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Geomechanical modeling of induced seismicity source parameters and implications for seismic hazard assessment, credited to Goertz-Allmann, BP, published in 2012. Published in Geophysics, volume 78, issue 1, in 2012.
Rather than simply enhancing invasion risk, climate change may also reduce invasive plant competitiveness if conditions become climatically unsuitable. Using bioclimatic envelope modeling, we show that climate change could result in both range expansion and contraction for five widespread and dominant invasive plants in the western United States. Yellow starthistle (Centaurea solstitialis) and tamarisk (Tamarix spp.) are likely to expand with climate change. Cheatgrass (Bromus tectorum) and spotted knapweed (Centaurea biebersteinii) are likely to shift in range, leading to both expansion and contraction. Leafy spurge (Euphorbia esula) is likely to contract. The retreat of onceintractable invasive species could create...
Operations including borehole fluid injections are typical for exploration and development of hydrocarbon or geothermic reservoirs. Microseismicity occurring during such operations has a large potential for understanding physics of the seismogenic process as well as in obtaining detailed information about reservoirs at locations as far as several kilometers from boreholes. We propose that the phenomenon of microseismicity triggering by borehole fluid injections is related to the process of the Frenkel-Biot slow wave propagation. In the low-frequency range (hours or days of fluid injection durations) this process reduces to the pore-pressure diffusion. We search for diffusion-related features of induced micro seismicity....
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Journal of Engineering Mechanics-Asce
This dataset is the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3800 observations representing 27 temperature manipulation studies, spanning nine biomes and nearly two decades of warming experiments. Data for this study were obtained from a combination of unpublished data and published literature values. We find that although warming increases soil respiration rates, there is limited evidence for a shifting respiration response with experimental warming. We also note a universal decline in the temperature sensitivity of respiration at soil temperatures >25°C. This dataset includes 3817 observations, from control (n=1812), first (i.e., lowest or sole) level...
Categories: Data,
Publication;
Types: Citation;
Tags: Boreal Forest,
Desert,
Ecology,
Meadow,
Northern Shrubland,
Changes in the composition, structure, and functions of forest ecosystems typically occur over long periods of time. In the Pacific Northwest region of the United States, for example, it is not unusual for individual dominant trees to survive for 500 years or longer (Franklin and Dyrness, 1973; Waring and Franklin, 1979). Significant compositional and structural changes may continue to occur 750 years after a stand-initiating disturbance (Franklin and Spies, 1991). Documenting and understanding these changes requires a variety of approaches. At least five complementary approaches have been taken to increase, scientific understanding of these intrinsically slow changes: chronosequences (Pickett, 1989); palynology...
Categories: Publication;
Types: Citation
In this study, we analyzed the above-ground biomass data for 631 trees with a diameter ⩾10 cm from different biogeographical regions in Colombia. The aims of this research were (1) to evaluate the accuracy of the most commonly employed pantropical allometric models for the estimation of above-ground biomass of natural forests in different sites located along a complex environmental gradient, (2) to develop new models that enable more precise estimations of current carbon stores in the above-ground biomass of natural forest ecosystems in Colombia, and (3) to evaluate the effect on allometric models of forest type classifications as determinants of above-ground biomass variation. The Brown et al. (1989) model for...
Categories: Publication;
Types: Citation
Summary 1. Metabolic scaling theory predicts that diameter growth rates of tree species are related to tree diameter by a universal scaling law. This model has been criticised because it ignores the influence of competition for resources such as light on the scaling of demographic rates with size. 2. We here test whether scaling exponents of abundant tropical tree species comply with the prediction of metabolic scaling theory and evaluate whether the scaling of growth with size depends on light availability. Light reaching each individual tree was estimated from yearly vertical censuses of canopy density, and a hierarchical Bayesian approach allowed quantifying confidence intervals for scaling exponents and accounting...
It is well know that every earthquake can spawn others (e.g., as aftershocks), and that such triggered events can be large and damaging, as recently demonstrated by L’Aquila, Italy and Christchurch, New Zealand earthquakes. In spite of being an explicit USGS strategic-action priority (http://pubs.usgs.gov/of/2012/1088; page 32), the USGS currently lacks an automated system with which to forecast such events and official protocols for disseminating the potential implications. This capability, known as Operational Earthquake Forecasting (OEF), could provide valuable situational awareness to emergency managers, the public, and other entities interested in preparing for potentially damaging earthquakes. With the various...
Categories: Data,
Project;
Tags: Active,
All Working Groups,
California,
Earthquakes,
Natural Hazards
There has been increasing attention placed on the need for water availability information at ungauged locations, particularly related to balancing human and ecological needs for water. Critical to assessing water availability is the necessity for daily streamflow time series; however, most of the rivers in the United States are ungauged. This proposal leverages over $1M currently allocated to the USGS National Water Census Program towards developing an integrated modeling approach to estimate daily streamflow at ungauged locations, with the ultimate goal of providing daily streamflow estimates at 160,000 ungauged catchments across the United States. By assembling a diverse and prolific group of international scientists,...
Abstract Hydrologic exchange fluxes (HEFs) vary significantly along river corridors due to spatio-temporal changes in discharge and geomorphology. This variability results in the emergence of biogeochemical hot-spots and hot-moments that ultimately control solute and energy transport and ecosystem services from the local to the watershed scales. In this work, we use a reduced-order model to gain mechanistic understanding of river bank storage and sinuosity-driven hyporheic exchange induced by transient river discharge. This is the first time that a systematic analysis of both processes is presented and serves as an initial step to propose parsimonious, physics-based models for better predictions of water quality...
Categories: Publication;
Types: Citation
A nested sampling network on the Colorado (CR) and Missouri Rivers (MR) provided data to assess impacts of large-scale reservoir systems and climate on carbon export. The Load Estimator (LOADEST) model was used to estimate both dissolved inorganic and organic carbon (DIC and DOC) fluxes for a total of 22 sites along the main stems of the CR and MR. Both the upper CR and MR DIC and DOC fluxes increased longitudinally, but the lower CR fluxes decreased while the lower MRs continued to increase. We examined multiple factors through space and time that help explain these flux patterns. Seasonal variability in precipitation and temperature, along with site-level concentration versus discharge relationships proved to...
The North America 2k (NAM2k) Working Group recently met at the USGS Powell Center to begin Phase 2 of the NAM2k project in earnest. Phase 2 aims to build on the success of the first phase by expanding the scope of the project, both by including a more diverse and comprehensive array of paleoclimatic evidence for the past two millennia in North America, and by analyzing additional indicators and reconstructions of parameters beyond surface temperature, most notably, hydroclimate. Twenty working group members with expertise in tree rings, lake and marine sediments, corals, speleothems, boreholes, ice cores, glacial landforms, and climate modeling participated in the meeting.
Categories: Publication;
Types: Citation
Migratory species support ecosystem process and function in multiple areas, establishing ecological linkages between their different habitats. As they travel, migratory species also provide ecosystem services to people in many different locations. Previous research suggests there may be spatial mismatches between locations where humans use services and the ecosystems that produce them. This occurs with migratory species, between the areas that most support the species' population viability - and hence their long-term ability to provide services - and the locations where species provide the most ecosystem services. This paper presents a conceptual framework for estimating how much a particular location supports the...
The prolonged history of industrialization, flood control, and hydropower production has led to the construction of 80,000 dams across the U.S. generating significant hydrologic, ecological, and social adjustments. With the increased ecological attention on re-establishing riverine connectivity, dam removal is becoming an important part of large-scale river restoration nationally, especially in New England, due to its early European settlement and history of waterpower-based industry. To capture the broader dimensions of dam removal, we constructed a GIS database of all inventoried dams in New England irrespective of size and reservoir volume to document the magnitude of fragmentation. We compared the characteristics...
Categories: Publication;
Types: Citation
Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a unique and complex mosaic of ecological risk from Hg impairment associated with differential methylmercury (MeHg) production and bioaccumulation. Understanding the landscape-scale variation in the magnitude and relative importance of processes associated with Hg transport, methylation, and MeHg bioaccumulation requires a multidisciplinary synthesis that transcends small-scale...
Categories: Publication;
Types: Citation
Abstract The processes and biomass that characterize any ecosystem are fundamentally constrained by the total amount of energy that is either fixed within or delivered across its boundaries. Ultimately, ecosystems may be understood and classified by their rates of total and net productivity and by the seasonal patterns of photosynthesis and respiration. Such understanding is well developed for terrestrial and lentic ecosystems but our understanding of ecosystem phenology has lagged well behind for rivers. The proliferation of reliable and inexpensive sensors for monitoring dissolved oxygen and carbon dioxide is underpinning a revolution in our understanding of the ecosystem energetics of rivers. Here, we synthesize...
Categories: Publication;
Types: Citation
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