Soil organic matter (SOM) is the terrestrial biosphere's largest pool of organic carbon (C) and is an integral part of C cycling globally. Soil organic matter composition typically can be traced directly back to the type of detrital inputs; however, the stabilization of SOM results as a combination of chemical recalcitrance, protection from microbial decomposition within soil structure, and organo-mineral interactions. A long-term manipulative field experiment, the Detrital Input and Removal Treatment (DIRT) Project, was established to examine effects of altering detrital inputs (above- vs. below-ground source, C and nitrogen (N) quantity, and chemical quality) on the stabilization and retention of SOM. Surface mineral soil was collected from two DIRT sites, Bousson (a deciduous site in western Pennsylvania) and H.J. Andrews (a coniferous site in the Oregon Cascade Mountains), to examine the influence of altering detrital inputs on decomposability and mean residence time of soil organic matter and different organic matter fractions. Soil organic matter was physically separated into light fraction (LF) and heavy fraction (HF) organic matter, by density fractionation in 1.6 g mL⁻¹ sodium polytungstate (SPT). Density fractionation in SPT resulted in the mobilization and loss of ~25% of total soil organic C and N during the physical separation and rinsing of fractions during recovery, which was also the most easily decomposed organic matter present in the bulk soil. At H.J. Andrews, this mobilized organic matter had a short mean residence time (MRT), indicating that it originated from fresh detrital inputs. In contrast, at Bousson, the organic matter mobilized had a long MRT, indicating that it originated from organic matter that had already been stabilized in the soil. Mean residence times of LF from Bousson varied widely, ~3 y from doubled litter and control plots and 78-185 y for litter removal plots, while MRT of HF was ~250 y and has not yet been affected by litter manipulations. Results from long term incubation of LF and HF material supported these estimates; respiration was greatest from LF of doubled litter and control plots and least from HF of litter removal plots. In contrast, MRT estimated for LF and HF organic matter from H.J. Andrews were similar to each other (~100 y) and were not affected by litter manipulation. These estimates were also supported by the incubation results; there was not a difference in cumulative respiration between detrital treatments or density fractions. The results from the coniferous site may be due to a legacy of historically large inputs of coarse woody debris on the LF and it may be decades before the signal of detrital manipulations can be measured. Alternatively, these highly andic soils may be accumulating C rapidly, yielding young HF ages and C that does not differ substantially in lability from coniferous litter-derived LF. The DIRT Project was intended to follow changes in soil organic matter over decades to centuries. As expected, manipulation of detrital inputs has influenced the lability and mean residence time of the light fraction before the heavy fraction organic matter; however, it will be on much more lengthy time scales that clear differences in organic matter stabilization in response to the alteration of detrital inputs will emerge. Soil CO₂ efflux is a compilation of CO₂ from many sources, including root respiration and the decomposition of different organic matter fractions, roots, and exudates. If the sources of CO₂ have different isotopic signatures, the isotope analysis of CO₂ efflux may reveal the dominant sources within the soil profile. In a short incubation experiment of density fractions from both sites, respired CO₂ reflected the isotopic signature of the organic matter fraction after 30 days, but was more enriched in ¹³C. Initially CO₂ was isotopically depleted in ¹³C relative to the organic matter fraction and the period of depletion related to the amount of easily degraded organic matter present at H.J. Andrews only. / Graduation date: 2006

In recent years considerable interest has been shown in the diversity of ammonia-oxidizing bacteria in soil communities. The majority of the research has been carried out in Northern Europe where soils have received high atmospheric inputs of nitrogen over the past two centuries. In contrast, although much work has been conducted on nitrogen cycling processes in nitrogen limited forest ecosystems in western North America, no studies have examined the characteristics of ammonia-oxidizing communities in those environments. I was interested in measuring nitrification potential along a high-elevation temperate meadow-to-forest gradient, and characterizing the ammonia-oxidizing communities along that gradient using both molecular and culturing methods. Two experimental sites (Lookout and Carpenter) were chosen in the H.J. Andrews Experimental Forest, located in the western Cascade Range of Oregon, at elevations of approximately 1500 meters. Although nitrification potential rates (NPRs) between sites were not significantly different (P=0.544), variation was observed both within and between sites for specific vegetation types. NPRs were significantly lower in forest (F) soil samples than in meadow (M) soil samples, averaging 5 and 2% of meadow NPRs at Lookout and Carpenter, respectively. In meadow soil samples, most probable number (MPN) population densities of ammonia-oxidizers ranged from 0.6 to 2.6 x 10⁴ cells gram⁻¹ of oven dry soil and 0.9 x 10³ to 1.1 x 10⁵ cells g⁻¹ OD soil at Lookout and Carpenter, respectively. In forest soil samples, population densities ranged from undetectable to 1.1 x 10⁴ cells g⁻¹ OD soil, and 0.9 x 10² to 2.3 x 10³ cells g⁻¹ OD soil at Lookout and Carpenter, respectively. Microbial community DNA was amplified using primers to the ammonia monooxygenase subunit A. Terminal restriction fragments polymorphism analysis with three different restriction enzymes (CfoI, TaqI, and AluI) revealed community profiles dominated by Nitrosospira species. One fragment from CfoI (66 bp) and one fragment from AluI (392-bp) were prominent in 47 soil samples from both sites, and represented between 32 to 100% of the Genescan fragment analyses of PCR products. A full length fragment from AluI digests (491-bp), and three fragments from CfoI (68, 100, and 135- bp) were found sporadically in fewer soil sample T-RFLPs, and within those samples represented smaller percentages of total peak areas. The CfoI 135-bp fragment length was associated primarily with M and meadow/forest (M/F) soils where it was observed in approximately 58 and 100% of the respective transect locations. Eight isolates recovered from soil samples were analyzed using the same molecular methods as the field samples. The T-RFLP patterns of the isolates corresponded with many of those found in the community fingerprints. Four unique amoA sequences were identified among these isolates, including one that possessed the dominant T-RFLP amoA fingerprint in soil samples. This sequence shared 99.8% similarity with Nitrosospira sp. Ka4, a cluster 4 ammonia oxidizer isolated in Norway. Sequence analysis phylogenetically associated the other three isolates (with unique amoA sequences) near Nitrosospira sp. Nsp 1 and Nitrosospira briensis, both cluster 3 ammonia oxidizers. Cloning and sequencing of soil DNA confirmed that ammonia oxidizers with these amoA sequences were present in the soil samples. Two additional amoA sequences were identified in clones that were 95% similar and paraphylogenetically positioned between representatives of clusters 3 and 4. So far, these sequences have not been found in any of the isolates analyzed. / Graduation date: 2003

Graduation date: 2002

A biological inventory of the butterflies of the H. J. Andrews Experimental Forest [HJA] in Linn/Lane County, Oregon was conducted during 1994 and 1995. It was the first comprehensive survey of HJA butterflies for the site and serves as a baseline for future butterfly research. A detailed ecological account is provided for each species documented during this and previous studies from the HJA. Patterns of butterfly richness and abundance are addressed both temporally and spatially. Within-year and between year differences in butterfly richness and abundance are explained. Butterfly richness and abundance were compared between forest, clear-cut, and meadow habitats, as well as along the roads within these habitats. Butterfly richness and abundance comparisons were also made between local butterfly hotspots and immediately adjacent areas. Lastly, the HJA butterfly fauna was compared to those of five other Oregon sites to put it into a regional perspective. Seventy-two species were recorded during this two year period and increased the total documented butterfly fauna of the HJA to seventy-nine species. Butterfly species richness was high from June through early August. Butterfly abundance increased gradually over the season and peaked in early August. Each butterfly species displayed one of four patterns of combined relative abundance and distribution: common and widespread, rare and local, common only at low elevations or common only at high elevations. The results of standardized butterfly counts suggested that subalpine meadows were much higher than clear-cuts or forests in butterfly richness and abundance, and that roads served to increase butterfly richness and abundance on a local scale in most cases. Butterfly hotspots on the HJA appear as relatively small areas of high butterfly richness and abundance and have a correspondingly high number of plant species when compared to adjacent areas. With virtually one-half of all butterfly species known for the state of Oregon, the HJA ranks among the most species-rich locations for its size within the state. This diversity originates from several biogeographical regions of origin, as defined within this study. A total of 31 HJA species have a generalized Western North American distribution, but several other biogeographical regions are also well represented. Some butterfly species appear to be at or near their geographical limits on the HJA. The assemblage of HJA butterfly species is virtually inclusive of those from Mary's Peak and McDonald Forest in northwestern Oregon, whereas it differs by 30% or more from the more biogeographically distinct faunas of Crater Lake National Park, Mount Ashland and Steens Mountain. Future butterfly work on the HJA is recommended. Oregon butterfly distribution maps suggest that several additional butterfly species should be found there. More biogeographical analyses combined with long term monitoring of HJA butterflies could help to both predict and document changes in the Pacific Northwest butterfly fauna due to human disturbance and global climate change. / Graduation date: 2004

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 131-140). Also available on the World Wide Web.

Thesis (M.A.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains v, 32 p. : ill. (some col.), maps Includes abstract. Includes bibliographical references (p. 31-32).

No description available.

A fire history study conducted for the Utah State University (USU) Experimental Forest using three distinct periods of fire frequency, historic (1700-1855), settlement (1856-1909), and suppression (1910-present), showed a decreased mean fire interval (MFI) during the settlement period and a greatly increased MFI during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of the nearby Cache Valley, located 40 kilometers to the west. The interaction of settlers with the resource during logging and livestock grazing activities encouraged the high MFI and created the vegetal mosaic now observed on the study area. The elevation of the study area, 2377 m to 2651 m, places the site in the Engelmann spruce-subalpine fir zone (Picea engelmannii, Parry ex Engelm.-Abies lasiocarpa (Engelm. ex. Wats)). The suppression era and its corresponding increase in MFI has permitted the advancement of tolerant species in the understory of the intoleran lodgepole pine (Pinus contorta var. latifolia (Engelm. ex. Wats)) and aspen (Populus tremuloides Michx.). Continue suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experienced the lowest MFI during the settlement period, to be further invaded by tolerant species, leading to a decrease in stand diversity and more intense fires when they do occur.

This thesis contributes to modeling the dynamics of forest community response to environmental gradients and disturbances over a mountain landscape. A gap model (FACET) was parameterized for species of various forest types (Tabonuco, Colorado, Dwarf and Palm), for many terrain conditions and was modified and extended to include species response to excess soil moisture and hurricanes. Landscape cover types were defined by dominance of species of each forest type and canopy height. Parameters of the landscape model (MOSAIC) were calculated from multiple runs of FACET. These runs were determined by combining terrain variables (elevation and soil) and hurricane risk. MOSAIC runs were analyzed for distribution patterns. Geographic Information Systems software was used to process terrain variables, hurricane risk and MOSAIC model output.

No description available.