Filling the gaps: A comprehensive understanding of diets and ecosystem interactions within the modern and fossil small mammal communities of Meade Basin, Kansas

The modern Great Plains ecosystem began shifting from a woodland biome to a grassland in the Miocene. Stable isotope analysis (SIA) of a diverse community of local consumers, in this case small mammals, provides both a paleoenvironmental record of the shift from woodland C3 biomass to grassland C4 biomass, and a paleoecological record of species interactions and community dynamics. The Meade Basin in southwestern Kansas contains a rich and fairly complete fossil record of a Great Plains small mammal community throughout the past 5 million years. SIA of fossil tooth enamel from Meade small mammals has revealed interesting dietary patterns among, and within, major lineages of rodents and lagomorphs. Yet, an incomplete understanding of ecosystem interactions in the modern small mammal community hinders our interpretation of these fossil isotopic datasets. Until now, the majority of the modern Meade dataset was derived from 5 years of live trapping across a range of prairie microhabitats, and this sample is inherently biased towards small bodied and nocturnal species. The goal of this project is to fill taxonomic gaps in the modern sample, and provide a complete interpretation of current small mammal dietary ecology that is directly comparable to the fossil data. Our samples are derived from biologic (owl pellets, raptor nests and prairie dog burrows), and anthropogenic (road kill) collections, which contain remains of previously under sampled taxa within the small mammal community. Preliminary results have already highlighted the importance of this work. For example, prairie dogs are the highest C4 grass consumers in the modern community, and without them we would underestimate the use of C4 resources by small mammals. As another example, rabbits have predominantly been mixed C3-C4 to strongly C3 plant consumers throughout the past 5 million years, and that diet appears to be maintained today. Our complete isotopic dataset consists of results for more than 50 specimens, and yields a comprehensive understanding of species and ecosystem interactions among small mammals in the Great Plains today

Comparing 40-year sediment records of aquatic ecosystem evolution in two large lakes in the blast zone of Mount St. Helens

The 1980 eruption of Mount St. Helens dramatically altered the surrounding landscape, removing vegetation and impacting hydrology. The pyroclastic debris flow partially filled Spirit Lake and dammed Coldwater Creek, creating Coldwater Lake. Spirit Lake was sterilized by the eruption, and fallen trees from the blast washed into the lake forming a floating log mat covering 20% of the surface. While significant research has gone into understanding the history of ecosystem recovery in Spirit Lake, nearby Coldwater Lake has not been studied as extensively. These two lakes provide a unique opportunity to study how volcanic eruptions alter freshwater environments. Recent research at Spirit Lake has focused on spatial heterogeneity in the post-eruption lake ecosystem related to patterns of log mat coverage, and our current work at Coldwater Lake provides an important point of comparison in a lake without the influence of woody debris. In order to study the evolution of the Coldwater Lake ecosystem, we collected four sediment cores (~30 centimeters each), extruded and sectioned the cores, and analyzed diatom abundance and diversity, and carbon and nitrogen biogeochemistry through time. These sediment records reflect changes in lake conditions, such as water chemistry, and in aquatic ecology. Our data show a substantial increase in diatom abundance and diversity through time, with highest levels in the top 15 centimeters of the cores. The percent carbon and nitrogen also increases in younger core sediments. Coldwater Lake displays some spatial variability in diatom abundance between deeper and shallower locations in the lake, but benthic taxa are dominant across the lake. Coldwater Lake has a lower ratio of pelagic to benthic diatom taxa than Spirit Lake, implying that Coldwater Lake is more nutrient poor. The differences between the two lakes can likely be mainly explained by the differences in their geologic formations, and both have come to ecological equilibrium

Termites Create Spatial Structure And Govern Ecosystem Function By Affecting N-2 Fixation In An East African Savanna

The mechanisms by which even the clearest of keystone or dominant species exert community-wide effects are only partially understood in most ecosystems. This is especially true when a species or guild influences community-wide interactions via changes in the abiotic landscape. Using stable isotope analyses, we show that subterranean termites in an East African savanna strongly influence a key ecosystem process: atmospheric nitrogen fixation by a monodominant tree species and its bacterial symbionts. Specifically, we applied the N-15 natural abundance method in combination with other biogeochemical analyses to assess levels of nitrogen fixation by Acacia drepanolobium and its effects on co-occurring grasses and forbs in areas near and far from mounds and where ungulates were or were not excluded. We find that termites exert far stronger effects than do herbivores on nitrogen fixation. The percentage of nitrogen derived from fixation in Acacia drepanolobium trees is higher (55-80%) away from mounds vs. near mounds (40-50%). Mound soils have higher levels of plant available nitrogen, and Acacia drepanolobium may preferentially utilize soil-based nitrogen sources in lieu of fixed nitrogen when these sources are readily available near termite mounds. At the scale of the landscape, our models predict that termite/soil derived nitrogen sources influence \u3e50% of the Acacia drepanolobium trees in our system. Further, the spatial extent of these effects combine with the spacing of termite mounds to create highly regular patterning in nitrogen fixation rates, resulting in marked habitat heterogeneity in an otherwise uniform landscape. In summary, we show that termite-associated effects on nitrogen processes are not only stronger than those of more apparent large herbivores in the same system, but also occur in a highly regular spatial pattern, potentially adding to their importance as drivers of community and ecosystem structure

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator-prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator-prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator-prey networks ( two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator-prey networks.Institute of Geophysics and Planetary PhysicsInstitute of Geophysics and Planetary PhysicsUC-Santa Cruz Committee-On-ResearchUCSanta Cruz CommitteeOnResearchNational Science Foundation Graduate Student Fellowship (NSFGRF)National Science Foundation Graduate Student Fellowship (NSF-GRF)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP

Spatial Dynamics and Ecosystem Functioning

Ecosystem functioning is dependent upon the way species become distributed across space

Galaxy Clusters Selected with the Sunyaev-Zel'dovich Effect from 2008 South Pole Telescope Observations

We present a detection-significance-limited catalog of 21 Sunyaev-Zel'dovich selected galaxy clusters. These clusters, along with 1 unconfirmed candidate, were identified in 178 deg^2 of sky surveyed in 2008 by the South Pole Telescope to a depth of 18 uK-arcmin at 150 GHz. Optical imaging from the Blanco Cosmology Survey (BCS) and Magellan telescopes provided photometric (and in some cases spectroscopic) redshift estimates, with catalog redshifts ranging from z=0.15 to z>1, with a median z = 0.74. Of the 21 confirmed galaxy clusters, three were previously identified as Abell clusters, three were presented as SPT discoveries in Staniszewski et al, 2009, and three were first identified in a recent analysis of BCS data by Menanteau et al, 2010; the remaining 12 clusters are presented for the first time in this work. Simulated observations of the SPT fields predict the sample to be nearly 100% complete above a mass threshold of M_200 ~ 5x10^14 M_sun/h at z = 0.6. This completeness threshold pushes to lower mass with increasing redshift, dropping to ~4x10^14 M_sun/h at z=1. The size and redshift distribution of this catalog are in good agreement with expectations based on our current understanding of galaxy clusters and cosmology. In combination with other cosmological probes, we use the cluster catalog to improve estimates of cosmological parameters. Assuming a standard spatially flat wCDM cosmological model, the addition of our catalog to the WMAP 7-year analysis yields sigma_8 = 0.81 +- 0.09 and w = -1.07 +- 0.29, a ~50% improvement in precision on both parameters over WMAP7 alone.Comment: 19 pages, 9 figures, 4 appendice

Instabilities in crystal growth by atomic or molecular beams

The planar front of a growing a crystal is often destroyed by instabilities. In the case of growth from a condensed phase, the most frequent ones are diffusion instabilities, which will be but briefly discussed in simple terms in chapter II. The present review is mainly devoted to instabilities which arise in ballistic growth, especially Molecular Beam Epitaxy (MBE). The reasons of the instabilities can be geometric (shadowing effect), but they are mostly kinetic or thermodynamic. The kinetic instabilities which will be studied in detail in chapters IV and V result from the fact that adatoms diffusing on a surface do not easily cross steps (Ehrlich-Schwoebel or ES effect). When the growth front is a high symmetry surface, the ES effect produces mounds which often coarsen in time according to power laws. When the growth front is a stepped surface, the ES effect initially produces a meandering of the steps, which eventually may also give rise to mounds. Kinetic instabilities can usually be avoided by raising the temperature, but this favours thermodynamic instabilities. Concerning these ones, the attention will be focussed on the instabilities resulting from slightly different lattice constants of the substrate and the adsorbate. They can take the following forms. i) Formation of misfit dislocations (chapter VIII). ii) Formation of isolated epitaxial clusters which, at least in their earliest form, are `coherent' with the substrate, i.e. dislocation-free (chapter X). iii) Wavy deformation of the surface, which is presumably the incipient stage of (ii) (chapter IX). The theories and the experiments are critically reviewed and their comparison is qualitatively satisfactory although some important questions have not yet received a complete answer.Comment: 90 pages in revtex, 45 figures mainly in gif format. Review paper to be published in Physics Reports. Postscript versions for all the figures can be found at http://www.theo-phys.uni-essen.de/tp/u/politi

1963: Abilene Christian College Bible Lectures - Full Text

THE CHRISTIAN AND MORALITY” Being the Abilene Christian College Annual Bible Lectures 1963 Price: $3.95 Published by ABILENE CHRISTIAN COLLEGE STUDENTS EXCHANGE ACC Station Abilene, Texa

Writing in Britain and Ireland, c. 400 to c. 800

No abstract available