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Experimental studies of dead-wood biodiversity — A review identifying global gaps in knowledge
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The importance of dead wood for biodiversity is widely recognized but strategies for conservation exist only in some regions worldwide. Most strategies combine knowledge from observational and experimental studies but remain preliminary as many facets of the complex relationships are unstudied. In this first global review of 79 experimental studies addressing biodiversity patterns in dead wood, we identify major knowledge gaps and aim to foster collaboration among researchers by providing a map of previous and ongoing experiments. We show that research has focused primarily on temperate and boreal forests, where results have helped in developing evidence-based conservation strategies, whereas comparatively few such efforts have been made in subtropical or tropical zones. Most studies have been limited to early stages of wood decomposition and many diverse and functionally important saproxylic taxa, e.g., fungi, flies and termites, remain under-represented. Our meta-analysis confirms the benefits of dead-wood addition for biodiversity, particularly for saproxylic taxa, but shows that responses of non-saproxylic taxa are heterogeneous. Our analysis indicates that global conservation of organisms associated with dead wood would benefit most by prioritizing research in the tropics and other neglected regions, focusing on advanced stages of wood decomposition and assessing a wider range of taxa. By using existing experimental set-ups to study advanced decay stages and additional taxa, results could be obtained more quickly and with less effort compared to initiating new experiments.
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Forecasting the response of Earth’s surface to future climatic and land use changes: A review of methods and research needs
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In the future, Earth will be warmer, precipitation events will be more extreme, global mean
sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes
will also occur at an accelerated rate as developed areas increase in size and population density. We now
have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC)
that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do
not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we
have the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models
and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system
modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to
forecast changes in the state of Earth’s surface as a result of likely future C&LUC. We also propose strategies
for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration
across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the
importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment
transport, as well as the importance of alternate stable states and extreme, rare events for understanding
and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process
zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in
detail.
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Formation of soil organic matter via biochemical and physical pathways of litter mass loss
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Soil organic matter is the largest terrestrial carbon pool (1). The pool size depends on the balance between formation of soil organic matter from decomposition of plant litter and its mineralization to inorganic carbon. Knowledge of soil organic matter formation remains limited (2) and current C numerical models assume that stable soil organic matter is formed primarily from recalcitrant plant litter (3) . However, labile components of plant litter could also form mineral-stabilized soil organic matter (4). Here we followed the decomposition of isotopically labelled above-ground litter and its incorporation into soil organic matter over three years in a grassland in Kansas, USA, and used laboratory incubations to determine the decay rates and pool structure of litter-derived organic matter. Early in decomposition, soil organic matter formed when non-structural compounds were lost from litter. Soil organic matter also formed at the end of decomposition, when both non-structural and structural compounds were lost at similar rates. We conclude that two pathways yield soil organic matter efficiently. A dissolved organic matter–microbial path occurs early in decomposition when litter loses mostly non-structural compounds, which are incorporated into microbial biomass at high rates, resulting in efficient soil organic matter formation. An equally efficient physical-transfer path occurs when litter fragments move into soil.
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Human mining activity across the ages determines the genetic structure of modern brown trout (Salmo trutta L.) populations
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Humans have exploited the earth’s metal resources for thousands of years leaving behind a legacy of toxic metal contamination and poor water quality. The southwest of England provides a well-defined example, with a rich history of metal mining dating to the Bronze Age. Mine water washout continues to negatively impact water quality across the region where brown trout (Salmo trutta L.) populations exist in both metal-impacted and relatively clean rivers. We used micro- satellites to assess the genetic impact of mining practices on trout populations in this region. Our analyses demonstrated that metal-impacted trout populations have low genetic diversity and have experienced severe population declines. Metal-river trout populations are genetically distinct from clean-river populations, and also from one another, despite being geographically proximate. Using approximate Bayesian computation (ABC), we dated the origins of these genetic patterns to periods of intensive mining activity. The historical split of contemporary metal-impacted populations from clean-river fish dated to the Medieval period. Moreover, we observed two distinct genetic populations of trout within a single catchment and dated their divergence to the Industrial Revolution. Our investigation thus provides an evaluation of contemporary population genetics in showing how human-altered landscapes can change the genetic makeup of a species.
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Impacts of mountaintop mining on terrestrial ecosystem integrity: identifying landscape thresholds for avian species in the central Appalachians, United States
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Reclaimed mine-dominated landscapes (less forest and more grassland/shrubland cover) elicited more negative (57 %) than positive (39 %) species responses. Negative thresholds for each landscape metric generally occurred at lower values than positive thresholds, thus negatively responding species were
detrimentally affected before positively responding species benefitted. Forest interior birds generally
responded negatively to landscape metric thresholds, interior edge species responses were mixed, and early
successional birds responded positively. The forest interior guild declined most at 4 % forest loss, while
the shrubland guild increased greatest after 52 % loss
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Novel climates, no-analog communities, and ecological surprises
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No-analog communities (communities that are compositionally unlike any found today) occurred frequently in the past and will develop in the greenhouse world of the future. The well documented no-analog plant communities of late-glacial North America are closely linked to “novel” climates also lacking modern analogs, characterized by high seasonality of temperature. In climate simulations for the Intergovernmental Panel on Climate Change A2 and B1 emission scenarios, novel climates arise by 2100 AD, primarily in tropical and subtropical regions. These future novel climates are warmer than any present climates globally, with spatially variable shifts in precipitation, and increase the risk of species reshuffling into future no-analog communities and other ecological surprises. Most ecological models are at least partially parameterized from modern observations and so may fail to accurately predict ecological responses to these novel climates. There is an urgent need to test the robustness of ecological models to climate conditions outside modern experience.
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Scenarios of future land use change around United States’ protected areas
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Land use change around protected areas can diminish their conservation value, making it important to
predict future land use changes nearby. Our goal was to evaluate future land use changes around protected
areas of different types in the United States under different socioeconomic scenarios. We analyzed
econometric-based projections of future land use change to capture changes around 1260 protected
areas, including National Forests, Parks, Refuges, and Wilderness Areas, from 2001 to 2051, under different
land use policies and crop prices. Our results showed that urban expansion around protected areas
will continue to be a major threat, and expand by 67% under business-as-usual conditions.
Concomitantly, a substantial number of protected areas will lose natural vegetation in their surroundings.
National land-use policies or changes in crop prices are not likely to affect the overall pattern of land use,
but can have effects in certain regions. Discouraging urbanization through zoning, for example, can
reduce future urban pressures around National Forests and Refuges in the East, while the implementation
of an afforestation policy can increase the amount of natural vegetation around some Refuges throughout
the U.S. On the other hand, increases in crop prices can increase crop/pasture cover around some protected
areas, and limit the potential recovery of natural vegetation. Overall, our results highlight that future
land-use change around protected areas is likely to be substantial but variable among regions and
protected area types. Safeguarding the conservation value of protected areas may require serious consideration of threats and opportunities arising from future land use.
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Sour Streams in Appalachia: Mapping Nature’s Buffer Against Sulfur Deposition
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Sulfur emissions are regulated by the Environmental Protection Agency, but sulfuric acid that has
leached into soil and streams can linger in the environment and harm vegetation and aquatic life. Some
watersheds are better able to buffer streams against acidification than others; scientists learned why in
southern Appalachia.
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Stoleson, Scott
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Expertise Search
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Temporal dynamics of a commensal network of cavity-nesting vertebrates: increased diversity during an insect outbreak
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Network analysis offers insight into the structure and function of ecological
communities, but little is known about how empirical networks change over time during
perturbations. ‘‘Nest webs’’ are commensal networks that link secondary cavity-nesting
vertebrates (e.g., bluebirds, ducks, and squirrels, which depend on tree cavities for nesting)
with the excavators (e.g., woodpeckers) that produce cavities. In central British Columbia,
Canada, Northern Flicker (Colaptes auratus) is considered a keystone excavator, providing
most cavities for secondary cavity-nesters. However, roles of species in the network, and
overall network architecture, are expected to vary with population fluctuations. Many
excavator species increased in abundance in association with a pulse of food (adult and larval
beetles) during an outbreak of mountain pine beetle (Dendroctonus ponderosae), which peaked
in 2003–2004. We studied nest-web dynamics from 1998 to 2011 to determine how network
architecture changed during this resource pulse.Cavity availability increased at the onset of the beetle outbreak and peaked in 2005. During and after the outbreak, secondary cavity-nesters increased their use of cavities made by five species of beetle-eating excavators, and decreased their use of flicker cavities. We found low link turnover, with 74% of links conserved from year to year. Nevertheless, the network
increased in evenness and diversity of interactions, and declined slightly in nestedness and
niche overlap. These patterns remained evident seven years after the beetle outbreak,
suggesting a legacy effect. In contrast to previous snapshot studies of nest webs, our dynamic approach reveals how the role of each cavity producer, and thus quantitative network architecture, can vary over
time. The increase in interaction diversity with the beetle outbreak adds to growing evidence
that insect outbreaks can increase components of biodiversity in forest ecosystems at various
temporal scales. The observed changes in (quantitative) network architecture contrast with the
relatively stable (qualitative) architecture of empirical mutualistic networks that have been
studied to date. However, they are consistent with recent theory on the importance of
population fluctuations in driving network architecture. Our results support the view that
models should allow for the possibility of rewiring (species switching partners) to avoid
overestimation of secondary extinction risk.
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