An Efficient Sampling Protocol for Sagebrush/Grassland Monitoring

Rangeland scientists and quantitative ecologists have developed numerous methods and monitoring techniques that can be used for vegetation sampling (Barbour et al. 1987). The methods used to position samples (transects, quadrats, lines, and points) vary and can be classed as selective, capricious, systematic, or random. One of the prerequisites for valid statistical inference is that samples are taken randomly. A random sampling procedure implies that all elements or units of the population being studied have an equal chance of being represented in the sample. It also implies that selection of an element or unit does not influence the chance of other units being sampled. Data that is collected using randomsampling procedures can be used to compare attributes of different populations or sites such as vegetative cover, density, production, growth rates, etc. This paper suggests a random sampling protocol that can be easily applied in the field for sagebrush/grassland monitoring

Wolves: A Primer for Ranchers

Ranch management has become more complex since wolves were reintroduced into Idaho and Wyoming in 1996. In wolf areas, livestock have experienced increased death loss and greater stress. Increased livestock aggressiveness has been observed, especially toward working dogs, making handling livestock more difficult. Additionally ranchers have reported a loss of body condition, lower conception rates, increased time and expense for management. Our study was designed to investigate the effect of wolf presence on cattle behavior, landscape use patterns, and resource selection by comparing high wolf density areas against low wolf density areas. This study also generated baseline information on cattle spatial behavior before wolves were on the landscape. A Before-After/Control-Impact Paired (BACIP) experimental design was used. Control study areas in Idaho (3) have high wolf presence while Impact study areas in Oregon (3) started with no wolf presence, and are shifting to elevated wolf presence. Paired Idaho and Oregon areas have similar topography, vegetation composition, wild ungulate prey bases, and livestock management. Cows are tracked at 5-minute intervals using GPS collars (10 per area) throughout the grazing season. Wolf presence is monitored by GPS, trail cameras, and scat surveys. Ten GPS-collared cattle in an Idaho study area encountered a GPS-collared wolf 783 times at less than 500 meters during 137 days in the 2009 grazing season. At 100 meters there were 53 encounters; 52 at night. Tests of naïve and experienced cattle exposed to a simulated wolf encounter found increased excitability and fear-related physiological stress responses in cows previously exposed to wolves. This was shown through increased cortisol levels, body temperature, and temperament scores. Cattle presence near occupied houses doesn’t offer protection from wolves. Data shows wolves within 500m of occupied houses 588 times during 198 days of tracking. Many confirmed depredations on this site were also close to houses

Effect of eicosapentaenoic and docosahexaenoic acid on resting and exercise-induced inflammatory and oxidative stress biomarkers: a randomized, placebo controlled, cross-over study

<p>Abstract</p> <p>Background</p> <p>The purpose of the present investigation was to determine the effects of EPA/DHA supplementation on resting and exercise-induced inflammation and oxidative stress in exercise-trained men. Fourteen men supplemented with 2224 mg EPA+2208 mg DHA and a placebo for 6 weeks in a random order, double blind cross-over design (with an 8 week washout) prior to performing a 60 minute treadmill climb using a weighted pack. Blood was collected pre and post exercise and analyzed for a variety of oxidative stress and inflammatory biomarkers. Blood lactate, muscle soreness, and creatine kinase activity were also measured.</p> <p>Results</p> <p>Treatment with EPA/DHA resulted in a significant increase in blood levels of both EPA (18 ± 2 μmol·L^-1vs. 143 ± 23 μmol·L^-1; p < 0.0001) and DHA (67 ± 4 μmol·L^-1vs. 157 ± 13 μmol·L^-1; p < 0.0001), while no differences were noted for placebo. Resting levels of CRP and TNF-α were lower with EPA/DHA compared to placebo (p < 0.05). Resting oxidative stress markers were not different (p > 0.05). There was a mild increase in oxidative stress in response to exercise (XO and H₂O₂) (p < 0.05). No interaction effects were noted. However, a condition effect was noted for CRP and TNF-α, with lower values with the EPA/DHA condition.</p> <p>Conclusion</p> <p>EPA/DHA supplementation increases blood levels of these fatty acids and results in decreased resting levels of inflammatory biomarkers in exercise-trained men, but does not appear necessary for exercise-induced attenuation in either inflammation or oxidative stress. This may be due to the finding that trained men exhibit a minimal increase in both inflammation and oxidative stress in response to moderate duration (60 minute) aerobic exercise.</p

Inferred summer precipitation for southern Ontario back to AD 610, as reconstructed from ring widths of Thuja occidentalis

We present a network of seven ring-width chronologies of eastern white-cedar (Thuja occidentalis L.) from the Niagara Escarpment in southern Ontario, Canada. Using principal component regression, a 350-year June-July precipitation reconstruction (SOR) is developed for the region. Prior to the 20th century, the SOR series shows reasonable coherence, particularly at the decadal scale, with an independent tree-ring-based reconstruction of the Palmer drought severity index (PDSI) for roughly the same region. A weakening of the tree-growth – climate relationship in recent decades results in a regression model explaining 21% of the variance in the original climate series when the recent data are used for calibration. We therefore compromise with a model, calibrated for the period 1900–1960, which explains 33% of the variance. The model, while not terribly strong, does pass verification tests, indicating some degree of predictive skill. The longest chronology in our network, the 2787-year Flowerpot Island (FLOW) chronology, also exhibits common variability with the PDSI reconstruction, particularly on decadal and longer time scales and was used to infer hydroclimatic conditions back to AD 610. The combined information of the SOR, PDSI, and FLOW series suggests that dry conditions existed for the periods 1700–1725, 1750–1800, and 1840–1900, and wet conditions for the periods 1675–1700, 1730–1750, and 1810–1840. Over longer time scales, the FLOW chronology shows that summer precipitation was particularly variable during the 7th, 9th, 13th, and 16th centuries

Direct measurement of the intermolecular forces confining a single molecule in an entangled polymer solution

We use optical tweezers to directly measure the intermolecular forces acting on a single polymer imposed by surrounding entangled polymers (115 kbp DNA, 1 mg/ml). A tube-like confining field was measured in accord with the key assumption of reptation models. A time-dependent harmonic potential opposed transverse displacement, in accord with recent simulation findings. A tube radius of 0.8 microns was determined, close to the predicted value (0.5 microns). Three relaxation modes (~0.4, 5 and 30 s) were measured following transverse displacement, consistent with predicted relaxation mechanisms.Comment: 11 pages, 3 figure

Supernova Enrichment of Dwarf Spheroidal Galaxies

(Abridged) Many dwarf galaxies exhibit sub-Solar metallicities, with some star-to-star variation, despite often containing multiple generations of stars. The total metal content in these systems is much less than expected from the heavy element production of massive stars in each episode of star formation. Such a deficiency implies that a substantial fraction of the enriched material has been lost from these small galaxies. Mass ejection from dwarf galaxies may have important consequences for the evolution of the intergalactic medium and for the evolution of massive galaxies, which themselves may have formed via the merger of smaller systems. We report here the results of three-dimensional simulations of the evolution of supernova-enriched gas within dwarf spheroidal galaxies (dSph's), with the aim of determining the retention efficiency of supernova ejecta. We consider two galaxy models, selected to represent opposite ends of the dSph sequence. For each model galaxy we investigate a number of scenarios, ranging from a single supernova in smooth gas distributions to more complex multiple supernovae in highly disturbed gas distributions. The results of these investigations suggest that, for low star-formation efficiencies, it is difficult to completely expel the enriched material from the galaxy. Most of the enriched gas is, however, lost from the core of the galaxy following multiple supernovae, especially if the interstellar medium is already highly disturbed by processes such as photo-ionization and stellar winds. If subsequent star formation occurs predominantly within the core where most of the residual gas is concentrated, then these results could explain the poor self-enrichment efficiency observed in dwarf galaxies.Comment: 29 pages, 10 figures, to appear in Astrophysical Journa

Spatial aspects of tree mortality strongly differ between young and old-growth forests

Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially auto-correlated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a three-decade record of tree mortality from replicated mapped permanent plots located in young (\u3c60-year-old) and old-growth (\u3e300-year-old) Abies amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strong density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatially aggregated, but was density independent and did not change the spatial pattern of surviving trees. These results extend current theory by demonstrating that density-dependent competitive mortality leading to increasingly uniform three spacing in young forests ultimately transitions late in succession to a more diverse tree mortality regime that maintains spatial heterogeneity through time

The Kinematics of the Globular Cluster System of NGC 5128 with a New, Large Sample of Radial Velocity Measurements

New radial velocity measurements for previously known and newly confirmed globular clusters (GCs) in the nearby massive galaxy NGC 5128 are presented. We have obtained spectroscopy from LDSS-2/Magellan, VIMOS/VLT, and Hydra/CTIO from which we have measured the radial velocities of 218 known, and identified 155 new, GCs. The current sample of confirmed GCs in NGC 5128 is now 605 with 564 of these having radial velocity measurements. We have performed a new kinematic analysis of the GC system that extends out to 45 arcmin in galactocentric radius. We have examined the systemic velocity, projected rotation amplitude and axis, and the projected velocity dispersion of the GCs as functions of galactocentric distance and metallicity. Our results indicate that the metal-poor GCs have a very mild rotation signature of (26 pm 15) km/s. The metal-rich GCs are rotating with a higher, though still small signature of (43 pm 15) km/s around the isophotal major axis of NGC 5128 within 15 arcmin. Their velocity dispersions are consistent within the uncertainties and the profiles appear flat or declining within 20 arcmin. We note the small sample of metal-rich GCs with ages less than 5 Gyr in the literature appear to have different kinematic properties than the old, metal-rich GC subpopulation. The mass and mass-to-light ratios have also been estimated using the GCs as tracer particles for NGC 5128. Out to a distance of 20 arcmin, we have obtained a mass of (5.9 pm 2.0) x 10^(11) M_(sun) and a mass-to-light ratio in the B-band of 16 M_(sun)/L_(B,sun). Combined with previous work on the ages and metallicities of its GCs, as well as properties of its stellar halo, our findings suggest NGC 5128 formed via hierarchical merging over other methods of formation, such as major merging at late times.Comment: Accepted for The Astronomical Journal, 14 pages plus 12 figures and 7 table

Dynamically Driven Evolution of the Interstellar Medium in M51

We report the highest-fidelity observations of the spiral galaxy M51 in CO emission, revealing the evolution of giant molecular clouds (GMCs) vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (so-called GMAs) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics --their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the inter-arm region and into the next spiral arm passage.Comment: 6 pages, including 3 figures. Accepted, ApJ