http://hdl.handle.net/1957/7888 Collection contains recent scholarly output of student majors in the Department of Rangeland Ecology and Management. Search the Channel search http://ir.library.oregonstate.edu/jspui/simple-search http://hdl.handle.net/1957/12102 Title: Vegetation and soil response to tree removal methods in invasive western juniper woodlands<br/><br/>Authors: O'Connor, Casey A.<br/><br/>Abstract: On piñon-juniper encroached sites that lack the understory fuels to carry a prescribed fire, treatment options are limited to mechanical methods. Cutting with chainsaws and leaving the trees on site has been the primary treatment method for such sites, however this method creates a potential fire hazard, particularly in the first 2-3 years when needles remain suspended on downed trees. Follow-up treatments to remove juniper fuels, such as broadcast burning downed trees or moving slash into piles with machinery followed by burning are becoming more common practices on private and public lands. There is limited information on the impacts of mechanical and fire treatments on herbaceous recovery and impacts to soil nutrients and characteristics. It is important to evaluate these treatments to provide resource managers with ecological information to assist in developing appropriate fuel reduction measures. This study sampled herbaceous vegetation andsoil attributes of three common mechanical treatments used to treat invasive western juniper (Juniperus occidentalis var. occidentalis Vasek) woodlands: Cut & Leave, Cut & Burn, and Pile & Burn. Sampling consisted of cover and density of herbaceous species and life forms (groups of species that function similarly), as well as total ground cover, and soil attributes including: carbon (C), nitrogen (N), carbon:nitrogen ratio (C:N), phosphorus (P), potassium (K), sulfate-sulfur (SO4-), calcium(Ca), magnesium (Mg), organic matter (OM~loss on ignition), cation exchange capacity (CEC), and power of hydrogen (pH). A randomized complete block experimental design (RCBD) was used with five 1-hectare blocks and three treatment plots per block (with piling plots being ½ hectare in size, and the other two treatment plots each ¼ hectare in size). Within each treatment plot, herbaceous vegetation sampling was stratified between three microsites: the slash microsite (beneath the three slash treatments; cut trees, burned trees, and burned piles), in the litter deposition microsite (litter zone around the stump) and the interspace microsite (between trees). Soil attributes were only sampled in the slash and interspace microsites, at two depths (0-4cm and 0-25cm). Each microsite within each plot was sampled by 40, 0.2m2 herbaceous frames and three composited soil samples from each depth. Mechanical treatments were completed in the fall of 2005 and prescribed fire treatments were completed in the fall of 2006. Treatment analysis compared pre and post treatment herbaceous data from 2005 and 2007, and soil attribute data from 2006 and 2007. Bare ground increased and litter and cover and density of most herbaceous species/life form groups declined beneath Cut & Burnand Pile & Burn treatments compared to the Cut & Leave treatment. The largest declines in cover and density of herbaceous species/life forms were recorded beneath burned piles. The largest changes measured adjacent to slash treatment locations (in the litter deposition and interspace microsites) were in the Cut & Burn plots due to fire spreading out burned trees. In the litter deposition microsite of the Cut & Burn treatment in 2007 total herbaceous cover was 1/3 and 1/2 that measured in the Cut & Leave and Pile & Burn plots, respectively. Contrarily the interspace microsite of the Cut & Burn treatment in 2007 indicated a slight (although insignificant) increase in herbaceous cover, with annual forb cover twice that measured in either of the other treatments. Concentrations of C, N, OM, and CEC were largely unchanged from pre-treatment levels in the compared treatments, however SO4, Mg, Ca, K, and pH all increased in response to burning compared to the Cut & Leave treatment. Implications of this research are limited to the first year post burn-treatment. However, these findings can be used as a general guide to choosing slash treatments to meet specific objectives.Determination of which of these treatments to use is largely dependent upon management objectives and site conditions. The high degree of vegetation disturbance and nutrient release measured beneath the Pile & Burn slash treatment could pose potential problems with invasive species establishment. However, the Cut & Burn treatment had similar, although less dramatic, vegetation disturbances and nutrient releases beneath burned slash, which covered a larger proportion of area than the Pile & Burn treatment. If a similar degree of invasive speciesestablishment occurs in both of these slash burning treatments, the Pile & Burn treatment may be a better option due to the smaller area impacted. Measurements indicated little impact to vegetation in the Cut & Leave treatment, however wildfire risk could diminish the short term benefits of this treatment. Long term monitoring of herbaceous vegetation and soil attribute response among these three slash treatments is needed to make solid inferences of the site recovery following treatments to assist in land management decisions.<br/><br/>Description: Graduation date: 2010 http://hdl.handle.net/1957/11278 Title: Linking greater sage-grouse habitat use and suitability across spatiotemporal scales in central Oregon<br/><br/>Authors: Freese, Mark T.<br/><br/>Abstract: Greater Sage-grouse (Centrocercus urophasianus) habitat research has historically focused on fine-scale (0.007 - 0.032 ha) vegetation structure and composition immediately surrounding sites selected by birds. However, little work has evaluated vegetation attributes important for Greater Sage-grouse at a landscape-scale or identified landscape attributes that influence habitat use patterns. Habitat use patterns by Greater Sage-grouse are complex and can occur across relatively large heterogeneous landscapes. This creates a major challenge for managers to interpret and predict habitat use patterns as well as to evaluate habitat suitability and prioritize habitats that are in need of ecological restoration. The goals of this research were to evaluate plot-level habitat characteristics found to be important in sustaining Greater Sage-grouse populations at a landscape-level and to identify landscape-level attributes associated with bird occurrence. Specific questions this research addressed were: 1) what is the variation in vegetation composition and structure at the plot versus landscape-level, 2) how does topography influence the distribution of vegetation composition and structure, and 3) what attributes at the landscape-level are most closely associated with Greater Sage-grouse habitat use? To address these questions we selected a 31,416 ha area in central Oregon surrounding a Greater Sage-grouse lek with a population that has been relatively stable since 1987. In February 2006, 50Greater Sage-grouse were trapped, radio collared, and then tracked for two consecutive years. Four-hundred eighty bird UTM (Universal Transverse Mercator) coordinate location points were recorded for the entire population of birds during the duration of this study. Each collared Greater Sage-grouse was located on average every 15 ± 0.56 (mean ± SE) days, ranging from 1 to 154 days. Vegetation for the entire study area was mapped by cover types, which were defined by the dominant shrub species. When shrubs were not present in the plant community, cover types were separated by other surface characteristics such as bare ground, water, meadow, etc. A total of 23 cover types were delineated. Cover types were mapped using 0.5-m NAIP (National Agricultural Imagery Program) imagery. In addition to cover type, a set of biophysical predictor variables were created for the entire study area in a GIS (Geographic Information System) to evaluate the association with Greater Sage-grouse location points. These variables included elevation, slope, aspect, curvature, solar radiation, ruggedness index, northing, easting, and distance from roads, leks, and mesic habitats. A stratified random sample with cover types serving as the stratum was used to select random locations for sampling plot-level habitat variables. A total of 352 plots were sampled from 18 cover types across the study area with a minimum of 15 plots per cover type. Vegetation measurements collected were similar to those reported in the habitat guidelines developed by Connelly et al. (2000) and the Bureau of Land Management et al. (2000). Measurements included vegetation cover, height, and density of forbs recognized as important Greater Sage-grouse food species. Plot elevation, slope, aspect, curvature and landscape position were also recorded. Summary statistics were used to describe means and ranges within and between cover types. A combination of multiple linear regression and analysis of variance (ANOVA) were used to evaluate the effects of topographic attributes on the distribution of vegetation composition and structure. To address the third question, maximum entropy software was used to develop models that predict Greater Sage-grouse seasonal habitat use, generate maps from those models, and describe the shapes of the response curves as it relates Greater Sage-grouse habitat preference to individual landscape predictor variables.Total shrub canopy cover across all cover types averaged 19.4%, ranging from 11.6 to 27.7%. Big (mountain and Wyoming) and low sagebrush canopy cover commonly varied between 2.6 and 16 fold within cover types. Deep-rooted perennial tussock grass cover averaged across all upland plots, was 26.7%, ranging from less than 1% to over 50%. Vegetation cover, Greater Sage-grouse food forb density, and sagebrush and grass height were significantly (P < 0.05) correlated with topographic attributes. Cover for the different plant life forms and food forb density increased with elevation. Cover for most of the herbaceous life forms was also greater on north than south aspects. Compared to Connelly et al. (2000) and the BLM et al. (2000) habitat guidelines, < 1% of the study area satisfied breeding and nesting guideline criteria, while < 31% satisfied the brood-rearing guideline criteria. Although most of the study area did not meet habitat recommendations presented in the guidelines, patches imbedded throughout the study area did and most areas satisfied many but not all of the guideline requirements. These results suggests that evaluating only mean values of community structure, both within and among cover types across the study area, limited the ability to fully identify patch variability and landscape heterogeneity as it relates to habitat suitability across large areas.Maximum entropy results suggest Greater Sage-grouse habitat use during the breeding season increases near leks and within cover types of low sagebrush and low sagebrush/mountain big sagebrush complexes. Preferred summer habitat includes areas relatively high in elevation, distances that are close to leks, and within or a close proximity to habitats that harbor succulent vegetation through much of the summer. With Greater Sage-grouse utilizing resources within expansive landscapes, understanding the attributes that can be applied at a landscape-scale that attract disproportionate levels of habitat use can help managers predict where birds are likely to occur across the landscape. With the ability to discriminate between areas that Greater Sage-grouse are likely to use or avoid, managers can allocate limited resources to more effectively create, manipulate, and administer habitat conservation efforts where bird use is predicted and prioritize areas across the landscape in need of ecological restoration.<br/><br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/11159 Title: Effects of plant community characteristics on insect abundance : implications for sage-grouse brood-rearing habitat<br/><br/>Authors: Ersch, Erica A.<br/><br/>Abstract: A causative factor in declining greater sage-grouse (Centrocercus urophasianus) populations is reduced annual recruitment due to poor habitat quality. Sage-grouse population decline is concurrent with a decline in the extent and quality of the sagebrush (Artemisia sp.) biome. However, current research has shown a positive relationship between sage-grouse brood and chick survival and the abundance of Lepidoptera larva (caterpillars of moths and butterflies). This two-year (2007-2008) study focused on linking the abundance of litter and ground dwelling insects with plant community characteristics in sagebrush steppe ecosystems, in anticipation of improving sage-grouse brood-rearing habitat management. Focus was placed on insects that have been found in the diet of sage-grouse chicks and included ants, grasshoppers, darkling beetles, and scarab beetles, with a special emphasis on caterpillars. Four sites were chosen in central Oregon for this research. Two sites were dominated by A. tridentata ssp. vaseyana (mountain big sagebrush) and were managed under two different seasons of cattle grazing, spring and winter. The remaining two sites were split between a Chrysothamnus viscidiflorus (yellow rabbitbrush) dominated upland and an Ericameria nauseosa (rubber rabbitbrush) dominated meadow. Line-point intercept, plant height, and basal gap intercept were employed to measure plant community structure and composition. Insect abundance was measured two ways: 1) pitfall traps for ground crawling insects, and 2) black light traps to capture adult moths. Identification of Lepidoptera species by caterpillars is difficult; therefore, documenting Lepidoptera species within an area by conducting an inventory of the adults was necessary. Results show the meadow site had more rabbitbrush, shrub, and vegetative cover, as well as taller shrubs and smaller basal gaps than the upland rabbitbrush site. Although the impact of grazing management was not quantified in this study, spring grazed sites exhibited more sagebrush and shrub cover, taller grasses and shrubs, and larger basal gaps when compared to the winter grazed sites. Within the A. tridentata ssp. vaseyana sites, forb cover, total vegetative cover, grass heights, and species richness were different between years. The meadow site provided the highest abundance of caterpillars compared to all other sites. Both rabbitbrush sites provided more caterpillars throughout May and June than the A. tridentata ssp. vaseyana communities, corresponding to early sage-grouse brood-rearing. The winter grazed A. tridentata ssp. vaseyana site and the upland rabbitbrush site exhibited the highest abundance of grasshoppers. Correlations of vegetation characteristics with insect abundance highlighted several relationships: 1) caterpillars were negatively associated with percent basal gap, mean basal gap size, and sagebrush cover, 2) caterpillars were positively associated with perennial grass cover, rabbitbrush cover, shrub height, and total vegetative cover, and 3) darkling beetles were positively associated with annual forb and annual grass cover. Moth abundance and species richness were highest during July, August, and September, with relatively few moths being caught in May or June. Overall, 222 moth species were present at the study location. Rabbitbrush and sagebrush sites had 145 species in common, with the rabbitbrush sites having 194 species overall and A. tridentata ssp. vaseyana sites having 173 species overall. Moth abundance was negatively correlated with perennial grass cover, basal cover, rabbitbrush cover, shrub and grass height, and total vegetative cover. Additionally, moth abundance was positively correlated with basal gap percent and size, as well as sagebrush cover. In conclusion, the upland rabbitbrush site exhibited the highest abundance of moths, whereas the meadow site presented the most diverse and unique number of moth species. The results of this study suggest rabbitbrush communities may be an important and intricate component within the sagebrush-steppe landscape, contributing to the quality of sage-grouse brood-rearing habitat.<br/><br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/10211 Title: Himalayan blackberry (Rubus armeniacus) and English ivy (Hedera helix) response to high intensity-short duration goat browsing<br/><br/>Authors: Ingham, Claudia S.<br/><br/>Abstract: The goal of this dissertation is to examine the effectiveness of high intensity-short duration goat browsing for the control of Himalayan blackberry (Rubus armeniacus) and English ivy (Hedera helix), two widespread noxious weeds in the Pacific Northwest. The effects of goat browsing on Himalayan blackberry vigor, as quantified by densities of different age class stems, are compared to mowing and goat browsing followed by mowing over a period of three years. Although total stem density and node density declined, primocane density increased after all types of treatment. This indicates that the population was still vigorous. Recruitment of new plants was reflected by an increase in seedling density. Changes in percent cover of vegetation functional groups were also examined. All three treatments produced a decline in Himalayan blackberry cover and an increase in perennial grass cover, though differences among treatment types were not significant. Perennial forb cover increased as a result of all treatment types. English ivy was successfully controlled by goat browsing as quantified by percent cover. Two years of browsing reduced percent cover more than one year of browsing. Both levels of browsing produced results that were significantly different when compared to the untreated control indicating that repeated high intensity-short duration browsing is justified for control of this invasive plant species.Differences in response of these two invasive, creeping perennials are attributed to differences in species growth rates, location of meristematic tissue in stolons vs. rhizomes and shade conditions at the research sites.<br/><br/>Description: Graduation date: 2009