Ecological Effects of Prescribed Fire Season: A Literature Review and Synthesis for Managers

Prescribed burning may be conducted at times of the year when fires were infrequent historically, leading to concerns about potential adverse effects on vegetation and wildlife. Historical and prescribed fire regimes for different regions in the continental United States were compared and literature on season of prescribed burning synthesized. In regions and vegetation types where considerable differences in fuel consumption exist among burning seasons, the effects of prescribed fire season appears, for many ecological variables, to be driven more by fire-intensity differences among seasons than by phenology or growth stage of organisms at the time of fire. Where fuel consumption differs little among burning seasons, the effect of phenology or growth stage of organisms is often more apparent, presumably because it is not overwhelmed by fire-intensity differences. Most species in ecosystems that evolved with fire appear to be resilient to one or few out-of-season prescribed burn(s). However, a variable fire regime including prescribed burns at different times of the year may alleviate the potential for undesired changes and maximize biodiversity

A framework for experimental-data-driven assessment of Magnetized Liner Inertial Fusion stagnation image metrics

A variety of spherical crystal x-ray imager (SCXI) diagnostics have been developed and fielded on Magnetized Liner Inertial Fusion (MagLIF) experiments at the Sandia National Laboratories Z-facility. These different imaging modalities provide detailed insight into different physical phenomena such as mix of liner material into the hot fuel, cold liner emission, or reduce impact of liner opacity. However, several practical considerations ranging from the lack of a consistent spatial fiducial for registration to different point-spread-functions and tuning crystals or using filters to highlight specific spectral regions make it difficult to develop broadly applicable metrics to compare experiments across our stagnation image database without making significant unverified assumptions. We leverage experimental data for a model-free assessment of sensitivities to instrumentation-based features for any specified image metric. In particular, we utilize a database of historical and recent MagLIF data including $N_{\text{scans}} = 139$ image plate scans gathered across $N_{\text{exp}} = 67$ different experiments to assess the impact of a variety of features in the experimental observations arising from uncertainties in registration as well as discrepancies in signal-to-noise ratio and instrument resolution. We choose a wavelet-based image metric known as the Mallat Scattering Transform for the study and highlight how alternate metric choices could also be studied. In particular, we demonstrate a capability to understand and mitigate the impact of signal-to-noise, image registration, and resolution difference between images. This is achieved by utilizing multiple scans of the same image plate, sampling random translations and rotations, and applying instrument specific point-spread-functions found by ray tracing to high-resolution datasets, augmenting our data in an effectively model-free fashion.Comment: 17 pages, 14 figure

Fire Treatment Effects on Vegetation Structure, Fuels, and Potential Fire Severity in Western US Forests

Forest structure and species composition in many western U. S. coniferous forests have been altered through. re exclusion, past and ongoing harvesting practices, and livestock grazing over the 20th century. The effects of these activities have been most pronounced in seasonally dry, low and mid-elevation coniferous forests that once experienced frequent, low to moderate intensity,. re regimes. In this paper, we report the effects of Fire and Fire Surrogate (FFS) forest stand treatments on fuel load profiles, potential fire behavior, and fire severity under three weather scenarios from six western U. S. FFS sites. This replicated, multisite experiment provides a framework for drawing broad generalizations about the effectiveness of prescribed. re and mechanical treatments on surface fuel loads, forest structure, and potential. re severity. Mechanical treatments without. re resulted in combined 1-, 10-, and 100-hour surface fuel loads that were significantly greater than controls at three of five FFS sites. Canopy cover was significantly lower than controls at three of five FFS sites with mechanical-only treatments and at all five FFS sites with the mechanical plus burning treatment;. re-only treatments reduced canopy cover at only one site. For the combined treatment of mechanical plus. re, all five FFS sites with this treatment had a substantially lower likelihood of passive crown. re as indicated by the very high torching indices. FFS sites that experienced significant increases in 1-, 10-, and 100-hour combined surface fuel loads utilized harvest systems that left all activity fuels within experimental units. When mechanical treatments were followed by prescribed burning or pile burning, they were the most effective treatment for reducing crown fire potential and predicted tree mortality because of low surface fuel loads and increased vertical and horizontal canopy separation. Results indicate that mechanical plus fire, fire-only, and mechanical-only treatments using whole-tree harvest systems were all effective at reducing potential. re severity under severe. re weather conditions. Retaining the largest trees within stands also increased. re resistance

Gravitational waves from inspiraling compact binaries: Validity of the stationary-phase approximation to the Fourier transform

We prove that the oft-used stationary-phase method gives a very accurate expression for the Fourier transform of the gravitational-wave signal produced by an inspiraling compact binary. We give three arguments. First, we analytically calculate the next-order correction to the stationary-phase approximation, and show that it is small. This calculation is essentially an application of the steepest-descent method to evaluate integrals. Second, we numerically compare the stationary-phase expression to the results obtained by Fast Fourier Transform. We show that the differences can be fully attributed to the windowing of the time series, and that they have nothing to do with an intrinsic failure of the stationary-phase method. And third, we show that these differences are negligible for the practical application of matched filtering.Comment: 8 pages, ReVTeX, 4 figure

Five High-Redshift Quasars Discovered in Commissioning Imaging Data of the Sloan Digital Sky Survey

We report the discovery of five quasars with redshifts of 4.67 - 5.27 and z'-band magnitudes of 19.5-20.7 M_B ~ -27. All were originally selected as distant quasar candidates in optical/near-infrared photometry from the Sloan Digital Sky Survey (SDSS), and most were confirmed as probable high-redshift quasars by supplementing the SDSS data with J and K measurements. The quasars possess strong, broad Lyman-alpha emission lines, with the characteristic sharp cutoff on the blue side produced by Lyman-alpha forest absorption. Three quasars contain strong, broad absorption features, and one of them exhibits very strong N V emission. The amount of absorption produced by the Lyman-alpha forest increases toward higher redshift, and that in the z=5.27 object (D_A ~ 0.7) is consistent with a smooth extrapolation of the absorption seen in lower redshift quasars. The high luminosity of these objects relative to most other known objects at z >~ 5 makes them potentially valuable as probes of early quasar properties and of the intervening intergalactic medium.Comment: 13 pages in LaTex format, two postscirpt figures. Submitted to the Astronomical Journa

Morphological Trait Evolution in Solanum (Solanaceae): Evolutionary Lability of Key Taxonomic Characters

Solanum is one of the world\u27s largest and economically most important plant genera, including 1245 currently accepted species and several major and minor crops (e.g., tomato, potato, brinjal eggplant, scarlet eggplant, Gboma eggplant, lulo, and pepino). Here we provide an overview of the evolution of 25 key morphological traits for the major and minor clades of this giant genus based on stochastic mapping using a well-sampled recently published phylogeny of Solanum. The most evolutionarily labile traits (showing \u3e100 transitions across the genus) relate to plant structure (growth form and sympodial unit structure), herbivore defence (glandular trichomes), pollination (corolla shape and colour), and dispersal (fruit colour). Ten further traits show evolutionary lability with 50–100 transitions across the genus (e.g., specialised underground organs, trichome structure, leaf type, inflorescence position and branching, stamen heteromorphism). Our results reveal a number of highly convergent traits in Solanum, including tubers, rhizomes, simple leaves, yellow corollas, heteromorphic anthers, dioecy, and dry fruits, and some unexpected pathways of trait evolution that could be explored in future studies. We show that informally named clades of Solanum can be morphologically defined by trait combinations providing a tool for identification and enabling predictive phylogenetic placement of unsampled species

Faint High Latitude Carbon Stars Discovered by the Sloan Digital Sky Survey: Methods and Initial Results

We report the discovery of 39 Faint High Latitude Carbon Stars (FHLCs) from Sloan Digital Sky Survey commissioning data. The objects, each selected photometrically and verified spectroscopically, range over 16.6 < r* < 20.0, and show a diversity of temperatures as judged by both colors and NaD line strengths. At the completion of the Sloan Survey, there will be many hundred homogeneously selected and observed FHLCs in this sample. We present proper motion measures for each object, indicating that the sample is a mixture of extremely distant (>100 kpc) halo giant stars, useful for constraining halo dynamics, plus members of the recently-recognized exotic class of very nearby dwarf carbon (dC) stars. Motions, and thus dC classification, are inferred for 40-50 percent of the sample, depending on the level of statistical significance invoked. The new list of dC stars presented here, although selected from only a small fraction of the final SDSS, doubles the number of such objects found by all previous methods. (Abstract abridged).Comment: Accepted for publication in The Astronomical Journal, Vol. 124, Sep. 2002, 40 pages, 7 figures, AASTeX v5.