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/1957/9025 Title: Patterns of crown damage within a large wildfire in the Klamath-Siskiyou bioregion <br/> <br/>Abstract: The 2002 Biscuit Fire burned through more than 200,000 ha of mixed conifer/ evergreen hardwood forests in southwestern Oregon and northwestern California. The remarkable size of the fire and the diversity of conditions through which it burned provided an opportunity to analyze the correlates of burn severity across vegetation types and disturbance histories and to describe the weather, topographical, and fuel conditions that gave rise to the mosaic of crown damage. In chapter two, I focused on a region that had burned previously by the 1987 Silver Fire then was subject, in part, to salvage-logging and conifer planting before being reburned by the Biscuit Fire. I used the Landsat-based differenced normalized burn ratio (dNBR) to quantify severity in both fires and took a hypothesis-testing approach to answering two questions: First, was severity in the Biscuit Fire associated with severity in the Silver Fire in unmanaged areas? And second, did areas that were salvaged-logged and planted with conifers after the Silver Fire burn more or less severely in the Biscuit Fire than comparable unmanaged areas? I found that areas that burned severely in 1987 tended to re-burn at high severity in 2002, after controlling for the influence of several topographical and biophysical covariates. Areas unaffected by the initial fire tended to burn at the lowest severities in 2002. In addition, areas that were salvage-logged and planted after the initial fire burned more severely than comparable unmanaged areas, suggesting that post-fire logging and planting did not reduce future fire severity as had been suggested by some. In chapter three, I again focused on the twice-burned landscape, but this time I used a temporal sequence of digital aerial photography plots (6.25 ha) to measure changes in shrub-stratum, hardwood, and conifer cover. I estimated the strength and nature of relationships between crown damage and several fuel, topographical, weather, and management variables. Median crown damage, including damage to the shrub-stratum, on unmanaged plots was 63% after the Biscuit Fire and was most strongly related to damage in the Silver Fire. Plots that burned severely in the Silver Fire and had succeeded to a mix of shrubs and tree regeneration experienced high levels of Biscuit Fire damage. Plots dominated by large conifer cover after the Silver Fire had the lowest levels of Biscuit Fire canopy damage. Median crown damage was 39% for conifer cover and 85% for hardwood cover, and was most strongly related to daily average temperature and "burn period," an index of fire weather and fire suppression effort. Damage in the tree-stratum was largely independent of Silver Fire severity. Plots that had experienced stand replacing fire in 1987 and then were logged and planted with conifers had median crown damage of 100%. Plots that experienced a stand replacing fire but were unmanaged had median crown damage of 95%. The managed areas were at higher topographical positions and had greater total pre-fire cover, which may explain the small difference. These results suggest that in productive, fire-prone landscapes, the patch mosaic of young regenerating forest created by mixed-severity fire can structure the severity pattern of future wildfires occurring at short intervals and support the previous studies findings that post-fire logging and planting did not reduce fire severity. In Chapter four, I expanded my focus to include the entire region burned by the Biscuit Fire and again used digital aerial photos taken before and after the fire to interpret patterns of crown damage and relate them to several fuel, topographical, weather, and management variables. Ninety-eight percent of plots experienced some level of crown damage, but only 10% experienced complete crown damage. The median level of crown damage on unmanaged plots was 74%. Median conifer damage was 52%. The most important predictors of total crown damage were the percentage of pre-fire shrub-stratum vegetation cover and average daily temperature. The most important predictors of conifer damage were average daily temperature and burn period. Increasing levels of shrub-stratum cover were associated with increasing levels of conifer damage and hardwood damage. Large conifers had 32% median crown damage while small conifers had 62% median crown damage. Owing largely to widespread shrub-stratum cover, low-productivity ultramafic soils had 92% median crown damage compared to 59% on non-ultramafic sites. Patterns of damage were similar within the area that burned previously in the 1987 Silver Fire and edaphically comparable areas without a recently history of fire. Median crown damage in conifer plantations was 89% and plantation age was, by far, the most important predictor of the level of damage. Plantations under 20 years old experienced the highest rates of damage. I conclude that weather and vegetation conditions--not topography--were the primary determinants of Biscuit Fire crown damage. These findings suggest that in productive fire-prone ecosystems, fuel treatments that open tree canopies and stimulate shrub-stratum development may be counterproductive. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8987 Title: Sitka spruce and western hemlock regeneration after selective harvesting, Tongass National Forest, southeast Alaska <br/> <br/>Abstract: The objectives of this study were to determine the species composition and density of natural conifer regeneration following selective logging in southeast Alaska. Therefore, we quantified the density and size of new cohort spruce and hemlock and current seedling bank in 17 selectively logged stands. All stands were in mixed hemlock-spruce forests that were logged between 1900 and 1984, located at or near sea level, and not managed after this first logging. New cohorts included trees that germinated after logging plus advanced regeneration that was shorter than 1.4 in (standard height for diameter measurement - diameter at breast height, d.b.h.) at time of logging. With the exception of one tree, we found new cohort spruce only in plots that had been logged. New cohort hemlock were common in both logged and unlogged plots. New cohort spruce basal area ranged from 2 to 19 m2 / ha. Individuals were as large as 104 cm d.b.h. but generally ranged between 19 and 55 cm d.b.h. New cohort hemlock basal area ranged from less than 1 to 32 m2 / ha. The largest tree was 102 cm d.b.h. but most ranged from 11 to 51 cm d.b.h. The absence of new spruce in unlogged plots strongly suggests that disturbance favors spruce recruitment. The seedling bank included trees 0 to 3 m tall and less than 2.5 cm d.b.h. These seedlings became established after logging. The seedling bank density of both species was high; spruce ranged from 3,000 to 114,000 and hemlock ranged from 47,000 to 723,000 seedlings / ha. Rooting substrate (logs or undisturbed forest floor) was significant for both species (spruce p = 0.05, hemlock p = 0.0001). There were always more seedlings on logs than on undisturbed forest floor. By leaving spruce seed trees, judicious soil disturbance, planned entries to regulate overstory density and possibly planting spruce seedlings where the seed source is poor, we believe spruce can be regenerated in these systems. Pre-commercial thinning may be necessary to keep vigorously growing cohorts of spruce and hemlock in these stands, just as it is necessary in young stands regenerated after clearcutting. <br/> <br/>Description: Graduation date: 1998 http://hdl.handle.net/1957/8956 Title: Stand development after 20-years of growth in Douglas-fir and red alder mixtures <br/> <br/>Abstract: This study examines the long-term role of interference on stand development of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and red alder (Alnus rubra Bong.) planted mixtures in the Central Cascades of Oregon, USA. The two species are common associates in naturally regenerated and planted conifer stands in the Pacific Northwest. Due to red alder's rapid height growth, Douglas-fir is often impeded when in the presence of red alder. However, because of red alder's ability to fix nitrogen and increase soil nutrient cycling rates Douglas-fir development can potentially be enhanced when in red alder presence. The relationship between current stand structure, tree mortality, tree size and varying mixtures of species proportions were examined in this study. Treatments included four proportions of red alder either planted simultaneously with the Douglas-fir or delayed 5-years after initial Douglas-fir planting. The objectives of this study were to determine if species mixtures were capable of a greater yield when compared to monocultures and then to determine which form of interference was taking place within and between species. A long-term replacement series study was established in 1986 to understand the role of interference on two commercially valuable species. Six treatments of each planting time were created with the following proportions (Douglas-fir/red alder, respectively): 1.0/0.0, 0.9/0.1, 0.7/0.3, 0.5/0.5, 0.25/0.75, 0.0/1.0. Each treatment was replicated three times in a randomized complete-block design. Measurement of diameter at breast height (cm) of each stem, total height (m), and number of live/dead stems were determined in 1988-1991, 1993, 1995, 1998 and 2007. Yields of both the 0.5/0.5 simultaneous and delayed treatment mixtures were notably higher than the monocultures. Per-tree basal area, height, and survival decreased for both the Douglas-fir and red alder as the relative density (proportion) of red alder increased in the simultaneously planted mixtures. In the delayed mixtures, Douglas-fir per-tree basal area, height, and survival increased as red alder density increased. Red alder development indicated only minor decreases in survival as its density increased in the delayed treatment mixtures. Competition was the dominant mechanism of stand development for all treatments. In the simultaneously planted treatments the Douglas-fir was driven most by interspecific competition, while red alder development exhibited trends for intraspecific competition. In the delayed planted treatments both species experienced intraspecific competition, although this effect was minor for red alder. These results support the competitive effects of red alder on Douglas-fir and itself when seedlings are established at the same time. The delayed treatments however, showed the importance of density on individual tree development over time. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8936 Title: The phytotoxic effects of herbicide and adjuvant application by physiological timing on the woody shrub salal (Gaultheria shallon) <br/> <br/>Abstract: Salal is plant species that is native to forestland throughout the PNW and northern California that has been identified as a competitor to early crop tree development. This study consisted of a field and a radioisotope laboratory study to test four commonly used herbicides on salal (imazapyr, triclopyr, glyphosate, and picloram) under various phenological states, using three adjuvants, and two herbicide application rates. In the field study, no herbicide or adjuvant was significantly more efficacious than the others tested. Spring treatments were more efficacious than faIl treatments (α ≤ 0.05) and high application rates were more efficacious than low rates (α ≤ 0.05). Only imazapyr exhibited significant (α ≤ 0.05 ) interaction with the treatments factors: adjuvant by season and adjuvant by herbicide rate. The radioisotope study investigated the absorption and translocation patterns ofthe herbicides within salal when applied at different phenological periods, and in formulation with surfactant products. The most efficacious products tested in this study were imazapyr (Chopper) and triclopyr (Triclopyr). These chemicals delivered the highest concentrations, by percent, ofherbicide into leaf structures and within biomass material. The phenological period that treatments were delivered was generaIly a significant factor. Spring (active foliar) treatments aided in leaf absorption and faIl (dormant) treatments incurred greater concentration of ¹⁴C-labeled material into below-ground structures. Surfactants generally aided the absorption ofherbicide. In particular methylated seed oil (MSO) was the most efficacious surfactant among all products tested. It is hypothesized that MSO aided cuticle penetration and leafsurface dispersion of herbicides like imazapyr and triclopyr than would be possible with a water carrier alone. <br/> <br/>Description: Graduation date: 2009