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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effects of climate change and other anthropogenic impacts on plant phenology and wildlife health in North America

Miller, Tara King 19 September 2023 (has links)
Plants and wildlife are being affected by climate change and human activities. We need to understand the patterns in these impacts to develop management strategies and policy solutions that will help us conserve ecosystems. Climate change is shifting the timing of key life stages in plants, but we do not fully understand the extent and implications of phenological shifts – or changes in the timing of seasonal events – for understudied stages like fruiting or for potential mismatches between plants in different canopy levels. Human activities and climate change impact and harm wildlife in many ways, from wildlife-vehicle collisions and lead poisoning to hurricanes and infectious diseases, but it has been difficult to form a comprehensive picture of these threats across many species and regions, and to discern which factors pose the greatest threat to at-risk species. Here, I collected and curated data from herbarium specimens and wildlife rehabilitation records to advance our understanding of the effects of climate change and human activities on plants and wildlife in North America. First, I found that metrics of first, peak, and last fruiting dates were strongly correlated between two historical datasets, suggesting that field observations and herbarium collections capture similar orders of fruiting times among plant species in New England. However, I found differences in the exact timing of first and last fruiting dates, indicating that researchers should match methodology when selecting historical records of phenology for present-day comparisons, especially when the exact timing is important. Next, I found that native trees, native shrubs, and non-native shrubs advanced their leaf-out or flowering times faster than native wildflowers advanced their flowering times with warming temperatures. As climate warming progresses, some native wildflower species, especially in warmer regions, are likely to be affected by phenological mismatch and lose access to early-season sunlight. Last, I found that human disturbances accounted for the largest proportion of wildlife injury and sickness in animals admitted to wildlife rehabilitation centers, and I identified the predominant reason for admittance for many species; these reasons included vehicle collisions, fishing incidents, and window or building collisions. I recommended possible interventions to help conserve wildlife, including using or changing wildlife road crossings, fishing and hunting regulations, lead and pesticide regulations, and disaster management plans. In this research, I compiled and analyzed innovative, newly-digitized data sources to provide new insights into the effects of climate change and human activities on plants and wildlife in North America. / 2024-09-18T00:00:00Z
2

The effects of soil warming on flowering phenology, reproductive strategy and attractiveness to pollinators in the herb Cerastium fontanum (Caryophyllaceae)

Johner, Julia January 2019 (has links)
Phenotypic plasticity plays an important role in organisms’ adaptability to environmental change such as global warming caused by greenhouse-gas emissions. One plastic response to increased temperatures is for organisms to shift their phenology. It is of great concern that the phenologies of interacting species, such as plants and pollinators, may be shifting at different rates, causing temporal mismatches, which for plants can lead to unsuccessful reproduction. The “reproductive assurance hypothesis” states that plants capable of self-pollination should be under high selection to employ this as their main reproductive strategy in the event of pollinator scarcity to ensure reproduction, and consequently invest less in attracting pollinators. This study examines how soil warming in the Hengill geothermal area in Iceland affects the flowering phenology, reproductive strategy and investment in attractiveness to pollinators in the self-compatible herb Cerastium fontanum (Caryophyllaceae), when grown in a common garden in Stockholm, Sweden. Previous research showed that C. fontanum from warmed soils flowered earlier in situ than plants from colder soils, and later when grown in a common environment. In this study, C. fontanum plants collected along a temperature gradient followed the same counter-gradient pattern, where plants from warmer soils flowered later than plants from colder soils. Soil temperature at site of origin positively affected flower number but had no effect on flower size, seed production from autogamous self-pollination or visitation rate. Based on my findings it does not appear that C. fontanum, despite having an earlier flowering phenology in situ, is under any selection to alter its reproductive strategy or investment in attractiveness to pollinators when grown in a common temperature, and therefore it seems unlikely that plants are experiencing a temporal mismatch with insect pollinators. However, it would be worthwhile to conduct a similar experiment in Iceland to better understand how an earlier flowering affects pollination systems.

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