Recent and anticipated global change has focused concern on the role of forests in ecosystem functioning and carbon sequestration. Of key importance is identifying relevant factors that drive carbon and nutrient dynamics and the consequences of changes in these processes. Systems undergoing invasion by invasive woody species are particularly prone to changes. This study examined the branch and crown biomass and decay dynamics for the invasive Chinese tallow tree in Mississippi, USA as well as the influences of stand and site conditions on biomass modeling and arthropod contributions to fine woody debris decay. Coupling biomass and decay models presents a method for modeling carbon sequestration and nutrient turnover rates at the stand level. These predictions will aid our understanding of the consequences of ecosystem change, especially those driven by invasive species.

Chinese privet (Ligustrum sinense) is an invasive plant species in the United States (U.S.). This study utilized the most effective control measures found in the literature, and used financial analysis to identify the most cost effective management regimes to eradicate this species under different conditions. Management regimes were assessed using simulated scenarios created using six components, based on real parameters from the southern U.S.: infestation level, field coverage, stand density, herbicide application method, herbicide, and mechanical removal of privet. Financial impact on land expectation values (LEV) was analyzed and discussed for each simulated area conditions. Results suggest that the most cost effective management regime controlling privet varies according to these components. Privet control is economically feasible, and a positive LEV can be achieved for every area conditions. Finally, this study can serve as a guide to develop policies and incentives for invasive species control programs.

Recreational firewood collected from campers in Mississippi State Parks was investigated for factors associated with insect presence and their diversity. Insects were found in 20% of firewood and evidence of past feeding was found in 64.8%. Representatives of 35 families of insects were reared from collected firewood. These included representatives of Buprestidae, Cerambycidae, Curculionidae, Formicidae, and Rhinotermitidae. The effects of firewood age, moisture content, and source were also examined as effects on insect presence in firewood. At the same time, a survey of campers’ beliefs and attitudes about non-native woodborers was conducted. Exposure to public awareness campaigns had the strongest association on reported sources of firewood and support for regulations on firewood movement. However, no association was found between attitudes and beliefs and camper firewood habits. No association was found between camper responses to survey questions and biological factors from firewood collected from them.

In 1888, the lake Hjälmaren underwent a process of lowering by almost 2 metres with the aim of gaining 19.000 ha of arable land. This process had a wide array of ecological implications, and in connection with other historical events, it also resulted in spatial and social cracks dividing the city of Örebro laying on Hjälmaren’s west shore. The changing physical aspects of the city have led us to question the relationship of humans and species to the lake, but also to the stream Svartån connecting the lake and the city. Örebro used to be a city of collective practices and shared resources. It had much stronger ties to water as it used to be more present and made the city more centre-oriented. This does not apply today - the city’s development is oriented outwards, its centre lacks in quality non-consumerist spaces and capitalism and individualism are at the forefront. With this explorative design thesis, we propose solutions to activate Hjälmaren and Svartån. Our project widens the offer of common spaces and resources in Örebro, giving its residents more opportunities to interact in the everyday presence of water – just like in the past, but with a more modern spin.

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Natural dispersal mechanisms and biogeographical barriers have shaped species' native distributional ranges over millions of years. However, over the last few centuries, humans have dispersed species beyond their natural ranges. Those species that undergo explosive population growth and rapid expansion in the introduced region are considered as invasive because they have the potential to cause negative effects on desirable species and/or ecosystem services. In chapter II, I identified what ecosystem characteristics are more closely associated with successful establishment of exotic and native species, to have a better idea of where to concentrate our efforts and resources to prevent invasion events while preserving native species. I found that native and exotic species were differently affected by ecosystem properties. Exotic species were favored by human activities and low native species abundance and diversity. However, in Chapter III, I found that species functional traits, such as growth form and phenology, are more important to explain their response to ecosystem characteristics than native status under certain circumstances. The abundance and reproductive capacity of the evaluated plants were reduced when disturbances occurred during their respective active growing periods. This finding suggests that we need to have into account species-specific responses to ecosystem characteristics when managing biological invasions. Chapter IV examined phenotypic differentiation of native, expansive, and introduced populations of Baccharis halimifolia L. occurring in different regions of the world. The results suggest that there are significant phenotypic differences in germination and early growth among native, expansive, and introduced populations, which could have contributed to the success of B. halimifolia in the introduced and expansive ranges. Finally, in Chapter V, I used the information that I learned in the past projects to predict the spread of 45 exotic plants across southeastern United States and evaluated what landscape factors make an area more susceptible to be invaded. I found that the influence of landscape composition and configuration on invasion risk is species-specific. This result suggests that not only we have to consider species functional traits when managing biological invasions, as we saw earlier in the experiment with disturbance timing, but also species habitat preferences.

Mosquitoes are a significant global public health threat, claiming hundreds of thousands of lives annually due to the various pathogens they transmit, which result in diseases including dengue, malaria, and Zika. While various strategies and practices are in place to manage mosquito populations, these methods may be challenged due to a rise in insecticide resistance in some mosquito species, the increasing impacts of global climate change, and invasive species populations. This work presents four distinct projects investigating Culex spp., Ae. albopictus, and Ae. j. japonicus mosquitoes using a range of methods and techniques to bring novel insight into the biology and ecology of these mosquitoes. The first project focuses on the thermal preference and response to thermal cues of three Culex species which vary in host preference and climate of origin. The second project explores the effects of different rearing temperatures and regions of origin on the thermal performance, life-history traits, and nutrient reserves of Ae. albopictus mosquitoes. The third project shifts to the optimization of a species-specific attractive toxic sugar bait (ATSB) trap targeted toward invasive Ae. j. japonicus mosquitoes. The fourth chapter, which is field oriented, focuses on determining the role of elevation on mosquito biodiversity and pathogen prevalence. Collectively, these works explore how mosquitoes interact with their environment to support research-informed decisions in future mosquito control practices. / Master of Science in Life Sciences / Mosquitoes are the deadliest animals in the world, causing over half a million deaths every year. Mosquitoes are disease vectors, meaning they are able to transmit pathogens (such as viruses or bacteria) that cause diseases including malaria and Zika, which can lead to severe illness and death because of the lack of treatment and vaccines, or even access to these in some instances. While there are current strategies in place to reduce mosquito population numbers in areas with high levels of pathogen transmission, we are seeing increasing difficulties in managing and predicting these mosquito populations. Certain mosquito species have become resistant to chemical treatments and the growing impacts of climate change (such as more extreme weather and temperatures) are two factors that are expected to greatly influence mosquito biology and global distribution in the near future, which may expose new human populations to mosquito-borne illnesses. These issues have inspired the following projects to gain more information on how mosquitoes interact with their environment and their hosts, to highlight traits or behaviors that could inform novel mosquito management strategies in the future.

Invasive alien species are a growing threat globally that causes negative effects on the environment, economy and human health. Part of the solution is to involve the public to help reduce the spread. The aim of this study was to examine the public knowledge and to analyze people's reactions when they receive information about invasive species. Further I analyze the information dissemination method used by the county board of Västerbotten and examine whether there was any difference between the property owner’s responses depending on what type of invasive species they had on their property. A survey was designed to acquire information from property owners in Västerbotten county who had an information letter by the Swedish authorities in 2021 about invasive species on their property. The survey was sent to 123 property owners and the response rate was 49%. The survey didn’t show any significant difference between the property owner’s responses depending on what kind of invasive species they had. Results showed that the majority of the respondents considered the information letter helpful and a large percentage had taken action to combat the invasive species after receiving the letter. The results showed that the property owner's knowledge increased after receiving the information letter. In conclusion, the study shows that information letters are an effective method for property owners to take action and increase their knowledge of invasive species.

Invasive plants can alter pollination dynamics by disrupting pollinator visitation and pollen transfer dynamics. However, a consensus regarding the direction of their overall effects (competitive vs. facilitative) remains elusive. Here, we evaluate the role of floral traits and spatial scale (community vs. floral neighborhood) in mediating invasive Cirsium arvense effects on resident plant species at multiple stages of the pollination process. C. arvense decreased pollinator visitation rate at the community level only for species with radial floral symmetry. At the floral neighborhood scale, pollinator visitation rate to all resident species was lower in the presence of C. arvense regardless of symmetry. C. arvense altered patterns of conspecific pollen receipt at the floral neighborhood scale, but the direction of the effect varied by plant species. We argue that these scale-dependent effects may be mediated by differences in foraging range and behavior of the main pollinators in the community. C. arvense, however, did not affect the overall reproductive success of resident species at either scale, suggesting that plants at our study sites may not be pollen limited. We further show evidence suggesting that C. arvense may alter the structure of community-level plant–plant interactions via heterospecific pollen transfer by subverting the roles of resident pollen donors within the pollen transfer network. Overall, our results suggest that generalized species (with radial flowers) may be more susceptible to invasive species’ effects than specialized ones (bilateral flowers) and highlight the need to consider scale-dependent effects in order to develop a more predictive understanding of invasive species effects in nature.

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