Theses (M.S.)--University of Hawai'i at Hilo, 2008. / Advisor : Mautz, William Bibliography : p.39-42.

<p>Biological invasion is a major and growing threat to global biodiversity and human well-being, but research on the impacts of invaders on their recipient environments lags behind that on the mechanisms driving invader establishment and spread. The total impact of an invader is defined by its range size, abundance per unit area, and per-capita effect, with both per-capita effects and abundance varying over time and across the invader’s range. These context-dependencies are determined, in part, by functional differentiation between the invader and its recipient system. In this thesis, I investigate how functional differentiation between invaders and their recipient communities regulates the impact of plant invaders on community diversity and/or biomass production.</p> <p>First, I compare the effects of invasive Callery pear (<em>Pyrus calleryana</em> Decne.) to functionally similar native trees in three early-successional meadow environments in Indiana’s eastern corn belt plains. Despite my prediction that <em>P. calleryana</em> would have greater negative effects on the total biomass and diversity of the understory plant community compared to native trees, I found that <em>P. calleryana</em> had no significant impact on total cover, species richness, or Shannon’s or Simpson’s diversity indices for the understory community, compared to native <em>Liriodendron tulipifera</em> L., <em>Platanus occidentalis</em> L., or non-tree control plots. Likewise, <em>P. calleryana</em> had no significant impact on the native, introduced, woody, or native tree subsets of the understory community. These results indicate that the trait differences between <em>P. calleryana</em> and functionally similar native trees – and thus the per-invader effect of <em>P. calleryana</em> on its recipient community – are not of a great enough magnitude to produce changes in the understory community composition of these highly invaded, low diversity meadow environments with relatively new and sparse <em>P. calleryana</em> invasions. </p> <p>I then investigate the role of functional overlap in moderating invader impacts in California serpentine grassland communities through the lens of classic niche theory, which predicts that functional differentiation minimizes competition and therefore allows functionally distinct invaders to achieve higher establishment success but lower per-capita effects on their recipient communities. I tested this prediction by establishing small-scale experimental communities composed of individual or multiple functional groups differentiated by phenology – early-season annuals, nitrogen-fixing early-season annuals, and late-season annuals – and seeding these communities with early- or late-season invaders. I found that as invader density increased, effects on resident community biomass depended on complex patterns of invader and resident functional overlap. Across all resident community functional groups, the high density of early-season invaders enables them to capture a greater portion of total community biomass than late-season invaders, but early-season invaders reduce the ratio of resident:total invader biomass production by less, per-unit-biomass, than late-season invaders. These results highlight the need to consider both niche and fitness differences in predicting invader impacts and the complex nature of resident-invader interactions, which may not be sufficiently captured by coarse functional groups.</p>

<div>Wetland-dwelling amphibians are of conservation interest for numerous reasons. They serve as biological indicators of water quality during their fully aquatic larval phase, and as carnivores that prey extensively on both terrestrial and aquatic invertebrates. These amphibians are an important link between terrestrial and aquatic food webs, and their wellbeing is an important factor when considering ecosystem health. Amphibians are facing global declines as their wetland habitats are being lost or degraded by human actions. There are efforts to restore wetland habitats, but it is far from certain which practices encourage amphibian occupancy.</div><div>I investigated which factors are important to the persistence of amphibians in restored and naturally formed wetlands to see if restored wetlands can accommodate similar species assemblages. Amphibians were surveyed over two years in a collection of 18 wetlands in Steuben and DeKalb counties, IN owned by The Nature Conservancy. Ambystomatid salamanders were surveyed using plastic minnow traps in springtime, and frogs were surveyed using call surveys in spring and summer. I used linear models to compare wetland plant dominance, wetland hydroperiod, restoration status, distance to nearest mature forest, adjacent forest age and basal area, and inter-wetland distance to amphibian species richness.</div><div>The species richness of Ambystoma salamanders was positively associated with larger wetlands, higher forest basal area, and central mudminnow presence; and negatively associated with older forests, distance to mature forests, and the presence of sunfishes. Ambystoma salamanders besides A. tigrinum were associated with ephemeral hydrology, naturally-formed wetlands, and a greater number of wetlands within one km; and negatively correlated with older forests.</div><div>Frog species richness was positively associated with larger wetland size, and negatively associated with seasonal wetlands, naturally-formed wetlands, distance to nearest mature forests, naturally formed wetlands, treatment for invasive plants, and number of other wetlands within 500m. Total amphibian species richness models did not perform well, but showed a preference for semi-permanent wetlands, smaller distance to mature forests, greater forest basal area, and greater distance between wetlands; and a preference against Scrub Shrub/Forest wetlands. Hylid frogs were negatively correlated with naturally formed wetlands. Ranid frogs were associated semi-permanent wetlands and negatively correlated with the number of other wetlands within 500 m.</div><div>Ambystomatid salamanders were found in restored wetlands, semi-permanent wetlands, and in wetlands containing central mudminnows. Frogs may dislike the disturbance from removing invasive grasses. Managers should factor the disparate habitat requirements of amphibian taxa into their plans for creating and managing restoration projects. Different amphibian groups appear to differ greatly in their habitat requirements, and diverse wetlands may enhance the species richness of an area. Skillfully restored wetlands appear to serve similar functions to original, naturally formed ones.</div>

<p>Fish communities in agricultural headwater streams are known to be impacted by a variety of factors, including water chemistry, habitat modification, and hydrology. Little research has been conducted on how climate change influences these communities, yet the effects of climate on lake and river fish have been well documented. I hypothesized that fish community metrics would be reduced by the effects of climate change. I examined the effects of climate and hydrology metrics on fish communities at nine sites in the Saint Joseph River, Indiana and Michigan and at 18 sites in the Upper Big Walnut Creek, Ohio watersheds, from 2006 to 2019. Air temperature, water temperature, precipitation, water discharge, width, velocity, and depth metrics were calculated seasonally for each sampling year. Fish were examined seasonally with backpack electrofishing and seine netting and identified to species level. Principal component analyses were used to create axes which represented gradients of climate and hydrology metrics. Linear mixed effect and logistic regression modeling suggested that hydrology is a stronger predictor than climate, but that both influence fish communities. Percent Percidae, percent herbivore, and percent open substrate spawner were positively correlated with precipitation and water temperature. Presence herbivore was negatively correlated with precipitation and positively correlated with water temperature. My data only somewhat supported the hypothesis that climate would reduce fish community metrics. Gradients of hydrology were observed to be stronger predictors than gradients of climate. However, one must acknowledge relationships between climate and hydrology and the potential for climate to have indirect effects on fish communities through influences on hydrology. This study increases understanding of how fish communities in agriculturally dominated headwater streams are influenced, and emphasizes the need for further research on how these fishes will be impacted by a changing climate. </p>

<p>Aquatic macroinvertebrates of channelized headwater streams in agricultural landscapes are exposed to alterations in chemistry and physical characteristics of benthic sediments. These habitat alterations are known to influence communities of aquatic macroinvertebrates. Benthic sediments can have a wide range of impacts and influences on aquatic macroinvertebrates. I hypothesized that sediments would play a significant role in determining macroinvertebrate community structure within agriculturally dominated headwater streams. I evaluated the influences of sediment chemistry characteristics and physical characteristics on aquatic macroinvertebrate communities in Cedar Creek, Indiana and Michigan, and the Upper Big Walnut Creek, Ohio, during 2017 and 2018. Macroinvertebrates were collected twice per year using artificial substrate and leaf pack samplers and identified to the family level. Sediments were sampled two times per year and analyzed for seven physical characteristics and twenty sediment chemistry characteristics. Principle component analyses were used to create axes that are indicators of gradients of sediment chemistry and physical characteristics that occur among the samples. Macroinvertebrate community metrics used in the analyses included abundance, Shannon Diversity Index, Hilsenhoff Biotic Index scores, Invertebrate Community Index scores, percentage of collector-filters, percentage of scrapers, percentage of Chironomidae and a Berger-Parker Reciprocal Index of dominance. Linear Mixed Effect Model analyses revealed that both sediment chemistry and physical characteristics influence macroinvertebrate community metrics. Aquatic macroinvertebrate abundance was negatively correlated with increasing concentrations of simazine and decreasing concentrations of calcium. Percentages of Chironomidae were positively correlated with increasing percentages of sand and decreasing percentages of clay and decreasing diversity of sediment particle sizes. My data supported the hypothesis that benthic sediments play an important role in determining aquatic macroinvertebrate community structure in headwater streams of agriculturally dominated landscapes. Gradients of chemical characteristics containing simazine and calcium were observed to be negatively correlated with macroinvertebrate abundance. Gradients of physical characteristics including percentages of sand and clay along with the diversity of particle sizes were observed to be positively correlated with percentage of chironomids. My research increases the knowledge that benthic sediments, chemically and physically, can lead to alterations in aquatic macroinvertebrate communities within Midwestern headwater streams. </p>

<p> Chameleon plant (<em>Houttuynia cordata</em> Thunb.) is native to Southern and Southeastern Asia. It can reproduce sexually through seeds and asexually through rhizomes and is invasive in multiple countries including the U.S. There has been much research on <em>H. cordata</em> as a medicinal species, and its potential as an invasive species is well documented. However, its herbicidal resistance has not previously been quantified. The objective of this study is to assess <em>H. cordata’s </em>resistance to herbicides. This study consisted of two rounds of tests to examine the resistance of <em>H. cordata</em> plants to three commonly used herbicides: SpeedZone, Weed-B-Gon, and Roundup. Two concentrations of each herbicide were used during each trial in the study: the recommended concentration and twice the recommended concentration. Herbicide treatments were applied outside the greenhouse. Herbicides were sprayed uniformly on the plants until the herbicide was dripping off the leaves. The growth of the treated plants was then monitored in the greenhouse. The herbicides generally reduced growth of the plants temporarily. However, plant extermination was not achieved. Plant samples from all herbicidal treatments regrew from rhizomes after all herbicide treatments. Results from the study showed that <em>H. cordata </em>could not be controlled by the recommended concentrations of herbicides commercially available for horticultural uses in the U.S. Doubling the recommended herbicide concentration was also ineffective in exterminating <em>H. cordata </em>plants. This research clearly showed that <em>H. cordata</em> has the potential to become a highly invasive species with the potential to negatively affect the ecological integrity of many communities in the U.S.</p>

Increased biodiversity generally enhances terrestrial ecosystem productivity. While niche-use efficiency is thought to drive the biodiversity-productivity relationship, the mechanisms within niche-use efficiency are not well understood. A potential mechanism for niche-use efficiency is nutrient-use efficiency. To measure nutrient-use efficiency, we calculated nitrogen-resorption efficiencies (NRE) because nitrogen is an important growth limiting nutrient for forest productivity. We used a plantation implemented as a full factorial design that included two levels of competition, implemented as different planting densities (one- and two-meter planting densities), and three diversity levels (monocultures, two-, and three-species plantings) that included three hardwood tree species (northern red oak (<i>Quercus rubra</i>), black cherry (<i>Prunus serotin</i><i>a</i>), and American chestnut (<i>Castanea dentata</i>). For our nitrogen-resorption efficiency data, we found that NRE increased as diversity and planting density decreased, but the magnitude of the response varied among species. This outcome suggests that while increased diversity likely provides a release from intra-specific competition, different combinations of species will play a critical role in shaping biodiversity-productivity relationships. Forest nutrient cycling can also be influenced by herbivory. To address the effects of forest diversity on herbivory rates, we monitored rates of foliar damage along with foliar nitrogen content. To measure foliar nitrogen content, we collected spectral data from early, midseason, and late season foliar samples. To assess foliar damage, we collected and imaged leaves from two canopy positions in order to measure late season foliar area and estimate pre damaged foliar area. We found that diversity and foliar nitrogen content have a positive relationship, and diversity does influence canopy damage but the effects vary among species and density. Upon further analysis, we found that foliar nitrogen content and canopy damage are correlated. Meaning individual trees showed a release from intraspecific competition, which lead to an increase in available nutrients and higher canopy quality, showing that stands with higher canopy quality experienced higher levels of damage.<br>

<p> Kudzu (Pueraria montana) is an invasive woody vine widespread throughout the  southeastern United States, with recent studies predicting that its habitat will expand northward.  New occurrences and recent studies using climatic parameters suggest that the Midwestern  region of the United States is at the greatest risk of kudzu invasion. As there have already been  25 reports of kudzu within the Great Lakes basin, and no previous landscape models exist for the  basin, I developed probability models from existing spatial data (land cover, hydrology, geology,  annual precipitation, elevation, aspect, and known kudzu locations) using generalized additive,  bioclimate envelope, and maximum entropy methods. I further expanded each model to include  the basin and a 2.25-degree buffer in order to include 193 reported kudzu sites. For each  predictive model, I determined the area under the curve (AUC) for a receiver operating  characteristic curve (ROC) comparing false positive and false negative rates. I performed field  surveys at eight known sites of kudzu presence in Michigan, Indiana, and Ohio. Each presence  site was paired with a control (known kudzu absence site). I collected environmental data  including canopy cover, volumetric soil moisture, soil pH, litter depth, midstory species diversity  and diameter at breast height (DBH), and overstory basal area. Each environmental measure was  compared between kudzu presence and control survey sites as well as between in-basin and out?of-basin survey sites using a two-way ANOVA. Maximum entropy models produced the highest  AUC in both the basin and buffer models during model development. These models showed that  urban and disturbed habitats resulted in the greatest probability of potential habitat for kudzu. I  found no statistically significant differences in environmental characteristics between kudzu  absent and presence sites or between in- and out-of-basin sites, suggesting kudzu might be  dispersal-limited rather than limited by environmental characteristics. Continuing existing  management and further monitoring of kudzu spread is likely necessary to limit further  introduction and to mitigate spread of kudzu within the Great Lakes region.  </p>

<p>This study is part of an ongoing project established in 2007 as an emerald ash borer (<em>Agrilus planipennis</em>) trapping study. The primary objective of this thesis was to assess how forests have changed following the loss of ash over a 15-year period, from 2007 to 2022. The study aimed to answer three key questions: 1) How has the loss of ash affected the regeneration and recruitment patterns of ash and other tree species? 2) Which specific species are driving forest regeneration and recruitment in the absence of ash? 3) Can the data be used to predict future changes in forest composition following the loss of ash? To achieve these objectives, I conducted analyses of 44 forests representing 19 different forest types in Indiana, Michigan, and Ohio. Forest composition was examined at the overstory, midstory and understory levels to capture the overall impact of ash loss on forest regeneration and succession. Despite the decline or total loss in overstory ash, ash regeneration continued at most sites from 2017 to 2022. However, ash regeneration was not observed at 15 sites, and competition from established shade-tolerant species, such as red maple and American elm, was identified as a primary factor hindering ash recruitment. The loss of ash did not lead to significant changes in forest types. Forest types at all sites remained stable, with only minor shifts in dominant species. Tree species that were already present in the overstory filled the space left by the lost ash, thereby maintaining the existing forest types. In terms of driving species, my findings demonstrated a rapid increase in red maple dominance across all sites, particularly in the absence of ash. Red maple exhibited vigorous growth, suggesting it plays a crucial role in shaping future forest composition following ash loss. Other species, including black cherry, American elm, and American basswood, also contributed to forest regeneration, with some sites showing a shift toward a higher abundance of these species. Although the loss of ash has led to changes in forest composition, existing species have shown resilience and adaptability in filling the niche left by the lost genus. The long-term effects of emerald ash borer infestation on forest ecosystems are complex and multifaceted. This study provides insights into the regeneration and recruitment patterns of ash and other tree species following ash loss. The data suggest that while forests have experienced loss of ash, the remaining understory and midstory individuals of this species may contribute to future overstory recruitment. Furthermore, the dominance of red maple highlights its potential as a key driver of forest composition in the wake of ash loss. </p>

<p dir="ltr">The Dorothy and Ray Garman Preserve is a 35.4 hectare tract of hydro-mesophytic forest that includes ephemeral pools and scrub-shrub wetlands with <i>Cephalanthus occidentalis</i> as the dominant species component, a previously farmed agricultural field (now planted with native trees), and areas within that field which have reverted into wetlands. Garman is located within the Cedar Creek Conservation Area of Allen County, a region of important biodiversity in northeast Indiana. To document the structure and composition of the plant communities at this property, I utilized random and systematic plot samping, as well as a meandering floristic survey. The focus of my efforts was to explore the forested portion of the property and its immediate margins. I counted 150 species, representing 53 genera and 50 families. Using the Floristic Quality Assessment (FQA) method, eleven species had coefficient of conservatism values of 8-10, ten of which were herbaceous and one arboreal species (<i>Populus heterophylla</i>). This indicates that Garman is a relatively high-quality site with some quality remnant components. The site has an FQA value of 46.4, and the mean coefficient of conservatism was 3.8. Furthermore, 95.3 percent of the total species documented were native, a relatively high mark for a fragment within a larger suburban area. Species potentially indicative of bog habitats such as <i>Sphagnum fimbriatum </i>(a non-vascular species of interest), <i>Ilex verticillata</i>, and <i>Viola nephrophylla</i>, as well as historical occurrences of other peatland communities in the area, indicate that Garman may have historically been a true bog that has since senesced into buttonbush wetland type due to anthropogenic impact. Overall, the vascular plant flora of Garman demonstrates that this site is of unique importance to the broader Cedar Creek Conservation Area, since it contains several plant species not present at other sites within this region, as well as intact natural plant communities.</p>