Spatiotemporal Variations in the Fire Regimes of Whitebark Pine (\u3cem\u3ePinus albicaulis\u3c/em\u3e Engelm.) Forests, Western Montana, USA, and Their Management Implications

Whitebark pine (Pinus albicaulis) is a long-lived tree species that exists throughout high elevation forest communities of western North America. It is the foundation of a diminishing ecosystem that supports Clark’s nutcrackers, red squirrels, grizzly bears, and black bears. The decline of this species is directly related to mortality from widespread mountain pine beetle outbreaks and infestation by the invasive white pine blister rust, and may be exacerbated by fire suppression. Prescribed fire will be a primary management tool in efforts to preserve whitebark pine on the landscape. My research used dendrochronology to investigate the fire history of whitebark pine stands on three mountains in the Lolo National Forest, Montana, via fire-scar and age structure analyses. I then used these data to assess the USDA Fire Regime Condition Classification (FRCC) fire regime types for my sites. Additionally, I utilized traditional superposed epoch analysis techniques in a novel manner to develop a multi-decadal superposed epoch analysis for fire-climate and fire-tree establishment analyses. I sampled between 40 and 50 fire-scarred trees, snags, and remnants, and collected age structure data in two 0.5 ha plots at each site. Samples at all sites recorded a frost event in AD 1601 related to southern hemisphere volcanic activity. The fire-history and stand-structure data indicate all three sites were characterized by mixed-severity fire regimes and generally agreed with the FRCC classifications. However, fires occurred with greater frequency than previously found in whitebark pine forests and distinct differences existed between the fire regimes of each of the three sites that are likely related to topography, forest cover, and climate conditions. A period of widespread fire activity at all three sites occurred from the mid-1700s to the early 1800s and may be the expression of interactions between several climate variables. Fire suppression led to a decline in fire activity in the 1900s, but subalpine fir trees began establishing between 300 and 140 years ago at all three sites. This suggests fire suppression may not be responsible for the advanced succession found in these whitebark pine forests and management decisions based on that assumption are inappropriate for these sites. In addition, the spatial and temporal variability in fire activity between these sites requires a refinement in the Fire Regime Condition Classification methods if they are to be used for managing whitebark pine forests

Solar Hydrogen Production by Solar Thermal Decoupled Electrolysis: Analysis of FE3O4 in Solution

The Valparaiso University Solar Research Project utilizes a solar thermal decoupled electrolysis process for the production of H2 from water. This study focuses on the electrochemical conversion of magnetite to hematite during the H2 production process. Laboratory experiments show that the expected amount of H2 gas forms at the cathode of the electrolytic cell, but we have encountered difficulties recovering the expected amount of solid hematite at the anode. An intensive study of the complex solution chemistry using cyclic voltammetry, Mossbauer spectroscopy, and solubility modeling showed that several dissolved iron species potentially exist in solution. Further work must be done to clarify which species are key participants in the overall electrochemical reaction. This information will help us to determine and implement reaction conditions that are favorable for precipitation of hematite or other oxidized iron species

Climate Response in Near-Treeline Bristlecone Pine

In the White Mountains of California, eight bristlecone pine (Pinus longaeva) tree-ring width chronologies were developed from trees at upper treeline and just below upper treeline along North- and South-facing elevational transects from treeline to ~90 m below. There is evidence for a climate-response threshold between approximately 60–80 vertical m below treeline, above which trees have shown a positive growth-response to temperature and below which they do not. Chronologies from 80 m or more below treeline show a change in climate response and do not correlate strongly with temperature-sensitive chronologies developed from trees growing at upper treeline. Rather, they more closely resemble lower elevation precipitation-sensitive chronologies. At the highest sites, trees on South-facing slopes grow faster than trees on North-facing slopes. High growth rates in the treeline South-facing trees have declined since the mid- 1990s. This suggests the possibility that the climate-response of the highest South-facing trees may have changed and that temperature may no longer be the main limiting factor for growth on the South aspect. These results indicate that increasing warmth may lead to a divergence between tree growth and temperature at previously temperature-limited sites

Multi-Element Abundance Measurements from Medium-Resolution Spectra. III. Metallicity Distributions of Milky Way Dwarf Satellite Galaxies

We present metallicity distribution functions (MDFs) for the central regions of eight dwarf satellite galaxies of the Milky Way: Fornax, Leo I and II, Sculptor, Sextans, Draco, Canes Venatici I, and Ursa Minor. We use the published catalog of abundance measurements from the previous paper in this series. The measurements are based on spectral synthesis of iron absorption lines. For each MDF, we determine maximum likelihood fits for Leaky Box, Pre-Enriched, and Extra Gas (wherein the gas supply available for star formation increases before it decreases to zero) analytic models of chemical evolution. Although the models are too simplistic to describe any MDF in detail, a Leaky Box starting from zero metallicity gas fits none of the galaxies except Canes Venatici I well. The MDFs of some galaxies, particularly the more luminous ones, strongly prefer the Extra Gas Model to the other models. Only for Canes Venatici I does the Pre-Enriched Model fit significantly better than the Extra Gas Model. The best-fit effective yields of the less luminous half of our galaxy sample do not exceed 0.02 Z_sun, indicating that gas outflow is important in the chemical evolution of the less luminous galaxies. We surmise that the ratio of the importance of gas infall to gas outflow increases with galaxy luminosity. Strong correlations of average [Fe/H] and metallicity spread with luminosity support this hypothesis.Comment: 17 pages, 5 figures; accepted for publication in ApJ; minor corrections in v3; corrected typographical errors in Tables 1 and 3 in v