One-year-old container-grown Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were outplanted on north, east, south, and west aspects on steep, skeletal Xerochrepts in southwest Oregon. After 2 years, survival rates were highest on north and south aspects, but biomass production (dry weight) was greatest on the west aspect. Shadecards, used to...
Seedlings of Gaultheria shallon, Pseudotsuga menziesii, Rhododendron macrophyllum and Tsuga heterophylla were grown together in the greenhouse in soils from three young managed Douglas-fir forests in the Oregon Coast Range. The main objectives were 1 )to evaluate the ability of ericaceous plants and overstory conifers to share compatible mycorrhizal fungi...
Small broomrape, a holoparasitic weed, is a relatively new weed introduction in the Pacific Northwest that has contaminated a limited number of red clover fields in Oregon. Greenhouse and field studies were conducted to evaluate small broomrape response to common crop and weed species in the Pacific Northwest. Host species...
Winter wheat is commonly grown in rotation with leguminous and non-leguminous crops in the Willamette Valley. For agronomic, economic, and environmental reasons it is important to understand the influence of previous crops on availability of N and other nutrients. Objectives of this study were: (1) to evaluate the effects of...
Previous studies have indicated that roots from five tree species (Picea sitchensis, Tsuga heterophylla, Pseudotsuga menziesii, Pinus ponderosa, and Pinus contorta) decompose at different rates across an environmental gradient in Oregon. Measurements of wood chemistry from each tree species as well as moisture and
temperature from each location do not...
Downed wood and antelope bitterbrush (Purshia tridentata) are often managed on federal ponderosa pine (Pinus ponderosa) forests in central Oregon to prevent catastrophic wildfires and provide wildlife habitat. However, although much is known regarding the roles of downed wood and bitterbrush in wildfire behavior, little is known regarding the relationships...
Western redcedar, western hemlock, and Douglas-fir seedlings were transplanted into pots in one of two soils representative of high and low levels of available NO3 (and total N). The soils were collected from sites at Cascade Head (Oregon Coast) and Wind River (Washington Cascades). Whole plant and component relative dry...
This study explored the relationship of mature ponderosa pine (Pinus ponderosa Dougl. ex Laws) tree vigor and competitive zone density following thinning and fuel reduction treatments. Competitive zone density (CZD) was defined as the total tree basal area (m²/ha) surrounding a given ponderosa pine tree within a 10m fixed radius...
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Figure 9. Relationship of environmental variables to water potential at Lookout Mountain (LM
Modeling and analyzing the combined effects of disease and population dynamics
is important in understanding the effects of mechanisms such as pathogen transmission
and direct competition between host species on the distribution and abundance of different
species in an ecological community. Mathematical analysis of such models in a
spatially explicit...
Defensive chemical and nutritive quality of young leaves were measured for 72 individual trees of Chrysolepis [Castanopsis] chrysophylla in conjunction with light intensities of two different stand types and population numbers of Habrodais grunus herri in the Cascade mountains of Oregon. Leaves were collected in the spring and leaf characteristics...