Tillage of forest soils compacted by ground-based logging systems is a practice that is becoming widely accepted in the Pacific Northwest. However, past research has failed to adequately define the conditions and specifications that particular tillage operations should meet in order to produce the maximum growth response from planted seedlings....
The effects of five tillage treatments on soil bulk density and
mechanical impedance were examined on Newburg sandy loam soil in the
Willamette Valley, Oregon, in 1987. Subsequent effects on seedling
emergence and yield of carrots (Daucus carota L., cvs. Orlando Gold
and Royal Chantenay) were also measured. Mechanical impedance...
Implements for tilling compacted forest soils were
tested on sites logged with ground-based machines in
Oregon. The sites covered a variety of soil conditions
ranging from a clay loam to a rock7 2C2 iplemeflts
tested included disk harrows (four aies), brusa blades
(three sites), standard subsoiler tines (two sites), wing.-...
Shovel logging is a relatively new ground-based method of yarding tinther. It involves moving logs from stump to landing by successive swinging with a hydraulic excavator modified into a log loader by replacing the shovel bucket with a grapple. Loaders used in shovel yarding can weigh in excess of 100,000...
Although previous research in central Oregon has shown soil compaction can lead to a decline in site productivity, the subject is not understood well enough to predict the growth changes resulting from a given level of soil compaction. A study was initiated to relate the basal area, height and volume...
An experiment was established in 1992 in the central Sierra Nevada Mountains of California to assess the effects of high levels of surface organic residues, severely compacted soil, and shrub competition on the development of mixed conifer plantations. This study was conducted in 1997 to determine if selected combinations of...
Forest soils contain a substantial portion of global terrestrial carbon stores. Forest management can influence the soil carbon pool and how soil organic matter functions. The long-term productivity of forests is an ongoing goal where land managers utilize biomass and timber. A site-specific understanding of intensively managed forests can ensure...
Leaf elongation is a major indicator of plant growth. It is
controlled by complex interactions of many factors including light
intensity, photoperiod, water availability, atmospheric conditions,
and plant water stress. In this study, the response of leaf elongation
to length of photoperiod and to plant water stress as indicated by...
A study, consisting of two sequential greenhouse experiments, was
designed to determine the effects of soil liming upon the fungal
partner in a mycorrhizal association. A Willamette Valley foothill
soil, of the Jory series, was limed in increments to achieve a range
of acidity and alkalinity. The P-deficiency and P-fixing...
This research evaluated the germination and early seedling
development response of two sources of bluebunch wheatgrass (Agropyron
spicatum) to a wide range of environmental conditions. Seeds collected near John Day, Oregon and Secar seed obtained from the Soil
Conservation Service were used in the investigations.
Evaluation of the germination response...
This study evaluated the effects of a crawler tractor, a rubber-tired skidder, and a torsion suspension vehicle on several soil and hydrologic properties in the western Sierra Nevada Mountains of California. Four sites, with soil textural classes ranging from a loam to a loamy sand and elevations between 680 and...
A special apparatus was developed in which the soil moisture
levels of several soil cells could be maintained independently by
various osmotic solutions at a selected temperature. The effect of
four soil moisture suctions and four soil temperatures on the rates
of transpiration, photosynthesis and respiration of monterey pine
seedlings...
The effect of moisture stress and nutrients on the rate of growth
of wheat (Triticum aestivum L. Var. Gaines) seedlings was studied.
A special apparatus in which the moisture stress of several perlite
cells could be maintained constant by osmotic solutions was used.
Predetermined amounts of nitrogen were added to...
Previous research had identified four serogroups of Rhizobium trifolii
indigenous to Abiqua soil (fine, mixed, mesic, Cumulic Ultic Haploxerolls).
Nodulation of subterranean clover (Trifolium, subterraneum L.) by two of the
serogroups, 6 and 36, was influenced by the application of CaC0₃ to the soil.
The studies described in this thesis...
The usefulness of preplant nitrogen (N) in establishing
alfalfa in colder production areas has not been
well characterized. This study was conducted to determine
the effect of preplant N and soil temperature on
yield, percent N derived from biological nitrogen fixation
(PBNF), and shoot N concentration in alfalfa (Medicago
sativa...
The role of moisture stress in seedling physiology and establishment
was studied in both the field environment and laboratory
experiments. Plant moisture stress was measured using the pressure
chamber technique. This technique was modified and tested using a
fascicle of pine needles as a sample, an improvement which allows the...