Life Sciences Commons^™

Evolutionary Origins Of Secondary Growth - The Periderm Perspective: Integrating Evidence From Fossils And Living Plants, Madison A.K. Lalica

Cal Poly Humboldt theses and projects

Periderm is a structural feature with roles in protection of inner plant tissues and wound healing. Knowledge of periderm occurrences in the fossil record and living lineages outside the seed plants is limited and its evolutionary origins remain poorly explored. Here, I review the known taxonomic distribution of canonical periderm (typical ontogenetic stage) and wound periderm (self-repair mechanism). To this sparse body of data I add new observations and experiments on living plant lineages and new occurrences from the fossil record. One of the latter, documented in the new early euphyllophyte species Nebuloxyla mikmaqiana, joins the oldest known periderm …

Building Detailed And Accurate Whole-Plant Concepts: A Morphometrics-Informed Reconstruction Of A Zosterophyll From The Lower Devonian Of Wyoming, Samar R. El-Abdallah

Cal Poly Humboldt theses and projects

The fragmentary state of plant fossils and the modular organization of plants make whole-plant reconstructions of fossil species desirable and feasible. Such reconstructions are key for integrating fossil species in systematic studies. The ca. 410 Ma Beartooth Butte Formation of Wyoming (USA) hosts the only rich Early Devonian plant assemblages in western North America, which fills a major gap in the phytogeography of this interval. I construct a whole-plant concept for a new zosterophyll from the Beartooth Butte Formation based on a detailed morphometric study. More than 600 fragments of the new zosterophyll were observed and 200 of those were …

Characterizing New Plant Fossils With Woody Growth From The Battery Point Formation Of Quebec (Canada), Emma T. Casselman

Cal Poly Humboldt theses and projects

The oldest woody growth has been recognized in several Early Devonian (ca. 410-395 Ma) euphyllophytes. Their taxonomic diversity is difficult to evaluate due to a lack of quantitative methods for comparing plants based on secondary xylem anatomy. In turn, this hinders understanding of their implications for the evolution of plant development. To develop metrics that quantify secondary xylem anatomy and allow for conclusive comparisons, I investigated extant taxa and Early Devonian fossil woody taxa. I developed multiple metrics for quantifying tracheid size as a function of position in the secondary xylem and tested them on a dataset of extant gymnosperms. …

Assessing Relocation Habitats And Assisted Migration Of The Lassics Lupine, An Endangered California Serpentine-Endemic, Caitlyn M. Allchin

Cal Poly Humboldt theses and projects

The Lassics lupine, Lupinus constancei, is a serpentine species endemic to the Lassics Mountains of northern California, listed as critically imperiled and federally endangered. Increased encroachment from reduced fire intervals has led to elevated herbivory from small mammals. While deployment of exclosure cages has decreased negative impacts, diminishing snowpack from shifting climate continues to threaten the Lassics lupine. To locate possible refugia, I evaluated alternative sites for assisted migration. I built a habitat suitability model (HSM) using MaxEnt software and WorldClim variables to predict optimal habitat. I then evaluated aerial imagery, topography, and geology to identify areas for microhabitat …

Environmental Implications Of Modern Food Production: An Analysis For The Conscious Consumer, Jessica T. Coming

Cal Poly Humboldt theses and projects

This project explores the pathways by which agriculture affects the environment and determines which foods have the greatest climate, water, and land impacts. Agricultural effects on the environment are extensive, from loss of habitat and declines in regional biodiversity to disruption of global nutrient cycles and climate change. Global food production accounts for 26-34% of annual anthropogenic greenhouse gas emissions, makes up 38-46% of habitable land, and is responsible for 70% of freshwater extraction. The effect of agriculture on the environment is most significantly dictated by what type of food is being produced. Animal-based food products consistently have the highest …

Changes And Relationships Of Soil Aluminum, Organic Matter, And Hydrogen Ion Concentration With Rye Cover Crop, Arron Wilder

Cal Poly Humboldt theses and projects

Soil acidity is a common agricultural problem worldwide, as approximately 50% of all potentially arable soils are affected by pH limitations. At soil pH 3+) is considered to be the chemical form of aluminum in acid soil that hinders plant growth the most. Potentially, soil organic matter (SOM) can ameliorate the toxic effects of Al³⁺ on plants and microbes by binding with Al³⁺, thus preventing Al³⁺ (and other species of aluminum) from interacting in the rhizosphere. Increasing SOM also increases soil health indicators (i.e., microbial activity, soil water holding capacity, aggregate stability, porosity, etc.) while the …

A Cladoxylopsid With Complex Vascular Architecture From The Early Devonian Battery Point Formation (Québec, Canada), Jessica Chu

Cal Poly Humboldt theses and projects

Cladoxylopsids are seed-free plants that formed the world’s earliest forests and gave rise to horsetails (sphenopsids), but their evolutionary origins are poorly understood. Here, I describe a new Early Devonian cladoxylopsid from the Emsian (400-395 Ma) Battery Point Formation (Québec, Canada). The structural features of this plant indicate taxonomic affinity to cladoxylalean cladoxylopsids and its phylogenetic position supports placement in genus Cladoxylon (the proposed name, Cladoxylon kespekianum sp. nov., to be formalized by peer-reviewed publication). Specimens of this plant are permineralized in calcium carbonate and were studied using the acetate peel technique with light and electron microscopy. Cladoxylon kespekianum is …

Assessing The Recovery Of Forest Understory Vegetation After Clearcut Logging Across A 445-Year Chronosequence, Molly Smith Metok

Cal Poly Humboldt theses and projects

The conversion of natural forested lands to managed forests has reduced the amount of older, structurally diverse forests worldwide. In conifer forests of the Pacific Northwest (USA) – where the understory plant communities comprise only 1% of forest biomass but represent 90% of the plant species richness – the long-term impacts of timber harvesting are not fully understood. I used a chronosequence of forests in southwestern Oregon that ranged from 25 to 445 years of age to compare changes in plant communities in logged (i.e., managed) stands with that of stands in late succession and old growth conditions. The chronosequence …

Macrolichen Inventory Of The Horse Mountain Botanical Area, Six Rivers National Forest, California, Usa, Sarah Norvell Conway

Cal Poly Humboldt theses and projects

Macrolichen diversity and community composition was determined for an area of high botanical interest in the Coast Ranges of Northern California – the Horse Mountain Botanical Area (HMBA) in Six Rivers National Forest. The Coast Ranges have been suggested to have high epiphytic macrolichen diversity, yet detailed site-specific macrolichen surveys are lacking for the area. Here we present comprehensive data on macrolichens of the HMBA integrated with environmental metadata at the landscape level. Twenty 0.4 ha sampling plots were positioned across the varying habitats of the HMBA and macrolichens were intensively sampled from all substrata. Out of 888 total collections, …

Degradation And Nitrogen Cycling In The Context Of Biodiversity-Ecosystem Function Relationships In The Inquiline Bacterial Community Of Darlingtonia Californica, Megan Teigen

Cal Poly Humboldt theses and projects

Biodiversity-ecosystem function (BEF) research aims to explain how species and their environments interact with each other. Microbial communities engage in vital biogeochemical pathways in a variety of natural ecosystems, and yet there are large knowledge gaps about the specific metabolic pathways in which they are involved. Degradation specifically contributes to nitrogen cycling globally through the breakdown of large organic nitrogen compounds into small inorganic nitrogen that is necessary for the survival of many other organisms. In this study, I focused on the degradative function of the inquiline microbial communities found within the carnivorous pitcher plant, Darlingtonia californica. Darlingtonia grows in …

Forecasting The Outcomes Of Managing A Rare Endemic Plant At Its Elevational Limit Under Climate Change Scenarios, Ethan Reibsome

Cal Poly Humboldt theses and projects

Lupinus constancei (Lassics lupine) is an exceptionally rare forb with a population that in 2020 consisted of 1,300 individuals located on two adjacent mountaintops in northwestern California, USA. Past work has demonstrated the species is threatened by high levels of seed predation by small mammals, which is likely the result of fire exclusion and the subsequent vegetation encroachment that both increases small mammal habitat and directly reduces suitable habitat for the species. Because of this, active management through caging of reproductive individuals to reduce seed consumption has been conducted every year since 2003. In addition, growing season temperatures have increased …

Conifer Encroachment And Removal In A Northern California Oak Woodland: Influences On Ecosystem Physiology And Biodiversity, Gabriel S. Goff

Cal Poly Humboldt theses and projects

Oregon white oak (Quercus garryana) woodlands across their range are becoming increasingly threatened by encroaching Douglas-fir encroachment (Pseudotsuga menziesii) as a result of fire exclusion. Using water potential (Ψ), stomatal conductance (g_s), xylem water stable isotopes (dD), and three metrics of biodiversity, this study investigates the effects of conifer encroachment and removal at the ecosystem-scale. The study was set in an Oregon white oak woodland in northern California and compared three levels of encroachment before and after conifer removal. Findings indicate that heavily encroached stands have the least amount of water stress and gas …

Exploring The Origins Of Secondary Growth – Two Lower Devonian (Emsian) Euphyllophytes From Gaspé, Canada, And Their Implications For The Evolution Of Secondary Growth, Kelly C. Pfeiler

Cal Poly Humboldt theses and projects

Secondary growth from a vascular cambium has a deep fossil record among euphyllophytes, with the earliest occurrence dated to 407 Ma. To date, Armoricaphyton and Franhueberia represent the only instances of secondary growth formally documented in the Early Devonian. Secondary growth diversified rapidly and was present in all major euphyllophyte lineages by the Middle Devonian. Here, I describe two new Early Devonian euphyllophytes exhibiting secondary growth, from the Emsian (c. 400-395 Ma) Battery Point Formation (Québec, Canada): Gmujij tetraxylopteroides gen. et sp. nov. and Perplexa praestigians gen et sp. nov. Both these plants possess mesarch actinosteles with Psilophyton-type …

The Effects Of Woody Vegetation Encroachment And Removal Within A Coastal Fen, Joseph Saler

Cal Poly Humboldt theses and projects

Early successional wetland habitat is being lost in temperate regions worldwide as a result of changes in disturbance regimes that allow for the establishment and dominance of woody species. In particular, this phenomenon is pronounced in fens, which harbor high numbers of rare herbaceous species that require early successional habitat. I investigated the relationship between woody vegetation encroachment and herbaceous species diversity within a Northern California coastal fen that has been undergoing encroachment by woody vegetation for ca. 80 years by recording species richness and cover data from 338 permanent plots throughout the fen. I also investigated the effect of …

Ectomycorrhizal Fungal Community Assembly On Seedlings Of A Neotropical Monodominant Tree, Carolyn Delevich

Cal Poly Humboldt theses and projects

Formation of ectomycorrhizae may facilitate early seedling survival of ectomycorrhizal tree species due to enhanced nutrient acquisition. This could be especially important in heavily shaded understories of tropical monodominant forests where host plant photosynthetic capacity is limited. Little information is available on ectomycorrhizal (ECM) fungal colonization or community development of monodominant seedling cohorts, which have high survival rates. Following a 2016 mast seeding event, we sequentially measured percent colonization and species composition of ECM fungi on live and recently dead seedlings of the tropical monodominant tree Dicymbe corymbosa. We also compared seedling ECM fungi to those of nearby adult …

Evaluation Of Restoration Techniques And Management Practices Of Tule Pertaining To Eco-Cultural Use, Irene A. Vasquez

Cal Poly Humboldt theses and projects

Tule (Schoenoplectus sp.) is a native plant commonly used by California tribes and Indigenous people throughout the world (Macía & Balslev 2000). Ecological, social and regulatory threats to its use in contemporary Indigenous culture highlight major issues concerning natural resource management. My ancestral homeland, what is now Yosemite National Park, stands as a figurehead in the intersection of land management and Indigenous peoples. An important element of Traditional Ecological Management (TEM) for quality basketry materials is prescribed fire, an element western science is increasingly acknowledging for creating a more biodiverse and heterogeneous landscape. This research was conducted in Mariposa and …

Seaweed Community Structure Along Environmental Gradients In An Ocean-Dominated Estuary, Saskia A. Raether

Cal Poly Humboldt theses and projects

Macrophyte community structure in estuaries that have been modified by the addition of hard substrata are poorly documented, especially in relation to the physical and environmental gradients that shape them. Therefore, this study describes the summer macrophyte flora that occurs on hard and soft substrata throughout Humboldt Bay, CA and tests how the macrophyte communities correlate to measures of horizontal and vertical environmental gradients. The percent cover of macroalgae, vascular plants, cyanobacteria, lichens, diatom film, sessile invertebrates, and substratum types were quantified during the summers of 2017 and 2018 at eleven intertidal locations in the bay and outer coast. Horizontal …

A New Anatomically-Preserved Plant From The Lower Devonian Of Quebec (Canada): Implications For Euphyllophyte Phylogeny And Early Evolution Of Structural Complexity, Selin Toledo

Cal Poly Humboldt theses and projects

An abrupt transition in the fossil record between Early Devonian plants with simple structure and structurally-complex later Devonian plants, has frustrated efforts to understand patterns of phylogeny across the Early/Middle Devonian boundary and the evolution of complex forms. Both these aspects have important implications for lignophyte and seed plant evolution. In the first chapter, I evaluate phylogenetic relationships between the earliest seed plants, Aneurophytales, and Stenokoleales, using comprehensive taxon sampling (28 species, including all relevant permineralized species) and a set of 40 discrete and nine continuous morpho-anatomical characters. Analysis of this dataset supports the three traditional taxonomic groups (seed plants, …

Jeweled Spider Flies (Eulonchus Tristis) Are Important Pollinators Of Iris Bracteata, A Rare Siskiyou Mountain Endemic, Jean-Paul E. Ponte

Cal Poly Humboldt theses and projects

Little is known about the pollination biology of the Pacific Coast Irises (Iris: series Californicae, hereafter PCI), especially who visits and pollinates their flowers. In general, Iris flowers are considered bee-pollinated, however, flies in the genus Eulonchus (Acroceridae) are known to visit some PCI members. Therefore, I assessed the relative importance of Eulonchus and other insect visitors to the pollination of a rare PCI species native to the Siskiyou Mountains, I. bracteata.

Methods. I quantified pollinator importance for all flower visitors at sites in northern California and southern Oregon as the product of average visit rate and …

Assessing Spatio-Temporal Patterns Of Forest Decline Across A Diverse Landscape In The Klamath Mountains Using A 28-Year Landsat Time-Series Analysis, Drew S. Bost

Cal Poly Humboldt theses and projects

Rates of tree mortality in California and the Pacific Northwest have greatly increased in recent years, driven largely by pest and pathogen outbreaks as well as the effects of hotter, warmer droughts. While there have been a multitude of regional-scale assessments of mortality and forest decline, landscape-level studies are necessary to better identify forests that are most vulnerable to decline and to anticipate future changes. This need is particularly notable in the remote and little-studied mountains of northwest California, which are renowned for their diverse, heterogeneous vegetation types. A recent observation of elevated levels of Shasta red fir (Abies …

Modeling The Spread Of Sudden Oak Death Across A Heterogeneous Landscape In Redwood National Park Using A Spatially-Explicit Epidemiological Model, Laura A. Morgan

Cal Poly Humboldt theses and projects

The pathogen Phytophthora ramorum, the causal agent of Sudden Oak Death (SOD), is responsible for the deaths of millions of oak (Quercus spp.) and tanoak (Notholithocarpus densiflorus) trees in California and Oregon (USA). A recent infection in Redwood National Park (RNP) in California (USA) provided an opportunity to adapt an existing SOD model to assess the efficacy of current and proposed management strategies. A common method of SOD treatment includes killing both infected and uninfected hosts in the area of infection, as well as the area surrounding the infection to create buffers to account for undetected …

Early Seral Mixed-Conifer Forest Structure And Composition Following A Wildfire Reburn In The Sierra Nevada, Erin Alvey

Cal Poly Humboldt theses and projects

Before the era of modern fire suppression, California’s northern Sierra Nevada mixed-conifer and yellow pine forests were self-regulating; recurring short-interval, low-mixed severity wildfires maintained forest structure and composition, which in turn exerted bottom-up controls on subsequent wildfires. As a result of fire suppression, and coupled with the effects of climate warming and other anthropogenic disturbances, the fundamental structure of mixed-conifer and yellow pine forests has shifted. Wildfires may now be increasing in size, severity, and frequency across western North America. However, little is known about the post-fire impacts of repeat wildfire on a forest after a long era of suppression. …