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Understanding how megaherbivores incorporate habitat features into their foraging behavior is key toward understanding how herbivores shape the surrounding landscape. While the role of habitat structure has been studied within the context of predator–prey dynamics and grazing behavior in terrestrial systems, there is a limited understanding of how structure influences megaherbivore grazing in marine ecosystems. To investigate the response of megaherbivores (green turtles) to habitat features, we experimentally introduced structure at two spatial scales in a shallow seagrass meadow in The Bahamas. Turtle density increased 50-fold (to 311 turtles ha−1) in response to the structures, and turtles were mainly grazing and resting (low vigilance behavior). This resulted in a grazing patch exceeding the size of the experimental setup (242 m2), with reduced seagrass shoot density and aboveground biomass. After structure removal, turtle density decreased and vigilance increased (more browsing and shorter surfacing times), while seagrass within the patch partly recovered. Even at a small scale (9 m2), artificial structures altered turtle grazing behavior, resulting in grazing patches in 60% of the plots. Our results demonstrate that marine megaherbivores select habitat features as foraging sites, likely to be a predator refuge, resulting in heterogeneity in seagrass bed structure at the landscape scale.

The Geo-mapping for Energy and Minerals (GEM) program has facilitated the availability of new and converted surficial geology maps and associated digital data sets for large sectors of northern Canada, leading to about 70% of the North being mapped and digitally available. Development of the Surficial Data Model and Canadian Geoscience Map (CGM) series has streamlined the publication process and created a common standard digital-map format and geodatabase. Based on traditional and more recent remote predictive mapping methodologies, there are now three types of surficial geology CGM maps produced: surficial geology, reconnaissance surficial geology, and predictive surficial geology. The considerable number of new surficial geology maps published during the two phases of the GEM program, as well as upcoming map publications, has resulted in an increase of 12% in map coverage north of 60°, constituting a significant legacy of the GEM program.

The GEM program has facilitated the availability of new and converted surficial geology maps and associated digital datasets for large sectors of northern Canada, leading to about 70% of the north being mapped and digitally available. Development of the Surficial Data Model (SDM) and Canadian Geoscience Map (CGM) series have streamlined the publication process and created a common standard digital map format and geodatabase. Based on traditional and more recent remote predictive mapping methodologies, there are now three types of surficial geology CGM maps produced: Surficial Geology, Reconnaissance Surficial Geology, and Predictive Surficial Geology. The considerable number of new surficial geology maps published during GEM-1 and GEM-2, as well as upcoming map publications, has resulted in an increase of 12% map coverage north of 60?, constituting a significant and lasting legacy of the GEM Program.

The Abitau Lake map area lies in the Rae Province of the Canadian Shield. Quaternary deposits are extensive and thick, with bedrock outcrop concentrated in the northwest and southwest. Till is extensively streamlined to the west-southwest by late deglacial ice flow from the Keewatin Ice Divide. The region is incised by west-southwest flowing subglacial meltwater corridors that extend across the map area, spaced 5 to 15 km apart. The ice flow chronology (Figure 1) is recorded both in the landforms and in the striae record. Rare measurements record an old flowset oriented northwest-southeast. Well defined indicators in cross-cutting relationships reveal a regional clockwise rotation in ice-flow directions evolving from an old southward to a late deglacial westward flow. Short-lived proglacial lakes, as evidenced by wave-cut scarps, terraced outwash, ice-contact deltas, and patches of glacial lake sediments, occupied a paleodrainage area not only of Hudson Bay but possibly also the headwaters of the Mackenzie River.

A new glacial geomorphology map covers approximately 415 000 km2 in a core region of the Laurentide Ice Sheet in Nunavut. The compilation builds on recent and legacy maps and is supplemented by visual digitization of glaciogenic features using high-resolution digital elevation (ArcticDEM) and Landsat 8 images. From this unprecedented, detailed inventory of over 156 000 features and more than 14 000 field observations, various glacial landsystems are identified, many of which are entirely new and others of which are significantly modified or updated. These include ice streams, palimpsest ice flows, and areas where basal-ice thermal regimes fluctuated between cold-based and warm-based. The GIS data comprise glacial features mapped at original and generalized scales, standardized field data sets, and interpreted glacial landsystems. These comprehensive georeferenced data sets can be used to reconstruct the glacial history in the interior portion of the Laurentide Ice Sheet in Nunavut and Northwest Territories and to identify distinct glacial-sediment transport patterns for applications to mineral exploration.

Discover a novel, self-contained approach to an important technical area, providing both theoretical background and practical details. Coverage includes mechanics and physical metallurgy, as well as study of both established and novel procedures such as indentation plastometry. Numerical simulation (FEM modelling) is explored thoroughly, and issues of scale are discussed in depth. Discusses procedures designed to explore plasticity under various conditions, and relates sample responses to deformation mechanisms, including microstructural effects. Features references throughout to industrial processing and component usage conditions, to a wide range of metallic alloys, and to effects of residual stresses, anisotropy and inhomogeneity within samples. A perfect tool for materials scientists, engineers and researchers involved in mechanical testing (of metals), and those involved in the development of novel materials and components.

This report releases the field datasets and analytical results from targeted surficial geology studies and till sampling completed in 2017 and 2018 in mainland Nunavut and eastern Northwest Territories as part of Natural Resources Canada's Geomapping for Energy and Minerals (GEM?2) Rae Synthesis of Glacial History and Dynamics Activity in the interior of the Keewatin Sector of the Laurentide Ice Sheet. Fieldwork consisted of targeted mapping of glacial flow indicators to resolve the relative ice-flow chronology, sampling material for geochronology to help reconstruct the glacial and post-glacial histories at a regional scale, and documenting the nature and composition of the glacial sediments in various glacial terrains. In addition to the field and analytical datasets, this report provides a detailed description of the field and analytical methods. In 2017, Quaternary geological field observations were made at 92 sites; 39 till and 16 geochronology samples were collected in 5 areas in the Baker Lake and Arviat regions, Nunavut. In 2018, the focus shifted to the Healey Lake area in eastern Northwest Territories and central mainland Kitikmeot region, Nunavut. Quaternary geological field observations were made at 72 sites; 44 till and 17 geochronology samples were collected. Till samples were analysed for matrix geochemistry and texture, gold grain counts, indicator mineral picking and probing, and pebble lithology counts.

For more than 50 years, researchers at the Geological Survey of Canada (GSC) have developed, tested, and refined till geochemical and indicator mineral methods as applied to mineral exploration, provenance studies, and environmental research in glaciated terrain across Canada. This cumulative experience and knowledge were used to produce and publish the GSC's first comprehensive field and laboratory methods protocol manual for till geochemical and mineralogical surveys in 2011. The publication being presented here provides an update and augmentation of this earlier version and presents the major concepts of till as a sample medium, glacial dispersal, and field and laboratory procedures. These protocols are used by the GSC to guide till sample collection, sample processing, geochemical and indicator mineral analyses, implementation of quality assurance/quality control (QA/QC) procedures, archiving methods, and data reporting by the Geological Survey of Canada. Using consistent sample media and making diligent field notes and observations are also considered fundamental to the protocols, and are presented herein. The protocols will be of value to provincial/territorial government geological agencies, the mineral exploration industry, and academia and we hope they will benefit from the use of this manual. Adopting a common set of protocols allows the GSC, other researchers, and exploration geologists to directly compare till geochemical and indicator mineral data sets from various parts of Canada and ensures proper minimum levels of QA/QC for all till geochemical and mineralogical data.

Carbonyl sulfide (OCS) provides a proxy for measuring photosynthesis and is the primary background source of stratospheric aerosols. OCS emissions due to biomass burning are a variable and substantial (over 10%) part of the current OCS budget. OCS emission ratios from open burning fires, coupled with 1997–2016 data from the Global Fire Emissions Database (GFED4), yield OCS biomass burning emissions with a global average annual flux of 60 ± 37 Gg(S) year⁻¹. A global box model suggests these emissions are more consistent with observations from global atmospheric composition monitoring networks than fluxes derived from previous synthesis papers. Even after considering the uncertainty in emission factor observations for each category of emissions and the interannual variation in total burned dry matter, the total OCS emissions from open burning are insufficient to account for the large imbalance between current estimates of global OCS sources and sinks.

Author(s): Campbell, JE; Whelan, ME; Berry, JA; Hilton, TW; Zumkehr, A; Stinecipher, J; Lu, Y; Kornfeld, A; Seibt, U; Dawson, TE; Montzka, SA; Baker, IT; Kulkarni, S; Wang, Y; Herndon, SC; Zahniser, MS; Commane, R; Loik, ME | Abstract: The future resilience of coast redwoods (Sequoia sempervirens) is now of critical concern due to the detection of a 33% decline in California coastal fog over the 20th century. However, ecosystem-scale measurements of photosynthesis and stomatal conductance are challenging in coast redwood forests, making it difficult to anticipate the impacts of future changes in fog. To address this methodological problem, we explore coastal variations in atmospheric carbonyl sulfide (COS or OCS), which could potentially be used as a tracer of these ecosystem processes. We conducted atmospheric flask campaigns in coast redwood sites, sampling at surface heights and in the canopy (~70nm), at the University of California Landels-Hill Big Creek Reserve and Big Basin State Park. We simulated COS atmosphere-biosphere exchange with a high-resolution 3-D model to interpret these data. Flask measurements indicated a persistent daytime drawdown between the coast and the downwind forest (45n±n6nppt COS) that is consistent with the expected relationship between COS plant uptake, stomatal conductance, and gross primary production. Other sources and sinks of COS that could introduce noise to the COS tracer technique (soils, anthropogenic activity, nocturnal plant uptake, and surface hydrolysis on leaves) are likely to be small relative to daytime COS plant uptake. These results suggest that COS measurements may be useful for making ecosystem-scale estimates of carbon, water, and energy exchange in coast redwood forests.

Future carbon management during energy production will rely on carbon capture and sequestration technology and carbon sequestration methods for offsetting non-capturable losses. The present study quantifies carbon sequestration via reforestation using measurements and modeling for recent and legacy surface coal mining grasslands that are re-restored through tree planting. This paper focuses on a case study of legacy coal mining sites in the southern Appalachia the United States. This five million-hectare region has a surface mining footprint of approximately 12% of the land area, and the reclamation method was primarily grassland. The results of the soil carbon sequestration rates for restored forest soils approach 2.0 MgC ha−1 y−1 initially and average 1.0 MgC ha−1 y−1 for the first fifty years after reclamation. Plant, coarse root and litter carbon sequestration rates were 2.8 MgC ha−1 y−1 with plant carbon estimated to equilibrate to 110 MgC ha−1 after forty years. Plant, root and litter carbon stocks are projected to equilibrate at an order of magnitude greater carbon storage than the existing conditions, highlighting the net carbon gain. Reforestation of legacy mine sites shows carbon sequestration potential several orders of magnitude greater than typical land sequestration strategies for carbon offsets. Projections of future scenarios provide results that show the study region could be carbon neutral or a small sink if widespread reforesting during reclamation was implemented, which is contrary to the business-as-usual projections that result in a large amount of carbon being released to the atmosphere in this region.

We measured carbonyl sulfide (COS) in air extracted from ice core samples from the West Antarctic Ice Sheet (WAIS) Divide, Antarctica, with the deepest sample dated to 54,300 years before present. These are the first ice core COS measurements spanning the Last Glacial Maximum (LGM), the last glacial/interglacial transition, and the early Holocene. The WAIS Divide measurements from the LGM and the last transition are the first COS measurements in air extracted from full clathrate (bubble-free) ice. This study also includes new COS measurements from Taylor Dome, Antarctica, including some in bubbly glacial ice that are concurrent with the WAIS Divide data from clathrate glacial ice. COS hydrolyzes in ice core air bubbles, and the recovery of an atmospheric record requires correcting for this loss. The data presented here suggest that the in situ hydrolysis of COS is significantly slower in clathrate ice than in bubbly ice. The clathrate ice measurements are corrected for the hydrolysis loss during the time spent as bubbly ice only. The corrected WAIS Divide record indicates that atmospheric COS was 250–300 parts per trillion (ppt) during the LGM and declined by 80–100 ppt during the last glacial/interglacial transition to a minimum of 160–210 ppt at the beginning of the Holocene. This decline was likely caused by an increase in the gross primary productivity of terrestrial plants, with a possible contribution from a reduction in ocean sources. COS levels were above 300 ppt in the late Holocene, indicating that large changes in the COS biogeochemical cycle occurred during the Holocene.

Carbonyl sulfide (COS) has recently emerged as an atmospheric tracer of gross primary production. All modeling studies of COS air-monitoring data rely on a climatological anthropogenic inventory that does not reflect present conditions or support interpretation of ice core and firn trends. Here we develop a global anthropogenic inventory for the years 1850 to 2013 based on new emission measurements and material-specific data. By applying methods from a recent regional inventory to global data, we find that the anthropogenic source is similar in magnitude to the plant sink, confounding carbon cycle applications. However, a material-specific approach results in a current anthropogenic source that is only one third of plant uptake and is concentrated in Asia, supporting carbon cycle applications of global air-monitoring data. Furthermore, changes in the anthropogenic source alone cannot explain the century-scale mixing ratio growth, which suggests that ice and firn data may provide the first global history of gross primary production.

Agriculture is historically a dominant form of global environmental degradation, and the potential for increased future degradation may be driven by growing demand for food and biofuels. While these impacts have been explored using global gridded maps of croplands, such maps are based on relatively coarse spatial data. Here, we apply high-resolution cropland inventories for the conterminous U.S. with a land-use model to develop historical gridded cropland areas for the years 1850-2000 and year 2000 abandoned cropland maps. While the historical cropland maps are consistent with generally accepted land-use trends, our U.S. abandoned cropland estimates of 68 Mha are as much as 70% larger than previous gridded estimates due to a reduction in aggregation effects. Renewed cultivation on the subset of abandoned croplands that have not become forests or urban lands represents one approach to mitigating the future expansion of agriculture. Potential bioenergy production from these abandoned lands using a wide range of biomass yields and conversion efficiencies has an upper-limit of 5-30% of the current U.S. primary energy demand or 4-30% of the current U.S. liquid fuel demand.

Emission trading programs (C&T) and renewable portfolio standards (RPS) are two common tools used by policymakers to control GHG emissions in the energy and other energy-intensive sectors. Little is known, however, as to the policy implications resulting from these concurrent regulations, especially given that their underlying policy goals and regulatory schemes are distinct. This paper applies both an analytical model and a computational model to examine the short-run implications of market interactions and policy redundancy. The analytical model is used to generate contestable hypotheses, while the numerical model is applied to consider more realistic market conditions. We have two central findings. First, lowering the CO2 C&T cap might penalize renewable units, and increasing the RPS level could sometimes benefit coal and oil and make natural gas units worse off. Second, making one policy more stringent would weaken the market incentive, which the other policy relies upon to attain its intended policy target.

The impact of Mexico City (MCMA) emissions is examined by studying its effects on air quality, photochemistry, and on ozone production regimes by combining model products and aircraft observations from the MILAGRO experiment during March 2006. The modeled influence of MCMA emissions to enhancements in surface level NOx [NO subscript x], CO, and O3 [O subscript 3] concentrations (10–30% increase) are confined to distances, United States. National Aeronautics and Space Administration, National Science Foundation (U. S.) (ATM award 0528227)

Climate models incorporate photosynthesis-climate feedbacks, yet we lack robust tools for large-scale assessments of these processes. Recent work suggests that carbonyl sulfide (COS), a trace gas consumed by plants, could provide a valuable constraint on photosynthesis. Here we analyze airborne observations of COS and carbon dioxide concentrations during the growing season over North America with a three-dimensional atmospheric transport model. We successfully modeled the persistent vertical drawdown of atmospheric COS using the quantitative relation between COS and photosynthesis that has been measured in plant chamber experiments. Furthermore, this drawdown is driven by plant uptake rather than other continental and oceanic fluxes in the model. These results provide quantitative evidence that COS gradients in the continental growing season may have broad use as a measurement-based photosynthesis tracer.

Understanding carbon dioxide (CO2) biospheric processes is of great importance because the terrestrial exchange drives the seasonal and inter-annual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential mean to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrievals of the atmospheric concentrations of both CO2 and OCS from measured solar absorption spectra. Here, we investigate co-located and quasi-simultaneous FTIR measurements of OCS and CO2 performed at three selected sites located in the Northern Hemisphere. These measurements are compared to simulations of OCS and CO2 using a chemical transport model (GEOS-Chem). The OCS simulations are driven by different land biospheric fluxes to reproduce the seasonality of the measurements. Increasing the plant uptake of Kettle et al. (2002a) by a factor of three resulted in the best comparison with FTIR measurements. However, there are still discrepancies in the latitudinal distribution when comparing with HIPPO (HIAPER Pole-to-Pole Observations) data spanning both hemispheres. The coupled biospheric fluxes of OCS and CO2 from the simple biosphere model (SiB) are used in the study and compared to measurements. The CO2 simulation with SiB fluxes agrees with the measurements well, while the OCS simulation reproduced a weaker drawdown than FTIR measurements at selected sites, and a smaller latitudinal gradient in the Northern Hemisphere during growing season. An offset in the timing of the seasonal cycle minimum between SiB simulation and measurements is also seen. Using OCS as a photosynthesis proxy can help to understand how the biospheric processes are reproduced in models and to further understand the carbon cycle in the real world.

Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil-COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from 5 new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, > 800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. While COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.

Experimental results are reported providing information on the downstream mixing evolution in axial pipe flow mixers where a scalar is introduced into the pipe via a coaxial injection tube. Experiments were conducted in a 25.4 mm diameter water pipe flow loop (25,700> R 28,500), in which a fluorescein dye was coaxially injected. The injection tube diameter was 1.5 mm. Three velocity ratios, V = 0.5, 1.0, and 2.0 were explored, where V =V /V . The present results indicate that the effects of velocity ratio on the scalar concentration statistics are mainly evident in the first several outer pipe diameters downstream. In the far field, velocity ratio effects are shown to be insignificant on the concentration statistics. All cases showed a similar trend of an initial increase in variance at the centerline as the injected fluid begins mixing with the main pipe flow. This is followed by a region of rapid "exponential-like" decay, followed by a much slower decay rate after approximately 50 pipe diameters. Space-time correlations of the scalar concentration between far field locations verify the low wavenumber motions as predicted by the recent theory of Kerstein and McMurtry [A. Kerstein and P. McMurtry, "Low-wave-number statistics of randomly advected passive scalars," Phys. Rev. E 50, 2057 (1994)], and are consistent with the slower than exponential downstream mixing rate. Copyright © 2004 by ASME. D R R jet main

Net photosynthesis is the largest single flux in the global carbon cycle, but controls over its variability are poorly understood because there is no direct way of measuring it at the ecosystem scale. We report observations of ecosystem carbonyl sulfide (COS) and CO2 fluxes that resolve key gaps in an emerging framework for using concurrent COS and CO2 measurements to quantify terrestrial gross primary productivity. At a wheat field in Oklahoma we found that in the peak growing season the flux-weighted leaf relative uptake of COS and CO2 during photosynthesis was 1.3, at the lower end of values from laboratory studies, and varied systematically with light. Due to nocturnal stomatal conductance, COS uptake by vegetation continued at night, contributing a large fraction (29%) of daily net ecosystem COS fluxes. In comparison, the contribution of soil fluxes was small (1–6%) during the peak growing season. Upland soils are usually considered sinks of COS. In contrast, the well-aerated soil at the site switched from COS uptake to emissions at a soil temperature of around 15 °C. We observed COS production from the roots of wheat and other species and COS uptake by root-free soil up to a soil temperature of around 25 °C. Our dataset demonstrates that vegetation uptake is the dominant ecosystem COS flux in the peak growing season, providing support of COS as an independent tracer of terrestrial photosynthesis. However, the observation that ecosystems may become a COS source at high temperature needs to be considered in global modeling studies.

To test the capabilities of newly available instrumentation and to explore the dynamics of carbonyl sulfide (COS) as a proxy for the measurement of canopy-scale gross primary production (GPP), we conducted an experiment to measure the simultaneous net transfer of COS and CO2 between the atmosphere and a growing wheat canopy, senesced wheat, and the harvested field (located in the Southern Great Plains of the U.S.) using the eddy covariance technique. We found that during the growing season, there was a strong uptake of COS by the canopy (roughly between −10 and −40 pmol m−2 s−1) with a strong diel signal that mirrored net CO2 fluxes. After senescence and over the harvested field, we observed a strong source of COS to the atmosphere (up to +40 pmol m−2 s−1) that exhibited a weaker diel pattern, again similar to CO2. These results suggest that the dynamics of COS are more complicated than once thought, but that it may still be possible to independently derive canopy-scale GPP from direct COS measurements and to use them as model constraints on the atmospheric carbon cycle. To demonstrate this, we computed an average value of leaf relative uptake (LRU) (the scaling factor between GPP and ratios of the fluxes of COS and CO2 and ratios of the atmospheric concentrations of COS and CO2) that is in good agreement with laboratory results.

Oviposition preference by European corn borers, Ostrinia nubilalis (Hubner), for or against transgenic corn would influence amounts of refuge required for resistance management. The objective of this research was to determine if various Bacillus thuringiensis (Bt) corn transgenic events influence O. nubilalis oviposition. All commercially available events (currently 5) were evaluated, plus 1 experimental event. Results from 3 independent studies are reported, including 3 field-cage experiments with vegetative corn, 2 field-cage experiments with reproductive corn, and 2 field experiments with natural O. nubilalis on reproductive corn. In each case, Bt corn hybrids are compared with their near isogenic hybrids by counting numbers of egg masses on each plant type. More extensive comparisons were made in 3 of the experiments by determining the number, size, and location of egg masses on the corn hybrids. Moths laid more egg masses on Bt corn than on non-Bt corn in 1 cage experiment. These results, however, were not found in any of the other experiments. There is evidence that suggests cage effects influence moth oviposition more than Bt protein. Four of the 5 cage experiments and 2 field experiments indicate that the tested Bt events do not influence O. nubilalis oviposition. Larval injury to isogenic corn during the vegetative stage did not influence adult oviposition during the corn reproductive stage when compared with Bt corn and noninjured isogenic corn. Based on these experiments, suggestions are made for future studies that use natural O. nubilalis rather than O. nubilalis in cages.