Th.--Sci.--Bordeaux 1, 1981. N°: 680. / Extr. en partie de Journal of physics. G. Nuclear physics, 6, 1980, 901-908.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.

Graduation date: 1981

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 been studied. Soil samples were taken from three sites located in the Willamette National Forest in 1992: paired sites that were either clear-cut without burning and clear-cut with burning 40 years ago. One hundred and eight samples were processed; the arthropods were separated, identified and counted. To study the biology and behavior of some arthropods, eight species of oribatid mites were reared in laboratory conditions. Their life cycle, feeding behavior and reproduction were studied. Results indicated that there were no statistical significant treatment differences either in terms of total numbers of organisms or biomass. However, the majority of the commonest taxa did show offsetting treatment responses. A total of 204 taxa were found in the three sites. The most important groups included Collembola, mites, and insects. Other groups also represented, but in smaller numbers, were spiders, symphylans, pseudoscorpions, and centipedes. Of all these groups, oribatid mites was the best represented and appears to be a useful indicator of disturbances. / Graduation date: 1995

Graduation date: 1966

Graduation date: 1985

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 133-147).

No description available.

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 and poorly described in the literature. We need to know how net precipitation varies in ecosystems because natural systems are driven by non-linear ecohydrological processes where mean values cannot capture localized effects or the cumulative consequences associated with an extremely heterogeneous input. In this thesis, we present two studies that investigate the heterogeneity of interception loss and throughfall in a forested catchment in the western Cascades range of Oregon. In one study, we examined the spatio-temporal patterns among point measurements of throughfall depth and isotopic composition to determine the cause of isotopic differences between throughfall and rainfall. Our results indicated that the residual moisture retained on the canopy from previous events plays a major role in determining the isotopic composition of the next event's throughfall. Differences between the isotopic composition of throughfall samples could indicate further partitioning of throughfall into various flow-paths from the canopy. The second project examined the question of how vegetation variability and terrain complexity drive interception loss heterogeneity at the whole-catchment scale. We applied a simple interception model to a watershed gridded at a 50 m resolution to investigate the relative importance of topographic and vegetative controls over the spatial variability of interception loss. We found that storm characteristics are crucial regarding the impact of spatial heterogeneities in vegetation and evaporation rates. In the Pacific Northwest climate, interception loss is not highly variable for the majority of the year because the annual precipitation is dominated by large storms with low interception losses. However, the net precipitation input to a watershed becomes extremely heterogeneous in the summer due to high interception loss variability. Summer interception loss could be an important control over the spatial variability of the availability of moisture, coinciding with when vegetation is most water-limited. / Graduation date: 2013

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) to preserve biodiversity, imitating the natural fire regime of large, but patchy fires that leave many live trees. How ecosystem management will affect growth and species composition of future forests is an important question. This study takes a retrospective approach to this question by using past disturbance as an analogue to green-tree retention following timber harvest. Using USDA Forest Service timber inventory plot data from the Cascade Mountains of Oregon and SW Washington, 132 unmanaged stands were identified with a tree cohort of 70-110 years old (regeneration) or a tree cohort of 70-110 years old with an overstory of large trees 200+ years old (remnants). All stands were in the Tsuga heterophylla (Raf.) Sarg. zone (Franklin and Dyrness 1973). Single-aged stands represented clearcuts, while two-aged stands served as analogues to stands harvested with green-tree retention. Regeneration basal area/hectare (ba/ha) declined when remnant-tree densities exceeded about 15 remnant trees/ha (R��=0.51) in a relationship roughly described by a sigmoidal curve. Conceptually removing remnant-tree space occupancy effects decreased remnant-tree density's value as a predictor of regeneration ba/ha by about 50% at management-level remnant densities (���45 remnant trees/ha). Thus, it appears that remnant "effects" were a result of both remnant-tree space occupancy and remnant resource use. Douglas-fir ba/ha in the regeneration also declined when remnant-tree densities exceeded about 15 remnant trees/ha (R��=0.60). Western hemlock ba/ha in the regeneration increased slightly with increasing remnant-tree densities (R��=0.19). Western redcedar ba/ha in the regeneration was apparently not related to remnant-tree density (R��=0.02). The degree of aggregation in remnant trees did not appear to affect regeneration ba/ha, but few stands contained the isolated clumps of remnant trees likely under a management scenario. Neither measured site characteristics nor regeneration density was related to regeneration ba/ha across species. Remnant-tree density was apparently unrelated to tree-species diversity in the regeneration. Total-stand ba/ha remained relatively constant across remnant densities. / Graduation date: 1994