Master of Science, Miami University, 2021, Biology

Invasive Amur honeysuckle and overabundant white-tailed deer affect the vertical plant cover and standing litter biomass of southwestern Ohio forests, causing invertebrate habitat quality and quantity changes. Increasing plant structure caused by honeysuckle invasion were hypothesized to provide more habitat for above-ground invertebrates. White-tailed deer were hypothesized to negatively affect litter-dwelling invertebrates due to indirect effects on litter biomass, which reduces litter habitat for invertebrates. We analyzed the long-term responses of litter spiders to experimental exclusion of deer and the removal of honeysuckle over time, 2011-2019, and shrub layer spiders in 2019. Winkler extraction of litter samples was used to collect litter-dwelling spiders, and systematic visual searches were used to collect above-ground spiders. All spiders were identified to guild and the lowest possible taxonomic class. Deer exclosure treatments and greater litter biomass were associated with increased species richness and abundance of litter spiders over nine years. Shrub layer spiders had reduced abundance when honeysuckle was removed, and space and sheet weavers had greater abundance in plots with higher foliage height diversity. Litter spider communities diverged over time based on site and deer treatment, while differences in the 2019 above-ground spider community were caused by honeysuckle treatment and site differences.

Committee: Thomas Crist (Advisor); Melany Fisk (Committee Member); Ann Rypstra (Committee Member) Subjects: Ecology

Master of Science (MS), Wright State University, 2021, Earth and Environmental Sciences

The non-native invasive shrub Amur honeysuckle, Lonicera maackii (Rupr.) Herder (Gorchov and Trisel, 2003), is one of the most prolific invasive plant species across Midwestern and Northeastern landscapes of the United States. The locations of 2,095 individual Amur honeysuckle stems were geolocated using handheld GPS units in the understory of mixed growth forests at two study sites located approximately 5 km apart in northwestern Greene County, OH. Each site has undergone different levels of anthropogenic disturbance through time. The stem position data was used to measure the spatial clumping distribution and the density of Amur honeysuckle. The spatial clumping of Amur honeysuckle stems was measured using the fractal box counting method at each study site without regard for streams, trails, or elevation. The density of Amur honeysuckle (number of stems per square meter) was measured in zones as a function of the horizontal distance perpendicular to the edge of streams, trails, and within elevation (area between contour lines). Amur honeysuckle density is found to be uncorrelated with its proximity to streams, trails, and elevation. The density of Amur honeysuckle as a function of distance from streams and trails does not reveal an edge effect. The fractal dimension (scaling exponent) was computed to be ~1.5 at each of the two sites which means that the spatial clustering is the same for actively managed (partial Amur honeysuckle removal) and unmanaged sites. These results suggest that the invasion potential of Amur honeysuckle is robust, and its distribution may not be constrained in riparian forests by the variables included in this study.

Committee: Christopher Barton Ph.D. (Advisor); David Peterman Ph.D. (Committee Member); Ryan McEwan Ph.D. (Committee Member) Subjects: Biology; Earth; Ecology; Environmental Science

Doctor of Philosophy, The Ohio State University, 2021, Environment and Natural Resources

Biological invasions threaten biodiversity and ecosystem functions. Stream ecosystems and their adjacent riparian zones are connected via a complex network of direct and indirect linkages, presenting a unique setting for the study of invasion. I investigated the effects of two different riparian invaders on stream biota and stream-riparian trophic linkages: an invasive insect (hemlock woolly adelgid Adelges tsugae; hereafter HWA) and an invasive shrub (bush honeysuckles Lonicera maackii and L. tatarica). Both sets of studies used the same basic approach at >20 streams across a gradient of invasion intensity: record geomorphology and water chemistry, collect and assess in-stream biota, quantify reciprocal subsidies, and determine riparian spider density, relative reliance on aquatically-derived energy (i.e., nutritional subsidies originating from periphyton), and invertebrate food-chain length (using naturally-abundant stable isotopes) at each study reach. I also conducted a before-after, control-impact (BACI design) honeysuckle removal experiment. My results suggest that in-stream physical and chemical alterations (i.e., large-wood characteristics and nutrient concentrations) associated with HWA invasion and subsequent hemlock decline drove changes in stream invertebrate diversity and trophic relationships. Evidence for ecological consequences of this invader was strongest at lower trophic levels. For example, periphyton biomass was greater at uninvaded reference sites than at severely invaded sites (x = 1.37 vs 0.52 mg cm-2), while relative abundance of herbivorous macroinvertebrates increased from 4 to 23% at the severely invaded sites. Spider (family Tetragnathidae) densities were 3.2 times higher at sites with severe hemlock decline and although density was not linked to emergent insect density overall, δ15N signatures of Araneidae and Pisauridae spider families tracked emergent insect δ15N (r2 = 0.42 and 0.78, respectively), suggesting a trophic linkage. (open full item for complete abstract)

Committee: S. Mazeika Sullivan (Advisor); Lauren Pintor (Committee Member); P. Charles Goebel (Committee Member) Subjects: Ecology; Environmental Science; Freshwater Ecology

Doctor of Philosophy, Miami University, 2020, Ecology, Evolution and Environmental Biology

This dissertation examines how an invasive woody plant, Lonicera maackii, temporally and spatially structures native bee communities of forest-edge habitat in agricultural landscapes. In Chapter 1, I measured bee species composition and pollination services ≤200 m from isolated forest patches in response to L. maackii flower removals. Removing flowers released a subset of small-bodied bees and increased pollination services after two years. Pollination services provisioned by large-bodied and generalist bee species (e.g. Bombus spp) increased when nearby plants were adjacent to intact L. maackii flowers. Findings suggest that L. maackii flowers suppress one component of the bee community and attract another to the forest patch that increases usage of the adjacent crop fields. In Chapter 2, I compared two components of the bee community and their responses to L. maackii density, floral resources of the forest patch, and the surrounding landscape. Bees sampled in pan traps were typically small, specialized, and responded to local patch features. Bees sampled in vane traps were larger in body size, social, and responded to landscape composition 3 km from the forest patch. These findings suggest that L. maackii floral resources support weaker foragers within the forest patch as well as larger bees that forage throughout the landscape. Both components of the bee community responded to tree community composition and were vertically stratified in the tree canopy. In Chapter 3, I measured bee diversity and community composition at different vertical strata in response to L. maackii density and flowering period as well as floral resource availability of woody plants. I found that L. maackii supports a component of the vertically stratified bee community which changes interactions with floral resources of the native woody vegetation at different vertical strata. Collectively, my studies demonstrate that L. maackii structures forest-edge bee communities through mechanisms invo (open full item for complete abstract)

Committee: Thomas Crist (Advisor); David Berg (Committee Member); Amelie Davis (Committee Member); David Gorchov (Committee Member); Jign Zhang (Committee Member) Subjects: Agriculture; Biology; Conservation; Ecology

Master of Science, Miami University, 2020, Biology

Shifts in forest composition could have significant effects on freshwater zooplankton due to changes in quality of inputs of terrestrially-derived Dissolved Organic Matter (DOM). DOM has been shown to have concentration dependent effects on primary production, but no consistent concentration dependent effects on zooplankton growth rates, raising questions about the potential importance of DOM source. Red maple (Acer rubrum), a native tree, and Amur honeysuckle (Lonicera maackii), an invasive shrub, were used to test the effects of DOM source on juvenile Daphnia ambigua. Amur honeysuckle-derived DOM was expected to have greater negative effects. Bioassays were conducted in the presence or absence of algae with no additional DOM, or red maple or Amur honeysuckle-derived DOM. Both Amur honeysuckle and red maple had negative effects on growth rates in the presence of algae with red maple inducing significantly lower growth rates. Red maple-derived DOM also had negative effects on survival. The negative effects seen in the presence and absence of algae provided evidence for both indirect effects likely due to phytotoxicity and direct negative effects respectively. Future studies accounting for DOM source could enhance our understanding of the complex roles of DOM in regulating consumers in aquatic ecosystems.

Committee: Craig Williamson (Advisor); Maria Gonzalez (Committee Member); Karsten Mauer (Committee Member) Subjects: Biology; Ecology; Freshwater Ecology; Limnology

Master of Science in Botany, Miami University, 2019, Biology

The secondary-growth hardwood forest of Rush Run Wildlife Area (RRWA), Preble County, Ohio was studied 54 years after an initial study was conducted in 1964. Although Dutch elm disease (DED) was likely present in the area by the late 1930s to early 1940s, American elm (Ulmus americana L.) was recorded as one of the dominant canopy species (avg. relative density = 15.1%) and subcanopy species (9.0%) in 1964. Seedlings of American elm were also noted to be abundant across RRWA. Of the 17 plots used in 1964, 10 were chosen based on the previously recorded high relative density of American elm and resurveyed. By 2018, American elm was absent from the canopy, subcanopy, and seedling layers. A secondary analysis of measurements taken in 2018 that included dead standing Fraxinus spp. showed that the current loss of ash was extensive but non-impactful upon other species. Findings oppose the previous predictions that American elm can persist indefinitely in forest stands following introduction of DED but restricted to subcanopy and smaller stature. It is possible that previous studies have not allowed adequate time after introduction of DED to accurately assess the effects on American elm.

Committee: Michael Vincent PhD (Advisor); Richard Moore PhD (Committee Member); David Gorchov PhD (Committee Member) Subjects: Botany; Ecology; Plant Sciences

Master of Science, Miami University, 2019, Botany

The North American beaver is a keystone riparian obligate which creates and maintains riparian areas by building dams. In much of the eastern U.S., invasive shrubs are common in riparian zones, but we do not know if beavers promote or inhibit these invasions. I investigated whether beavers use the invasive shrub, Amur honeysuckle (Lonicera maackii), preferentially compared to other woody species and the causes of differences in L. maackii electivity among sites. At eight sites, I identified woody stems on transects, recording stem diameter, distance to the water's edge, and whether the stem was cut by beaver. To determine predictors of cutting by beaver, I conducted binomial generalized regressions, using distance from the water's edge, diameter, and plant genus as fixed factors and site as a random factor. To quantify beaver preference, I calculated an electivity index (Ei) for each genus at each site. Lonicera maackii was only preferred at two of the eight sites though it comprised 41% of the total cut stems. Stems that were closer to the water's edge and with a smaller diameter had a higher probability of being cut. Among sites, L. maackii electivity was negatively associated with the density of stems of preferred genera.

Committee: David Gorchov (Advisor); Susan Hoffman (Committee Member); Bartosz Grudzinski (Committee Member) Subjects: Botany; Ecology

Doctor of Philosophy, Miami University, 2019, Ecology, Evolution and Environmental Biology

The goals of this dissertation were to examine the effects of overabundant white-tailed deer and invasive Amur honeysuckle on forest floor invertebrates and ecosystem processes in an eastern deciduous forest. In Chapter 1, I examined responses of the soil organic layer and exotic earthworms to the experimental exclosure of deer and honeysuckle removal through time. Earthworm density declined in response to deer exclusion, with earthworm density decreasing over time in deer exclosures relative to deer access plots. Litter biomass decreased over time in deer access plots. In contrast, honeysuckle removal had little effect on earthworm density and litter biomass. Yet, there was an interaction between deer and honeysuckle on earthworm biomass, with honeysuckle removal reducing earthworm biomass in deer exclosures. These results suggest white-tailed deer and exotic earthworms are highly linked and that it is difficult to parse the effects of deer from those of earthworms in exclosure studies, as these effects are likely interrelated. In Chapter 2, I determined the impact of deer exclosure and honeysuckle removal on litter-dwelling ant communities through time. Ant abundance and species richness increased with time in deer exclosures, but not in deer access plots. Honeysuckle removal reduced abundance and richness of ants. There was little evidence that treatments directly influenced ant species diversity or functional diversity. However, all ant measures were positively related to litter biomass. These findings suggest ants respond strongly to ecosystem drivers of deer, honeysuckle, and earthworms; specifically, ants responded strongest to changes in litter biomass. In Chapter 3, using litter boxes with different mesh sizes (0.25 and 10 mm openings), I quantified litter decomposition rates in response to experimental deer, honeysuckle, and earthworm removal. Decomposition rates were drastically faster in coarse mesh treatments compared to fine mesh treatments. Decomposit (open full item for complete abstract)

Committee: Thomas Crist (Advisor); Melany Fisk (Committee Member); David Gorchov (Committee Member); Thomas Rooney (Committee Member); Jing Zhang (Committee Member) Subjects: Ecology

Master of Science (MS), Wright State University, 2018, Biological Sciences

Since industrialization, anthropogenic carbon emissions have led to excess atmospheric carbon dioxide that may alter the stability of ecosystem processes. Microorganisms are essential in mitigating excess carbon and play a notable role in the breakdown of organic material. This process, decomposition, is essential in forested ecosystems where microorganisms can recycle nutrients and store carbon in soil organic matter or release it through respiration. Fungi participate in decomposition through the release of enzymes responsible for carrying out the chemical reactions that break down plant material. Species introductions have the potential to alter decomposition dynamics. In the Midwestern US, the invasive shrub species Lonicera maackii has overtaken many forests and is likely altering decay dynamics and the destiny of carbon within the region. Thus, it is essential to monitor the decay of woody debris under invasion pressures of L. maackii in order to monitor nutrient cycling in this region. I placed blocks of native Quercus rubra and economically important Pinus radiata in an L. maackii invaded forest for one year to determine environmental, enzymatic and fungal drivers of decomposition. Decomposition was faster for oak wood than pine wood, and decomposition rate was not directly altered by L. maackii. Instead, L. maackii increased the moisture of the decomposing wood, leading to higher amounts of hydrolytic enzyme activity which structured fungal communities within decaying wood. This insinuates that despite not altering decomposition rates directly, L. maackii is priming native woody debris for faster decomposition and therefore increasing the rate of nutrient turnover. Thus, L. maackii imposes shifts to fungal communities and their functionality and the soil environment. These changes could become especially important in later stage decay where there will likely be perceptible differences in decay rates as altered by L. maackii. The changes L. maackii imposes o (open full item for complete abstract)

Committee: Megan Rúa Ph.D. (Advisor); Don Cipollini Ph.D. (Committee Member); Thomas Rooney Ph.D. (Committee Member) Subjects: Biology; Ecology; Environmental Science; Plant Sciences; Soil Sciences

Master of Science in Botany, Miami University, 2018, Biology

In the fragmented forests of Ohio, native tree recruitment has been reduced by abundant white-tailed deer and invasion of Amur honeysuckle (Lonicera maackii). While shrubs compete with tree seedlings, live shrubs can facilitate growth and survival of native tree seedlings in the presence of deer. It is less clear if dead shrubs can have this same effect. In this study, I tested the hypothesis that dead L. maackii shrubs provide refuge for native tree seedlings from deer browse and facilitate growth and survival. In the Miami University Natural Areas in Oxford, OH, I planted 512 native tree seedlings within plots comparing controls to three different L. maackii removal strategies: complete shrub removal, felling of shrubs leaving branches on the ground, and basal bark herbicide application. I found that dead branches in the Felling treatment provided refuge from browse and facilitated growth and survival for Carpinus caroliniana, but did not facilitate growth and survival for Quercus alba, Celtis occidentalis, or naturally occurring seedlings. This result partially supports the hypothesis that dead L. maackii branches facilitate growth and survival of native tree species, but demonstrates that the effect varies among tree species and may be dependent on deer browse preference.

Committee: David Gorchov Dr. (Advisor); Melany Fisk Dr. (Committee Member); Thomas Crist Dr. (Committee Member) Subjects: Biology; Botany; Ecology; Natural Resource Management

Master of Science, Miami University, 2018, Biological Sciences

I measured the relative importance of honeysuckle invasion, forest edge, and surrounding land uses on the population densities of white-tailed deer in southwest Ohio. I tested the following hypotheses: (1) deer populations are facilitated in forests invaded by honeysuckle, (2) forest stands that are surrounded by agriculture support higher deer densities in summer due to the availability of supplemental food outside of forest patches; and (3) forest stands with the greatest amount of edge habitat support higher deer densities due to deer use of both forest and open habitats. Using line transects established in eight early to mid-successional forest stands, I estimated deer population densities in early spring (March - April) and summer (June - July) and compared them to levels of honeysuckle invasion along transects. Distance sampling methods were used to estimate deer densities from pellet counts, and stand-level estimates of deer densities were related to honeysuckle cover along transects, as well as the amounts of forest edge habitat and different land cover types in the landscapes surrounding each forest stand using linear models. I found honeysuckle cover, mixed forest cover, and deciduous forest cover were strong predictor variables of deer densities in Southwest Ohio.

Committee: Thomas Crist Dr. (Advisor) Subjects: Biology; Ecology

Master of Science (M.S.), University of Dayton, 2017, Biology

Terrestrial-to-aquatic linkages are an important vector for the transfer of nutrients from one habitat to another. Therefore, the biology of headwater streams is strongly influenced by the surrounding terrestrial riparian vegetation. Amur honeysuckle (Lonicera maackii) is an invasive shrub that thrives in disrupted habitats including stream riparian zones. Although, extensive research has shown the detrimental effects of L. maackii on terrestrial systems, little research has been done on how cross boundary subsidies such as leaves and woody debris are impacted by the dense and often overarching L. maackii invasion in headwater stream riparian zones. Therefore, the aim of this study is to understand the influence of a gradient of L. maackii density in riparian habitats on the contribution of organic subsidies in stream systems in Southwestern Ohio. Across the established gradient of L. maackii invasion leaf litter biomass, fruit biomass, falling twig biomass, terrestrial and aquatic fine woody debris (0.5-9.9 cm diameter) volume and count, and terrestrial and aquatic coarse woody debris (>9.9cm diameter) volume were accessed. We hypothesized that sites with a higher density of L. maackii would have a decreased total leaf litter biomass deposition due to the dense overarching riparian L. maackii over the stream increasing the potential of litter getting caught in the canopy. Additionally, based on the intentionally established gradient of sites we also expected L. maackii leaf biomass to increase as invasion intensity increased. Lastly, we hypothesized that woody biomass in the form of both fine and coarse woody debris would decrease along the invasion gradient due to the dense shrub architecture. The only significant treatment effects in regards to site were found for L. maackii only leaf litter biomass (p = <0.0001), count of aquatic fine woody debris (p = 0.03292), and fruit biomass (p = 0.00597). In all cases the observed treatment effect did not follow our hypot (open full item for complete abstract)

Committee: Ryan McEwan Ph.D. (Committee Chair); Albert Burky Ph.D. (Committee Member); Mark Nielsen Ph.D. (Committee Member) Subjects: Biology; Ecology

Master of Science, Miami University, 2017, Botany

Selectivity by overabundant, generalist herbivores leads to intensive browsing on preferred species, which may allow less-preferred invasive species to flourish. Recent work from our lab indicated that an invasive shrub (Lonicera maackii) comprises a large proportion of deer diet in Miami University Natural Areas, but this may reflect high frequency of L. maackii rather than preference. I tested three hypotheses: (1) Deer prefer to browse on L. maackii versus other woody plants, (2) L. maackii is not a preferred source of browse, but consumed when alternative foods are depleted or (3) L. maackii is a unique food resource for deer, e.g. a nutritious food during a season of scarcity. We assessed preference for L. maackii and co-occurring woody plants across 8 sites in southwest Ohio by counting browsed and unbrowsed twigs of each species and calculated an electivity index.L. maackii electivity was negative at most sites, indicating it is not preferred, but lack of support for a negative trend between L. maackii browse and more-preferred twig densities indicates it is not strictly low preference. A negative trend betweenL. maackiibrowse and L. maackii density supports the importance of L. maackii as a source of browse during early spring.

Committee: David Gorchov (Advisor); Richard Moore (Committee Member); Thomas Crist (Committee Member) Subjects: Ecology; Plant Sciences

Master of Environmental Science, Miami University, 2016, Environmental Sciences

Invasive species represent one of the largest threats to native biodiversity and ecosystem processes. Landscape managers require time expedient techniques other than in-field monitoring in ascertaining and mapping the presence of various invasive plants. While several remote sensing techniques have been used to identify invasive plants we discuss the use of two techniques in tandem; space-based multi-spectral satellite imagery (Landsat and WorldView 3) and Light Detection and Ranging (LiDAR), to determine the prevalence of invasive woody plants. Our study was to test whether remotely-sensed vegetation indices and forest structure profiles correlated with surveyed measurements of Amur honeysuckle (Lonicera maackii) at Rush Run Wildlife Area in Southwest Ohio. LiDAR derived canopy height profiles revealed that vegetation of height 1-4 meters was positively correlated to L. maackii with an R2 value of 0.6318 within a distance of 2 meters from census transects. Additionally, spectral vegetation indices combined with LiDAR derived metrics did not improve the prediction over LiDAR height profiles alone. Our results show that determining understory structure via LiDAR via specific workflows may reveal areas of invasive plant clusters not detected by spectral means.

Committee: Mary Henry (Advisor); Sarah Dumyahn (Committee Member); David Gorchov (Committee Member); Suzanne Zazycki (Committee Member) Subjects: Ecology; Environmental Science; Geographic Information Science; Remote Sensing

Doctor of Philosophy, Miami University, 2016, Ecology, Evolution and Environmental Biology

While invasive plants and generalist herbivores have negative direct effects on plant communities, their indirect and interactive effects have received far less focus. I address the effects of an abundant herbivore, White-tailed deer (Odocoileus virginanus), and the invasive shrub Amur honeysuckle (Lonicera maackii) on forest plant communities, focusing on determining whether their interactions are synergistic, antagonistic, or additive. Within the Miami University Natural Areas, I sampled plant species richness and cover in five 20 x 20 m2 deer exclosures and paired controls, each with L. maackii removed from half of the plot. I found antagonistic interactions of L. maackii and deer on the tree seedling cover, suggesting that L. maackii mitigates the negative effect of deer on trees, facilitating tree survival and growth. To investigate whether L. maackii provides a refuge for tree seedlings from deer browse, I planted tree seedlings under and away from the L. maackii canopy, with and without deer exclosures, and measured their growth, survival and browse status. I found facilitation by L. maackii on survival and leaf count of Acer saccharum seedlings: where deer had access, seedlings planted under L. maackii had higher survival and more leaves. This suggests that L. maackii serves as a refuge for tree seedlings from deer browse. Finally, I explored the direct effects of deer on L. maackii, addressing whether deer browse on L. maackii is sufficient to reduce its cover. In the 20 x 20 m2 plots I scored leaf frequency of L. maackii in the height ranges browsed by deer, as well as basal area (BA) of all stems of L. maackii. I found access to deer strongly reduced L. maackii leaf frequency within the height range of deer browse, and modestly reduced BA growth. This suggests that deer affect the architecture of L. maackii more than its growth. These results indicate that considering interactive effects is fundamental to understanding the roles of thes (open full item for complete abstract)

Committee: David Gorchov (Advisor); M. Henry Stevens (Committee Member); Melany Fisk (Committee Member); R. James Hickey (Committee Member); Thomas Crist (Committee Member) Subjects: Biology; Botany; Ecology

Master of Science (MS), Ohio University, 2015, Plant Biology (Arts and Sciences)

Since the loss of Castanea dentata (American chestnut) from eastern hardwood forests, invasive species have occupied many of the forests where chestnut once resided. Even though agencies have begun to replant hybrid chestnuts into the forests, no one has examined how invasive species might interact with American chestnut. In this study, allelopathic impacts on chestnut were mimicked by adding aqueous extracts or biomass of three allelopathic invasive species tree of heaven (Ailanthus altissima (Mill.) Swingle), garlic mustard (Alliaria petiolata (M.Bieb.) Cavara and Grande), and Amur honeysuckle (Lonicera maackii ( Rupr. ) Maxim.)) to soils supporting chestnut seedlings. In greenhouse experiments, chestnut seeds were treated weekly with aqueous extracts of biomass from the invasives. Chestnut seedlings were also planted in gardens and treated with root or shoot biomass from the invasives. Finally, chestnut seedlings were planted in a forest at sites with garlic mustard present and at sites where garlic mustard had been regularly removed for 8 yrs. Growth factors of chestnut, such as height, mass, and basal area, were measured. Chestnut seedlings treated with tree of heaven extracts had lower heights and more re-sprouts than the control groups. However, results were not consistent among the experiments. Chestnut seedlings treated with some invasive plant biomass, including tree of heaven biomass, had heights statistically similar to the control groups. When treated with roots of garlic mustard, chestnut heights were statistically lower than the negative control. Chestnut seedlings planted in garlic mustard plots in the forest were only statistically taller the first time they were measured, but were not statistically different thereafter. The results from these initial experiments suggest that the allelopathic effects from tree of heaven may negatively impact reintroduction of American chestnut; however, other invasives may be less problematic.

Committee: Brian McCarthy Dr. (Advisor); Jared Deforest Dr. (Committee Member); David Rosenthal Dr. (Committee Chair) Subjects: Ecology; Plant Biology

Master of Science, Miami University, 2013, Botany

I tested whether the invasive shrub Lonicera maackii (Amur honeysuckle) competes with tree seedlings for water by either of two mechanisms: 1) intercepting rainwater during light rain events; (2) absorbing large amounts of water through its fine roots. To test the two hypothesized mechanisms I selected plots near large L. maackii shrubs and control plots away from any large L. maackii shrubs in the forest understory. Within each plot I placed a trenched and an untrenched subplot. I measured precipitation above and below L. maackii canopies, and soil water content and stomatal conductance of naturally-occurring Acer saccharum and Carya sp. seedlings in each trenched and untrenched subplot. The results somewhat supported the hypothesis that L. maackii competes with tree seedlings by interception, but were inconclusive regarding the hypothesis of competition by water uptake. A novel dataset shows that L. maackii fine roots are disproportionately common in shallow soil.

Committee: David Gorchov PhD (Advisor); Alfredo Huerta PhD (Committee Member); Melany Fisk PhD (Committee Member) Subjects: Biology; Botany; Conservation; Ecology; Plant Biology; Plant Sciences

PhD, University of Cincinnati, 2008, Arts and Sciences : Biological Sciences

In the Midwest US, invasion by Amur honeysuckle (Lonicera maackii) reduces diversity, growth, and reproduction of native plants, and browsing by overabundant white-tailed deer (Odocoileus virginianus) may compound these impacts. Few studies, however, have determined whether these species act in concert to alter native plants, or whether these species impact litter invertebrate communities or forest soil. Using a combination of exclusion of white-tailed deer and removal of Amur honeysuckle, I measured individual and combined impacts of these species on diversity, abundance, and community composition of understory herbs and litter-dwelling invertebrates. I also examined whether deer or honeysuckle affected litter substrate composition, litter depth, soil compaction, and soil microbial activity. Amur honeysuckle, but not white-tailed deer, altered composition of forest understory herb and invertebrate communities, and had variable, but significant, effects on abundance and diversity of different herb species and invertebrate orders. Deer reduced invertebrate abundance but did not affect diversity or composition of invertebrates. Neither deer nor honeysuckle affected composition of litter substrate, mass of leaf fall, or litter depth. Leaf decomposition was similar across treatments. Soil compaction was greater in plots containing either deer or honeysuckle, but removal of honeysuckle and exclusion of deer reduced this effect. There were no interactions between deer and honeysuckle on decomposition of leaf litter or compaction of soil. Microbial activity was greater in homogenized topsoil when topped with decomposing leaves of honeysuckle than when under leaves of sugar maple. However, microbial activity in soil taken from an invaded area of forest was similar to that from adjacent uninvaded areas. The variable effects of white-tailed deer and Amur honeysuckle on different taxa and levels of organization requires that management of these species utilize habitat and taxa (open full item for complete abstract)

Committee: Guy Cameron (Committee Chair); Theresa Culley (Committee Member); George Uetz (Committee Member); Eric Maurer (Committee Member); David Gorchov (Committee Member) Subjects: Biology; Botany; Ecology; Forestry; Zoology

Doctor of Philosophy, The Ohio State University, 2008, Natural Resources

Effective conservation of biodiversity in urban areas ultimately requires that ecologists understand both the patterns and mechanisms of urban-associated influences on native plant and animal communities. A neglected consequence of urbanization is the seasonal timing of life cycle events, particularly the tendency of many urban birds to breed earlier in the spring than their rural-breeding counterparts. The overall objectives of this dissertation were to (1) describe phenological and biological differences in avian reproduction in urban and rural forests, (2) identify underlying ecological mechanisms responsible for observed patterns, and (3) identify demographic consequences of phenological shifts in reproduction. First I evaluated vegetation phenology and temperature patterns, two potentially important variables influencing bird breeding phenology. There was an overall pattern of advanced phenology (e.g., bud break, leaf elongation) within species in more urban landscapes which might be associated with elevated temperatures in more urban areas. Results suggest that shifts in plant communities along the urbanization gradient, especially the increased dominance of the invasive and exotic Amur honeysuckle (Lonicera maackii) in urban forests, drove the earlier green-up of urban areas. Avian breeding phenology was also influenced by urbanization, although patterns, causes, and consequences differed between my two focal species. The non-migratory Northern Cardinal (Cardinalis cardinalis) nested earlier in urban versus rural sites, a pattern that was best explained by early spring temperatures. Contrary to findings from other studies, early-breeding cardinals apparently received no benefit in terms of survival or reproduction compared to later-breeding pairs. In contrast, the Neotropical migratory, Acadian Flycatcher (Empidonax virescens) arrived and initiated breeding later in the more urban landscapes – a phenological shift that ultimately reduced reproductive produ (open full item for complete abstract)

Committee: Amanda Rodewald (Advisor); Tomas Koontz (Committee Member); Thomas C. Grubb, Jr. (Committee Member) Subjects: Ecology

Master of Science (MS), Ohio University, 2004, Environmental Studies (Arts and Sciences)

The invasive Lonicera maackii (Amur honeysuckle) is a woody shrub that dominates the landscape of the Midwest. My objective was to evaluate how leaf physiological and morphological characters relate to biomass allocation and fecundity patterns of L. maackii . Specifically, I investigated the plasticity of L. maackii's photosynthetic and biomass allocation patterns across a light gradient. Individual shrubs were selected in open ( N =5), forest edge ( N =23), and forest interior habitats ( N =24) in southwestern Ohio. Gas exchange measurements were made on a sub-sample of shrubs throughout the 2003 growing season to evaluate physiological performance and leaf nitrogen content. All shrubs were harvested at the end of the season to assess biomass allocation and fruit production. In most cases, open-grown shrubs outperformed interior/edge shrubs, which performed similarly. Although edge- and interior- grown shrubs were found to be significant sources of propagules, open-grown shrubs should be targeted for control due to unusually high fecundity.

Committee: Kim Brown (Advisor) Subjects: Biology, Ecology