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Articles 1 - 15 of 15
Full-Text Articles in Life Sciences
Longevity Of Prescribed Fire Effectiveness In Mixed-Evergreen Forests Of The Klamath Mountains, Kaily M. Fineran
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 …
Knobcone Pine Response To Shading From Competing Chaparral Shrubs Following Stand-Replacing Wildfire, Sean T. Lindley
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 …
Assessing The Recovery Of Forest Understory Vegetation After Clearcut Logging Across A 445-Year Chronosequence, Molly Smith Metok
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 …
Investigating Seed Maturation And Mortality: A Mechanism For Post-Fire Regeneration In Non-Serotinous Conifers, Madeleine A. Lopez
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
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 …
Conifer Encroachment And Removal In A Northern California Oak Woodland: Influences On Ecosystem Physiology And Biodiversity, Gabriel S. Goff
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 (gs), 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 …
Influences On Conifer Drought Responses In Northern California, Wallis L. Robinson
Influences On Conifer Drought Responses In Northern California, Wallis L. Robinson
Cal Poly Humboldt theses and projects
California is experiencing increasingly severe and prolonged droughts, which are contributing to changes in tree stress and forest mortality. Many factors affect a tree’s drought response, including competition, climate, and site and tree characteristics. Northern California provides a suitable venue to explore the effects of these factors, as it spans a variety of site conditions and includes habitat for conifers with different adaptations and requirements. This study used annual 13C discrimination and growth metrics to assess differences in drought resistance and resilience in conifers adapted to coastal and montane ranges at both wet and dry sites, as well as …
Evaluating Immaturity Risk In Young Stands Of The Serotinous Knobcone Pine (Pinus Attenuata), Katherine Marlin
Evaluating Immaturity Risk In Young Stands Of The Serotinous Knobcone Pine (Pinus Attenuata), Katherine Marlin
Cal Poly Humboldt theses and projects
As wildfire becomes increasingly frequent, many plant populations risk local extirpation if fire recurs too soon, a problem dubbed “immaturity risk”. We studied the regeneration of a serotinous conifer species, knobcone pine (Pinus attenuata), as a function of the time between high-severity fires (6-79 years). We evaluated age, cone production, and regeneration at two burned sites in northern California, the Ranch Fire (2018) in Mendocino National Forest, and the Carr Fire (2018) in Whiskeytown National Recreation Area. We found an average of 30.5 filled seeds in closed, brown cones (42% viability of filled seeds). The bulk of the …
Alternative Water Sources In Western Conifers Via Foliar Uptake And Hydraulic Redistribution, Ariel Sol Weisgrau
Alternative Water Sources In Western Conifers Via Foliar Uptake And Hydraulic Redistribution, Ariel Sol Weisgrau
Cal Poly Humboldt theses and projects
Water is often the most limiting resource in a plant’s environment. Plants that can maximize their ability to acquire water improve their chances of success. Outside of the traditional soil-plant-atmosphere continuum, plants can alternatively acquire water via foliar uptake of water and hydraulic redistribution (HR) of deep water. This study used greenhouse-based experiments to investigate water use and physiology in four conifer species native to the western U.S.: Picea sitchensis (Bong.) Carriére (PISI), Pseudotsuga menziesii (Mirb.) Franco (PSME), Sequoia sempervirens (D. Don) Endl. (SESE), and Thuja plicata Donn ex. D. Don (THPL). First, this work investigated the capacity for foliar …
Competition, Climate, And Drought Effects On Tree Growth In An Encroached Oak Woodland In Northern California, Jill J. Beckmann
Competition, Climate, And Drought Effects On Tree Growth In An Encroached Oak Woodland In Northern California, Jill J. Beckmann
Cal Poly Humboldt theses and projects
Oregon white oak (Quercus garryana Douglas ex Hook.) is experiencing increasing competition from Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) across its range at the same time as climate models are predicting increasing climate variability, including drought. Management recommendations that consider competition dynamics between these species under a changing climate are therefore needed for oak woodlands, but we do not currently understand the combined effects of competition, climate, and drought in this ecosystem. This research examines radial tree growth and drought response in Oregon white oak and Douglas fir in an encroached oak woodland near Kneeland, California. Stem maps …
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
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 …
Ninety-Two Years Of Tree Growth And Death In A Second-Growth Coast Redwood Forest, Benjamin Iberle
Ninety-Two Years Of Tree Growth And Death In A Second-Growth Coast Redwood Forest, Benjamin Iberle
Cal Poly Humboldt theses and projects
Mature second-growth coast redwood (Sequoia sempervirens) forests are an important and uncommon resource in the redwood region. Development of second-growth redwood forests beyond rotation age (~50 years) is not well understood. Continuous long-term data are especially lacking, considering that the maximum possible age of second-growth stands is now over 150 years. Two permanent observation plots in Arcata, CA, established in 1923 by Woodbridge Metcalf and last measured in 1990, provide a unique opportunity to examine the development of coast redwood forest regenerating after logging in ~1880. We surveyed the Metcalf plots using modern methods and assembled a complete …
Early Seral Mixed-Conifer Forest Structure And Composition Following A Wildfire Reburn In The Sierra Nevada, Erin Alvey
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. …
Soil Organic Matter Distribution In A Douglas-Fir-Tanoak Forest, Humboldt County, California, Hollie A. Ernest
Soil Organic Matter Distribution In A Douglas-Fir-Tanoak Forest, Humboldt County, California, Hollie A. Ernest
Cal Poly Humboldt theses and projects
Soil carbon (C) affects the active gases in the atmosphere, nutrient cycling, and diversity of flora and fauna. Soil organic matter (SOM) is partially comprised of C, and a widely-accepted ratio of 0.58 organic carbon (OC) to organic matter (OM) is used to measure soil C on a landscape scale. However, this ratio varies according to vegetation, depth, hydrology, and may lead to miscalculations of soil C and SOM estimates. Soil C and SOM are inherently complex and it is not completely understood which environmental factors have the most influence in their formation, which occurs on a time scale of …