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For two centuries, questions about the origin of terrestrial plants and their impacts on the Earth systemhave occupied palaeobotanists. This essay attempts to synthesise the state of research to date, and outlineareas where major questions remain. Fossil evidence for land plants first appears in rocks of MiddleOrdovician age (~ 470 Ma), but it was not until the Devonian that vascular plants became the dominantgeobiological agents on the continents. Plants began as small organisms, lacking any vascular tissues,and essentially confined to wetlands. Key developments in their reproductive biology and the evolutionof mycorrhizal symbiosis subsequently enabled early plants to exploit a broader range of environments,enhancing water uptake and absorption of nutrients. In turn, the evolution of plant roots has significantlyimpacted terrestrial landscapes. The Devonian rise of plants led to a modification of the weathering rateand a sharp increase in the rate of mudrock production. This was driven by the impacts that plants exerted on watercourses, with the creation of meandering rivers and deltas that retained fine siliciclasticmaterials. This increase in weathering rate, combined with the development of leaves and the intensification of photosynthesis also had consequences for the carbon cycle and atmosphere, reducing the levelof CO2 and increasing that of O2 in the atmosphere. The increased proportion of oxygen and creation ofcombustible material is also thought to have led to the planets first wildfires, whilst the decrease in CO2lowered global temperatures. Via a complex set of feedbacks, these modifications may even have drivena series of anoxic events in the oceans, generating one of the five major mass extinctions at the end ofthe Devonian. / Paleobotanik är studien om fossiliserade växter. Då växter ursprungligen först saknades från jordens ytahar deras utveckling och kolonisering av kontinenterna (för 450 miljoner år sedan) haft många effekter.Ursprungligen var de första landväxter små och liknande modernt gräs. Deras små rötter begränsadedem till närvaron av vattenkällor (hav, flod, träsk…). En symbios med svampen (kallad mykorrhizalsymbios) underlättade landväxtens upptag av näring samt utvecklingen av djupare rötter, vilket ocksåunderlättade deras upptag av vatten. Då landväxter nu kunde migrera till torrare landskap har antaletlandväxter ökat med tiden. Det växande antalet landväxter var viktigt för bildningen av exempelvis kol,vilket är slutprodukten av dött växtmaterial som begravts och utsatts för höga tryck och temperaturförhållanden. Den geologiska perioden Karbon (359–299 miljoner år sedan) namngavs tack vare av denenorma andelen kol som kan dateras tillbaka till denna tid. Genom fotosyntes kan växter även absorbera CO2 och frigöra syre, och på så vis förändra atmosfärenssammansättning. På grund av högre syrehalter i atmosfären blev bränder ett allt vanligare fenomen eftersom det försågs med växter och syre som bränsle, som i sin tur även förbättrade bevarandet av frönoch växtvävnader i form av träkol. Oavsett om det är växtens frigöring av syre, minskning av CO2 (som är en växthusgas) eller genombränder, har uppkomst av landväxter haft en stor inverkan på atmosfärens sammansättning, och därföräven klimatet. På grund av en hastig nedgång av temperatur och syrehalt i haven mellan 450–375 miljoner år sedan (från 40 till 25 °C), utrotades nästan 75% av allt djurliv. Upphovet av denna massutrotning, genom försämringen av vattenkvalité, och uppkomsten av syrefritt vattenmiljöer tros bero på näringsläckage av jordar orsakat av ett ökat tillstånd av alger som spreds i samband med landväxters rotutveckling.

Lean flame blowout is investigated experimentally within a high-speed combustor to analyze the temporal extinction dynamics of turbulent premixed bluff body stabilized flames. The lean blowout process is induced through fuel flow reduction and captured temporally using simultaneous high-speed particle imaging velocimetry (PIV) and CH* chemiluminescence. The evolution of the flame structure, flow field, and the resulting strain rate along the flame are analyzed throughout extinction to distinguish the physical mechanisms of blowout. Flame-vortex dynamics are found to be the main driving mechanism of flame extinction; namely, a reduction of flame-generated vorticity coupled with an increase of downstream shear layer vorticity. The vorticity dynamics are linked to hydrodynamic instabilities that vary as a function of the decreasing equivalence ratio. Frequency analysis is performed to characterize the dynamical changes of the hydrodynamic instability modes during flame extinction. Additionally, various bluff body inflow velocity regimes are investigated to further characterize the extinction instability modes. Both equivalence ratio and flow-driven instabilities are captured through a universal definition of the Strouhal number for the reacting bluff body flow. Finally, a Karlovitz number-based criterion is developed to consistently predict the onset of global extinction for different inflow velocity regimes.

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Societal Impact Statement Plants play fundamental roles in ecosystems, yet merely 10% of species have an assessment of their global extinction risk. Through the integration of national Red Lists and comprehensive global plant distribution data, we identify previously unassessed plant species in Europe that are threatened throughout their geographic range and thus at risk of global extinction. Our workflow can be replicated to facilitate the integration of disparate national monitoring efforts around the world and help accelerate global plant risk assessments. Summary • A comprehensive extinction risk assessment for plant species is a global biodiversity target. However, currently, only 10% of plant diversity is assessed in the global Red List of Threatened Species. To guide conservation and restoration actions in times of accelerated species extinction, plant risk assessments must be expedited. • Here, we examine the extinction risk of vascular plant species in Europe through the integration of two data streams: (1) national Red Lists and (2) global plant distribution data from Kew's Plants of the World Online database. For each species listed on a national Red List, we create a list of countries that form part of its range and indicate the threat status in these countries, allowing us to calculate the percentage of the range in which a given species is listed as threatened. • We find that 7% to 9% of European vascular plant diversity is threatened in its entire range, the majority of which are single-country endemics. Of these globally threatened species, 84% currently have no assessment in the global Red List. • With increasing national biodiversity monitoring commitments shaping the post- 2020 policy environment, we anticipate that integrating national Red Lists with global plant distribution data is a scalable workflow that can help accelerate global risk assessments of plants.

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This thesis is an interdisciplinary study that traces colloquial engagements with extinction in Victorian print culture (1859-1901). Extinction’s broad cultural life demonstrates the extent that scientific and cultural topics intricately entangled within Victorian print networks. Non-specialist Britons absorbed and transmitted evolutionary (particularly, Darwinian) knowledges within public discursive spaces instead of exclusively institutional settings. Class stratification did not bar non-specialists from absorbing and perpetuating cultural conversations about collapses, conservationism, and overconsumption. My project thus seeks to amend the critical discourse that assumes that Victorians passively accepted impending catastrophes or paid scant attention to extinction pressures. I recover multiple subjects formerly hidden in the vast Victorian archives: obscure non-specialists of the working and middle classes, obscurer animals cohabiting the Victorian’s everyday spaces, and the popular (and in some cases, underappreciated) literary texts demonstrating how Victorians circulated extinction discourses. Chapters One and Two explore the non-literary side of print culture, recovering widely disseminated but now largely unknown periodical artifacts (the domain of Punch, The Times, or Funny Folks). Chapter One focuses on cultural reactions to collapses of England’s domestic birds. Chapter Two traces the economized conservationism of the Brooke Brothers, popular game and meat traders. In both chapters, I determine how experienced evolutionary knowledges revealed the human-caused tenuousness of a trans-species milieu. Chapters Three and Four concentrate on scientific romances originally serialized in periodicals, including my key literary case studies, H.G. Wells’s The Time Machine (1895) and M.P. Shiel’s The Purple Cloud (1901). Musing on extinction led to a mindset that acknowledged entanglement with nonhuman others as an ethical imperative. However, some case studies demonstrate a profound ambivalence toward the human’s self-extinction, resulting in a complicated engagement with future forms that often re-privileges the human from within a radical ontology. / Thesis / Doctor of Philosophy (PhD) / This study examines how Victorians absorbed and communicated ideas about extinction, especially as informed by evolutionary theory. Throughout Victorian newspapers, journals, and literature, extinction was adopted for disparate uses. A culturally, economically, and philosophically muddied topic, extinction provoked reconsiderations of the natural world and humankind’s place within it. I begin by examining advertisements, articles, and illustrations from popular newsprint and periodical sources that communicated fears about the extinction of common animals and concerns about controlling or maintaining bird and game populations in everyday Victorian life. When I turn my attention to my literary case studies, H.G. Wells’s The Time Machine and M.P. Shiel’s The Purple Cloud, I analyze the period’s preoccupation with the human’s future forms, looking at both posthuman evolutionary outcomes and the experience of becoming-nonhuman itself. Significantly, this project recovers underappreciated Victorians and texts, filling important gaps in Victorian periodical studies and animal studies.

The late Cambrian-early Ordovician transition contains several trilobite extinctions. The first of these extinctions (the end-Marjuman) is thought to coincide with the Steptoean Positive Carbon Isotope Excursion or SPICE, a large and rapid excursion in the marine carbon isotope record. This excursion, which is expressed in sedimentary successions globally, is thought to represent a large perturbation to the carbon cycle during this time. Additionally, a limited amount of carbon isotope data from the Deadwood Formation in the Black Hills of South Dakota suggests the possibility of a small negative ẟ¹³C excursion near the extinction and preceding the SPICE. Previous high-resolution biostratigraphy has identified an expanded record of extinction event within the Nolichucky Formation of the Southern Appalachians making it an excellent candidate for the study of the precise relationship between the extinction and changes in the carbon cycle. This investigation confirms the onset of the SPICE occurs at the extinction boundary however no negative ẟ¹³C excursion occurs at the extinction boundary. Further there is no systematic relationship between local facies changes and ẟ¹³C or the extinction interval across the basin, which suggests that global environmental changes were responsible for both the ẟ¹³C record and the extinction event. / Master of Science