EFFECTS OF WILDFIRE AND POST-FIRE SALVAGE LOGGING ON RILL NETWORKS AND SEDIMENT DELIVERY IN CALIFORNIA FORESTS

Wildfires can increase soil erosion by orders of magnitude over rates in unburned forests and negatively impact aquatic resources. Rill erosion is a dominant erosion and sediment transport mechanism in burned forests, and hydrologically connected rills can form networks on burned hillslopes. At the swale scale (\u3c 10,000 m2), little is known about how rill networks develop under different burn severities over time, their relationship with sediment yields, and the effect of post-fire salvage logging on rill networks and sediment yields. The first study assessed rill networks and sediment yields in three burn severities in the inland Coast Range of California, USA, after the 2015 Valley Fire. The results indicated the rill networks in high burn severity areas reached nearly the entire extent of the burned hillslopes. Rill densities in high burn severity areas were significantly higher (19-23 cm m-2) than low and moderate severity areas (0.5-2.1 cm m-2). Sediment yields from high burn severity areas (13-15 Mg ha-1) were significantly higher than the low to moderate burn severity areas (0.1-3.4 Mg ha-1), and highly correlated with rill density (r2 = 0.97). Results indicate that the extensive rill networks in high burn severity areas can greatly increase connectivity, resulting in increased sediment delivery downslope. The second study assessed the effects of post-fire salvage logging on soil bulk density, field saturated hydraulic conductivity, ground cover, rill networks and sediment yields in the central California Sierra Nevada following the 2013 Rim Fire. Post-fire logging resulted in 9-56% percent soil disturbance, which was dominated by high traffic skid trails (9-29%). Feller buncher tracks averaged 2% of swale areas, while mixed traffic areas averaged 7% and were only found in five of nine logged swales. Within high traffic logging disturbance soil bulk density was increased, field saturated hydraulic conductivity reduced, and bare soil increased. When scaled up to the swale scale, logging had no significant effect on ground cover, but did result in significantly higher wood cover relative to unlogged swales. High traffic skid trails typically initiated extensive rill networks, with up to 20 cm m-2 sourced from skid trails. Rills in skid trails were typically concentrated at waterbars and directed downslope, where they often connected to the outlet. Control swales had 4-18 rills from untrafficked areas, and logged swales had 0-15 rills from untrafficked areas and 1-12 rills from disturbed areas. As with the ground cover, rill densities in logged and unlogged swales were not significantly different. Mean annual sediment yields in logged and unlogged swales were not significantly different, and the high input of wood cover from logging did not have a significant effect on rill density or sediment yield. In unlogged and logged swales, both rill density and sediment yield appeared to be reduced by large areas of undisturbed ground with high surface roughness, which disconnected rills from the stream network. To reduce rill connectivity and sediment delivery from logging disturbance, land managers should optimize skid trail layouts to reduce the spatial footprint of skid trails, increase ground cover on skid trails and below waterbar outlets, and retain buffers with high ground cover between logging disturbance and ephemeral channels

Senior Recital: Jacob Greifinger, trumpet

This recital is presented in partial fulfillment of requirements for the degree Bachelor of Music in Performance. Mr. Greifinger studies trumpet with Michael Tiscione.https://digitalcommons.kennesaw.edu/musicprograms/2224/thumbnail.jp

Stellar luminosity functions of rich star clusters in the Large Magellanic Cloud

We show the results of deep V and I HST photometry of 6 rich star clusters in the Large Magellanic Cloud with different ages and metallicities. The number of stars with measured magnitudes in each cluster varies from about 3000 to 10000. We build stellar density and surface brightness profiles for the clusters and extract half-light radii and other structural parameters for each. We also obtain luminosity functions, Phi (Mv), down to Mv ~ 6 (m/msun > 0.6), and investigate their dependence with distance from the cluster centre well beyond their half-light radius. In all clusters we find a systematic increase in the luminosity function slope with radial distance from the centre. Among the clusters displaying significant mass segregation are the two youngest in the sample: NGC 1805 and NGC 1818. For these two clusters we obtain present-day mass functions. The NGC 1818 mass function is in excellent agreement with that derived by other authors, also using HST data. They young cluster mass function slopes differ, that of NCG 1805 being systematically steeper than NGC 1818. Since these are very young stellar systems (age < 40 Myrs), these variations may reflect the initial conditions rather than evolution due to internal dynamics.Comment: 10 pages, 24 figure

Mt. Baker Highway SR 542-East Church Mountain Road realignment

The Washington State Department of Transportation (WSDOT) proposes to realign State Route 542 away from the North Fork Nooksack River in order to reduce environmental impacts from repetitive roadway maintenance, and to improve fish passage at Chain-up Creek. Work includes: realigning approximately 1,600 linear feet of roadway up to 80 feet away from the North Fork Nooksack River, replacing a 5-foot diameter, 80-foot long culvert with a 30-foot long, 40-foot wide bridge over Chain-up Creek, and installing 5 porous weirs and 2 anchored large woody debris structures in the restored stream channel

The Star Formation History of the Large Magellanic Cloud

We present the first-ever global, spatially-resolved reconstruction of the star formation history (SFH) of the Large Magellanic Cloud (LMC), based on the application of our StarFISH analysis software to the multiband photometry of twenty million of its stars from the Magellanic Clouds Photometric Survey. The general outlines of our results are consistent with previously published results: following an initial burst of star formation, there was a quiescent epoch from approximately 12 to 5 Gyr ago. Star formation then resumed and has proceeded until the current time at an average rate of roughly 0.2 solar masses/yr, with temporal variations at the factor-of-two level. The re-ignition of star formation about 5 Gyr ago, in both the LMC and SMC, is suggestive of a dramatic event at that time in the Magellanic system. Among the global variations in the recent star formation rate are peaks at roughly 2 Gyr, 500 Myr, 100 Myr and 12 Myr. The peaks at 500 Myr and 2 Gyr are nearly coincident with similar peaks in the SFH of the Small Magellanic Cloud, suggesting a joint history for these galaxies extending back at least several Gyr. The chemical enrichment history recovered from our StarFISH analysis is in broad agreement with that inferred from the LMC's star cluster population, although our constraints on the ancient chemical enrichment history are weak. We conclude from the concordance between the star formation and chemical enrichment histories of the field and cluster populations that the field and cluster star formation modes are tightly coupled.Comment: 20 pages, with color figures. Accepted for publication in A

ROSAT X-ray sources in the field of the LMC. II.Statistics of background AGN and X-ray binaries

About 200 X-ray sources from a sample of spectrally hard ROSAT PSPC sources, given in the catalog of Haberl & Pietsch (1999), and observed in a ~60 square degree field of the LMC during several archival pointed observations with a wide range of exposure times have been reanalyzed. For these sources accurate count rates and hardness ratios have been recalculated. In comparison to Haberl & Pietsch (1999) we used merged data from all available observations and we derived average source parameters by investigating each source individually. From a simulation powerlaw spectral tracks have been derived in the HR1 - HR2 plane and ~170 sources have been classified as background X-ray sources or as LMC X-ray binaries. 80% of the spectrally hard X-ray sources with more than 50 observed counts have been found to be consistent with background X-ray sources and 20% with LMC X-ray binaries (53 sources with AGN and 15 with X-ray binaries). The discovery of a new supersoft source RX J0529.4-6713 at the southern HI boundary of the supergiant shell LMC4 is reported. We find two new candidate X-ray binary systems which are associated with the optical bar of the LMC and additional candidate X-ray binaries which are associated with supergiant shells.Comment: 13 pages, accepted for publication in A&A, March 22 200

Inbreeding shapes the evolution of marine invertebrates

Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of nonrandom mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self-fertilization and its consequences for automatic selection, inbreeding depression, purging, and reproductive assurance, whereas studies of animal mating systems have often assumed that inbreeding is rare, and that natural selection favors traits that promote outbreeding. Given that many sessile and sedentary marine invertebrates and marine macroalgae share key life history features with seed plants (e.g., low mobility, modular construction, and the release of gametes into the environment), their mating systems may be similar. Here, we show that published estimates of inbreeding coefficients (FIS) for sessile and sedentary marine organisms are similar and at least as high as noted in terrestrial seed plants. We also found that variation in FIS within invertebrates is related to the potential to self-fertilize, disperse, and choose mates. The similarity of FIS for these organismal groups suggests that inbreeding could play a larger role in the evolution of sessile and sedentary marine organisms than is currently recognized. Specifically, associations between traits of marine invertebrates and FIS suggest that inbreeding could drive evolutionary transitions between hermaphroditism and separate sexes, direct development and multiphasic life cycles, and external and internal fertilization

Ages and Luminosities of Young SMC/LMC Star Clusters and the recent Star Formation History of the Clouds

In this paper we discuss the age and spatial distribution of young (age$<$1Gyr) SMC and LMC clusters using data from the Magellanic Cloud Photometric Surveys. Luminosities are calculated for all age-dated clusters. Ages of 324 and 1193 populous star clusters in the Small and the Large Magellanic Cloud have been determined fitting Padova and Geneva isochrone models to their resolved color-magnitude diagrams. The clusters cover an age range between 10Myr and 1Gyr in each galaxy. For the SMC a constant distance modulus of $(m-M)_0$ = 18.90 and a metallicity of Z = 0.004 were adopted. For the LMC, we used a constant distance modulus of $(m-M)_0$ = 18.50 and a metallicity of Z = 0.008. For both galaxies, we used a variable color excess to derive the cluster ages. We find two periods of enhanced cluster formation in both galaxies at 160Myr and 630Myr (SMC) and at 125Myr and 800Myr (LMC). We present the spatially resolved recent star formation history of both Clouds based on young star clusters. The first peak may have been triggered by a close encounter between the SMC and the LMC. In both galaxies the youngest clusters reside in the supergiant shells, giant shells, the inter-shell regions, and toward regions with a high H$\alpha$ content, suggesting that their formation is related to expansion and shell-shell interaction. Most of the clusters are older than the dynamical age of the supergiant shells. No evidence for cluster dissolution was found. Computed V band luminosities show a trend for fainter magnitudes with increasing age as well as a trend for brighter magnitudes with increasing apparent cluster radii.Comment: 17 pages, 14 figures, Accepted for publication in A&

Isoforms of U1-70k control subunit dynamics in the human spliceosomal U1 snRNP

Most human protein-encoding genes contain multiple exons that are spliced together, frequently in alternative arrangements, by the spliceosome. It is established that U1 snRNP is an essential component of the spliceosome, in human consisting of RNA and ten proteins, several of which are post- translationally modified and exist as multiple isoforms. Unresolved and challenging to investigate are the effects of these post translational modifications on the dynamics, interactions and stability of the particle. Using mass spectrometry we investigate the composition and dynamics of the native human U1 snRNP and compare native and recombinant complexes to isolate the effects of various subunits and isoforms on the overall stability. Our data reveal differential incorporation of four protein isoforms and dynamic interactions of subunits U1-A, U1-C and Sm-B/B’. Results also show that unstructured post- ranslationally modified C-terminal tails are responsible for the dynamics of Sm-B/B’ and U1-C and that their interactions with the Sm core are controlled by binding to different U1-70k isoforms and their phosphorylation status in vivo. These results therefore provide the important functional link between proteomics and structure as well as insight into the dynamic quaternary structure of the native U1 snRNP important for its function.This work was funded by: BBSRC (OVM), BBSRC and EPSRC (HH and NM), EU Prospects (HH), European Science Foundation (NM), the Royal Society (CVR), and fellowship from JSPS and HFSP (YM and DAPK respectively)