http://hdl.handle.net/1957/7867 Collection contains recent scholarly output of student majors in the Forest Science Department Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9462 Title: Cavity resources in Oregon white oak and Douglas-fir stands in the mid-Willamette Valley, Oregon <br/> <br/>Abstract: Previous studies of bird communities in the mid-Willamette Valley, Oregon, indicated that Oregon white oak (Ouercus garryana) stands supported more cavity-using bird species than sympatric stands of Douglas-fir (Pseudotsuga menziesii). Mature Oregon oak stands are being harvested and few are regenerating. I compared cavity availability for hole-using fauna among 10 types of stands in the mid-Willamette Valley and adjacent Coast Range foothills (6 Oregon white oak, 3 Douglas-fir and 1 mixed Oregon oak/Douglas-fir). Thirty stands (3/type of stand) were classified by their predominant tree species, average diameter class (20.0-to-34.9 cm, 35.0-to-49.9 cm, and 50.0+ cm at breast height) and area (groves <4 ha, stands >4 ha). Origin, location and estimated size were recorded for 735 cavities found in 3300 trees. Sixty-three percent of the trees examined were Oregon oak, but 93.7% of the cavities were in Oregon oak. Most cavities (70%) were products of decay following infection. Two-thirds of the cavities had entrance hole diameters between 2.5-to-5.0 cm. Groves of medium- and large- diameter oaks and stands of large-diameter oaks had the most cavities, Cavity availability was higher in the oak stands than in the Douglas-fir and mixed stands. Declines in densities of cavities through a progressive replacement of larger Oregon white oak by smaller, managed Douglas-fir will unquestionably reduce the abundance of cavities in the mid-Willamette Valley. Maintenance of existing oak stands and regeneration of Oregon oak in the mid-Willamette Valley may be desirable to maintain habitat for indigenous cavity-using fauna. <br/> <br/>Description: Graduation date: 1991; Presentation date: 1991-04-24 Tue, 23 Apr 1991 22:58:59 GMT http://hdl.handle.net/1957/9355 Title: Songbird populations of precommercially thinned and unthinned stands of ponderosa pine in east-central Washington <br/> <br/>Abstract: Populations of breeding birds and forest composition and structure were examined in preconimercially thinned and unthinned ponderosa pine (Pinus ponderosa Laws.) stands in east-central Washington. Stands were composed of predominantly ponderosa pine with a multi-aged structure made up of small even-aged clumps. Thinning reduced the density and foliage volume of small trees (< 24 cm) and created a substantial slash component. Shrub volume and herbaceous cover also were different between treatments but these differences were probably unrelated to the thinning. Differences in bird densities between thinned and unthinned areas could be directly or indirectly related to these vegetation differences. Total bird densities and avian community structure were similar for unthinned and thinned stands. However, there were differences in bird species composition. Precommercial thinning is likely to result in local increases in the abundance of some species and decreases for others. The avian community structure, however, is likely to be unaffected by precommercial thinning of multi-aged ponderosa pine. <br/> <br/>Description: Graduation date: 1983; Presentation date: 1983-04-28 Wed, 27 Apr 1983 22:58:59 GMT http://hdl.handle.net/1957/9240 Title: Height-related trends in structure and function of Douglas-fir foliage <br/> <br/>Abstract: This dissertation investigated the impacts of tree height upon a range of physiological and structural characteristics of Douglas-fir foliage; relationships between structural and functional trends with height; and compensatory mechanisms that mitigate height-related growth constraints. Height-related trends in foliar physiological and anatomical characteristics were examined both within trees as well as between trees of different heights. Emphasis was placed on discovering the mechanistic nature of the observed growth constraints and adaptive strategies. This research was conducted in the interest of enhancing our knowledge of the causes of age- and size-related decline in forest productivity. The research conducted for this dissertation explored several previously uninvestigated mechanisms for size-related reductions in forest productivity that are associated with tree foliar structure and function. Height-related trends in foliar turgor associated with the gravitational hydrostatic pressure gradient were identified as well as subsequent impacts on leaf and shoot morphology. Osmotic potential declined with height providing evidence of osmotic adjustment to offset the height-related decline in leaf turgor. This osmotic adjustment occurred only seasonally, and not during the spring when turgor maintenance is most important for leaf expansion. Gradients in leaf turgor were reflected in height-related trends in leaf and shoot morphology. Previous work has documented height-related trends in foliar morphological characteristics and earlier studies have examined osmotic adjustment as an adaptation to drought and salinity stress. Height-related trends in foliar morphological characteristics have typically been attributed to light gradients along vertical profiles. The work in this dissertation is the first to evaluate the effects of the gravitational component of water potential on the osmotic, morphological and growth characteristics of foliage along a height gradient in tall trees. Trends in leaf hydraulic efficiency and safety along a height gradient were examined, and correlations between changes in leaf hydraulic conductance (Kleaf) and changes in stomatal conductance (gs) were identified that provided evidence of a control mechanism for gs. A consistent relationship was discovered between changes in Kleaf and gs providing evidence that leaf tracheid embolism is associated with stomatal closure during periods of declining water availability. Hydraulic vulnerability curves of foliage collected at different heights indicated that increased height is correlated with reduced hydraulic efficiency and increased hydraulic safety. These opposing trends suggest the existence of a compensatory mechanism in foliage that functions to reduce hydraulic vulnerability at the expense of transport capacity. The research in this dissertation is the first to examine the dynamic relationships between leaf hydraulics and stomatal behavior in temperate conifers, and the first to examine how these characteristics are affected by tree height. Height-related trends in leaf xylem anatomical characteristics were examined and strong correlations were identified between these anatomical characteristics and the patterns of leaf hydraulic efficiency and safety that were observed in previous work for this dissertation. Theoretical estimates of leaf hydraulic efficiency (Kleaf-theoretical) based upon the Hagen-Pouseille equation and measured leaf tracheid anatomical characteristics were strongly correlated with laboratory measurements of Kleaf, providing further evidence of a causal relationship between height-related trends in both leaf tracheid anatomical properties and leaf hydraulic function. Earlier studies have documented connections between leaf anatomical characteristics and leaf physiological characteristics such as correlations between leaf architecture and gas exchange and leaf architecture and transport efficiency. The research in this dissertation however, is the first to examine the impact of tree height on leaf anatomical characteristics and associated shoot physiological properties. Trends in gas-exchange along a height gradient were identified, independent of the immediate effects of path length and gravitational resistance. Photosynthesis under ambient [CO2] declined with height in a manner that was consistent with height-related trends in mesophyll anatomy and independent of leaf nitrogen content. Analyses of mesophyll resistance from assimilation versus internal CO2 concentration (A-Ci) curves indicated that height-related trends in mesophyll resistance were correlated with trends in both photosynthesis and mesophyll anatomy along a height gradient. Analyses of integrated and instantaneous water use efficiency indicated that height-related trends in integrated water use efficiency are attributable to the effects of path length and gravity on stomatal behavior as opposed to a height-related trend in intrinsic foliar properties. The research in this dissertation is the first to isolate the influence of height-related trends in foliar structure on different gas exchange properties such as assimilation and mesophyll conductance, independent of the direct effects of vertical gradients in xylem tension on stomatal and photosynthetic physiology. <br/> <br/>Description: Graduation date: 2009 Tue, 15 Jul 2008 22:58:59 GMT http://hdl.handle.net/1957/9223 Title: Historical changes in anadromous fish habitat in the Upper Grande Ronde River, Oregon, 1941-1990 <br/> <br/>Abstract: The U.S. Bureau of Fisheries (now National Marine Fisheries Service) conducted stream habitat surveys in the Upper Grande Ronde River Basin in 1941. This survey was part of an extensive inventory of stream habitat conditions for anadromous salmonids (Oncorhynchus spp.) throughout the Columbia River Basin. The survey systematically inventoried 158 km of streams within the 3000 km2 watershed. Stream habitat was degraded from land-use activities (riparian timber harvest, splash dams, stream channelization, livestock grazing, and mining) prior to the 1941 survey. A 1990 resurvey determined how stream habitat conditions had continued to change. The historical survey and the 1990 resurvey inventoried streams according to pool and substrate characteristics. Pools were classified by size and depth criteria, while substrate was divided into size-classes. Losses in total pools/km (> 20m2 area and > 0.5 m depth) ranged from 43 to 83% (mean = 65%, 12.2 to 4.31km), while the loss in large pools/km (> 20m2 and > 1.0 m depth) ranged from 20 to 89% (mean = 68%, 6.2 to 2.0/1cm) for individual streams. The loss of variability in pool frequencies from 1941 to 1990 (total pools/km a2 = 43.9 to 2.8, large pools/km a2 = 23.2 to 3.2) demonstrates that stream channels have become less diverse. Classifying streams by reach types indicated that the decline in pool frequencies was not significantly related to geomorphic constraints. Substrate composition appears to have shifted toward smaller size-classes, with an increase in fine sediments (< 6mm) in the headwaters. Livestock grazing declined 78% (229,000 to 51,000 aum) from 1911 to 1990, while annual timber harvest increased 172% (36 to 98 mmbf) from the pre-survey period (1896-1940) to the post-survey period (1940-1990). Road densities have increased concurrent with timber harvest, currently averaging 4 miles/mile2. Base discharge has increased 51% (18.5 to 28.0 cfs), while there has been a 27% decrease in annual precipitation (22.0" to 16.0") and snowpack (April 1 water equivalent) (15.0" to 10.5") from 1941 to 1990. In an era of presumably improving management (1941-1990), large-scale losses in the fish habitat necessary for the continued viability of resident and anadromous fish populations continued to occur. <br/> <br/>Description: Graduation date: 1992; Presentation date: 1992-02-18 Mon, 17 Feb 1992 22:58:59 GMT