Sagebrush-dominated ecosystems are being transformed by wildfire, rangeland improvement techniques, and exotic plant invasions. These disturbances have substantial effects on the composition and structure of native vegetation, but the effects on ecosystem C and N dynamics are poorly understood. To examine whether differences in dominant vegetation affect the quantity and quality of plant organic matter inputs to soil, ecosystem C and N pools and rates of plant turnover were compared among historically grazed Wyoming big sagebrush, introduced perennial crested wheatgrass, and invasive annual cheatgrass communities. Since low soil moisture during the summer may inhibit the microbial colonization of plant detrital inputs and result in C-limitations to microbial growth, soils were treated with an in situ pulse of plant detritus prior to the onset of the summer dry-season, and rates of soil C and gross N cycling were compared between treated and untreated soils. Finally, because plant detritus is the dominant form of labile C input to soil microbes over a large portion of the year, the decomposition of 13C-labeled annual grass detritus was used to determine the importance of plant detritus versus soil organic matter as microbial substrate. Results revealed large differences in ecosystem C and N pools, and in the quantity of plant C and N inputs to soil among vegetation types, but differences in soil C and N cycling rates were more subtle. Plant biomass pools were greatest for sagebrush stands, but plant C and N inputs to soil were greatest in cheatgrass communities, such that rates of plant C and N turnover appeared to be accelerated in disturbed ecosystems. Earlier release of plant biomass to soil detrital pools stimulated N availability to a greater extent than C availability relative to untreated soils, and this effect could not be predicted from the C:N stoichiometry of plant detritus. Finally, in situ decomposition of cheatgrass detritus was rapid; however, there was no clear evidence of a time-lag during summer in microbial colonization of recently released plant detritus, and microbial consumption of plant detritus did not result in N-limitations to microbial growth.

The Puerto Rican coqui frog, Eleutherodactylus coqui, was introduced to Hawaii in the late 1980s via the commercial horticulture trade. Previous research has shown that coquis can change invertebrate communities, but these studies were conducted at small scales using controlled, manipulative experiments. The objective of this research was to determine whether coqui invasions change invertebrate communities at the landscape scale across the island of Hawaii. At each invasion front, we measured environmental variability on either side of the front and removed sites that were too variable across the front to ensure that the impacts we measured were the result of the invasion. After doing this, there remained 15 sites for which we compared invertebrate communities in 30 m x 30 m plots situated on either side of coqui invasion fronts. In each plot, we collected invertebrate samples from three invertebrate communities, the leaf litter, foliage, and flying invertebrate communities. Multivariate analyses show that coqui frogs change leaf litter communities, by reducing microbivore and herbivore abundances. Coqui also change flying community composition, but have no measurable effect on foliage communities. Across sites, we found that coquis reduced the number of leaf litter invertebrates by 27%, and specifically abundant Acari by 36%. We also found that coquis increased the abundance of flying Diptera by 19% across sites. We suggest that the leaf litter community is altered through direct coqui predation and that Diptera increase because of increased frog carcasses and excrement in invaded plots. Results support previous studies conducted in more controlled settings, but add to our understanding of the invasion by demonstrating that coqui effects on invertebrate communities are measurable at the landscape scale.

Coccinella septempunctata L. (Coleoptera: Coccinellidae) has been introduced to North America in recent decades, raising concerns of adverse impacts on native lady beetles, including the congeneric C. transversoguttata richardsoni (Brown). The central focus of my dissertation is to understand the importance of reproduction, in particular, in promoting invasion of C. septempunctata and its replacement of native lady beetles in alfalfa fields of western North America. Studies were conducted to compare reproductive tactics of the invasive C. septempunctata and the native C. transversoguttata, by addressing: 1) maximum rate of reproduction of overwintered lady beetles, 2) population dynamics of the invasive and native lady beetles and their aphid prey, and seasonal reproductive patterns, over a 3-year period (2004'2006) in alfalfa fields, 3) reproductive tactics and plasticity in response to various prey availabilities, and 4) ovarian dynamics and observation of oosorption in response to prey removal. The invasive C. septempunctata gained a reproductive advantage over native, North American lady beetles from its larger body size when feeding on abundant prey. The invasive species gained additional advantage by its allocation of prey to larger numbers of relatively small eggs. In alfalfa fields, females of C. septempunctata reproduced more readily and laid more eggs than females of C. transversoguttata even at low prey density. C. septempunctata females collected from the field were also more successful in approaching their maximum body weights and reproduction, as observed under ideal conditions, than were females of native C. transversoguttata. In the laboratory, C. septempunctata females produced larger numbers of relatively small eggs, and they maintained their body weights even as they were producing eggs at low rates when aphids were provided in limited numbers. More immediate adjustment of reproductive effort with prey removal, and higher recovery of reproductive rate when prey again became available, were observed in C. septempunctata, compared with C. transcersoguttata. These reproductive abilities of C. septempucntata may contribute to its invasion success and dominance in alfalfa fields. Further studies are needed to determine why females of C. septempunctata are in better physiological condition than are females of C. transversoguttata in spring alfalfa fields.

The greenhouse frog, Eleutherodactylus planirostris, native to Cuba and the Bahamas, was recently introduced to Hawaii. Studies from other invaded habitats suggest that it may impact Hawaiian ecosystems by consuming and potentially reducing endemic invertebrates. However, there have been no studies on the greenhouse frog in Hawaii. The first component of this study was to conduct a diet analysis. We conducted a stomach content analysis of 427 frogs from 10 study sites on the island of Hawaii. At each site, we also collected invertebrates using two different sampling methods: leaf litter collection and sticky traps to characterize available resources. Greenhouse frogs consumed predominantly leaf litter invertebrates. Dominant prey items consisted of Hymenoptera: Formicidae (32.4%), Acari (19.2%), and Collembola (17.4%). Greenhouse frogs consumed more Formicidae than was measured in the environment. At one study site, we estimated there were 12,500 frogs ha-1 using mark-recapture methods and greenhouse frogs consumed 129,000 invertebrates ha-1 night-1 at this site. The second component of this study was to determine the distribution of the greenhouse frog on the island of Hawaii, with a male breeding call presence/absence survey at 446 points along the major road network. The greenhouse frog was detected at 61 sites (14%), and found mostly in lowland areas, in habitats of native shrublands and forests, nonnative forests, agricultural lands, and pastures on the southwestern and eastern sides of the island. We determined detection probabilities of the greenhouse frog and the invasive coqui frog, E. coqui. Detection probability of the greenhouse frog was low on the first two surveys and improved by the third survey. Detection probability of the coqui was higher than the greenhouse frog, but overall site occupancy estimates were similar for both species. Because the greenhouse frog appears to be as widespread as the coqui, we recommend that research be conducted to investigate its impacts ecologically to determine whether control efforts should also be aimed at this species.

The invasive species Saltcedar is affecting water and land resources throughout the western states of America. Because of great water use capabilities and other ecosystem detriments, Saltcedar has been targeted for treatment. For successful management of Saltcedar, individual landowners need to be aware of the costs and benefits of treating Saltcedar. Eleven of the most commonly reported treatment methods were evaluated for firm level economic feasibility. Evaluated on the basis of treatment cost, treatment effectiveness, Saltcedar water-use, and re-vegetation water-use, a production plan of ten years was created for each treatment method. Some treatment methods required re-treatment and were evaluated with re-treatments most commonly found in the literature. Of the treatment methods evaluated, five treatment methods were determined to be most feasible. Landowner valuation of environmental changes in the ecosystem brought on by Saltcedar is very important in the decision of which treatment method to implement. Personal valuation, over a period of ten years, will often determine which treatment methods are most cost efficient.

Invasive species exact important ecologic, economic, and cultural tolls in forests. This research focused on the intersections of invasive ecology, forest management, and a forest commodity. Invasive ecology was explored through an assessment of two potential biological control agents of hemlock woolly adelgid. The two species of silver fly (Leucopis spp.) from the Pacific Northwest were first examined for temporal resource partitioning patterns. The niches of these species were then examined spatially by developing a species distribution model. Leucopis spp. exhibited sinusoidal patterns of daily emergence when examined over a 29-day period, with peak daily abundances that were inversely related. Spatially, however, landscape-scale and climatic indicators were not significant in predicting the presence of Leucopis spp. in the Pacific Northwest. This adds important information about niche dynamics of Leucopis spp. in the Pacific Northwest, which may have logistical and operational implications for their use in the USDA Forest Service’s Hemlock Woolly Adelgid Initiative. Additionally, the potential opportunities and risks of using wood that has been impacted by invasive species and pests was explored through a literature analysis focused on three species posing a threat to northeastern US forests: emerald ash borer, hemlock woolly adelgid, and southern pine beetle. Based on this review, I concluded that although opportunities for the use of this wood are sometimes recognized, the phytosanitary risks in feedstock pre-treatment are not being directly addressed in US-related literature. These studies provide important evidence for adaptive solutions to forest pests that consider both forest health and forest economics.

Pannes are rare intradunal wetlands. Though small, they are known to exhibit extremely diverse and sensitive vegetation and are home to a number of reptile and amphibian species. In the United States, pannes are known to occur only around the Great Lakes Basin and Cape Cod. At Indiana Dunes National Lakeshore, the fifteen known pannes have an unusually large variety of plant species for such a small geographic area and provide habitat for plant species found nowhere else in Indiana. However, these sensitive ecosystems have been exposed to over a century of atmospheric pollutants from the surrounding steel and coal industries. Since 1986, the native vegetation of the area is slowly being replaced by invasive species like Phragmites australis and Typha spp. This study attempts to explain the shift in vegetation. Pannes in two other locations, at a distance from the industrial complex, were used as control sites as they were not expected to be exposed to the same levels of heavy metal concentrations. Four of the fifteen pannes at the Indiana Dunes National Lakeshore, two of the four pannes at Sleeping Bear Dunes National Lakeshore, Michigan, and two of the three pannes at Warren Dunes State Park, Michigan, were studied, resulting in a total of eight pannes. The pannnes were stratified and sampled by hydroperiod. Surface soil samples and sediments at depth, were recovered from each of the pannes considered in this study and analyzed for heavy metal, phosphorus, carbon and nitrogen content. Results show that high levels of organic matter coupled with high nutrients and high metals, in the soil, are a combination that may be considered a risk factor for future invasion of pannes by invasive species. It appears to be difficult for the native vegetation to deal with the high metals and high nutrients which are deleterious to the native vegetation and facilitate establishment of invasive vegetation which is more tolerant to the altered geochemical conditions.

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Environmental education (EE) is important for environmental awareness and stewardship. Involving youth and adults in EE ensures current and future generations will conserve natural resources. This thesis explores impacts of delivery methods on participants’ environmental attitudes and behaviors toward nature through middle school classroom- and camp-based EE instruction, focus group interviews with rural minority youth, and adult responses to aquatic conservation outreach messaging. I observed no difference in environmental attitudes between online versus in-person delivery of EE lessons for middle-schoolers. Outdoor-based learning may be more impactful for EE than experiential, classroom-based learning. Focus group outcomes suggested youth EE programs should capitalize on exploratory learning that allows for independence and safety from wildlife and community violence. Arkansas anglers who reside near aquatic invasive species (AIS) are more aware of Clean, Drain, Dry (CDD) messaging despite all anglers’ likeliness to perform pro-environmental behaviors. Consistent, targeted CDD messaging could help minimize AIS spread.