Davies K.W.,Eastern Oregon Agricultural Research Center |
Petersen S.L.,Brigham Young University |
Johnson D.D.,Oregon State University |
Madsen M.D.,Eastern Oregon Agricultural Research Center |
And 2 more authors.
Rangeland Ecology and Management | Year: 2010
Western juniper (Juniperus occidentalis subsp. occidentalis Hook.) woodlands are expanding from their historic range and causing significant declines of other plant communities. However, landscape-scale restoration projects are hindered by time-consuming and expensive methods to inventory juniper cover and prioritize landscapes based on developmental phase of juniper encroachment. We investigated the ability of feature-extraction software to estimate western juniper cover from color aerial photographs obtained from the National Agriculture Imagery Program (NAIP) and explored the relationships between juniper cover at stand closure (potential juniper cover) and environmental/site indices (heat load, site exposure, and integrated moisture index) and characteristics measured from commonly available geospatial data layers. Estimates of juniper cover derived from NAIP imagery and ground measurements were similar (R2=0.74; P<0.01). Neither method consistently estimated juniper cover higher or lower than the other method (P=0.79). Environmental indices were either not correlated or weakly correlated with juniper cover at stand closure. However, the environmental/site characteristics (slope, aspect, and elevation) could be used to explain 40 of the variation in juniper cover at stand closure (R2=0.40; P<0.01). Thus, commonly available geospatial data layers can be used to assist in determining potential juniper cover. This information can then be compared to current juniper cover to determine juniper woodland developmental phase. Knowing the developmental phase is important because management strategies and effectiveness of restoration treatments differ among phases of juniper encroachment. Our results suggest that NAIP imagery can be a valuable tool to estimate juniper cover over large areas effectively to make landscape-scale restoration more feasible. The model of the relationship between environmental/site characteristics measured from commonly available geospatial data layers and potential juniper can be used to assist in restoration planning and prioritization, but could be improved with further refinement. © 2010 Society for Range Management.
Tanaree D.D.,Oregon State University |
Duringer J.M.,OSU |
Bohnert D.W.,Eastern Oregon Agricultural Research Center |
Craig A.M.,11 Veterinary Research Laboratory
World Mycotoxin Journal | Year: 2013
'Fescue toxicosis' is a disease in livestock caused by ingestion of ergot alkaloids produced by the fungal endophyte Neotyphodium coenophialum in tall fescue; it is estimated to cost 1 billion USD in damages per year to the beef industry alone. Clinical signs include decreased reproductive fitness, necrosis of extremities, and reduced average daily gain and milk production. Little is known about the cellular mechanisms that mediate these toxic sequelae. We evaluated the effects of ergovaline-based fescue toxicosis on gene expression via oligonucleotide microarray. Liver biopsies were obtained from steers (n=4) pre- and post-exposure (0 and 29 days) to feed containing 579 ng/g ergovaline. Analyses were performed using both ANOVA with false discovery rate correction and Storey's optimal discovery procedure. Overall, down-regulation of gene expression was observed; heart contraction and cardiac development, apoptosis, cell cycle control, and RNA processing genes represented the bulk of differentially expressed transcripts. 2 CYPs (CYP2E1 and CYP4F6) were amongst the significantly upregulated results. Thus, exposure of cattle to toxic levels of ergovaline caused widespread changes in hepatic gene expression, which can both help explain macroscopic clinical signs observed in ruminant animals, and reinforce previous findings in monogastric models.
Polley H.W.,U.S. Department of Agriculture |
Emmerich W.,U.S. Department of Agriculture |
Bradford J.A.,Plant Physiologist |
Sims P.L.,Southern Plains Range Research Station |
And 11 more authors.
Rangeland Ecology and Management | Year: 2010
Rangelands occupy 50% of Earth's land surface and thus are important in the terrestrial carbon (C) cycle. For rangelands and other terrestrial ecosystems, the balance between photosynthetic uptake of carbon dioxide (CO2) and CO2 loss to respiration varies among years in response to interannual variation in the environment. Variability in CO2 exchange results from interannual differences in 1) environmental variables at a given point in the annual cycle (direct effects of the environment) and in 2) the response of fluxes to a given change in the environment because of interannual changes in biological factors that regulate photosynthesis and respiration (functional change). Functional change is calculated as the contribution of among-year differences in slopes of flux-environment relationships to the total variance in fluxes explained by the environment. Functional change complicates environmental-based predictions of CO2 exchange, yet its causes and contribution to flux variability remain poorly defined. We determine contributions of functional change and direct effects of the environment to interannual variation in net ecosystem exchange of CO2 (NEE) of eight rangeland ecosystems in the western United States (58 site-years of data). We predicted that 1) functional change is correlated with interannual change in precipitation on each rangeland and 2) the contribution of functional change to variance in NEE increases among rangelands as mean precipitation increases. Functional change explained 10-40% of the variance in NEE and accounted for more than twice the variance in fluxes of direct effects of environmental variability for six of the eight ecosystems. Functional change was associated with interannual variation in precipitation on most rangelands but, contrary to prediction, contributed proportionally more to variance in NEE on arid than more mesic ecosystems. Results indicate that we must account for the influence of precipitation on flux-environment relationships if we are to distinguish environmental from management effects on rangeland C balance. © Society for Range Management.
Johnson C.G.,U.S. Department of Agriculture |
Vavra M.,U.S. Department of Agriculture |
Willis M.,Eastern Oregon Agricultural Research Center |
Parks C.G.,U.S. Department of Agriculture
Rangelands | Year: 2013
On the Ground Managers charged with managing landscapes influenced by elk are challenged to establish monitoring protocols that identify when impacts are responsible for declining ecological condition. We assessed the impact of elk herbivory on plant communities on an elk winter range by comparing canopy cover of common species that represented subjectively selected heavy and light elk impacts. Winter elk use has little direct impact on existing bunchgrasses, but winter elk traffic disrupts soils and provides the potential for invasive plant establishment. © 2013 by the Society for Range Management.
Davies K.W.,U.S. Department of Agriculture |
Bates J.D.,U.S. Department of Agriculture |
Nafus A.M.,Eastern Oregon Agricultural Research Center
Rangeland Ecology and Management | Year: 2012
A decrease in fire frequency and past grazing practices has led to dense mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana [Rydb.] Beetle) stands with reduced herbaceous understories. To reverse this trend, sagebrush-reducing treatments often are applied with the goal of increasing herbaceous vegetation. Mechanical mowing is a sagebrush-reducing treatment that commonly is applied; however, information detailing vegetation responses to mowing treatments generally are lacking. Specifically, information is needed to determine whether projected increases in perennial grasses and forbs are realized and how exotic annual grasses respond to mowing treatments. To answer these questions, we evaluated vegetation responses to mowing treatments in mountain big sagebrush plant communities at eight sites. Mowing was implemented in the fall of 2007 and vegetation characteristics were measured for 3 yr post-treatment. In the first growing season post-treatment, there were few vegetation differences between the mowed treatment and untreated control (P>0.05), other than sagebrush cover being reduced from 28% to 3% with mowing (P<0.001). By the second growing season post-treatment, perennial grass, annual forb, and total herbaceous vegetation were generally greater in the mowed than control treatment (P<0.05). Total herbaceous vegetation production was increased 1.7-fold and 1.5-fold with mowing in the second and third growing seasons, respectively (P<0.001). However, not all plant functional groups increased with mowing. Perennial forbs and exotic annual grasses did not respond to the mowing treatment (P>0.05). These results suggest that the abundance of sagebrush might not be the factor limiting some herbaceous plant functional groups, or they respond slowly to sagebrush-removing disturbances. However, this study suggests that mowing can be used to increase herbaceous vegetation and decrease sagebrush in some mountain big sagebrush plant communities without promoting exotic annual grass invasion.
Nafus A.M.,Oregon State University |
Davies K.W.,Eastern Oregon Agricultural Research Center
Invasive Plant Science and Management | Year: 2014
The spread of medusahead across the western United States has severe implications for a wide range of ecosystem services. Medusahead invasion reduces biodiversity, wildlife habitat and forage production, and often leads to increased fire frequency and restoration costs. Medusahead is problematic in the Intermountain West and California Annual Grasslands. The last review of medusahead ecology and management was completed 20 years ago. Since the last review, there have been scientific advances in medusahead management suggesting a significant need to develop an up-to-date synthesis. Medusahead continues to pose a serious threat to rangeland ecosystems. In this synthesis, we present new information regarding the ecology of medusahead, suggest a framework for managing medusahead based on invasion level, and identify research needs to further improve management of this invasive annual grass. Success of different management practices varies between the Intermountain West and California Annual Grasslands, signifying that the best management practices are those specifically tailored with consideration of climate, soil, plant community characteristics, and management objectives. Prevention and control treatments that are useful in the Intermountain West may not be practical or effective in the California Annual Grasslands and vice-versa. Nomenclature: Medusahead, Taeniatherum caput-medusae (L.) Nevski; ELYCM.
Mueller C.J.,Oregon State University |
Mueller C.J.,Eastern Oregon Agricultural Research Center |
Sexson C.,Oregon State University |
Mills R.R.,Oregon State University
Professional Animal Scientist | Year: 2013
Sixty-four (224 ± 33 kg) Angus-cross calves were stratified by BW and sex and then randomly allotted to one of four 35-d preconditioning diets to evaluate the effect of supplemental vitamin E with or without dietary oil on BW gain and carcass characteristics. Diets were based on ad libitum grass hay (6.2% CP) and the following concentrates: corn and soybean meal only (CON), CON plus vitamin E (VITE), VITE plus 1.5% safflower oil (ELA), or VITE plus 1.5% flaxseed oil (ELNA). Vitamin E amounts were targeted for 150 IU/kg of total DMI (supplement plus hay). Following preconditioning, calves were shipped to a commercial feedlot and received a modified-live intranasal vaccine against infectious bovine rhinotracheitis and parainfluenza-3 following arrival to stimulate immune activity. Blood samples were obtained before transit and 30 d posttransit to quantify glucose and antibody titers. Data were evaluated as a randomized complete block design with sex as block using the preplanned contrasts of CON versus VITE, VITE versus oil (mean of ELA and ELNA), and ELA versus ELNA. No differences (P. >. 0.10) were observed for either preconditioning or feedlot ADG or for any carcass traits. Morbidity rates were less than 1% and consistent across treatments. No differences (P. >. 0.10) were observed for infectious bovine rhinotracheitis, parainfluenza-3, or IgM antibody titer concentrations across treatments. Preconditioning diets containing 150 IU of vitamin E/kg of DMI, regardless of oil, showed limited to no change in performance, immune, or carcass characteristics of weaned beef calves. © 2013 American Registry of Professional Animal Scientists.
Davies K.W.,Eastern Oregon Agricultural Research Center |
Bates J.D.,Eastern Oregon Agricultural Research Center
Environmental Management | Year: 2010
Big sagebrush (Artemisia tridentata Nutt.) occupies large portions of the western United States and provides valuable wildlife habitat. However, information is lacking quantifying differences in native perennial forb characteristics between mountain big sagebrush [A. tridentata spp. vaseyana (Rydb.) Beetle] and Wyoming big sagebrush [A. tridentata spp. wyomingensis (Beetle & A. Young) S.L. Welsh] plant communities. This information is critical to accurately evaluate the quality of habitat and forage that these communities can produce because many wildlife species consume large quantities of native perennial forbs and depend on them for hiding cover. To compare native perennial forb characteristics on sites dominated by these two subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Mountain big sagebrush plant communities produced almost 4.5-fold more native perennial forb biomass and had greater native perennial forb species richness and diversity compared to Wyoming big sagebrush plant communities (P < 0.001). Nonmetric multidimensional scaling (NMS) and the multiple-response permutation procedure (MRPP) demonstrated that native perennial forb composition varied between these plant communities (P < 0.001). Native perennial forb composition was more similar within plant communities grouped by big sagebrush subspecies than expected by chance (A = 0.112) and composition varied between community groups (P < 0.001). Indicator analysis did not identify any perennial forbs that were completely exclusive and faithful, but did identify several perennial forbs that were relatively good indicators of either mountain big sagebrush or Wyoming big sagebrush plant communities. Our results suggest that management plans and habitat guidelines should recognize differences in native perennial forb characteristics between mountain and Wyoming big sagebrush plant communities. © 2010 US Government.
Hamerlynck E.P.,Eastern Oregon Agricultural Research Center |
Sheley R.L.,Eastern Oregon Agricultural Research Center |
Davies K.W.,Eastern Oregon Agricultural Research Center |
Svejcar T.J.,Eastern Oregon Agricultural Research Center
Ecosphere | Year: 2016
Developing land-use practices that lead to sustainable net primary productivity in rangelands are important, but understanding their consequences to population and community processes is not often accounted for in basic ecosystem studies. Grazed and ungrazed upland ecosystems generally do not differ in net ecosystem CO2 exchange (NEE), but the underlying mechanisms and the concurrent effects of defoliation to vegetative and reproductive biomass allocation are unclear. To address this, we measured evapotranspiration (ET), NEE, and its constituent fluxes of ecosystem respiration (Reco) and gross ecosystem photosynthesis (GEP) with live canopy leaf area index (LAIlive; m2 live leaf area/m2 ground area) and aboveground leaf, culm, and reproductive biomass in plots of clipped and unclipped squirreltail (Elymus elymoides) and bluebunch wheatgrass (Pseudoroegneria spicata) growing in intact sagebrush steppe. Clipping reduced LAIlive by 75%, but subsequent re-growth rates in clipped plots was similar to LAIlive accumulation in unclipped plots. Concurrently, ET and NEE was similar between clipped and unclipped plots, with NEE primarily determined by GEP. GEP was initially lower in clipped plots, but then converged with unclipped GEP even as LAIlive continued to increase in both treatments. GEP convergence was driven by higher whole-plant photosynthesis (GEPlive = GEP/LAIlive) in clipped plots. Ecosystem water use efficiency (GEP/ET) was reduced by 16% with clipping, due to low GEP/ET 2 weeks following defoliation, but GEP/ET converged before GEP levels did. Proportional reproductive biomass was higher in E. elymoides (21.4% total biomass) than in P. spicata (0.5% total biomass) due to lower allocation to specific leaf and culm mass. Clipping reduced reproductive effort in E. elymoides, in terms of total reproductive biomass (-56%), seed mass per unit leaf area (-64%), and seed mass per flowering head (-77%). We concluded defoliation increased canopy-level light penetration, facilitating rapid recovery of ecosystem fluxes, but that allocation to vegetative regrowth supporting this led to lower reproductive effort in these range grasses. Insights from studies such as this will be useful in formulating systems-based land management strategies aimed at maintaining annual productivity and long-term population and community goals in semiarid rangeland ecosystems. © 2016 Hamerlynck et al.
PubMed | Eastern Oregon Agricultural Research Center
Type: Journal Article | Journal: Environmental management | Year: 2010
Big sagebrush (Artemisia tridentata Nutt.) occupies large portions of the western United States and provides valuable wildlife habitat. However, information is lacking quantifying differences in native perennial forb characteristics between mountain big sagebrush [A. tridentata spp. vaseyana (Rydb.) Beetle] and Wyoming big sagebrush [A. tridentata spp. wyomingensis (Beetle & A. Young) S.L. Welsh] plant communities. This information is critical to accurately evaluate the quality of habitat and forage that these communities can produce because many wildlife species consume large quantities of native perennial forbs and depend on them for hiding cover. To compare native perennial forb characteristics on sites dominated by these two subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Mountain big sagebrush plant communities produced almost 4.5-fold more native perennial forb biomass and had greater native perennial forb species richness and diversity compared to Wyoming big sagebrush plant communities (P < 0.001). Nonmetric multidimensional scaling (NMS) and the multiple-response permutation procedure (MRPP) demonstrated that native perennial forb composition varied between these plant communities (P < 0.001). Native perennial forb composition was more similar within plant communities grouped by big sagebrush subspecies than expected by chance (A = 0.112) and composition varied between community groups (P < 0.001). Indicator analysis did not identify any perennial forbs that were completely exclusive and faithful, but did identify several perennial forbs that were relatively good indicators of either mountain big sagebrush or Wyoming big sagebrush plant communities. Our results suggest that management plans and habitat guidelines should recognize differences in native perennial forb characteristics between mountain and Wyoming big sagebrush plant communities.