Study objectives were to survey and compare physical and chemical characteristics of soils within two thirdorder montane riparian ecosystems: a 500-year old Douglas fir (Pseudotsuga menzlesii) forest at Mack Creek, and a mature red alder (Alnus rubra) forest occupying a 35-year old clearcut at Quartz Creek, both near Blue River,...
Despite the recognized role of soil arthropod fauna on nutrient cycling
and decomposition processes, many aspects of the effects of sylvicultural
methods in forest ecosystems upon their biology remain poorly understood.
The long term effects of prescribed fires on soil arthropods in forest
ecosystems in the Pacific Northwest have never...
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...
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...
The abundance and spatial heterogeneity of coarse woody debris (CWD) on the forest floor is a prominent feature of Pacific Northwest (PNW) forest ecosystems. The effect of CWD on soil solution chemistry, nutrient cycling and availability, soil physical structure and formation of soil organic matter, however, remains unknown. Therefore, studies...
Dense hyphal mats formed by ectomycorrhizal (EcM) fungi are prominent features in Douglas-fir (Pseudotsuga menziesii) forest soils and have been estimated to cover up to 40% of the forest floor in some stands. Although previous studies have examined various aspects of EcM fungi, little is known about their associated microbial...
Fire is a major disturbance process in many forests. Long-term studies of the biogeochemical effects of fires, especially on soils, are very rare.
Consequently, long-term effects of fire on soils are often hypothesized from
short-term effects. In a chronosequence study, I studied 24 western Cascades
(Oregon) forest stands thought to...
The objectives of this thesis were to examine the links between soil microbial community composition and function using the nitrogen (N) cycle as a model for these interactions and to assess the impact of environmental factors such as microclimate, vegetation type, and nutrient availability on microbial diversity and N transformations...
Forest soils contain a substantial portion of global terrestrial carbon stores. Forest management can influence the soil carbon pool and how soil organic matter functions. The long-term productivity of forests is an ongoing goal where land managers utilize biomass and timber. A site-specific understanding of intensively managed forests can ensure...
Soils are a globally significant carbon (C) pool and have the potential to respond to elevated CO2 and environmental changes through positive feedback cycles that enhance the turnover of soil organic matter (SOM). Understanding the mechanisms governing the turnover of SOM is particularly important for modeling the fate of C...
Soils representative of several landscape units in the H. J.
Andrews Experimental Forest, Western Cascade Range, were sampled,
analyzed, and tentatively classified. Genetic inferences were
drawn relating soils to landscape position and other factors of soil
formation. Descriptive information and nutrient capital data were
provided to support ecosystem modelling efforts...
As a result of a warming climate, subsequent declining snowpack, and a century of fire suppression, forest fires are increasing across the western United States. However, we still do not fully understand how forest fire effects snowpack energy balance, nor the volume and availability of snow melt and associated water...
Rainfall interception is a primary control over the moisture input to a forested ecosystem through the partitioning of precipitation into throughfall, stemflow, and an evaporated component (i.e. the interception loss). Rainfall interception is a spatially and temporally varying process at multiple scales, but heterogeneity in interception processes are poorly understood...
Knowledge of stand structure, stand dynamics, and production ecology of species mixtures lags well behind that of single-species, even-aged stands. Two mixed-species spacing trials in central Oregon allowed investigation of mixed-species dynamics in a controlled experimental setting. The first site, Pringle Butte, is a mixture of ponderosa pine (Pinus ponderosa...
Twenty sites of uniform topography and soil were select ed in the
montane forest found on the East flank of the Central Oregon Cascades.
These sites were located along a vegetational gradient composed of
five plant communities: Abies/Pachistima, Pinus/Ceanothus, Pinus
Arctostaphylos-Purshia, Pinus/Purshia/Festuca, and Juniperus
Festuca. An attempt was made to...
Nutrient and particulate matter balances were established for five ecosystems dominated by Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in the western Cascades, Oregon. Carriers of N and P were particulate matter (dust in precipitation and sediment in streams) and dissolved matter in both precipitation and stream water. The input and outflow...
Montane forest vegetation as it occurs on the east flank of the
central Oregon Cascades has provided excellent conditions for a
"natural experiment" in the use of various methodologies in studying
vegetational distribution. This "experiment" has reflected on some
theory and practice for the discipline of plant synecology. Detailed
descriptions,...
National Forest management in the Pacific Northwest is shifting
from a focus on commodity production to ecosystem management, in which
the health of the entire forest ecosystem is considered, rather than that
of a few key species. Ecosystem management includes retention of some
live trees following timber harvest (green-tree retention)...
Experimental prescriptions compare agroforestry systems designed to increase financial returns from high-elevation stands in the southern Oregon Cascade Range. The prescriptions emphasize alternative approaches for joint production of North American matsutake mushrooms (also known as North American pine mushrooms; Tricholoma magnivelare) and high-quality timber. Other agroforestry byproducts from the system...
This study evaluated the effect of soil compaction on the growth
of natural regeneration on volcanic ash-influenced soils in the
southern Washington Cascades. Growth of 9 to 18 year-old sapling-.
sized Ponderosa pine (Pinus ponderosa Laws.) was studied on sites
ranging from 915 to 1006 m elevation in an area...