http://hdl.handle.net/1957/7887 Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9114 Title: Ecological effects of spring and fall prescribed burning on basin big sagebrush : Idaho fescue--bluebunch wheatgrass communities <br/> <br/>Abstract: The vegetation response of spring and fall prescribed fires in basin big sagebrush (Artemisia tridentata subsp. tridentata Nutt.)/Idaho fescue (Festuca idahoensis Elmer)--bluebunch wheatgrass (Agropyron spicatum Pursh. (Scribn. & Smith)) communities was measured at the John Day Fossil Beds National Monument in eastern Oregon. Objectives of the study were to quantify fuel loads, environmental conditions, fire behavior and vegetation response corresponding to these two fire treatments. Pretreatment fuel loads in the experimental units ranged from 5 to 12 Mg/ha, with the fall treatment units averaging 10.5 Mg/ha, and the spring units averaging 6.2 Mg/ha. Both treatments contained large amounts (> 3 Mg/ha) of herbaceous fuels. Moisture content of grass and herb fuels were significantly greater in the spring burned units. This is believed to be largely responsible for the less severe fire behavior observed in the spring burn treatment. Flame lengths averaged 4.2 m in fall burns, compared to a mean of 1.7 m in the spring plots. Similarly, rate of spread was significantly greater in the fall units, averaging 1.6 m/s, compared to 0.2 m/s in the spring treatment. Fireline Intensity was seven times greater, and total energy release was twice was great in the fall burns. Neither burn treatment resulted in significant mortality of bluebunch wheatgrass, but fall burning did cause significant mortality of Idaho fescue, where 20% of the population was killed. Fall burning stimulated tillering of bluebunch wheatgrass, as the average basal area increased both one and two years following burning. Average basal area per plant of Idaho fescue was reduced by 23% the first year following fall burning; however plants recovered to 90% of their preburn size by the second post-fire year. Spring burning resulted in no significant change in basal area of either species. Fall burning significantly reduced the number of flowering culms on bluebunch wheatgrass plants the first post-fire year (from 36 to 12 per plant); however, by the second post-fire year, number of flowering culms was significantly greater than either pre-burn or control levels (59/plant). Similarly, fall burning of Idaho fescue averaged 60% more flowering culms per plant as adjacent controls (11 compared to 7/plant). Spring burning reduced flowering of both species the first year following burning. Both burn treatments reduced the frequency of annual grasses, while causing no change in frequency of perennial grasses. Annual forbs increased in abundance following both burn treatments. Fire resulted in replacement of exotic annual grasses with annual forb species. Dominant perennial forbs responded variably in both burn treatments, as well as control plots. Frequency of sagebrush increased significantly in both spring and control experimental units in 1989 (one year after spring burning), while fall burns (two years posttreatment) demonstrated no such increase. Apparently, factors relating to the greater fire severity (e.g. consumption, total energy) in the fall burns reduced the rate and degree of reinvasion by sagebrush in the fall burn plots. Densities of annual grasses and woody species were significantly reduced by both burn treatments. Cheatgrass (Bromus tectorum L.) density before burning averaged 446 and 552/m2 in fall and spring units, respectively, as compared to 10 and 85/m2, respectively, the first post-fire year. Big sagebrush was completely eliminated by the fall fire, while spring burning resulted in an 84% decrease in density. Density of western juniper (Juniperus occidentalls Hook.) was reduced 100% by both burn treatments. Species diversity, as measured by the Shannon-Weaver Index (H'), was reduced by fall burning from 2.69 before treatment to 2.53 the first year following burning , but increased to 2.81 second post-fire year. Control plots behaved similarly, although changes were not as great. Changes were most evident in terms of rare species, many of which were not present prior to burning. Spring burning resulted in an no change in species diversity the first year after burning, although, species richness increased from 34 to 41. Both burn treatments appeared effective at changing stand structure to that of a dominance by native perrenial grasses and forbs. The reduced competition from woody plants has, and presumably will continue to favor surviving herbaceous plants. Overall fire effects appear to fit into land management policy of the National Park Service in regard to maintaining wildlands in a pristine state. Specifically, both spring and fall burning reduced fuel hazard, and increased the relative abundance of native species, indicating that prescribed burning may be an effective land management tool for the National Park Service and others managing similar rangelands. <br/> <br/>Description: Graduation date: 1990; Presentation date: 1990-03-01 http://hdl.handle.net/1957/8922 Title: Winterfat seed viability and dormant season livestock grazing <br/> <br/>Abstract: Krascheninnikovia lanata (winterfat) is a valuable forage species with an average of 10% crude protein during winter when there are few nutritious options for livestock and wildlife. However, excessive grazing throughout the west has negatively impacted survival of winterfat stands. We hypothesized that four years rest from dormant season livestock grazing, along with rest from antelope and rabbit browse, would result in greater seed viability and aboveground biomass relative to grazed plots. In locations across the Catlow Valley, Oregon with winterfat communities, two 40 x 40 m plots, a control and an exclosure, were established at each of 15 locations divided among three pastures: north, middle and south. The control plot could be grazed by livestock and wildlife in all seasons (although cattle were only in the study area during the dormant season). The second plot at each location was a large animal exclosure that prevented grazing by cattle and antelope. At four locations a cattle/antelope/rabbit exclosure was also installed. This total of 34 plots was used to test the effects of location and type of use on winterfat seed viability and aboveground plant biomass. Four years rest from dormant season grazing did not affect the viability of winterfat seed or the levels of aboveground winterfat biomass; however, location across the study area did affect the levels of winterfat aboveground biomass. There was significant variation in the data attributable to unknown factors but represented by the influence that pasture location had on seed state (viable, dead and empty) and winterfat plant biomass. In the most productive locations, increases in winterfat aboveground biomass were correlated with increases in seed viability and decreases in density of winterfat m² while increases in winterfat seed viability were correlated with decreases in the percentage of empty seed. In the locations with the highest levels of dead seed, increases in dead seed were correlated with increases in winterfat density m² and decreases in empty winterfat seed. Plants in the cattle/antelope/rabbit exclosures had the highest winterfat density, the lowest plant biomass, lower levels of empty seed and the highest level of dead seed, the reverse of the most viable plots in the study area. From observation, these plants have a greater amount of woody base growth from prior years and appear more decadent. Further research is needed to see if winterfat seed viability and biomass production is associated with some level of browse. Nuttall's saltbush is the dominant shrub on the site, and its increase is correlated with increases in winterfat aboveground biomass and decreases in the level of dead winterfat seed. These results suggest that resources which vary by pasture location such as precipitation, soil nutrients, texture, or moisture holding capacity determined levels of winterfat aboveground plant biomass, winterfat seed state, and the density of Nuttall's saltbush and that on high resource sites, winterfat allocates resources to existing plants in rather than creating the new individuals The lack of response to four years rest from dormant season grazing, the low levels of viable seed, the low density of winterfat, and the encroachment of Nuttall's saltbush all suggest reduced vigor of winterfat in this study area. One possible explanation is that, since recovery toward a later successional stage would be expected with reduced grazing pressure (Dyksterhuis 1949), these arid lands are significantly degraded by stress or disturbance (Westoby et al. 1989; Laycock 1991) and that recovery is no longer possible without significant intervention. This suggests that the study area has crossed an ecological threshold. An alternate possibility is that since recruitment of winterfat is episodic and driven by precipitation events, climatic fluctuations may have prevented the sequence of good precipitation years needed for stand maintaining winterfat recruitment (Pechanec 1964). Further study is needed to evaluate these possibilities. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/8756 Title: Woody riparian species patterns along northeast Oregon mountainous streams and the relationship to riparian capability <br/> <br/>Abstract: Woody riparian vegetation is an essential component of riparian ecosystems, responsible in part for the maintenance of functional ecological processes. The plant community composition and distribution provide an indication of the underlying mosaic of environmental attributes and processes. Restoration and management of riparian communities have been hindered by the lack of measurable criteria for the assessment of a riparian systems modified by human imposed infrastructures. The woody vegetation community offered a quantifiable indicator of the underlying mosaic of environmental, physical, and hydrological attributes, while allowing the investigation of the concept of riparian potential versus riparian capability. The examination of riparian condition was measured through the determination of species-environmental relationships along three mountainous channels in northeast Oregon. The physical and environmental attributes of channel morphology, hydrology, understory community composition, surface particle characteristics, and microclimate variables were quantified and analyzed in relation to the woody vegetation composition and distribution across the three separate streams and within flood-frequency elevation zones. The second component of the study evaluated and described methods for quantifying the concept of riparian capability, based on the measured species-environmental relationships and channel morphology. The evaluation of condition was measured against the reference baseline of Rosgen hierarchical classification and regional hydraulic geometry curves. Multivariate analyses indicated that vegetation transects grouped by stream and vegetation belt transects weakly grouped by flood zone, based on the species composition quantified within the vegetation transects and flood zones. Secondly, channel geometry, canopy cover, air temperature, channel particle size, understory composition attributes, and flood zone distance were found to be overall gradients, which described the variation in species composition across the three streams in northeast Oregon. Direct individual species-environmental relationship conclusions were weak due to the close clustering of species and multiple physical and environmental gradients. Riparian condition at the Grande Ronde River and North Fork Catherine Creek was determined to be functioning at riparian capability. Channel geometry measurements at the two stream reaches aligned with Rosgen stream type criteria and regional hydrologic curves, while species composition represented characteristics of potential natural communities. Meadow Creek was concluded to have departed from the highest attainable condition, thus riparian condition was less than capability. The results suggested that woody riparian vegetation response was a function the physical sttributes: channel morphological widths, bankfull, floodprone, 25-year flood width, valley width, channel sinuosity, and channel slope. Environmental attributes, floodplain canopy cover, air temperature, and understory composition, were further factors that influenced the woody riparian vegetation community variation. The results also suggested species richness and diversity were associated with specific physical and environmental attributes. Finally, the results provided the determination of riparian capability along montane streams in northeast Oregon and criteria acceptable for the determination of riparian capability. These criteria included the physical channel measurements assessed against Rosgen hierarchiecal classification and regional channel geometry curves; and woody vegetation presence and distribution assessed against potential natural community plant associations. Further research should be done across a variety of riparian systems to determine both indicator species and reference values for the physical and environmental attributes that could be utilized for the assessment of riparian capability. <br/> <br/>Description: Graduation date: 2008 http://hdl.handle.net/1957/8588 Title: Watershed response to western juniper control <br/> <br/>Abstract: Western juniper (Juniperus occidentalis) encroachment has been associated with increased soil loss and reduced infiltration resulting in the loss of native herbaceous plant communities and the bird and animal species that rely on them. Hydrologically, however, change in water yield has been linked with the amount of annual precipitation a site received. Studies published in the 1970’s and 1980’s, suggest that a minimum 4500 mm (18 inches) of annual precipitation was necessary before an increase in water yield manifested itself following vegetation manipulation. In 1993, a paired watershed study was initiated in the Camp Creek drainage, a tributary of the Crooked River of central Oregon, to evaluate the impacts of cutting western juniper on the hydrologic function of those sites. The study involved a paired watershed approach using watersheds of approximately 110 hectares (270 acres) each to evaluate changes in a system’s water budget following the reduction of western juniper. The 30 year average annual precipitation for the area is 3500 mm (13.75) and during the study period, annual precipitation ranged from 80 percent to 129 percent of average. In 2005, following 12 years of pretreatment monitoring in the 2 watersheds (Mays and Jensen) all post-European aged juniper (juniper < 140 years of age) were cut from the treatment watershed (Mays). Analysis indicated that juniper reduction significantly increased late season spring flow by 225 percent (alpha > .05), increased days of recorded ground water by an average of 41 days (alpha > .05) and increased the relative availability of late season soil moisture at soil depths of .76 m (27 inches) (alpha > 0.1). Ephemeral channel flow did not show a predictable trend during 2 years of post treatment measurements. Channel flow is dependent on spring snow melt and severe summer thunderstorm activity. When winter soils were greater than 0 degrees Celsius (32 degrees F), the source of channel flow in Mays was observed to be seepage from the channel banks. Channel flow in Jensen appeared to be a result of rock forcing subsurface flows to the surface. Vegetative responses showed significant increases in perennial forb canopy cover (alpha > .01) and annual forb and annual grass basal cover (alpha > .05). Increases were also found in reduction of percent bare ground and increase in shrub cover, but were not significant. A statistically insignificant decrease in perennial grass cover was noted in the treated watershed however a large amount of reproductive culms were noted in the treated watershed in 2007 compared to the control watershed. Hillslope erosion and channel morphology showed no predictable trend following treatment. Inherent differences in channel morphology between the two watershed prior to treatment existed. This difference may be a product of the two channels being at different evolutionary or successional stages relative to each other and thus indicating that channel recovery would be different for each watershed. The Camp Creek project illustrated that for this system, managing vegetation for water yield may be obtainable at a much lower precipitation threshold than what was previously reported in the literature. <br/> <br/>Description: Graduation date: 2008