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Thayer 1974.pdf
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Resources
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TRB Library
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THA-TUD
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The 5 Principles of Soil Health
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Presented by Tony Richards, a conservation planner in Tremonton, UT.
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Training
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Videos and Webinars
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The 2010 Amazon Drought
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Several global circulation models (GCMs)
project an increase in the frequency and
severity of drought events affecting the
Amazon region as a consequence of anthropogenic
greenhouse gas emissions (1). The proximate
cause is twofold, increasing Pacific sea surface
temperatures (SSTs), which may intensify El Niño
Southern Oscillation events and associated periodic
Amazon droughts, and an increase in the frequency
of historically rarer droughts associated with
high Atlantic SSTs and northwest displacement of
the intertropical convergence zone (1, 2). Such
droughts may lead to a loss of some Amazon forests,
which would accelerate climate change (3).
In 2005, a major Atlantic SST–associated drought
occurred, identified as a 1-in-100-year event (2).
Here, we report on a second drought in 2010, when
Atlantic SSTs were again high.
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Climate Science Documents
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The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorologic Extremes
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In this paper, we present preliminary results showing that the two record setting extreme events during 2010 summer, i.e., the Russian heat wave/wild fires and Pakistan flood were physically connected. We find that the Russian heat wave was associated with the development of an extraordinary strong and prolonged extratropical atmospheric blocking event, and excitation of a large-scale atmospheric Rossby wavetrain spanning western Russia, Kazakhstan, and northwestern China/Tibetan Plateau region. The southward penetration of upper level vorticity perturbations in the leading trough of the Rossby wave was instrumental in triggering anomalously heavy rain events over northern Pakistan and vicinity in mid-to-late July. Also shown are evidences that the Russian heat wave was amplified by a positive feedback through changes in surface energy fluxes between the atmospheric blocking pattern and an underlying extensive land region with below- normal soil moisture. The Pakistan heavy rain events were amplified and sustained by strong anomalous southeasterly flow along the Himalayas foothills and abundant moisture transport from the Bay of Bengal in connection with the northward propagation of the monsoonal intraseasonal oscillation. This is a preliminary PDF of the author-produced manuscript that has been peer-reviewed and accepted for publication. Since it is being posted so soon after acceptance, it has not yet been copyedited, formatted, or processed by AMS Publications. This preliminary version of the manuscript may be downloaded, distributed, and cited, but please be aware that there will be visual differences and possibly some content differences between this version and the final published version.
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Climate Science Documents
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The anatomy of predator–prey dynamics in a changing climate
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1. Humans are increasingly influencing global climate and regional predator assemblages,
yet a mechanistic understanding of how climate and predation interact to affect
fluctuations in prey populations is currently lacking.
2. Here we develop a modelling framework to explore the effects of different predation
strategies on the response of age-structured prey populations to a changing climate.
3. We show that predation acts in opposition to temporal correlation in climatic
conditions to suppress prey population fluctuations.
4. Ambush predators such as lions are shown to be more effective at suppressing
fluctuations in their prey than cursorial predators such as wolves, which chase down
prey over long distances, because they are more effective predators on prime-aged adults.
5. We model climate as a Markov process and explore the consequences of future
changes in climatic autocorrelation for population dynamics. We show that the presence
of healthy predator populations will be particularly important in dampening prey
population fluctuations if temporal correlation in climatic conditions increases in the
future.
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Resources
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Climate Science Documents
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The beaver meadow complex revisited – the role of beavers in post-glacial floodplain development
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We evaluate the validity of the beaver-meadow complex hypothesis, used to explain the deposition of extensive fine sediment in broad, low-gradient valleys. Previous work establishes that beaver damming forms wet meadows with multi-thread channels and enhanced sediment storage, but the long-term geomorphic effects of beaver are unclear. We focus on two low-gradient broad valleys, Beaver Meadows and Moraine Park, in Rocky Mountain National Park (Colorado, USA). Both valleys experienced a dramatic decrease in beaver population in the past century and provide an ideal setting for determining whether contemporary geomorphic conditions and sedimentation are within the historical range of variability of valley bottom processes. We examine the geomorphic significance of beaver-pond sediment by determining the rates and types of sedimentation since the middle Holocene and the role of beaver in driving floodplain evolution through increased channel complexity and fine sediment deposition. Sediment analyses from cores and cutbanks indicate that 33–50% of the alluvial sediment in Beaver Meadows is ponded and 28–40% was deposited in-channel; in Moraine Park 32–41% is ponded sediment and 40–52% was deposited in-channel. Radiocar- bon ages spanning 4300 years indicate long-term aggradation rates of ~0.05 cm yr-1. The observed highly variable short-term rates indicate temporal heterogeneity in aggradation, which in turn reflects spatial heterogeneity in processes at any point in time. Channel complexity increases directly downstream of beaver dams. The increased complexity forms a positive feedback for beaver-induced sedimentation; the multi-thread channel increases potential channel length for further damming, which increases the potential area occupied by beaver ponds and the volume of fine sediment trapped. Channel complexity decreased significantly as surveyed beaver population decreased. Beaver Meadows and Moraine Park represent settings where beaver substantially influence post-glacial floodplain aggradation. These findings underscore the importance of understanding the historical range of variability of valley bottom processes, and implications for environmental restoration. Copyright © 2011 John Wiley & Sons, Ltd.
KEYWORDS: floodplain; sedimentation; beaver; Holocene
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Climate Science Documents
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The bigger they come, the harder they fall: body size and prey abundance influence predator −prey ratios
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Large carnivores are highly threatened, yet the processes underlying their population declines are still poorly understood and widely debated. We explored how body mass and prey abundance influence carnivore density using data on 199 populations obtained across multiple sites for 11 carnivore species. We found that relative decreases in prey abundance resulted in a five- to sixfold greater decrease in the largest carnivores compared with the smallest species. We discuss a number of possible causes for this inherent vulnerability, but also explore a possible mechanistic link between predator size, ener- getics and population processes. Our results have important implications for carnivore ecol- ogy and conservation, demonstrating that larger species are particularly vulnerable to anthropo- genic threats to their environment, especially those which have an adverse affect on the abundance of their prey.
Keywords: carnivore ecology; predator–prey relationships; abundance scaling; climate change; metabolism
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Climate Science Documents
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The Biofuels Landscape Through the Lens of Industrial Chemistry
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Replacing petroleum feedstock with biomass in the production of fuels and value-added chemicals carries considerable appeal. As in industrial chemistry more broadly, high-throughput experimentation has greatly facilitated innovation in small-scale exploration of biomass production and processing. Yet biomass is hard to transport, potentially hindering the integration of manufacturing-scale processes. Moreover, the path from laboratory breakthrough to commercial production remains as tortuous as ever.
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Climate Science Documents
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The challenge of hot drought
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1st paragraph: rought is heating up around the warm- ing world. Particularly hot drought has cost more than US$40 billion and claimed 218 human lives since 2010 in the United States alone1. These hot and dry conditions have also contributed to unusually widespread and devastating wildfires1, fuelled by wide expanses of weakened and dead trees that were unable to deal with heat stress and subsequent insect attack2. Yet, to get a real sense of how this recent change in drought severity might shape the future, one has to look to the past. An analysis of regional and pan- continental North American drought over the past 1,000 years, reported by Cook et al.3 in the Journal of Climate, makes it clear that recent droughts, as costly as they have been, are only a taste of what might lie ahead, independently of any big climate change.
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Resources
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Climate Science Documents
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The challenge to keep global warming below 2 °C
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The latest carbon dioxide emissions continue to track the high end of emission scenarios, making it even less likely global warming will stay below 2 °C. A shift to a 2 °C pathway requires immediate significant and sustained global mitigation, with a probable reliance on net negative emissions in the longer term.
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Climate Science Documents
