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Scholarly Works (3 results)

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  • Peer Reviewed
UC Santa Cruz Electronic Theses and Dissertations (2023)

Phenology, the timing of recurring biological events, is nature’s calendar. Changes in phenology are among the most sensitive biological responses to global changes. Anthropogenic climate change has driven widespread phenological shifts, such as the advancement of spring events; human activities also alter phenology more directly in croplands, pastures, and urban landscapes. Phenological change in turn affects human society such as through food security and pollen allergy.This dissertation offers a multiperspective examination of phenology at the intersection of ecology, climate, and human society. Firstly, I develop a theoretical framework and a novel approach to quantify phenological mismatch, in the broader context of ecological synchrony under climate change. Using this framework and approach, I systematically assess phenological mismatch and investigate the influence of anthropogenic land use. Recognizing the complex responses in phenology and the need for extensive data, I explore an innovative method for inferring pollen phenology, offering potential applications in public health. Lastly, I focus on understanding the human perceptions of pollen phenology, which in turn provides insights for natural science research and climate change communication. Chapter 1 presents a generalizable theoretical framework for phenological mismatch under climate change. A prediction-based approach can be used to quantify multiple types of phenological mismatch across landscapes, demonstrated by empirical case studies and simulations. Chapter 2 highlights that climate-phenology mismatch is widespread and more pronounced in human-dominated landscapes. Chapter 3 introduces a method for inferring the flowering and pollen phenology of wind-pollinated plants using high-resolution satellite imagery, even at locations without prior observations. Chapter 4 reveals that social media users accurately detect variations in pollen phenology but are ideologically biased in attribution to climate change, underscoring the potential of social sensing and the challenges in climate change communication. In summary, this dissertation has contributed to our understanding of various forms of socio-ecological coupling related to phenology. Knowledge of such interactions has valuable implications for global change ecology, sustainable management of vegetation, public health, and climate change mitigation. In the Anthropocene, the study of phenology calls for advancements in generalizable theories, the integration of models and data, and an interdisciplinary approach to future research.

    Cover page: Phenology in the Anthropocene: Interactions between ecology, climate change, and human societyCreative Commons 'BY-NC-SA' version 4.0 license
    • Article
    • Peer Reviewed
    UC Santa Cruz Previously Published Works (2024)
    Coastal upwelling supplies nutrients supporting primary production while also adding the toxic trace metal mercury (Hg) to the mixed layer of the ocean. This could be a concern for human and environmental health if it results in the enhanced bioaccumulation of monomethylmercury (MMHg). Here, we explore how upwelling influences Hg cycling in the California Current System (CCS) biome through particle scavenging and sea-air exchange. We collected suspended and sinking particle samples from a coastal upwelled water parcel and an offshore non-upwelled water parcel and observed higher total particulate Hg and sinking flux in the upwelling region compared to open ocean. To further investigate the full dynamics of Hg cycling, we modeled Hg inventories and fluxes in the upper ocean under upwelling and non-upwelling scenarios. The model simulations confirmed and quantified that upwelling enhances sinking fluxes of Hg by 41% through elevated primary production. Such an enhanced sinking flux of Hg is biogeochemically important to understand in upwelling regions, as it increases the delivery of Hg to the deep ocean where net conversion to MMHg may take place.
      Cover page: Upwelling Enhances Mercury Particle Scavenging in the California Current System.Creative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Santa Cruz Previously Published Works (2024)
      Many terrestrial plant communities, especially forests, have been shown to lag in response to rapid climate change. Grassland communities may respond more quickly to novel climates, as they consist mostly of short-lived species, which are directly exposed to macroclimate change. Here we report the rapid response of grassland communities to climate change in the California Floristic Province. We estimated 349 vascular plant species' climatic niches from 829,337 occurrence records, compiled 15 long-term community composition datasets from 12 observational studies and 3 global change experiments, and analysed community compositional shifts in the climate niche space. We show that communities experienced significant shifts towards species associated with warmer and drier locations at rates of 0.0216 ± 0.00592 °C yr-1 (mean ± s.e.) and -3.04 ± 0.742 mm yr-1, and these changes occurred at a pace similar to that of climate warming and drying. These directional shifts were consistent across observations and experiments. Our findings contrast with the lagged responses observed in communities dominated by long-lived plants and suggest greater biodiversity changes than expected in the near future.
        Cover page: Rapid shifts in grassland communities driven by climate changeCreative Commons 'BY' version 4.0 license
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