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).

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

Measuring habitat selection by bats is complicated by their intricate life cycle. Scaling habitat measurements to reflect a hierarchal habitat selection process can help to define habitat associations of bats. I assessed day roost habitat of female long-legged myotis at four scales: the roost structure, micro-habitat surrounding the roost, the stand level, and landscape level. I radio-tracked 16 female long-legged myotis (Myotis volans) for an average of eight days per bat, July through August of 1993, 1994, and 1995 in two drainages in the central Oregon Cascades (Quentin Creek and Lookout Creek) to locate day roost structures. Forty-one day roost structures were identified, of which 1 was a rock face, 4 were green trees, and 36 were snags. The average height of all roost structures was 40 m (SE=2.5). The average dbh for all snags and trees used as day roosts was 100 cm (SE=6.1). Large snags including partially live, hollow western redcedar trees (Thuja plicata) averaging 97 cm dbh (SE=6.6) and 38 m (SE=2.8) high were the most commonly used roost structures. Individuals radio-marked at the same night roost did not use one common day roost. Individual bats were found roosting in one roost for several days, or using multiple day roosts within discrete roost areas. The area which encompassed one night roost and all known day roosts covered 3,258 ha in the Quentin Creek drainage and 6,391 ha in Lookout Creek. I compared physical characteristics and habitat within 20 meters of 33 roost snags with 66 randomly selected snags. The odds that a snag is used as a day roost is associated with roost height; given height, the odds of use is associated with the height of the stand within 20 meters of the snag. There is some indication that the presence of an open canopy around the snag, and the percentage of bark on the snag also could be factors that influence the selection of snags as day roosts. The frequency of occurrence of roost structures within young and late seral stands did not differ from what was expected to occur by chance in these two stand conditions. Roosts did not occur in stands with a harvest history vs. stands without a harvest history disproportionate to availability. I compared the distance to class I (largest) through class IV (smallest) streams between 34 day roosts and 102 randomly selected points. Day roosts were located closer to streams than randomly selected locations in both Lookout and Quentin Creek drainages with 1 exception (Lookout class III). In two cases day roosts were significantly closer to streams than randomly selected locations. Day roosts tended to be closer to streams where night roosts were located than did randomly selected points, regardless of stream class. / Graduation date: 1997

This thesis includes four separate studies. The first two studies assessed edge effects in a 700-year-old forest. After 20 years of exposure, epiphyte assemblages on the clearcut edge were similar to those of the forest interior, but there were some differences in vertical distribution patterns. Several species restricted to the upper canopy of the forest interior occurred farther down in the crowns of trees on the clearcut edge. Many species were associated with thick moss mats. Thalli of two cyanolichen species were reciprocally transplanted among four tree crowns. Lobaria oregana grew less on the clearcut edge than in the forest interior. Populations of Pseudocyphellaria rainierensis had acclimated to the edge environment. The third study evaluated whether these two species require old growth and/or thick, underlying moss mats to achieve normal rates of growth and mortality. Thalli were transplanted into tree crowns in 13 forest stands representing 4 age classes: old growth, mature, young, and recent clearcut. Wooden racks were used instead of trees in clearcuts. Half of the cyanolichen thalli were transplanted onto thick moss mats, half onto bare bark. Both species grew at least as well in the younger forests as they did in old growth, but growth rates were significantly lower in clearcuts. Mortality rates were very low in young, mature, and old-growth forests but high in clearcuts. P. rainierensis grew significantly better on moss than bare bark. The fourth study evaluated the long-term potential of live tree retention for cyanolichen conservation. Lichen litterfall was sampled in a natural, multiple-age stand containing remnant trees and regenerating forest. Two lichen species (L. oregana and Sphaerophorus globosus) were strongly associated with remnant trees. Biomass of both species was highest near remnant trees and was significantly higher within groves of remnant trees than at the edges of these groves or near isolated trees. Cyanolichen populations appear to have persisted on remnant trees since before the last fire. They are slowly recolonizing the regenerating forest. Retention of live trees, including hardwoods, combined with longer rotation periods, has great potential to maintain cyanolichens in managed forests. / Graduation date: 1996

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1986. / Bibliography: leaves 361-395. / Photocopy. / xviii, 395 leaves, bound ill. 29 cm