The internal moisture stress of Douglas-fir was determined on foliage collected in the Siskiyou Mountains of southwestern Oregon. Internal moisture stress integrates both climatic and edaphic environmental effects as they influence a plants moisture regime. In this study two laboratory techniques were modified to permit stress measurements to be taken...
Over the last decade a new perspective on how forest ecosystems operate has emerged. Ecosystems appear much more flexible than we once thought. Even the most persistent is still evolving in composition. Yet for all their diversity, very similar processes are seen as operating in all forests, providing a point...
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...
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...
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,...
The control that stand leaf area exerts upon individual tree vigor was tested on a heterogeneous, even-aged Douglas-fir stand infected by Phellinus root rot. Tree vigor, or growth efficiency ratio, was defined as the current basal area growth per unit of leaf area. Because of a close relationship between sapwood...
Two physiological factors are of major importance to tree and stand growth: (1) the photosynthetic rate of foliage and (2) the amount of foliage. If carbohydrate allocation patterns remain constant, stand growth should be related directly to total canopy photosynthesis. From a literature analysis I assess methods of relating photosynthetic...