The resistance of a leaf to molecular gaseous diffusion
is an important physiological response. Control of
leaf resistance enables a plant to control its transpired
water loss and regulates photosynthesis.
Four study sites representing a gradient in available
moisture and evaporative demand, were chosen in western
Oregon for the study...
Four study sites were selected along an altitudinal gradient on Mt. Ashland in the Siskiyou Mountains of southern Oregon. The altitudinal gradient roughly corresponded to a gradient in temperature and water availability ranging from very hot and dry to cool and moist. Air and soil temperatures were continuously measured on...
Clearcutting is a sound silvicultural practice when exercised
in the proper environmental location. Foresters have learned through
bitter experience that clearcutting Douglas-fir forests, located on
droughty south-facing slopes, often leaves uncorrectable regeneration
problems. Thousands of acres of unproductive grass and brush throughout
the Douglas-fir region are unavoidable reminders of inappropriate...
In a mountainous region of southwestern Oregon where temperature, moisture and nutritional status of forest communities have already been classified, the influence of tight upon conifer growth and plant distribution was investigated. Light, measured in calories cm day' (400-700 nm) during clear summer days was used as an index to...
When trees from 16 populations of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco. var. menziesii) were grown at ten geographically diverse locations for seven years, those from a Vancouver Island source were among the top three for height growth on nine of the ten plantations (Rowe and Ching, 1974). In contrast, growth...
To understand the effect of human-induced stresses on forests, there is a need for a method to separate effects of imposed stress from effects of natural climate stress. I developed an approach to predict forest response to climate stress using as indicators stable carbon isotopes in tree foliage and growth-rings....
The over-arching theme of this work is that soil data affect the performance and realism of vegetation models with particular focus on their ability to predict or explain disturbances such as fire or disease. We tested the sensitivity of the Excel version of the 3-PG model to soil properties and...
Xylem conducting tissue or sapwood is an important storage organ
for water, carbohydrates, and nutrients, and this storage helps trees
accommodate environmental change. However, the living ray parenchyma
cells in sapwood, which store the carbohydrates and nutrients,
require energy for maintenance. I examined how sapwood maintenance
costs vary among species,...
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...
Douglas-fir (Pseudotsuga menziesii Mirb. Franco)
seedlings at a nursery in western Oregon were fertilized
with nitrogen in October. Free amino acid (FAA) and total
nitrogen concentrations in needles, stems and fine roots
were followed from before fertilization until just prior
to budbreak the following spring. Before budbreak in
mid-March, the...
