprunger PhD (Committee Member); Scott Demyan PhD (Committee Member) Subjects: Soil Sciences

Master of Science (MS), Ohio University, 2018, Environmental Studies (Voinovich)

Bioenergy could help reduce CO2 emissions from agriculture that contribute to climate change, while at the same time supply energy to a growing population. Varying levels of inputs within bioenergy crop fields, such as pesticide use or annual tilling, can impact arthropod biodiversity and abundance. The research presented here examines the impact of habitat type (Miscanthus x giganteus, Panicum virgatum, abandoned agriculture, and forested edge) on the diversity and abundance of arthropods in small (The Ridges Land Lab) and larger (The Wilds) planted plots in southeastern Ohio. A variety of collection methods (sweep nets, flight traps, and Berlese funnels) were used over a three month period to collect arthropods from different trophic groups. Overall, 25,390 arthropods were captured with the highest abundance consistently seen in forested edge habitats, followed by abandoned agriculture, switchgrass, and lastly miscanthus. Flying insects found in the forested edge were three fold more abundant than those found in miscanthus plots, with intermediate levels in switchgrass and abandoned agriculture. Dominant flying arthropod groups included leaf hoppers, flies and rove beetles. Abundance of litter arthropods was almost two fold higher in switchgrass than in miscanthus plots: dominant taxa included oribatid mites, ants, ground beetles, and collembolans. Taxonomic richness and Shannon diversity were lower in litter samples compared to flight/ sweep samples. Compared to forested edges, miscanthus supported fewer omnivores, pollinators, and predator/parasites. Detritivorous arthropod abundances did not differ across habitat types. No significant differences were noted between arthropod diversity and abundance between the larger fields of biofuel grasses at the Wilds compared to the Ridges Land Lab. This current study shows that cellulosic ethanol crop type does have an impact on arthropod communities; with miscanthus consistently supporting the least diverse and lowest ar (open full item for complete abstract)

Committee: Kelly Johnson (Committee Chair); Sarah Davis (Committee Member); Arthur Trese (Committee Member) Subjects: Agriculture; Alternative Energy; Entomology; Environmental Studies

Doctor of Philosophy, The Ohio State University, 2015, Evolution, Ecology and Organismal Biology

Planting of semi-domesticated grasses for habitat restoration and bioenergy has raised concerns about potential ecological consequences, for instance, genetic swamping of wild populations through crop-to-wild gene flow, and introgression of crop traits into wild relatives resulting in more invasive wild populations. In this dissertation, I explored different aspects of gene flow in two popular bioenergy candidates — switchgrass (Panicum virgatum) and Miscanthus (Miscanthus spp.) — and aimed to provide necessary information to mitigate potential gene flow from new switchgrass and Miscanthus cultivars. Switchgrass cultivars have been planted in Conservation Reserve Program (CRP) areas when wild seed sources are limited. However, the close proximity of CRP areas and remnant prairies may have allowed rapid crop-to-wild gene flow. In the first chapter, I investigated ploidy levels, genetic diversity, and genetic structure of seventeen prairie and sixteen CRP populations in eastern Kansas, along with five standard cultivars. The results suggested that the prairie and CRP populations were genetically similar, and the CRP populations were mainly established using local prairie seeds rather than cultivars. In addition, the prairie populations still harbor unique alleles that are of conservation value. Sufficient isolation distance between cultivated plants and their wild relatives is essential to prevent crop-to-wild gene flow, especially when the crop carries transgenes. In the second chapter, I documented the pattern and predicted the extent of pollen-mediated gene flow in switchgrass using two small field experiments with ~100 pollen donor plants and regression models. Data suggested that the pattern of gene flow was best described by a negative exponential model, and the estimated minimum isolation distance for a threshold of 0.01% gene flow was 60m and 109m for the experimental arrays. Seed-mediated gene flow could result in volunteers when favorable conditions (open full item for complete abstract)

Committee: Allison Snow (Advisor); Kristin Mercer (Committee Member); Maria Miriti (Committee Member); Andrea Wolfe (Committee Member) Subjects: Ecology

Doctor of Philosophy, The Ohio State University, 2012, Evolution, Ecology and Organismal Biology

Extensive gene flow between cultivated plants and wild relatives can be of concern because crop alleles may persist in wild populations and dilute the native gene pool or confer traits that enhance lifetime fitness, perhaps increasing the wild populations' tendency toward weediness. Switchgrass (Panicum virgatum L.) is a warm-season North American perennial that is widely planted for forage and soil conservation. Certain switchgrass cultivars have undergone a limited degree of breeding for use as a biofuel crop and could be planted on a large scale in the near future. However, very little research has examined the potential impact that mass plantings will have on wild populations. The goals of my research were to examine the potential for crop-to-wild gene flow and associated fitness effects by studying ploidy levels, flowering phenology, fitness components, and volunteer establishment. First, I determined ploidy levels of eight wild populations in Ohio and three in Illinois. Eight populations were tetraploid (4x), one was octaploid (8x), and two had mixed ploidy. In 2008 and 2009, I planted two common garden experiments at Ohio State University in Columbus, Ohio, with plants from three wild Ohio populations and seven cultivars: Kanlow (4x), Advanced Kanlow (4x), Summer (4x), Shawnee (8x), Trailblazer (8x), and two Advanced Octaploid strains (8x). I then compared the height and numbers of florets, filled seeds, and shoots of two- and three-year-old plants. Ohio native biotypes were similar to each other in all measured characteristics. Flowering times of native biotypes and the cultivars overlapped, but the degree of overlap varied, with Kanlow-type plants flowering much later than the rest. Kanlow-type plants were taller and produced four times as many florets as native biotypes, while Kanlow and Summer produced twice the number of filled seeds as the native biotypes. All other cultivars were similar to the native plants, except one Advanced Octaploid strain, which (open full item for complete abstract)

Committee: Allison Snow PhD (Advisor); Karen Goodell PhD (Committee Member); Kristin Mercer PhD (Committee Member); Maria Miriti PhD (Committee Member) Subjects: Ecology; Plant Sciences

Doctor of Philosophy, The Ohio State University, 2010, Environment and Natural Resources

A paradigm shift from maximum to sustainable agricultural production also applies to cultivation of bioenergy crops. Nitrogen (N) fertilization is needed to sustain the biomass yield of switchgrass as a biofuel feedstock and, consequently, may influence the potential for soil quality improvement through soil organic carbon (SOC) sequestration. Because changes in soil quality can feed back to affect the sustainability of biomass production, the impacts of N application on switchgrass biomass production and soil quality need to be evaluated together. Therefore, the overall objective of this study was to assess the effects of N fertilization on switchgrass biomass, changes in SOC concentration and pool, and soil structural properties. This objective was realized by conducting field experiments in Ohio and Tenessee, and a laboratory incubation study in Ohio. The aboveground biomass of switchgrass was more strongly influenced by N fertilization than the belowground biomass. Even when the aboveground biomass was harvested and removed, N fertilization led to an increase in SOC, both in Ohio and Tennessee. The data from laboratory incubation study showed that N additions could retard the decomposition of organic matter, which may contribute towards higher SOC pools in N fertilized plots. The results from the Tennessee experiments indicated the important role of roots in stabilizing soil structure. Despite higher SOC concentrations in plots receiving a high rate of N fertilization, higher soil structural stability was associated with greater root biomass and longer root length in plots receiving none or a low rate of N fertilizer. These data indicated that root growth is a crucial driver of surface soil structure.

Committee: Rattan Lal PhD (Advisor); Peter Curtis PhD (Committee Member); David Barker PhD (Committee Member); Julie Jastrow PhD (Committee Member) Subjects: Soil Sciences