Water availability is a critical limiting element in semi-arid ecosystem productivity and presents particular challenges in Sahelian countries such as Senegal. The landscapes are characterized by the presence of two common semi-arid shrubs (Piliostigma reticulatum and Guiera senegalensis), both of which may be important hydraulic regulators in these water-limited ecosystems....
Laboratory experiments were used to investigate the mechanism
of plant response to water stress by determining the sensitivity of leaf
elongation, photosynthesis and transpiration in young corn plants to a
decrease in leaf water potential.
In initial experiments, 9 day old corn plants were grown at soil
water potentials of...
An adequate stand at the optimum time is an important factor
affecting potential yield and soil erosion control. However, obtaining
adequate stands of fall planted winter wheat in the dryland areas of the
Pacific Northwest is often complicated by marginal seed zone soil
moisture. The purpose of this laboratory study...
A series of experiments was designed to investigate differential
flood-tolerance and the phenomenon of flood-induced stomatal closure
of several fruit tree species. The first two experiments were conducted
with potted plants submerged outdoors 5-10 cm above the soil line.
Plant morphology, growth, leaf conductance (cL), and soil oxygen diffusion
rate...
The use of chemicals such as the triazines (especially atrazine) and mixtures of the triazines and 2,4-D or 2,4,5-T has become almost standard practice in some parts of the world for selectively controlling grasses and other herbaceous weeds to conserve moisture for and/or prevent the smothering of newly-planted conifers. In...
The major objectives of this study were an
evaluation of the Meteorological Office Rainfall and
Evaporation Calculation System (MORECS) evapotranspiration
(ET) model using the Penman-Monteith equation and
comparison of the MORECS and measured surface resistance.
Meteorological, soil and plant parameters were measured in
an alfalfa field over two growing seasons....
Farmlands, grasslands, and savannas in semi-arid sub-Sahelian Africa have the potential to store
carbon (C) in soil. There is a great need to manage ecosystems to increase C storage in semipermanent
soil pools. This will improve soil quality, impede desertification and by reducing
atmospheric CO₂ levels, will slow climate change....
Published May 1931. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Coffee trees growing in the Kona district of Hawaii
were treated with different concentrations of either BA,
GA3, or Promalin, and pruned at the time of flowering. No
significant differences in the flowering and fruit ripening
pattern were found. High concentrations (100 mg/1) of
growth regulators decreased fruit fresh weight....
This thesis research examines the effects of film-forming antidesiccants applied to dormant pondexosa pine (Pinus ponderosa Dougl.) seedlings after being lifted and to actively growing seedlings. The basic proposition was that antidesiccants would have a positive effect on reducing water loss in ponderosa pine seedlings. In order to evaluate the...
The relationships among total water potential (psi), osmotic potential ([pi]), pressure potential (P), and relative water content (R*) were determined during four consecutive soil drying cycles for shoots of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings. In each cycle, seedlings were sampled for pressure-volume determinations as soil water was depleted gradually...
The principles of continuum mechanics provide a consistent
framework for the derivation of mathematical statements describing
transport of water and solute, and growth in plant tissue. These
derivations are based upon the explicit consideration of the tissue as
a mathematical continuum composed of a cell wall matrix, water, and
solute...
Evaluation and sensitivity analysis of a soil-water---
atmosphere-plant simulation model, SWATRE, developed by
Feddes et al (1978) in The Netherlands was conducted.
The evaluation was performed with the observed data
obtained by Cuenca (1978) for three different irrigation
levels in UC82 variety tomato fields in Davis,
California. SWATHE requires about...
Under adverse soil moisture conditions a critical water stress
or water potential develops in the plant and productivity is reduced,
or in extreme cases, terminated. Research to determine the soil
moisture status for maximum production of specific crops has been
conducted for decades. The results have done much to increase...
One of many important physical properties that must be known
to understand transport phenomena in soils is pore size distribution.
Presently the pore size distributions of soils are most commonly
obtained from soil water characteristic curves. The soil water characteristic
curves are usually obtained by the pressure plate technique.
It...
Xylem anatomy is a strong determinant of water transport efficiency and is therefore an important component of the overall hydraulic strategy of any woody plant.
However, in addition to its role in water transport, xylem also serves in mechanical
support, and these two functions may represent conflicting design requirements. To...
Managers of forest and plantation ecosystems are encountering growing problems involving plant pathogens and the expanding geographic ranges of these pathogens. Historically unexposed stands are exceptionally vulnerable when a non-native pathogen is introduced because these pathogens can cause devastating disease in a host population that lacks co-evolved resistance mechanisms. One...
The effect of soil water suction and soil temperature on rates
of transpiration, photosynthesis, respiration and nitrogen fixation of
soybean (Glycine max. Merrill, var. Chippewa 64) seedlings was
studied. A special apparatus was developed in which the soil water
suction of several cells with soybeans growing in them could be...
Vegetation as a soil-forming factor was studied under forest
transition and grass while attempting to keep other soil forming factors
constant in the western part of the Willamette Valley, Oregon. The
physiographic units consist chiefly of the interior foothills and slopes
formed from an old basaltic flow with some interspersed...
Agronomic and microbiological studies were conducted on "Anchor" alfalfa (Medicago sativa L.) established from uninoculated seed on three Aridisols in central Oregon. Significant responses to 230 Kg N per ha (NH₄NO₃), which was applied in mid-April and after each first and second harvests, were observed in yield parameters of the...
Published June 1983. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
I studied the water relations traits, twig conductivity, C'3 isotopic composition,
and wood density of three conifer and five angiosperm species in western Oregon. This
study took place from spring 2002 to fall 2003 on four sites. Species were selected to
represent the diversity of drought tolerance of woody plants...
Understanding how the interactions and feedbacks between plant function, climate, and soils ultimately affects the terrestrial water balance and subsurface flow processes is major challenge in scientific hydrology. This dissertation summarizes the findings of a manipulative climate warming experiment, an observational field study that utilized stable-isotope tracers, and associated modeling...
In deciduous species, water exits stems mainly through leaf traces
attached to the outer growth ring and yet we know that water ascends
throughout the entire cross-section of the sapwood. There is an increasing
amount of information on sap flow and sapwood hydraulic properties from
separate studies, but little information...
Desert plant communities are among the most sensitive to changes in soil water conditions. In areas with shallow aquifers, it is important to understand both the effects of groundwater alterations on vegetation and how changes in surface-soil water affect plant water uptake. Studies in arid environments have evaluated the effect...
Water treatments were applied to young ponderosa pine trees in the Eastern Cascades, Oregon during the 2003 growing season, and shade treatments were applied during the 2003 and 2004 growing seasons to understand how photosynthesis and soil respiration, particularly the root/rhizosphere fraction (R[subscript rrh]), would respond to increased moisture availability...
Map delineations of soil and vegetation for a 14,000
acre (5,800 hectare) site in the Oregon Coast Range were
compared. Research objectives were to ascertain the
types of information that could be extracted from delineation
comparisons and to develop a methodology suited
to this purpose. The latter objective was achieved...
Pseudotsuga menziesii var. menziesii (coast Douglas-fir) is a tree of ecological, economic, and cultural value in its native North American Pacific Northwest (PNW) distribution. P. menziesii is host to a variety of well-documented endophytic foliar microorganisms, including the fungus Nothophaeocryptopus gaeumannii, the causal agent of Swiss needle cast (SNC), and...
Soil organic matter levels, soil temperature and moisture, and vegetation properties were measured along a sequence of death and
regeneration in a mountain hemlock (Tsuga mertensiana) forest. The sequence is produced by slowly moving waves of the root pathogen Phellinus weirii. While analysis of variance for all sampled soil layers...
Field experiments were conducted with cauliflower (Brassica oleracea var.
botrytis cv. Snowball Y ) to determine crop development, yield, quality and
maturity response to various seasonal water levels, and to specific water stress
timing in relation to curd initiation. The effects of nitrogen rate, timing, and
source and the application...
Evaluation of meta-sedimentary bedrock as a source of stored water available
to plants in a mediterranean climate is presented based on: root length distribution
(RLD), root morphology, rock water holding capacity and seasonal pattern of water
depletion. Studies were performed in southwestern Oregon under young stands of
whiteleaf manzanita, ponderosa...
Diurnal changes in stem circumference at the 1954 and 1963 internodes of a 22-year-old Douglas-fir were monitored using automated
band dendrometers. Determinations of internal tree water potential and estimates of transpiration were used to characterize the water status of the tree. Environmental monitoring included the measurement
of air temperature along...
Victoria blight of oats is caused by the fungus Cochhobolus victoriae. This fungus is pathogenic due to its ability to produce the host-selective toxin victorin. Previously, a 100-kD protein that binds victorin in vivo only in susceptible genotypes was identified as
the P protein of the glycine decarboxylase complex (GDC)....
Winter squash (Cucurbita maxima) grown in Oregon’s Willamette Valley for edible seed, frozen foods, and fresh markets is susceptible to an undiagnosed soilborne disease. Diseased squash fields exhibit symptoms of stunting, root and crown rot, vascular discoloration, and late-season wilt, which in extreme cases can lead to total crop failure....
A 1.5 ha mixed conifer stand in the Blue Mountains of Oregon
was intensively examined to assess the impact of logging disturbance
on soils and herbaceous vegetation. Sampling was conducted six
years after much of the timber overstory was removed in a
shelterwood cut and yarded by crawler tractor. A...
While current theories describing the insect-plant interaction
have emphasized the biochemical aspects of the relationship,
morphological components can also play a significant role in
determining which plants or tissues are susceptible to insect attack.
Xylem sap on which spittlebugs feed may lack many of the plant
compounds responsible for host...
Infiltration, soil erosion, nitrogen loss and soil profile
characteristics were measured on 36 sites representing land occupied
by Artemisia tridentata ssp. tridentate, wyomingensis, and vaseyana.
Infiltration, soil erosion, and nitrogen loss were strongly correlated
but highly variable. Soil loss, but not infiltration or nitrogen
loss was significantly different between subspecies....
Rates of germination and emergence of corn were measured as
influenced by soil physical parameters using blotter paper and a sandy
loam soil as growth media. The corn seeds used were a hybrid of
Funk's (DJ7xLH93).
Experimental conditions were soil temperature of 20°C, 25°C,
30°C, and 35°C, soil water potential...
Annual applications of fresh or composted dairy manure were assessed for their effects on root rots of sweet corn and snap bean and damping-off of cucumber in a field soil. Soil biological and physical properties were measured as possible indicators of root rot suppressive potential. Regardless of amendment type or...
Craterellus tubaeformis is a small to medium-sized forest mushroom that is fairly common in the Douglas-fir/western hemlock forests of the Pacific Northwestern United States and is most often associated with decayed coarse woody debris. In this study, the mycorrhizae of Craterellus tubaeformis in western Oregon is identified by DNA analysis...
Mass wasting events are a principal form of erosion that occurs on steep forest land throughout the Pacific Northwest. Numerous studies have reported that tree roots help stabilize steep forest land. A complete
understanding of the mechanism by which roots strengthen soil would enable modeling to more closely approximate field...
Data collected from permanent sample plots at medium and high elevations in Oregon's coastal forest clearly indicate that snow damage adversely influences stand development. Sapling stands of western hemlock and Douglas-fir were subjected to severe snow damage above 1,000 feet in the early parts of 1965 and 1966 and above...
In the Coniferous Forest Biome, many of the understory as well as
dominant plants are evergreen and thus water uptake is a year around
process. The flow of water from the soil through plants to the atmosphere
affects the entire forest ecosystem. As water is evaporated, it absorbs
heat and...
This dissertation investigated the impacts of tree height upon a range of physiological and structural characteristics of Douglas-fir foliage; relationships between structural and functional trends with height; and compensatory mechanisms that mitigate height-related growth constraints. Height-related trends in foliar physiological and anatomical characteristics were examined both within trees as well...
Preliminary results of a comprehensive study of hydraulic fluctuations in Douglas-fir (Pseudotsuga menziesii) stems in response
to plant water status and environment are presented. Diurnal changes in stem circumference near DBH of a dominant Douglas-fir were monitored using automated band dendrometers. Measurements of transpiration rate, internal moisture stress and stomata...
Agrobacterium species transform plant cells by targeting a portion of plasmid-encoded bacterial DNA to the host nucleus. Genetic transformation by A. tumefaciens and A. rhizogenes requires secreted effector proteins. The tumor-inducing (Ti) plasmid from virulent A. tumefaciens encodes VirE2, a secreted single-stranded DNA-binding protein required for efficient transformation of hosts....
Biology of Scaptomyza apicalis Hardy (Diptera: Drosophilidae) was studied in
relation to its host, meadowfoam, Limnanthes alba, a recent oil seed crop grown in the
Willamette Valley, Oregon. Populations of flies and larvae were monitored weekly over
three consecutive crop-years beginning in 1996. Yellow sticky traps gave relative
population estimates...
Small remnants of 'natural' habitats exist today throughout much of the world. Upland prairies in the Willamette Valley, Oregon have been nearly eliminated by conversion to agriculture and other uses. As a result, very few prairies remain and at least four butterfly species that require this habitat appear to be...
During the summer of 1971, diurnal patterns of water status were monitored in Acer circinatum. Measurements of transpiration rate, internal moisture stress, and relative leaf resistance were used to characterize
the water status of the tree. For the days examined, the diurnal and seasonal
fluctuations of water status in relation...
This study was undertaken to determine both the amount and the
spatial variability of sand, silt, clay, and six fractions of coarse
fragments in soils representing harsh sites for reforestation. Particle size data were collected because of their direct relationship to
water holding capacity and the plantability and survivability of...
This research assessed certain specific plant-soil and community
interrelationships in eastern Oregon habitat types dominated by
subspecies of Artemisia tridentata.
The first evaluation described plant-induced soil chemical patterns for Artemisia tridentata plant communities of high perennial
grass-low shrub and low perennial grass-high shrub composition. Soil
concentrations of total nitrogen, organic...
Relationships between sagebrush-dominated plant communities and
soil-site characteristics were examined on 372 relatively undisturbed
rangeland sites of the Humboldt National Forest, in northeastern
Nevada. Plant species production data were analyzed by TWINSPAN to
develop a hierarchical, floristic-based community type (C.T.) classification.
Seventeen C.T.s were identified in this analysis and named...
Pyrenophora tritici-repentis, causal agent of tan spot of wheat, produces multiple
host-selective toxins (HSTs), including Ptr ToxA, encoded for by ToxA, Ptr ToxB,
encoded for by ToxB, and Ptr ToxC. Variable distribution of these three HSTs among
different isolates of P. tritici-repentis, both singularly and in all possible combinations,
defines...
Tall fescue is thought to have co-evolved with the fungal endophyte Acremonium coenophialum to form a mutualistic relationship. Endophyte-infected (EI) plants can have increased growth and survival when compared with endophyte-free (EF) plants. Responses to endophyte-infection vary and are host-genotype and fungal-biotype specific. Mechanism(s) by which endophyte-infection confers increased growth...
Symbioses between microbes and multicellular eukaryotes are found in all biomes, and encompass a spectrum of symbiotic lifestyles that includes parasitism and disease, commensalism, and mutually beneficial interdependent host-microbe relationships. Regardless of outcome, these symbiotic lifestyles are governed by a complex molecular "courtship" between microbe and potential host. This courtship...
Stream systems in the Pacific Northwest have come to be understood in the absence of beaver (Castor canadensis). To understand the effect of beaver upon riparian plant communities, four basins in the lower Alsea drainage were examined to determine the effect of beaver and their impoundments on streamside herbaceous/shrub and...
The state of Oregon has two distinct climate types bisected by the crest of the Cascade Mountain range. The western side of the Cascades experiences high levels of precipitation and mild temperatures due to the maritime influence of the Pacific Ocean, while the eastern side lies in the rain shadow...
................................................................................................. 1
Chapter 2 - Relationship between sapwood capacitance, vulnerability to
embolism and water
Measurement of plant moisture stress of 1-2 m understory conifers
was made in "reference stands" on the H. J. Andrews Experimental
Forest in 1970-1972. Maximum stress each year (measured between midnight
and dawn) is closely correlated with the position of each community
along one axis of an ordination of the...
Vegetation diversity in the Wyoming big sagebrush/Thurber needlegrass (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young/Achnatherum thurberianum (Piper) Barkworth. syn. Stipa thurberiana Piper) plant association was studied across a condition class gradient in southeastern Oregon. All observable vascular plant species were counted during 6 seasons and 2 years and diversity...
Many ecological systems follow a seasonal cycle affecting primary production,carbon flux, and vegetative gas emissions. The seasonal variation of ecological systems are both affected by and have effects upon climatic factors. A quantitative estimate of the seasonal variation of vegetation is required to characterize ecological systems and their interaction with...
The probing behavior and feeding activity of green peach aphid, Myzus persicae
Sulzer, on Bacillus thuringiensis ssp. tenebrionis- transgenic potatoes, insecticide
treated potatoes, and host plants with different preference were electronically
monitored. I found that first, transgenic potatoes had no effect on green peach aphid
probing suggesting that transmission of...
Thesis research focused on: 1) Water and fertilizer gradients
within the plant root zone, and effects of chemical and physical
gradients on Trichoderma harzianum populations. 2) Regulation of root
growth physically with permeable fabric containers and chemically with
copper compounds. 3) Effects of copper coatings for fabric containers
on Glomus...
Population dynamics, plant communities, and abiotic environments of three narrowly endemic, allopatric mariposa lilies (Calochortus Pursh) are described and compared. All were restricted to ultramafic soils in southwestern Oregon with high concentrations of nickel, zinc, and chromium, and low calcium to magnesium ratios. Soils inhabited by the three species differed...
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...
Vegetation patterns and species distributions are strongly linked to soil moisture regimes, and populations within a species from contrasting climatic regimes could exhibit differences in the degree to which certain functional traits related to establishment are expressed. Tree seedling survival is crucial for forest regeneration, and thus may be a...
Canopy structure has a significant impact on the canopy hydrology of
Douglas-fir forests in the Pacific Northwest (PNW). Whole canopy rainfall
interception was measured for young Douglas-fir forest and compared to an
old-growth Douglas-fir forest. The old-growth forest had significantly greater
canopy water storage capacity (5) and direct throughfall fraction...
Concerns about the extent to which major Pacific Northwest floods over the last decade might have been exacerbated by logging have heightened the need for a better scientific understanding of the role of forest maturity on snow accumulation and melt. To address this need, a multi-scale field and modeling study...
Rhizopogon is a large genus of ectomycorrhizal (EM) fungi that grows in association with host trees of the family Pinaceae. We have conducted a series of studies investigating the ecology and evolutionary biology of the EM symbiosis shared between R. subgenus Villosuli and trees of the genus Pseudotsuga. Two members...
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...
The accurate simulation of snowpack deposition and ablation beneath forested areas is confounded by the fact that the vegetation canopy strongly affects the snow surface energy balance. The canopy alters the radiation balance of the snowcover, and reduces the wind speed at the snow surface. Data collected as part of...
The hypothesis that inoculation of transplants with vesicular-arbuscular mycorrhizal (VAM) fungi before planting into saline soils would alleviate salt effects on growth and productivity was tested on lettuce (Lactuca sativa L.) and onion (Allium cepa L.). A secondary hypothesis was that the fungi isolated from a saline soil would be...
The biology and behavior of the codling moth, Cydia pomonella (L.), was studied to
determine factors responsible for differences in susceptibility to moth damage among apple
and pear cultivars.
In release experiments, codling moth adults were intercepted in significantly greater
numbers in host (apple, pear) than in non-host (maple) trees,...
Common root rot is a major disease of commercially grown snap bean (Phaseolus vulgaris L.) on the irrigated sandy soils of central Wisconsin. The objective of this study was to determine the relationships between soil properties and suppressiveness to common root rot of snap bean (causal agent Aphanomyces euteiches) in...
Symbiosis is the close and protracted interaction between organisms. The molecular interactions that occur during symbiosis are complex with multiple barriers that must be overcome. Many Gram-negative, host-associated bacteria use a type III secretion system to mediate associations with their eukaryotic hosts. This secretion system is a specialized apparatus for...
The effect of serial (multiple-year) organic matter (OM) amendment on soil properties has been described in some cropping systems, although less is known about the effect of serially amended field soils on soil-borne plant diseases. The objectives of this study were to describe the effects of the third and fourth...
Live western larch, Larix occidentalis Nutt., a tree species resistant to the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, produces the monoterpene 3-carene in higher concentrations compared to Douglas-fir, the preferred host of D. pseudotsugae (Reed et al. 1986). The inhibitory effects on attraction to aggregation pheromones and toxicity of 3-carene to...
Mycorrhizae are important for plant growth, particularly in nutritionally poor soils. Vesicular-arbuscular mycorrhizae (VAM) are the primary form of mycorrhizae found in tropical plants, and their persistence in the soil as colonizing fungal propagules following deforestation cannot be directly
measured. Utilizing the "most probable number" (MPN) method for estimating infective...
Three studies on Douglas-fir beetle (DFB), Dendroctonuspseudotsuae, were conducted to investigate its basic and applied biology. Studies included investigations into the spatial relationship of DFB infestations over multiple years and multiple landscapes, relationships between DFB brood adult lipid levels and position of development along the length of tree boles, and...
Disease is often overlooked as a natural disturbance agent in plant communities. This study examines what effects, if any, a disease-mediated disturbance has on the plant community as a whole in old-growth and mature forests of western Oregon. Phellinus weirii (Murrill) Gilbertson (Family: Hymenochaetaceae) is a native root-rotting pathogen that...
Factors affecting the persistence of mussels (Mytilus californianus) and their associated epibiont species were studied along the central Oregon coast. Interactions between mussels and their algal epibionts (Endocladia
muricata) varied in sign and strength with environmental conditions. In extreme temperatures mussel—epibiont interactions determined survival of individual mussels,
and persistence of...
Invasive plants have the capacity to transform landscapes and alter ecosystem function, causing significant economic and ecological damage. These effects include displacement and reduction of native flora and fauna, altered fire regimes, modification of biotic and abiotic soil properties, as well as local, regional, and global economic impacts. With such...
Production of the host selective toxin victorin is causal to pathogenesis of Cochliobolus victoriae on oats. The dominant Vb gene confers oat sensitivity to victorin, and is genetically inseparable from Pc2, which confers resistance to Puccinia coronata f. sp. avena. Victorin induces apoptotic-like cell death, and cell death is a...