bluuebunny/crossref_metadata_2025_split huggingface dataset:
A characterization of autumn nocturnal migration detected by weather surveillance radars in the northeasternUSA
Authors: Farnsworth Andrew , Van Doren Benjamin M. , Hochachka Wesley M. , Sheldon Daniel , Winner Kevin , Irvine Jed , Geevarghese Jeffrey , Kelling Steve 
Published: May 2016

AbstractBillions of birds migrate at night over North America each year. However, few studies have described the phenology of these movements, such as magnitudes, directions, and speeds, for more than one migration season and at regional scales. In this study, we characterize density, direction, and speed of nocturnally migrating birds using data from 13 weather surveillance radars in the autumns of 2010 and 2011 in the northeasternUSA. After screening radar data to remove precipitation, we applied a recently developed algorithm for characterizing velocity profiles with previously developed methods to document bird migration. Many hourly radar scans contained windborne “contamination,” and these scans also exhibited generally low overall reflectivities. Hourly scans dominated by birds showed nightly and seasonal patterns that differed markedly from those of low reflectivity scans. Bird migration occurred during many nights, but a smaller number of nights with large movements of birds defined regional nocturnal migration. Densities varied by date, time, and location but peaked in the second and third deciles of night during the autumn period when the most birds were migrating. Migration track (the direction to which birds moved) shifted within nights from south‐southwesterly to southwesterly during the seasonal migration peaks; this shift was not consistent with a similar shift in wind direction. Migration speeds varied within nights, although not closely with wind speed. Airspeeds increased during the night; groundspeeds were highest between the second and third deciles of night, when the greatest density of birds was migrating. Airspeeds and groundspeeds increased during the fall season, although groundspeeds fluctuated considerably with prevailing winds. Significant positive correlations characterized relationships among bird densities at southern coastal radar stations and northern inland radar stations. The quantitative descriptions of broadscale nocturnal migration patterns presented here will be essential for biological and conservation applications. These descriptions help to define migration phenology in time and space, fill knowledge gaps in avian annual cycles, and are useful for monitoring long‐term population trends of migrants. Furthermore, these descriptions will aid in assessing potential risks to migrants, particularly from structures with which birds collide and artificial lighting that disorients migrants.
Sperm whales reduce foraging effort during exposure to 1–2 kHz sonar and killer whale sounds
Authors: Isojunno Saana , Curé Charlotte , Kvadsheim Petter Helgevold , Lam Frans‐Peter Alexander , Tyack Peter Lloyd , Wensveen Paul Jacobus , Miller Patrick James O'Malley 
Published: May 2016

AbstractThe time and energetic costs of behavioral responses to incidental and experimental sonar exposures, as well as control stimuli, were quantified using hidden state analysis of time series of acoustic and movement data recorded by tags (DTAG) attached to 12 sperm whales (Physeter macrocephalus) using suction cups. Behavioral state transition modeling showed that tagged whales switched to a non‐foraging, non‐resting state during both experimental transmissions of low‐frequency active sonar from an approaching vessel (LFAS; 1–2 kHz, source level 214 dB re 1 μPa m, four tag records) and playbacks of potential predator (killer whale, Orcinus orca) sounds broadcast at naturally occurring sound levels as a positive control from a drifting boat (five tag records). Time spent in foraging states and the probability of prey capture attempts were reduced during these two types of exposures with little change in overall locomotion activity, suggesting an effect on energy intake with no immediate compensation. Whales switched to the active non‐foraging state over received sound pressure levels of 131–165 dB re 1 μPa during LFAS exposure. In contrast, no changes in foraging behavior were detected in response to experimental negative controls (no‐sonar ship approach or noise control playback) or to experimental medium‐frequency active sonar exposures (MFAS; 6–7 kHz, source level 199 re 1 μPa m, received sound pressure level [SPL] = 73–158 dB re 1 μPa). Similarly, there was no reduction in foraging effort for three whales exposed to incidental, unidentified 4.7–5.1 kHz sonar signals received at lower levels (SPL = 89–133 dB re 1 μPa). These results demonstrate that similar to predation risk, exposure to sonar can affect functional behaviors, and indicate that increased perception of risk with higher source level or lower frequency may modulate how sperm whales respond to anthropogenic sound.
Gene–environment interactions influence feeding and anti‐predator behavior in wild and transgenic coho salmon
Authors: Sundström L. F. , Lõhmus M. , Devlin R. H. 
Published: May 2016

AbstractEnvironmental conditions are known to affect phenotypic development in many organisms, making the characteristics of an animal reared under one set of conditions not always representative of animals reared under a different set of conditions. Previous results show that such plasticity can also affect the phenotypes and ecological interactions of different genotypes, including animals anthropogenically generated by genetic modification. To understand how plastic development can affect behavior in animals of different genotypes, we examined the feeding and risk‐taking behavior in growth‐enhanced transgenic coho salmon (with two‐ to threefold enhanced daily growth rates compared to wild type) under a range of conditions. When compared to wild‐type siblings, we found clear effects of the rearing environment on feeding and risk‐taking in transgenic animals and noted that in some cases, this environmental effect was stronger than the effects of the genetic modification. Generally, transgenic fish, regardless of rearing conditions, behaved similar to wild‐type fish reared under natural‐like conditions. Instead, the more unusual phenotype was associated with wild‐type fish reared under hatchery conditions, which possessed an extreme risk averse phenotype compared to the same strain reared in naturalized conditions. Thus, the relative performance of genotypes from one environment (e.g., laboratory) may not always accurately reflect ecological interactions as would occur in a different environment (e.g., nature). Further, when assessing risks of genetically modified organisms, it is important to understand how the environment affects phenotypic development, which in turn may variably influence consequences to ecosystem components across different conditions found in the complexity of nature.
Multiyear drought‐induced morbidity preceding tree death in southeastern U.S. forests
Authors: Berdanier Aaron B. , Clark James S. 
Published: May 2016

AbstractRecent forest diebacks, combined with threats of future drought, focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large‐scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long‐term, whole‐stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre‐drought growth rates died within 10 yr. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought‐induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multiyear drought‐induced morbidity in models, experiments, and management decisions.
The adaptive capacity of lake food webs: from individuals to ecosystems
Authors: McMeans Bailey C. , McCann Kevin S. , Tunney Tyler D. , Fisk Aaron T. , Muir Andrew M. , Lester Nigel , Shuter Brian , Rooney Neil 
Published: May 2016

AbstractAquatic ecosystems support size structured food webs, wherein predator‐prey body sizes span orders of magnitude. As such, these food webs are replete with extremely generalized feeding strategies, especially among the larger bodied, higher trophic position taxa. The movement scale of aquatic organisms also generally increases with body size and trophic position. Together, these body size, mobility, and foraging relationships suggest that organisms lower in the food web generate relatively distinct energetic pathways by feeding over smaller spatial areas. Concurrently, the potential capacity for generalist foraging and spatial coupling of these pathways often increases, on average, moving up the food web toward higher trophic levels. We argue that these attributes make for a food web architecture that is inherently ‘adaptive’ in its response to environmental conditions. This is because variation in lower trophic level dynamics is dampened by the capacity of predators to flexibly alter their foraging behavior. We argue that empirical, theoretical, and applied research needs to embrace this inherently adaptive architecture if we are to understand the relationship between structure and function in the face of ongoing environmental change. Toward this goal, we discuss empirical patterns in the structure of lake food webs to suggest that ecosystems change consistently, from individual traits to the structure of whole food webs, under changing environmental conditions. We then explore an empirical example to reveal that explicitly unfolding the mechanisms that drive these adaptive responses offers insight into how human‐driven impacts, such as climate change, invasive species, and fisheries harvest, ought to influence ecosystem structure and function (e.g., stability, secondary productivity, maintenance of major energy pathways). We end by arguing that such a directed food web research program promises a powerful across‐scale framework for more effective ecosystem monitoring and management.
Fishery consequences of marine reserves: short‐term pain for longer‐term gain
Authors: Hopf Jess K. , Jones Geoffrey P. , Williamson David H. , Connolly Sean R. 
Published: May 2016

AbstractMarine reserves are often established in areas that support fisheries. Larval export from reserves is argued to help compensate for the loss of fishable habitat; however, previous modeling studies have focused on long‐term equilibrium outcomes. We examined the transient consequences of reserve establishment for fished metapopulations, considering both a well‐mixed larval pool and a spatially explicit model based on a coral trout (Plectropomus spp.) metapopulation. When fishing pressure was reallocated relative to the area protected, yields decreased initially, then recovered, and ultimately exceeded pre‐reserve levels. However, recovery time was on the order of several years to decades. If fishing pressure intensified to maintain pre‐reserve yields, reserves were sometimes unable to support the increased mortality and the metapopulation collapsed. This was more likely when reserves were small, or located peripherally within the metapopulation. Overall, reserves can achieve positive conservation and fishery benefits, but fisheries management complementary to reserve implementation is essential.
Assessing cumulative impacts of forest development on the distribution of furbearers using expert‐based habitat modeling
Authors: Bridger M. C. , Johnson C. J. , Gillingham M. P. 
Published: May 2016

AbstractCumulative impacts of anthropogenic landscape change must be considered when managing and conserving wildlife habitat. Across the central‐interior of British Columbia, Canada, industrial activities are altering the habitat of furbearer species. This region has witnessed unprecedented levels of anthropogenic landscape change following rapid development in a number of resource sectors, particularly forestry. Our objective was to create expert‐based habitat models for three furbearer species: fisher (Pekania pennanti), Canada lynx (Lynx canadensis), and American marten (Martes americana) and quantify habitat change for those species. We recruited 10 biologist and 10 trapper experts and then used the analytical hierarchy process to elicit expert knowledge of habitat variables important to each species. We applied the models to reference landscapes (i.e., registered traplines) in two distinct study areas and then quantified the change in habitat availability from 1990 to 2013. There was strong agreement between expert groups in the choice of habitat variables and associated scores. Where anthropogenic impacts had increased considerably over the study period, the habitat models showed substantial declines in habitat availability for each focal species (78% decline in optimal fisher habitat, 83% decline in optimal lynx habitat, and 79% decline in optimal marten habitat). For those traplines with relatively little forest harvesting, the habitat models showed no substantial change in the availability of habitat over time. The results suggest that habitat for these three furbearer species declined significantly as a result of the cumulative impacts of forest harvesting. Results of this study illustrate the utility of expert knowledge for understanding large‐scale patterns of habitat change over long time periods.
Influences of prior wildfires on vegetation response to subsequent fire in a reburned Southwestern landscape
Authors: Coop Jonathan D. , Parks Sean A. , McClernan Sarah R. , Holsinger Lisa M. 
Published: May 2016

AbstractLarge and severe wildfires have raised concerns about the future of forested landscapes in the southwestern United States, especially under repeated burning. In 2011, under extreme weather and drought conditions, the Las Conchas fire burned over several previous burns as well as forests not recently exposed to fire. Our purpose was to examine the influences of prior wildfires on plant community composition and structure, subsequent burn severity, and vegetation response. To assess these relationships, we used satellite‐derived measures of burn severity and a nonmetric multidimensional scaling of pre‐ and post‐ Las Conchas field samples. Earlier burns were associated with shifts from forested sites to open savannas and meadows, oak scrub, and ruderal communities. These non‐forested vegetation types exhibited both resistance to subsequent fire, measured by reduced burn severity, and resilience to reburning, measured by vegetation recovery relative to forests not exposed to recent prior fire. Previous shifts toward non‐forested states were strongly reinforced by reburning. Ongoing losses of forests and their ecological values confirm the need for restoration interventions. However, given future wildfire and climate projections, there may also be opportunities presented by transformations toward fire‐resistant and resilient vegetation types within portions of the landscape.
Fire severity unaffected by spruce beetle outbreak in spruce‐fir forests in southwestern Colorado
Authors: Andrus Robert A. , Veblen Thomas T. , Harvey Brian J. , Hart Sarah J. 
Published: May 2016

AbstractRecent large and severe outbreaks of native bark beetles have raised concern among the general public and land managers about potential for amplified fire activity in western North America. To date, the majority of studies examining bark beetle outbreaks and subsequent fire severity in the U.S. Rocky Mountains have focused on outbreaks of mountain pine beetle (MPB;Dendroctonus ponderosae) in lodgepole pine (Pinus contorta) forests, but few studies, particularly field studies, have addressed the effects of the severity of spruce beetle (Dendroctonus rufipennisKirby) infestation on subsequent fire severity in subalpine Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) forests. In Colorado, the annual area infested by spruce beetle outbreaks is rapidly rising, whileMPBoutbreaks are subsiding; therefore understanding this relationship is of growing importance. We collected extensive field data in subalpine forests in the eastern San Juan Mountains, southwestern Colorado, USA, to investigate whether a gray‐stage (<5 yr from outbreak to time of fire) spruce beetle infestation affected fire severity. Contrary to the expectation that bark beetle infestation alters subsequent fire severity, correlation and multivariate generalized linear regression analysis revealed no influence of pre‐fire spruce beetle severity on nearly all field or remotely sensed measurements of fire severity. Findings were consistent across moderate and extreme burning conditions. In comparison to severity of the pre‐fire beetle outbreak, we found that topography, pre‐outbreak basal area, and weather conditions exerted a stronger effect on fire severity. Our finding that beetle infestation did not alter fire severity is consistent with previous retrospective studies examining fire activity following other bark beetle outbreaks and reiterates the overriding influence of climate that creates conditions conducive to large, high‐severity fires in the subalpine zone of Colorado. Both bark beetle outbreaks and wildfires have increased autonomously due to recent climate variability, but this study does not support the expectation that post‐beetle outbreak forests will alter fire severity, a result that has important implications for management and policy decisions.
Long‐Term Corn Yield Impacted by Cropping Rotations and Bio‐Covers under No‐Tillage
Authors: Ashworth Amanda J. , Allen Fred L. , Saxton Arnold M. , Tyler Donald D. 
Published: May 2016

Cropping diversity and bio‐covers are perceived as integral components of conservation tillage because of increased pest control and soil organic matter. Consequently, effects of cropping sequences and bio‐covers on corn (Zea mays L.) yields were assessed. Main effects were 10 cropping sequences of corn, cotton (Gossypium hirsutum L.), and soybean (Glycine max L.) on a Loring silt loam (fine‐silty, mixed, thermic Oxyaquic Fragiudalf) at the Research and Education Center (REC) at Milan, and seven cropping sequences of corn and soybean at the Middle Tennessee REC on a Maury silt loam (fine, mixed, active, mesic Typic Paleudalf). Sequences were repeated in 4‐yr cycles (i.e., Phases I, II, and III) from 2002 to 2013. Strip‐plot bio‐covers consisted of hairy vetch (Vicia villosa L.), Austrian winter pea (Pisum sativum L. sativum var. arvense), wheat (Triticum aestivum L.), poultry litter, and fallow control. Across 12‐ yr, bio‐covers, and locations, continuous corn and yields from all rotations were equivalent (7.6 and 7.9 Mg ha−1, respectively; P = 0.07). However, among phase × sequence interactions, corn–soybean–corn–soybean rotation was highest yielding during Phase III (10.1 Mg ha−1), which was greater than continuous corn during all phases (P < 0.05). Bio‐covers, particularly poultry litter and hairy vetch, increased yields (across locations and years) when compared to wheat (P < 0.05). Incorporating soybean or cotton once within 4‐yr cropping cycles was equivalent to continuous corn (P > 0.05). However, including soybean and cotton twice increased yields by 6 and 7%, respectively (P < 0.05). Results suggest including two crops within a 4‐yr phase increases yields compared to continuous corn.Core Ideas

Increasing cropping sequence diversity promotes greater yields when two species are included in a rotation compared to continuous corn.
Including soybean and cotton twice increased yields by 6 and 7%, respectively.
Bio‐covers, particularly poultry litter and hairy vetch, increased corn yields compared to wheat cover crops.
Total Phosphorus Concentration Trends in 40 Iowa Rivers, 1999 to 2013
Authors: Wang Chao , Chan Kung‐Sik , Schilling Keith E. 
Published: May 2016

Excessive phosphorus (P) in rivers is prompting states to develop strategies to reduce P concentrations and export. The goal of this study was to assess the current condition by analyzing trends in total P (TP) concentrations at 40 river monitoring sites in Iowa for the period 1998 to 2013. We used monthly river monitoring data collected by the State of Iowa at ambient sites located beyond the influence of point sources or cities. Study objectives were to assess the presence of any linear trends in the TP concentration data using a time‐series method that accounted for temporal correlation in the data and discharge and to combine the trend information from individual sites into an assessment of the statewide rate of change in river TP concentrations. Results indicated that annual TP concentrations were significantly decreasing at 12 sites (p < 0.05), with concentrations ranging from 7.5% (Maple River) to 2.6% (Boyer River) and averaging 4.1% for the 12 sites. No statistically significant change was measured at 28 sites (p > 0.05), although all but four of these sites had decreasing concentrations. As a population of sampled rivers across Iowa, TP concentrations were declining at an annual rate of approximately 2.6%. The decreasing trends are consistent with reported reductions in sediment concentrations measured in the Raccoon River and with decreasing trends detected in other midwestern rivers. We attribute the decreasing TP trends primarily to improvements in conservation and land management. Although reducing nonpoint source TP concentrations in Iowa rivers will be a tremendous challenge for the agricultural community, progress is being made toward meeting this goal with existing programs.Core Ideas
Phosphorus concentrations were assessed at 40 Iowa rivers.
Phosphorus concentrations were decreasing by 4.1% at 12 sites.
Across Iowa, P concentrations are declining annually by 2.6%.
Reductions are most likely attributable to conservation.