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...
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...
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...
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...
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...
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
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...