Browsing by Subject "Climatic changes"

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    Acclimation of Ginkgo biloba Photosynthetic Biochemistry Under Elevated Carbon Dioxide: Paleo-proxy and Conservation Consequences
    (2021) Dougherty, James Fitzmyer; Wilson, Jonathan
    Climate change poses an enormous threat to the world's ecosystems (Shukla et. al 2019). As a result, it is important to evaluate the ecological consequences of other climates in Earth's history. A valuable way to approximate paleo-CO2 concentrations is by using plant proxies, such as the Ginkgo biloba stomatal index - paleo-CO2 model (Barlcay and Wing 2016). To determine the reliability of G. biloba as a paleo-CO2 proxy, it is necessary to understand whether G. biloba photosynthetic biochemistry acclimates to elevated CO2. If the biochemistry is significantly different than it is under ambient conditions, researchers will need to reassess the model. We planted three ages of G. biloba in open-top chambers with different CO2 concentrations, measured photosynthetic data using a Li-cor 6400XT, and calculated biochemical parameters utilizing the Plantecophys package in R. These results suggest that the G. biloba paleo-CO2 proxy should not need major modification, since a change in Jmax is less disruptive than a change in Vcmax.
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    Live Fast, Die Young: Examining Hydraulic Conductivity Of The Extinct Lepidophloios And Extant Wollemia Nobilis
    (2024) Korgen, Jessica; Wilson, Jonathan
    The climate is changing at a scale never before seen by humans, and it is impossible to anticipate with certainty how these changes will affect the planet. The best way to attempt to predict how species and ecosystems will respond to our ever-evolving climate is to look to the past. Paleobotany—the study of plant fossils—can inform us about the environment in deep time and how plants previously interacted with, responded to, and influenced a changing climate. The Carboniferous period is the most recent climate parallel we have to today. Although the world looked very different 300 million years ago, with the supercontinent Pangea and so-called “primitive” plants dominating the Earth, there were several similarities to the modern climate. Carboniferous CO 2 fluctuations were within the range anticipated for the twenty-first century and, like we are seeing today, these variations in atmospheric CO 2 were associated with large decreases in sea ice volume, rising sea levels, and the cyclical restructuring of the planet's most extensive tropical forests (Montañez et al., 2016). This was also the last time the planet had complete deglaciation, a phase that we are currently on the trajectory for, so Carboniferous floral transitions during its glacial-interglacial periods could provide insight for what is to come. Several Carboniferous plants are reviewed in relation to their hydraulic efficiency and safety, providing insight to their plant function and the environments they inhabited. An important factor in the hydraulic capacities of plant fossils is the size, shape, and porosity of their pit membranes: the permeable barrier separating xylem cells which water passes through. A larger, more porous pit membrane allows water to pass through the plant quickly while a smaller pit membrane better protects the plant from the entrance of gas and possible embolism. Arborescent lycophytes (lycopsids)—which dominated the first 20 million years of the Carboniferous—are analyzed in particular. Hydraulic elements from lycopsid fossils are measured and considered in the context of the biomes they occupied. The extant Wollemi pine is also measured to contrast with the extinct lycopsid. Consequences for plants with low hydraulic safety when the Carboniferous climate changed and implications for modern plants are discussed.