Forest Sciences Commons^™

Factors Influencing Tree Vigor And Structural Failure Along Powerline Corridors In Northern California: A Multi-Species Analysis, David Justin Dorval

Cal Poly Humboldt theses and projects

Tree failures (e.g., stem breakage, uprooting, or branch drop) can pose significant risks to public safety, particularly along powerline corridors for the risk of power outages and wildfire ignitions. In California, tree-related powerline failures have led to severe ecological and human costs in recent years. Despite extensive research on tree failure in urban environments and post-disturbance contexts, comparatively little empirical work has examined where powerlines intersect largely unmanaged stands. This study evaluates tree failure trends across multiple forest types in Northern California by examining how tree-level characteristics influence recent growth and failure occurrence in regionally dominant tree species. Specifically, the …

Early Successional Response To Stream Daylighting In Redwood National And State Parks, Orick, California, Rylee Rawson

Cal Poly Humboldt theses and projects

In-channel stream restoration projects can act as both disturbance and recovery mechanisms, disrupting existing conditions to reestablish the hydrologic and ecological processes that sustain stream ecosystems. These interventions initiate successional trajectories in which channel form and biological communities reorganize over time. In Redwood National and State Parks (California, USA), the Redwoods Rising initiative restores buried headwater channels by recontouring legacy logging roads and daylighting streams buried by Humboldt crossings. Using the National Park Service Klamath Network wadable stream monitoring protocol, I evaluated nine restored reaches spanning one to five years post-restoration, alongside old-growth reference reaches and available pre-treatment data. I …

Forest Management Options For The Wildland Urban Interface: Comparative Analysis Of Stand Development, Economics, And Forest Carbon Over 100 Years In Sierra Nevada Ponderosa Pine, Kassandra A. Mcdaniel

Cal Poly Humboldt theses and projects

This thesis presents a simulation study of various forest stand treatments and their long-term effects on ponderosa pine-dominated forests in the Sierra Nevada Mountain Range of the western USA. The goal was to create recommendations for forest management in the wildland urban interface (WUI) of the Tahoe National Forest and other locations with similar conditions. This study simulates current United States Forest Service (USFS) - Truckee Ranger District silvicultural treatment alternatives repeated over a 100-year period using the USFS Forest Vegetation Simulator (FVS). Proposed treatment alternatives include restoration, resilience, transition, conservation, and no management. Treatments are to be compared in …

Regeneration And Fuel Loading With Varying Overstory Retention In Redwood Stands 10 Years After Transformation To Multiaged Management, Jud Fisher

Cal Poly Humboldt theses and projects

Forest managers using retention forestry in western forests need information on regeneration dynamics and fuel development to design stands that are both productive and fire resilient. This study analyzes 10-year remeasurement data from the Redwood Multiaged Experiment in Jackson Demonstration State Forest, California, comparing regeneration and fuel responses across group selection (GS), aggregated (HA), and dispersed (LD, HD) retention treatments. Target relative density (RD) of the residual stand was zero in GS, 13% in LD, and 21% in HA and HD. Measurements included sprout growth and size of redwood and tanoak, seedling and sprout density, and surface fuel loading.

Redwood …

Ectomycorrhizal Fungi Associated With Pinus Species Of California's Northwestern Coast, Monika Audrey Richardson

Cal Poly Humboldt theses and projects

Ectomycorrhizal (ECM) fungi are vital for increasing host plant uptake of nutrients and stress tolerance within ECM forest ecosystems. The species assemblage of ECM fungi can vary locally in response to numerous biotic and abiotic environmental factors. In California’s northwestern coast the occurrence of three Pinus species, along with a disjunction between populations of Pinus muricata in Mendocino and Humboldt Counties, offer a unique opportunity to investigate the spatial and host effects on pine-associated ECM fungi. Ectomycorrhizal fungal community structure was quantified from host tree roots and sequenced sporocarps occurring at the same sites to create a project specific ITS …

Following The Water: Tree Water Sources In Coastal Northern California Forests, Kaitlyn Briggs

Cal Poly Humboldt theses and projects

Increasing drought intensity and declining summer water availability in Mediterranean- climate forests raise concerns about forest resilience and streamflow persistence. This study evaluated how tree water sources vary with hillslope position, season, species, and watershed context across three coastal northern California forests. Stable isotopes of hydrogen (δD) and oxygen (δ18O), soil moisture time series, linear mixed-effects models, and site-specific Bayesian mixing models (MixSIAR) were used to estimate proportional contributions of shallow soil, deep soil, stream-associated, and fog water to tree xylem water. Across sites, xylem water isotopic signatures overlapped primarily with soil water, indicating dominant reliance on subsurface sources, while …

Relational Approaches To Fire Resilience: Designing A Living Shaded Fuel Break With Indigenous Knowledge Systems, Natalee Nicole Lopes

Cal Poly Humboldt theses and projects

Escalating wildfire severity across California reflects not only changing climatic conditions but also the cumulative impacts of colonial land management systems that have disrupted Indigenous fire stewardship and altered forest structure and function. This project examines how wildfire mitigation infrastructure, specifically linear fuel treatments, such as fuel breaks, can be reimagined through Indigenous relational frameworks of care-based land stewardship. Grounded in Happy Camp (Athithúfvuunupma), California, within the ancestral homelands of the Karuk Tribe along the mid-Klamath River, this research is carried out in collaboration with Karuk knowledge holders, centering Indigenous knowledge systems and priorities.

Using a mixed-methods approach that integrates …

Effects Of Conifer Encroachment On Oregon White Oak Crown Structure And Nonvascular Epiphyte Communities, Courtney Jonell Copper

Cal Poly Humboldt theses and projects

Oregon white oak (Quercus garryana, QUGA) is an ecologically and culturally important broadleaf tree species native to northern California and the Pacific Northwest. Fire suppression and subsequent encroachment by Douglas-fir (Pseudotsuga menziesii, PSME) and other conifers have made QUGA woodlands among the most threatened habitat types in the region. This study examines the influence of conifer encroachment on QUGA crown structure and nonvascular epiphyte (NVE) communities using ground- and crown-based sampling techniques.

Twenty-four trees were sampled across four sites in northern California along a gradient of conifer encroachment that was quantified as PSME basal area (BA). A …

Long-Term Relationships Between Tree Growth And Climate In The Trinity Alps Wilderness, Klamath Mountains, California, Usa, Emma R. Knepp

Cal Poly Humboldt theses and projects

The Trinity Alps Wilderness is a unique setting for evaluating late-Holocene climate variability because former glaciers occupied comparatively low elevations in a region influenced by both coastal and interior climate patterns. Tree-ring chronologies were developed from four conifer species—Shasta red fir (Abies magnifica var. shastensis), western white pine (Pinus monticola), Brewer’s spruce (Picea breweriana), and mountain hemlock (Tsuga mertensiana)—sampled at high elevations (1950 - 2300 m) near Emerald and Grizzly Lakes in the Trinity Alps Wilderness in northern California. The final chronologies included 12 Shasta red fir trees, 12 western white pine …

Baker Cypress (Hesperocyparis Bakeri) In A Changing Fire Landscape: Characterizing Fire Refugia And Guiding Post-Fire Reforestation, Olivia Lorraine Moskowitz

Cal Poly Humboldt theses and projects

Increasing wildfire frequency threatens serotinous, fire-obligate species that depend on sufficient fire-free intervals to develop seed banks for reproduction. These species require fire intense enough to trigger seed release and create favorable substrate and light levels for regeneration, yet consecutive fires that reburn populations before they reach maturity can cause local population contraction or extirpation. Understanding the environmental drivers of natural regeneration and mature tree survival, as well as when and how active reforestation should supplement natural recovery, is critical for managing fire-adapted species under altered fire regimes.

This thesis uses Baker cypress (Hesperocyparis bakeri [Jeps.] Bartel), a rare …

An Assessment Of The California Logging Workforce, Kendra Jean Gerstenberg

Cal Poly Humboldt theses and projects

There is limited literature describing the capacity and capabilities of the logging workforce in California. This study examines the logging workforce in California to quantify the number of logging crews, assess demographic diversity, and evaluate capacity and capabilities. The target population was California Licensed Timber Operators (LTOs) who have the legal right to harvest timber. A survey was developed and distributed to LTOs on the CAL FIRE database. Surveys were also distributed at regional logging conferences or collected by phone. Data were analyzed using Statistical Package for the Social Sciences (SPSS) and emergent coding for follow-up interviews was conducted. There …

An Evaluation Of Fuel Model Accuracy And Multi-Scale Mitigation Strategies In The Wildland-Urban Interface Of Southern Humboldt County, Julia I. Cavalli

Cal Poly Humboldt theses and projects

Strategic placement of fuel treatments is critical for mitigating wildfire risk and reducing potential structure losses in wildland-urban interface (WUI) communities. As wildfire activity accelerates across the western United States, the need to identify high-impact fuel treatment locations grows increasingly urgent. Concurrently, housing development in the WUI is expanding, intensifying the exposure of homes and infrastructure to wildfire threats. In response, many communities are looking to mitigate the likelihood and severity of losses during wildfire events. The success of these efforts depends, in part, on robust data to support strategic placement of effective treatments that reduce fuel availability.

This study …

Can We Help Coast Redwood Adapt To Climate Change? A Provenance Study On Genetic Variation And Climate Transfer Distance, Aidan J. Murphy

Cal Poly Humboldt theses and projects

The climate is changing more rapidly than many species can adapt or migrate. Coast redwood (Sequoia sempervirens) is a unique, long-lived conifer and remains California’s most valuable and economically important timber species. The species is threatened in its natural range due to anthropogenic climate change and human activity. Redwood favors asexual reproduction which restricts its ability to migrate naturally. The consequences of asexual reproduction when faced with a rapidly changing climate may make some form of assisted migration necessary for long-lived organisms like redwood.

This study evaluates drivers of variation in redwood growth and the influence of climate …

Effects Of Experimental Structural Retention Position And Aggregation On Avian Communities In Managed Forests Of The Pacific Northwest, U.S., Aidan M. Healey

Cal Poly Humboldt theses and projects

Managed forest lands in Oregon and Washington produce wood products and host diverse bird communities, though standing dead snags are often limited. State forest practices rules governing forest harvest dictate retention of a minimum number of trees when forests are clearcut harvested. However, little research has explored how the slope position and aggregation of retention, and the supplemental inclusion of mechanically created snags, affects use of these forest units by wildlife, especially highly mobile taxa such as birds. I used an avian point count sampling approach, within a replicate-block experiment dictating unit-level slope position, aggregation, and snag retention treatments, to …

Modeling Forest Stewardship In Goukdi’N: An Assessment Of Carbon, Wildlife Habitat, And Fire Resilience In A University Forest, Benjamin Stock

Cal Poly Humboldt theses and projects

This thesis presents a forest management plan for Goukdi’n (also known as the Jacoby Creek Forest University Tract), a coast redwood–tanoak–Douglas-fir forest within the ancestral homelands of the Wiyot Tribe. This project addresses the need for a forest stewardship approach that supports ecological resilience, cultural values, and long-term forest health in a landscape shaped by industrial logging, fire exclusion, and decades of under-management. To evaluate potential management pathways, forest growth modeling was conducted using the USFS Forest Vegetation Simulator (FVS) to compare three management prescriptions focused on carbon storage, fire resilience, and structural heterogeneity and a no-action alternative. Model outputs …

Longevity Of Prescribed Fire Effectiveness In Mixed-Evergreen Forests Of The Klamath Mountains, Kaily M. Fineran

Cal Poly Humboldt theses and projects

Prescribed fire is a common management tool used across the western United States to create wildfire-resilient ecosystems and communities. The Klamath Mountains of northern California, USA has experienced numerous, large wildfires in recent years. This is due in part to a combination of highly flammable fuels, uncharacteristic weather events, and high fuel accumulations as a result of fire exclusion and forest management practices. Within the last decade, local land management organizations and the Karuk Tribe have begun re-introducing prescribed fire in low elevation, mixed evergreen forests. While the long-term effects of fuel treatments are not well-known, these efforts provided a …

Post-Fire Persistance Of Sequoia Semperviens In A Secondary Forest: Examining Drivers Of Basal Resprouting Response, Jackson T. Carrasco

Cal Poly Humboldt theses and projects

Historically frequent-fire forest ecosystems are now facing increased size, frequency, and severity of fires attributed to climate change, intensive forest management, and fire exclusion. Understanding post-fire resilience in forest ecosystems is critical amidst escalating challenges posed by recent increases in fire activity. This study examined the basal resprouting response of coast redwood (Sequoia sempervirens) in a secondary forest two years after the CZU Lightning Complex fire on the central coast of California. Robust allometric equations were developed to quantify redwood resprout biomass and leaf area, revealing strong explanatory power for biomass equations (R² > 0.85). Probability of …

Satellite-Based Phenology And Climate Anomaly Analysis In Evaluating The Response Of Puerto Rico And The U.S. Virgin Islands Tropical Forests To The 2015-2016 Drought, Sean Fleming

Cal Poly Humboldt theses and projects

The health and overall resilience of tropical forest ecosystems are closely tied to the timing of phenological events. One must consider how forests react to significant climate anomalies to forecast the possible effects of climate change. This research study utilized U.S. Forest Service Forest Inventory Analysis (FIA) plot-level data and Landsat satellite data together to determine if these datasets are valuable techniques to understand the impacts of the 2015-2016 drought on Puerto Rico and the U.S. Virgin Islands (PRVI). I did remote sensing analysis on PRVI to produce repaired and near cloud-free satellite imagery, producing dozens of phenometrics of all …

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 …

Factors Contributing To Legacy Hardwood Mortality Following Prescribed Fire, Heather D. Rickard

Cal Poly Humboldt theses and projects

Interruption of Indigenous stewardship has resulted in hardwood decline along what is now known as the middle Klamath River in northern California related to adverse effects to Tribal food sovereignty and community wellbeing. The survivors of a “legacy” of Indigenous stewardship are highly valued by the Karuk and neighboring Tribes for a myriad of culturally beneficial ecological associations and sources of traditional staple foods. Prescribed fire, following a century of fire exclusion, has resulted in unanticipated mortality of legacy tanoak (Notholithocarpus densiflorus), California black oak (Quercus kelloggii), and madrone (Arbutus menziesii), warranting further investigation. …

Knobcone Pine Response To Shading From Competing Chaparral Shrubs Following Stand-Replacing Wildfire, Sean T. Lindley

Cal Poly Humboldt theses and projects

In northern California, fire regimes are shifting towards more frequent and larger severe wildfire. There is growing concern that this shift poses a threat to biodiversity in the form of cover type change at the landscape scale, resulting in the extirpation of some species in favor of +AD617:AD649well-adapted ones. In northern California, mature serotinous conifers, such as knobcone pine (Pinus attenuata), and resprouting shrub species easily regenerate in severe patches of any size. There is no general consensus regarding the effects of shrub competition on conifer recruitment; conifer response varies with shade tolerance and other abiotic factors. Knobcone …

Carnivore And Ungulate Occurrence In A Fire-Prone Region, Sara J. Moriarty-Graves

Cal Poly Humboldt theses and projects

Increasing fire size and severity in the western United States causes changes to ecosystems, species’ habitat use, and interspecific interactions. Wide-ranging carnivore and ungulate mammalian species and their interactions may be influenced by an increase in fire activity in northern California. Depending on the fire characteristics, ungulates may benefit from burned habitat due to an increase in forage availability, while carnivore species may be differentially impacted, but ultimately driven by bottom-up processes from a shift in prey availability. I used a three-step approach to estimate the single-species occupancy of four large mammal species: mountain lion (Puma concolor), coyote …

Establishing A Market Capacity And Economic Baseline For Forest Biomass Utilization In The Southern Cascade And Northern Sierra Nevada Mountain Range, California, Clarke Stevenson

Cal Poly Humboldt theses and projects

Attempts to address wildfire risk and forest resilience have increased substantially over the last 20 years with specific interest in removing excess vegetation from stands, commonly referred to as “forest biomass”. However, the market capacity for and the economics of biomass utilization have been a limiting factor to achieving statewide goals for forest health and fire resilience. This thesis looks at the Southern Cascade and Northern Sierra Nevada biomass supply chain to benchmark current market capacity for biomass utilization through mapping and harvest record analysis. It also calculates the net revenue of biomass mobilization based on costs developed from a …

Investigating Tribal Co-Management Of Caifornia’S Public Lands, Zachary Joseph Erickson

Cal Poly Humboldt theses and projects

Collaborative management with Indigenous groups is becoming increasingly common as many Indigenous communities continue to assert their inherent rights to self-determination. Due to the removal from and dispossession of lands, tribes often rely on access to public properties for various uses including ceremonies and gathering of culturally important plants. Some believe that the absence of indigenous involvement has also led to a decline in both the quality and abundance of culturally important resources, as well as limited the intergenerational transfer of traditional ecological knowledge, or TEK. There is increasing momentum toward re-engaging tribes as stewards of their ancestral lands through …

Physical Characteristics And Fine Roots Within Duff Mounds Of Old-Growth Sugar And Jeffrey Pine In A Fire-Excluded Sierran Mixed-Conifer Forest, Jules Bartley

Cal Poly Humboldt theses and projects

Fire exclusion has profoundly impacted frequent fire forests in western North America, disrupting fundamental ecological processes while leaving large, old pine trees vulnerable to drought, insects and disease, and fire. Forest managers want to increase the pace and scale of prescribed burning, yet heavy accumulations of organic material (duff mounds) at the bases of large pines can smolder for prolonged periods, damaging the cambium or consuming fine roots occupying the O horizon and/or upper mineral soil horizons. Increased duff mound depth is associated with greater mortality risk during prescribed fire, yet the biotic and abiotic drivers of duff mound accumulation …

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 …

Assessing Soil Disturbance From Tethered Logging On Steep Slopes In Northern California, Karolyn Marie Fagundes

Cal Poly Humboldt theses and projects

The implementation of tethered harvesting allows for the expansion of mechanized logging onto steeper slopes. Recent updates to the California Forest Practice Rules have explicitly removed the slope limitation for logging equipment, provided it’s tethered. California is now witnessing the reintroduction of ground-based logging equipment on steep slopes. Previously, operating equipment on steep slopes was considered detrimental due to the potential for soil disturbance. However, tethered equipment interacts with the soil in a new way due to the use of a winch. Relatively few studies have attempted to quantify soil disturbance with this new practice. The goal of this study …

Investigating Seed Maturation And Mortality: A Mechanism For Post-Fire Regeneration In Non-Serotinous Conifers, Madeleine A. Lopez

Cal Poly Humboldt theses and projects

Climate warming and associated dry conditions are contributing to increased fire frequency, severity, and size, for many regions in western North America. These changes in fire activity have prompted concern over the long-term persistence of some conifer species, specifically those not adapted to withstand high-severity fire. However, regeneration of non-serotinous conifer species is possible if the timing of fire occurs following seed maturation, and within a heat range that seeds can withstand, in a regenerative mechanism termed “facultative serotiny.” To address this mechanism, I determined the timing of conifer seed maturation using viability testing for four California conifer species: ponderosa …

Drought, Tree Mortality, And Regeneration In Northen California, Sophia Lb Lemmo

Cal Poly Humboldt theses and projects

The 2012-2016 California drought was the most severe in the state’s recorded history, contributing to the death of millions of trees. While the effects of this drought on forests are relatively well studied in the central and southern Sierra Nevada, less is known about its effects on the heavily timbered and diverse forests of northern California. Through sampling 54 0.25 ha plots in northern California, this study compared tree mortality and regeneration patterns before, during, and after California’s most recent record-setting drought. This study evaluated 1) the influence of habitat and competitive covariates on mortality and regeneration trends using ridge …

Drought Responses Across Diverse Conifer Species, Habitats, And Competitive Gradients In Northern California, Gabriel J. Roletti

Cal Poly Humboldt theses and projects

Frequent and intense drought events are rapidly altering stand dynamics in western North American forests. Climate, competition, and site characteristics can affect the growth responses of individual trees to drought stress. The ecological and geographical diversity of northern California provides a unique opportunity to measure these responses across species, habitat types, and levels of competitive pressure. This study used dendrochronological techniques and linear mixed-effects models to assess growth responses to drought in four montane and two coastal conifer species across 54 study sites (nine sites per species and 540 trees total) in northern California. Growth was evaluated from 2002-2018 and …