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The chemical and isotopic compositions of sedimentary organic matter (SOM) from two mid-slope sites of the northern Cascadia margin were investigated during Integrated Ocean Drilling Program (IODP) Expedition 311 to elucidate the organic matter origins and identify potential microbial contributions to SOM. Gas hydrate is present at both locations (IODP...

The role of introduced avian malaria Plasmodium relictum in the decline and extinction of native Hawaiian forest birds has become a classic example of the potential effect of invasive diseases on biological diversity of naïve populations. However, empirical evidence describing the impact of avian malaria on fitness of Hawai‵i's endemic forest birds...

Alluvial clay soil samples from six boreholes advanced to depths of 400-450 cm (top of limestone bedrock) from the Chattanooga Coke Plant (CCP) site were examined micromorphologically and geochemically in order to determine if pedogenic siderite (FeCO3) was present and whether siderite occurrence was related to organic contaminant distribution. Samples...

Increasingly, groundwater management requires more accurate hydrogeologic frameworks for groundwater models. These complex issues have created the demand for innovative approaches to data collection. In complicated terrains, groundwater modelers benefit from continuous high‐resolution geologic maps and their related hydrogeologic‐parameter estimates. The USGS and its partners have collaborated to use airborne...

We used near-term climate scenarios for the continental United States, to model 12 invasive plants species. We created three potential habitat suitability models for each species using maximum entropy modeling: (1) current; (2) 2020; and (3) 2035. Area under the curve values for the models ranged from 0.92 to 0.70,...

Drought- and insect-associated tree mortality at low-elevation ecotones is a widespread phenomenon but the underlying mechanisms are uncertain. Enhanced growth sensitivity to climate is widely observed among trees that die, indicating that a predisposing physiological mechanism(s) underlies tree mortality. We tested three, linked hypotheses regarding mortality using a ponderosa pine...

The disputed age of the deep crust of the Colorado Province is central to hypotheses for Paleoproterozoic crustal growth in the region. We studied the high-grade Big Creek Gneiss, southeastern Wyoming, as a potential exposure of pre-1780 Ma basement rocks. New geologic mapping and U-Pb geochronological data indicate that the...

The release of the saltcedar beetle (Diorhabda carinulata) has resulted in the periodic defoliation of tamarisk (Tamarix spp.) along more than 1000 river km in the upper Colorado River Basin and is expected to spread along many other river reaches throughout the upper basin, and possibly into the lower Colorado...

The conventional view that the basement of the southern and central Appalachians represents juvenile Mesoproterozoic crust, the final stage of growth of Laurentia prior to Grenville collision, has recently been challenged. New whole-rock Pb and Sm‑Nd isotopic data are presented from Mesoproterozoic basement in the southern and central Appalachians and...

No abstract available....

As a fundamental unit of the landscape, hillslopes are studied for their retention and release of water and nutrients across a wide range of ecosystems. The understanding of these near-surface processes is relevant to issues of runoff generation, groundwater-surface water interactions, catchment export of nutrients, dissolved organic carbon, contaminants (e.g....

One anticipated benefit of ecosystem restoration is water quality improvement. This study evaluated NO3-N and phosphorus in subsurface waters during prairie establishment following decades of row-crop agriculture. A prairie seeding in late 2003 became established in 2006. Wells and suction cup samplers were monitored for NO3-N and phosphorus. Nitrate-N varied...

In the classic microseismic band of 5-20 sec, seismic noise consists mainly of fundamental mode Rayleigh and Love waves; however, at shorter periods seismic noise also contains a significant amount of body-wave energy and higher mode surface waves. In this study we perform a global survey of Earth's short-period seismic...

This study involved analyses of kerogen petrography, gas desorption, geochemistry, microporosity, and mesoporosity of the New Albany Shale (Devonian-Mississippian) in the eastern part of the Illinois Basin. Specifically, detailed core analysis from two locations, one in Owen County, Indiana, and one in Pike County, Indiana, has been conducted. The gas...

Impacts of global climate change, such as sea level rise and severe drought, have altered the hydrology of coastal salt marshes resulting in submergence and subsequent degradation of ecosystem function. A potential method of rehabilitating these systems is the addition of sediment-slurries to increase marsh surface elevation, thus ameliorating effects...

The morphologies of some martian gullies appear similar to terrestrial features associated with debris flow initiation, erosion, and deposition. On Earth, debris flows are often triggered by shallow subsurface throughflow of liquid water in slope-mantling colluvium. This flow causes increased levels of pore pressure and thus decreased shear strength, which...

Mechanisms reported to promote landscape self‐organization cannot explain vegetation patterning oriented parallel to flow. Recent catastrophic shifts in Everglades landscape pattern and ecological function highlight the need to understand the feedbacks governing these ecosystems. We modeled feedback between vegetation, hydrology, and sediment transport on the basis of a decade of...

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are...

Groundwater modeling has become a vital component to water supply and contaminant transport investigations. An important component of groundwater modeling under steady state conditions is selecting a representative hydraulic conductivity (K) estimate or set of estimates which defines the K field of the studied region. Currently, there are a number...

Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (???10 mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling....

Pollen and microscopic charcoal examined in Holocene sediment core samples record major environmental modifications affecting Alexandria's Eastern Harbor through time. We assess whether such changes on Egypt's coastal margin were influenced primarily by natural, or natural plus human, or primarily human factors. We focus on (1) the times when pollen...

Age- and sex-specific survival and dispersal are important components in the dynamics and genetic structure of bird populations. For many avian taxa survival rates at the adult and juvenile life stages differ, but in long-lived species juveniles' survival is logistically challenging to study. We present the first estimates of hatch-year...

Temperatures in southwestern North America are projected to increase 3.5-4 ??C over the next 60-90 years. This will precipitate ecological shifts as the ranges of species change in response to new climates. During this shift, rapid-colonizing species should increase, whereas slow-colonizing species will at first decrease, but eventually become reestablished...

The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have...

Riparian vegetation composition, structure and abundance are governed to a large degree by river flow regime and flow-mediated fluvial processes. Streamflow regime exerts selective pressures on riparian vegetation, resulting in adaptations (trait syndromes) to specific flow attributes. Widespread modification of flow regimes by humans has resulted in extensive alteration of...