Many higher plants have mycorrhizae associated with their roots. These structures are often essential for survival and growth (Harley & Smith 1983). Mycorrhizae are known for the abilities to enhance nutrient absorption. While nitrogen-fixing organisms are found as components of the mycorrhizosphere, mycorrhizal fungi are not presently known to fix...
I used greenhouse and field studies to investigate how intraspecific and
interspecific competition, soil disturbance, and fertilization affect the biomass and
reproductive output of Senecio sylvaticus and Epilobium paniculatum, common winter
annuals which invade and dominate western Cascades forests during the first two seasons
after clearcutting and slashburning.
Field work...
This research addressed the opportunity to obtain baseline data for both stream chemistry and soil resources for an intensively managed forest watershed, encompassed by the North and South Forks of Hinkle Creek Watershed Research and Demonstration Area Project near Sutherlin, Oregon. A solid representative database for both stream and soil...
Information about forest substrate respiration, nitrogenase activity and
mineralizable nitrogen may be incorporated into carbon and nitrogen budgets that comprise an important element of forest management planning. In this study, substrate respiration, nitrogenase activity and mineralizable nitrogen were measured in two western Oregon Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands within...
In this study, biological and chemical characteristics were determined for two high-elevation meadow-to-forest transitions located in the Central Oregon Cascades. The chloroform fumigation incubation method (CFIM) was used to determine microbial biomass C(MBC) and the N flush due to fumigation (NF), and meadow values were compared to forest values for...
Seven case studies of 11 ecosystems were used to examine the effects of nitrogen-fixing alders in Douglas-fir plantations. The
first case study quantified nitrogen (N) fixation and aboveground net primary production in a young Sitka alder [Alnus sinuata (Regel) Rydb.] ecosystem. At 5 yr of age, the N fixation (C₂2H₂...
Denitrification, the biological or chemical reduction of ionic nitrogen oxide or dinitrogen, has not been widely studied in forest ecosystems despite widespread interest in other facets of the forest nitrogen economy. This study had three main objectives: to determine whether potential for denitrification exists in forest riparian and hill slope...
Effects of partial understory removal on belowground and aboveground ecosystem properties were investigated in 5 and 15 yr old Douglas-fir (Pseudotsuga menziesll (Mirb.) Franco) experimental plantations in western Oregon. Seedling survival was not affected by understory removal at age 5 yr.
But through age 15 yr, understory removal increased seedling...
Seedlings of Acacia senegal were grown in a glass greenhouse to study the effect of nitrogen and irrigation regimes on dry matter
production and allocation to different plant organs, net photosynthesis per unit leaf area, and nitrogen content in the different plant organs. Ammonium nitrate (NH4NO3) was used in this...
Soil effects from mountain beaver (Aplodontia rufa ) burrowing were
investigated in Oregon Coast Range soils formed from Tyee sandstone. The potential
for observed changes in soil to affect productivity was assessed. Soil horizons from
mountain beaver mound soil and adjacent unmounded profiles were collected with a
monolith-type quantitative sampler....