Dense hyphal mats formed by ectomycorrhizal (EcM) fungi are prominent features in Douglas-fir (Pseudotsuga menziesii) forest soils and have been estimated to cover up to 40% of the forest floor in some stands. Although previous studies have examined various aspects of EcM fungi, little is known about their associated microbial...
Forests and forest soils are some of the largest biologically active carbon reservoirs in the world. Therefore, understanding how disturbances, such as forest harvest, influence biogeochemical cycling is particularly important for managing forests sustainably. Timber harvest can have large impacts on forest soils, which may affect the long-term productivity and...
The objective of this study was to examine the variation among ammonia-oxidizing and denitrifying communities in soils of a natural Fennoscandian boreal forest and of a forest with a long history of fertilization with different levels of nitrogen (N), and to examine whether there are any changes in the microbial...
Ryegrass residue consists of three main C fractions: readily available soluble C, intermediately available cellulose and hemicellulose, and slowly available lignin. Changes in chemical composition during decomposition influence rate of degradation as well as composition of the microbial community involved. Use of ¹³C-labeled plant material coupled with analysis of phospholipid...
The cycling of root-deposited photo synthate (rhizodeposition) through the
soil microbial biomass is widely recognized as a critical component of ecosystem
functioning. Little is currently known about the flow of photosynthate through the
microbial biomass however. My research goal was to examine if and how the flow
of root-deposited photo...
The objectives of this thesis were to examine the links between soil microbial community composition and function using the nitrogen (N) cycle as a model for these interactions and to assess the impact of environmental factors such as microclimate, vegetation type, and nutrient availability on microbial diversity and N transformations...
Inoculation trials were set up in fumigated nursery beds for red alder (Alnus rubra Bong.) seedling production. Frankia inoculum was applied in eight treatments: control, nodule suspension, and three levels of cell suspension (strain ArI5) applied with and without a peat carrier. Seedlings were evaluated at midseason and lifting. The...
The evolutionary relationship between Frankia and actinorhizal plants was evaluated
by reconstructing molecular phylogenetic trees from nifH, 16S rDNA, and rbcL
nucleotide sequences. Subgroupings in Frankia phylogenetic trees reconstructed from
nifH and from 16S rDNA sequences were consistent in terms of plant origins of Frankia
strains. Although the branching order...
Changes in the type and amount of plant inputs can occur gradually, as with succession, or rapidly, as with harvesting or wildfire. With global change it is anticipated that both gradual and immediate scenarios will occur at increasing frequency. Changes in vegetation inputs alter the quality and quantity of soil...
Prior to 2005, ammonia oxidation, the first step of nitrification, was thought mediated mainly by ammonia-oxidizing bacteria (AOB). However, the discovery of Thaumarchaeota carrying the genes coding for the ammonia monooxygenase (AMO) enzyme led to the discovery that ammonia-oxidizing archaea (AOA) also contribute to nitrification. Despite the uptick in studies...
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DavidD. Myrold
Prior to 2005, ammonia oxidation, the first step of nitrification, was
Frankia from root nodules of nine different species of Ceanothus were
characterized. DNA was amplified directly from nodular material using the polymerase
chain reaction (PCR). The amplified region includes the 3' end of the 16S rRNA gene,
the intergenic spacer (IGS), and a large portion of the 23S rRNA gene....
Nitrification and denitrification are major biological processes transforming nitrogen (N) in soils to plant available N, highly leachable nitrate (NO₃⁻) and gaseous N oxides. Although many studies in the past have studied N cycling communities, the effect of increased N inputs on ammonia-oxidizer and denitrifier population dynamics is still under...
Few studies have directly compared denitrifying community composition and activities in soils by coupling molecular-genetic techniques and traditional measures of denitnfication. I investigated communities of denitrifying bacteria from adjacent meadow and forest soils in the Cascade Mountains, Oregon. A key gene in the denitrification pathway, N₂O reductase (nosZ), served as...
Soil nitrogen exists largely as organic matter, including plant liter, dead animal matter, and microbial necromass. About 90% of soil organic nitrogen is proteinaceous material that is too large for plants and microorganisms to assimilate directly. Protein depolymerization therefore plays a critical role in mobilizing this organic source of nitrogen,...
Forests are one of the largest repositories of terrestrial C. Understanding factors that drive organic matter transformations and nutrient efflux from these systems is therefore highly important. Temperate forests are of particular significance due to the large fraction of C that is stored below ground in the soil. Characterizing nutrient...
My research has focused on understanding N and C cycling in soils at small scales. Isotope dilution methods commonly used to estimate gross rates of soil chemical transformations assume homogeneous distribution of label. I explored the effects of diffusion limitations on isotope dilution experiments in soil aggregates using spherical diffusion-reaction...
Algae have shown great potential as a source for renewable fuels. However, current production schemes have not been able to prove a sustainable energy return on investment due in part to the high costs of nutrient addition and the energy required for drying the biomass. Integrated algae-dairy production systems have...
Temperate coniferous forests, such as those that cover vast areas of the western US and Canada, have evolved to depend on cycles of disturbance for succession of species and overall ecosystem maintenance. Many of these forest systems are managed, often for timber production, where disturbances are of anthropogenic origin and...
Algae can be used in a variety of wastewater systems to capture nutrients while fixing carbon dioxide from the atmosphere. I conducted field trials at three locations in Oregon with both corn and potato crops to assess the agronomic value and environmental impact of using the resulting algal biomass as...
Red alder (Alnus rubra Bong.) is recognized as an important source of nitrogen to
ecosystems that it inhabits. I examined N dynamics within alder trees, alder leaf litter, and the soil beneath alder leaf litter. ¹⁵Nitrogen, a stable isotope of N, was used as a tracer to follow the movement...
Soils are a globally significant carbon (C) pool and have the potential to respond to elevated CO2 and environmental changes through positive feedback cycles that enhance the turnover of soil organic matter (SOM). Understanding the mechanisms governing the turnover of SOM is particularly important for modeling the fate of C...
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DavidD. Myrold Kate Lajtha
Soils are a globally significant carbon (C) pool and have the
Forest harvest persists as one of the most globally important industries, and crucially provides raw wood products for both building and fuel materials. Mechanistically complex abiotic and biotic processes curb ecosystem recovery following timber harvest and it is of great importance to understand the effects of this practice on biogeochemical...
Amendments and fertilizers applied to optimize crop production and improve soil health also supply inputs of soil organic matter (SOM) and nutrients that affect soil microorganisms. In the dairy-intensive Pacific Northwest, dairy manure is stored as slurry mixtures until conditions are appropriate for soil application. During storage, the manure begins...
Sagebrush steppe ecosystems in the Great Basin have become increasingly threatened by the proliferation of cheatgrass (Bromus tectorum L.), an invasive annual grass. Diverse sagebrush and perennial bunchgrass landscapes can be converted to homogenous cheatgrass grasslands mainly through the effects of fire. Although the consequences of this conversion are well...
Nitrification is a critical step in the global nitrogen cycle involving the biological oxidation of ammonia (NH₃) to nitrite (NO₂⁻ ) and then to nitrate (NO₃⁻). The first step in nitrification is carried out by NH₃-oxidizing bacteria (AOB) and archaea (AOA), and the second by NO₂⁻-oxidizing bacteria (NOB). In addition...
The use of high throughput molecular methods that allow for the study of bacterial communities in environmental samples is commonplace in microbial ecology. Until recently, fungal community ecology has
focused on isolation, collection of sporocarps, or collection of ectomycorrhizal roots. The techniques used to extract and amplify DNA from environmental...
Ectomycorrhizal fungi (EmF) form symbioses with trees. These symbioses profoundly influence forest ecology. Certain EmF form specialized profusions of hyphae, known as ectomycorrhizal fungal mats (mats) which are visible to the naked eye, alter forest soil biogeochemistry, substantially contribute to soil microbial biomass/respiration and support unique microbial communities. Piloderma and...
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DavidD. Myrold Jane E. Smith
Ectomycorrhizal fungi (EmF) form symbioses with
Most carbon (C) transformations in soil are carried out by a diverse and complex soil microbial community. The size and composition of the soil microbial community is determined by poorly understood interactions between the quantity and chemical composition of plant inputs, as well as climate. Given the metabolic diversity of...
Burkholderia cepacia complex (Bcc) bacteria reside in soil, plant rhizospheres, and water, but the prevalence of Bcc in outdoor environments is not clear. In this study, we sampled a variety of soil and rhizosphere environments with which people may have contact: playgrounds, athletic fields, parks, hiking trails, residential yards and...
In horticultural nurseries for container-grown plants, production and sales have been threatened by the presence of a quarantined plant pathogen, Phytophthora ramorum (causal agent of sudden oak death). Infested nursery beds are an important source of P. ramorum, which can initiate disease through movement with surface water to infect roots...
ABSTRACT
Wetlands are considered critically important in the delivery of ecosystem services such as water quality improvement, flood protection, and conservation of native biodiversity. A common measure of the effectiveness of these ecosystem services is denitrification, an anaerobic microbial process that converts nitrate (NO3-), a common water pollutant, into dinitrogen...
Nitrogen incorporation from red alder (Alnus rubra Bong.) into an Oregon upland mesic forest soil was studied by tracing the fate of 15N added as 15N-labeled alder leaf litter. The recovery of 15N in vegetation, litter, light- and heavy-fractions of the soil, the chloroform-labile (microbial biomass) pool, and the whole...
Although ammonia-oxidizing archaea (AOA) and bacteria (AOB) coexist in most non-acidic agricultural soils, the factors that influence their relative contributions to soil nitrification activity remain unclear. A 2- to 4-d whole soil microcosm assay was developed, utilizing the aliphatic C₈ alkyne 1-octyne to inactivate AOB-driven nitrification activity without impacting AOA...
Proteinaceous compounds are abundant forms of organic nitrogen in soil and aquatic ecosystems, and the rate of protein depolymerization, which is accomplished by a diverse range of microbial secreted peptidases, often limits nitrogen turnover in the environment. To determine if the distribution of secreted peptidases reflects the ecological and evolutionary...
The use of smart tracers to study hydrologic systems is becoming more widespread. Smart tracers are compounds that irreversibly react in the presence of a process or condition under investigation. Resazurin (Raz) is a smart tracer that undergoes an irreversible reduction to resorufin (Rru) in the presence of cellular metabolic...
Seasonality is defined as a change in mood and behavior with the seasons. Research shows there is a possible connection between vitamin D levels and mood (Murphy & Wagner, 2008; Lansdowne & Provost, 1998). Given that vitamin D is produced when skin is exposed to sunlight and varies with sun...
Use of high-strength steel (HSS) reinforcing bars could provide constructability and economic benefits for the construction of structures, reducing the initial and ultimately the life-cycle cost of bridge and building structural elements. This thesis summarizes work performed in a research project on the use of HSS reinforcing bars for concrete...
The role of insect herbivores in the nutrient cycling dynamics of forest ecosystems remains poorly understood. Although past research in herbivory has focused primarily on the deleterious effects that insects can have on tree growth and mortality, the overall effects of herbivory are more complex. Herbivores have the potential to...
My thesis explores the later work of author J.D. Salinger, including two narratives featured in Nine Stories, "A Perfect Day for Bananafish," and "Teddy," and Franny and Zooey, "Raise High the Roof Beam, Carpenters," and "Seymour: an Introduction." Through my analysis I argue that the religious nature of Salinger's fiction...
Sagebrush steppe ecosystems are one of the most widespread but endangered ecosystems in North America. A diverse array of human-related stressors has gradually compromised these ecosystems' resilience to disturbance and invasion by Bromus tectorum (cheatgrass). The role of the foundational shrub Artemisia as a driver of herbaceous community structure and...
After three decades of active research in hydrology and stream ecology, the connection between solute transport, stream metabolism and nutrient dynamics is still unresolved. This existing gap obscures the functionality of stream ecosystems and how they interact with other landscape processes. To date, determining rates of metabolism is accomplished with...
The Levels-of-Growing-Stock Studies in Douglas-fir is a regional cooperative to investigate the effects of levels of growing stock on young stand growth. The Hoskins
installation, in western Oregon, was established in a dense, high site natural stand at total age 20 years. The initial thinning resulted in an immediate 131...
It is well known that the ratio of ammonia oxidizing archaea (AOA) and bacteria (AOB) ranges widely in soils, but no data exist on what might influence this ratio, its dynamism, or how changes in relative abundance influences the potential contributions of AOA and AOB to soil nitrification. By sampling...
Human cathelicidin antimicrobial peptide (CAMP/LL-37) is a cationic antimicrobial peptide that is widely expressed by myeloid and epithelial cells at the human-environment interface. It possesses broad spectrum antimicrobial capacity against bacteria, fungi and viruses. In addition to its direct antimicrobial activity, CAMP/LL-37 also attracts and recruits monocytes, neutrophils and other...
Soil dissolved organic carbon (DOC) is a small but crucial part of the forest carbon cycle. Characterizing the relationship between detrital inputs and soil DOC chemistry is crucial to understanding the ultimate fate of root carbon, fallen wood and needles. Chemical differences in the DOC pool may help to explain...
The role of the nonionic surfactant Tween 80 on the behavior of the therapeutic recombinant protein Factor VIII (rFVIII) was investigated at solid/liquid and air/water interfaces. In order to provide a model system to compare results obtained for the complicated rFVIII-Tween system, a well-characterized globular protein lysozyme was used. The...
Coastal blue carbon ecosystems offer a variety of important ecosystem services, including exceptional rates of carbon sequestration and long-term carbon storage. Because these ecosystems disproportionately influence global carbon cycling, understanding their soil characteristics may help guide long-term climate change mitigation and adaptation strategies. Recently, Kauffman et al. (2020) observed the...
The objective of this research was to improve our understanding of how
changes in the environment affect ecological processes. Change detection is often
confounded by the large variation found in ecological data due to the difficulty of
finding replicates in nature. Intertidal communities were chosen for studies of biophysical
interactions...
Amphibian biodiversity is in rapid global decline, due in part to the fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd). Susceptibility to Bd and chytridiomycosis varies between species and populations. Skin peptides and symbiotic skin bacteria appear to be important mechanisms of Bd resistance. However, not much is known about...
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Appendix D: A prototype containment device for housing frogs during a challenge study 81
The anaerobic and highly reductive conditions found in the ovine rumen are considered favorable for the degradation of the nitroaromatic explosives such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). In this study, we used stable-isotope-probing to determine the bacteria responsible for the degradation of RDX in the rumen. Results indicate 10 μg mL⁻¹ (45...
The installation of engineered log jams (ELJs) is a common river restoration practice, implemented to modify flow structure and increase hydraulic complexity for the benefit of streambank protection and fish habitat. However, few studies have directly assessed the effects of ELJs on flow structure and complexity. This study presents a...
To determine whether shading increases drought-induced
root mortality by changing the chemical
composition of roots, I conducted an experiment in which
high and low light treatments in combination with high
and low soil moisture treatments were applied to
seedlings of Douglas-fir (Pseudotsuqa menziesii Mirb.
Franco). Because synthesis of suberin (a...
Fire exclusion in the western U.S.A. has caused fuel loads to build up and overall forest health to decline. Managers are now looking for ways to reduce these fuel loads while reintroducing some of the desired effects of natural wildfire. One method to do this is thinning using mechanical harvesting...
In intensively managed forest plantations in the northern Oregon Coast Range, herbicides are often applied during site preparation and early stand regeneration to reduce competition for resources for planted conifer seedlings. In addition to reducing competition for crop trees, herbicide applications may affect soil processes including decomposition and nutrient cycling,...
Throughout the course of this thesis, I argue that the prose of David Foster Wallace, specifically his posthumously published novel The Pale King, inhabits a middle ground between universal sincerity and the particularized authenticity of postmodern irony. I examine Lionel Trilling's definitions of sincerity and authenticity before moving toward an...
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Congressman
David Wu, of
Oregon First
Congressional
District, speaks
to young
feminists about
his role
To gain a better understanding of how rapidly microbial communities respond to different magnitudes of perturbation that mimic minor or catastrophic disturbances.
Two montane sites in the western Cascade Mountains of Oregon with adjacent areas of forest and meadow vegetation were studied. A reciprocal transplant experiment evaluated both minor (soil...
The central purposes of this study were to review the
historical sources of David Kolb's formulation of experiential
learning theory, and to determine the effect and
application of Kolb's theory and Learning Style Inventory
as reflected in the literature between 1971 and 1990.
It was found that Kolb based his...
The production of high value non-conventional products, such as long utility poles; or the production of low value bulky products, such as chips or grindings; provide opportunities for forest owners to increase value from their forests. The transport of these products requires the use of specialized trucks and trailers. However,...
Transpiration (T), or the evaporation of water through plant stomata, plays a critical role in climate and biophysical processes at the earth’s surface. While T makes up a majority of the terrestrial evapotranspiration (ET) flux on a global scale, the partitioning of ET is variable and remains elusive. Because photosynthetic...
Two case studies of 5 ecosystems were used to examine the nitrogen fixation rate of red alder (Alnus rubra Bong.), varnishleaf (Ceanothus velutinus var. laevigatus (Hook.) T. & G.), deerbrush (C. i ntegerrimus H. & A.), and snowbrush (C. velutinus var. velutinus Dougl. Ex Hook). The first case study assayed...
Tree species directly and indirectly affect soil nutrient cycles. I sought to characterize soils and foliage associated with four common canopy tree species (Douglas-fir, western hemlock, western redcedar, and bigleaf maple) in mixed-species old-growth forests of the Oregon Coast Range and to determine whether and how soils differ among the...
After three decades of active research coupling hydrology and stream ecology, the connection among solute transport, metabolism and processing is still unresolved. These knowledge gaps obscure the functioning of stream ecosystems and how those ecosystems interact with other landscape processes. We must resolve these challenges to wisely manage water resources,...
In recent years considerable interest has been shown in the diversity of ammonia-oxidizing bacteria in soil communities. The majority of the research has been carried out in Northern Europe where soils have received high atmospheric inputs of nitrogen over the past two centuries. In contrast, although much work has been...
Arctic soils are warming, making vast stores of organic carbon available for conversion to CO₂. This could create a positive feedback loop and accelerate global warming, but the processes that convert this carbon into CO₂ are not well understood. We investigated how the combined activities of sunlight and microbes degrade...
The response of adjacent structural systems to earthquake motions is investigated using the finite element framework OpenSees. Results of sensitivity analyses demonstrate that structural response quantities can increase in either or both of the adjacent structures for specific configurations. The structural models used include steel moment-resisting frames and rigid shear...
Pyrenophora tritici-repentis (Ptr) is the necrotrophic fungus responsible for tan spot of wheat (Triticum aestivum). Ptr causes disease on susceptible wheat cultivars through the production and secretion of host-selective toxins (HSTs). HSTs are compounds that are only known to be produced by fungi and considered to be primary determinants of...
As a key historic component of prairies in the Pacific Northwest, Camassia spp. should play a role in the restoration of these ecosystems. To do so effectively, further study of Camassia spp. propagation is warranted. Thus, the growth, N uptake and allocation, and seasonal thermoperiodicity of Camassia spp. was examined....
Reestablishing native perennial vegetation in annual grass-invaded rangelands is critical to restoring ecosystems, especially following wildfires. Controlling invasive annual grasses is essential to increasing revegetation success; however, pre-emergent herbicides used to control annual grasses prohibit immediate seeding due to non-target herbicide damage. Thus, seeding is often delayed one year following...
Two types of boundary element models are developed for the interaction of waves with trenches. The first type is for a two-dimensional domain in the horizontal plane and employs the linear long wave approximations. It is shown that appropriate selection of pit geometries leads to a significant reduction in wave...
The HAPEX-MOBILHY regional experiment provided an significant opportunity to analyze
the partition of energy and distribution of water over land surfaces. The combination of
remotely sensed data and ground instrument networks over the large-scale in situ experiment
allowed investigation of spatial and temporal variation of such hydrologic parameters as the...
The author of the Highway Safety Manual (HSM) Part B developed a predictive method for safety management. A software tool for highway safety system analysis called the SafetyAnalyst is developed basing on HSM Part B. The author describes an effort to evaluate the feasibility of SafetyAnalyst in Oregon. Seven sample...
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APPENDIX D SAFETYANALYST CRASH (ALTACCIDENT) VARIABLE NAME
PAIRED WITH ODOT VARIABLE
Research in warm-climate biomes has shown that invasion by symbiotic dinitrogen (N₂)-fixing plants can transform ecosystems in ways analogous to the transformations observed as a consequence of anthropogenic, atmospheric nitrogen (N) deposition: declines in biodiversity, soil acidification, and alterations to carbon and nutrient cycling, including increased N losses through nitrate...
Since the late 1880's western juniper has expanded in range and
increased in density in sagebrush-bunchgrass, riparian, and forested plant
communities of the Pacific Northwest. Succession to western juniper
woodland has been shown to reduce the productivity and diversity of the
understory component, result in concentration of soil nutrients beneath...
A method was developed for assessing the vulnerability
of groundwater to contamination from contaminant sources
at the soil surface, using a numerical groundwater flow
model linked to a digital map database. The method was
applied using the pcARC/INFO Geographic Information System
(GIS) to input, store, and manipulate base maps, resulting...
Ammonia (NH₃)-oxidizing bacteria (AOB) and thaumarchaea (AOA) co-occupy most soils, yet no short-term growth-independent method exists to determine their relative contributions to nitrification in situ. Microbial monooxygenases differ in their vulnerability to inactivation by aliphatic n-alkynes, and we found that NH₃ oxidation by the marine thaumarchaeon Nitrosopumilus maritimus was unaffected...
Amino sugars in fungal cell walls (such as chitin) represent an important source of nitrogen (N) in many forest soil ecosystems. Despite the importance of this material in soil nitrogen cycling, comparatively little is known about abiotic and biotic controls on and the timescale of its turnover. Part of the...
Forest Vegetation Management (VM) is an important tool used in the Pacific Northwest (PNW) for reforestation. It has been well documented that VM increases seedling survival and crop tree volume growth. What is less understood, is how altering the plant community and successional trajectory affects the way the ecosystem uses...
This thesis summarizes work completed over the previous four years primarily focusing on chloroplast phylogenomic inquiry into the genus Pinus and related Pinaceae outgroups using next-generation sequencing on Illumina platforms. During the time of our work, Illumina sequence read lengths have essentially been limited to 25 to 100 base pairs,...
Geohumus is a new, unique hybrid soil amendment made of polyacrylic acid, igneous rock flour, and quartz sand. It is biodegradable and is marketed to increase soil porosity, increase plant yield, and increase plant available water by up to 30%, all while using a low inclusion rate of only 1...
MIKE SHE is a fully distributed, physically-based hydrologic model that can simulate water movement over and under the Earth's surface. Evapotranspiration (ET) is one of the components of this model. MIKE SHE uses a modification of the Kristensen -Jensen (1975) method to calculate actual ET. This method is based on...
Understanding the aggregation behavior of engineered nanomaterials (ENMs) in aqueous environments is essential to understanding their fate, transport, and toxicity. Because naturally occurring colloids will likely be present at much higher concentrations than ENMs in environmental systems, heteroaggregation and attachment with these natural colloids could significantly influence ENM fate and...
Reed Canarygrass (RCG) is an aggressive invader in aquatic ecosystems that swiftly modifies the environment and decreases biodiversity. A physical model was used to investigate the mechanisms by which RCG spreads. Experimental trials were implemented to examine feedbacks between a mid-channel patch of the flexible RCG, hydraulics, and bedform evolution...
A model was developed for analysis of the soil water balance of
individual reforestation sites in western Oregon. The numerical
procedure for this model was programmed in compiled BASIC language and
calculations for an entire season are made in about 180 seconds on an
IBM AT microcomputer.
The processes that...
Denitrifying bioreactors are an edge-of-field treatment technology particularly well suited for nitrate removal from subsurface (tile) drainage effluent of agricultural lands. The effectiveness of a proposed denitrifying bioreactor is site-specific and depends upon the complicated interplay of field and environmental parameters controlling discharge events, nitrate concentrations, subsurface temperatures, dissolved oxygen...
Soil water repellency is one cause of rill soil erosion and overland flow that results in the loss of fertile topsoil. Previous research suggests that since microbial growth depends on temperature/moisture and follows diurnal and seasonal cycles, a biological mechanism would be able to explain the observed seasonality and climate...
Sites in need of restoration typically have one or more environmental factors that limit seedling establishment; identifying ecophysiological responses to environmental stressors can be advantageous in growing seedlings able to overcome such constraints on survival. To maximize survival after outplanting, seedlings should be grown in a manner that considers both...
The first project of this thesis is an in vitro study. This study was performed with 8 hydrocortisone topical products on the market for the purpose of comparing one Tec Lab product, a Corticool gel, to the other seven common products on the market. The permeation of these products was...
The objectives of this study were to: 1) determine how organic matter (incorporated vs. surface mulch) and nitrogen fertilization rate impact northern highbush blueberry (Vaccinium corymbosum L.) plant biomass, carbon accumulation, plant losses and allocation, and mycorrhizal infection in mature plants, and 2) determine the magnitude of carbon fluxes (carbon...
Responses of biological indicators of soil quality to winter cover cropping were measured on soil samples collected from 6 commercial growers' fields and two experiment research stations in the Willamette Valley of Oregon. The research stations were the North Willamette Research and Extension Center (Aurora, OR), and the Oregon State...
Ectomycorrhizal (ECM) fungi of the genera Piloderma and Ramaria form dense hyphal mats in the organic and upper mineral soil layers, respectively, in coniferous forest floors of the Pacific Northwest. Previous studies have determined that fungal mats change the chemical, physical, and biological properties of the soil within. Little information...
I conducted two separate studies, both related to the impacts of spring and fall prescribed fire on ponderosa pine (Pinus ponderosa Dougl. ex Loud.) forest soils in Eastern Oregon. The studies were either conducted at or linked to four stands of ponderosa pine, in the Malheur National Forest. Each stand...
Attributional and consequential life cycle assessments are useful in evaluating the environmental impacts of a process, product, or decision. Both types of life cycle assessments differ however in their scope and their ability to answer specific questions. In order to fully understand and compare the environmental impacts of a sugarcane...
A better understanding of grass seed crop and soil fertility is necessary to
improve fertilizer practices and preserving water quality in Willamette Valley,
Oregon, where 55% of land-use is in grass seed production that directly impacts
adjacent waterways containing native protected fish species. I determined tillage
effects on soil N...