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71.
Featured Collection Introduction: Connectivity of Streams and Wetlands to Downstream Waters
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Laurie C. Alexander Ken M. Fritz Kate A. Schofield Bradley C. Autrey Julie E. DeMeester Heather E. Golden David C. Goodrich William G. Kepner Hadas R. Kiperwas Charles R. Lane Stephen D. LeDuc Scott G. Leibowitz Michael G. McManus Amina I. Pollard Caroline E. Ridley Melanie K. Vanderhoof Parker J. Wigington Jr. 《Journal of the American Water Resources Association》2018,54(2):287-297
Connectivity is a fundamental but highly dynamic property of watersheds. Variability in the types and degrees of aquatic ecosystem connectivity presents challenges for researchers and managers seeking to accurately quantify its effects on critical hydrologic, biogeochemical, and biological processes. However, protecting natural gradients of connectivity is key to protecting the range of ecosystem services that aquatic ecosystems provide. In this featured collection, we review the available evidence on connections and functions by which streams and wetlands affect the integrity of downstream waters such as large rivers, lakes, reservoirs, and estuaries. The reviews in this collection focus on the types of waters whose protections under the U.S. Clean Water Act have been called into question by U.S. Supreme Court cases. We synthesize 40+ years of research on longitudinal, lateral, and vertical fluxes of energy, material, and biota between aquatic ecosystems included within the Act's frame of reference. Many questions about the roles of streams and wetlands in sustaining downstream water integrity can be answered from currently available literature, and emerging research is rapidly closing data gaps with exciting new insights into aquatic connectivity and function at local, watershed, and regional scales. Synthesis of foundational and emerging research is needed to support science‐based efforts to provide safe, reliable sources of fresh water for present and future generations. 相似文献
72.
73.
Angela M. Bayer Heather E. Danysh Mijail Garvich Guillermo Gonzálvez William Checkley María Álvarez Robert H. Gilman 《Disasters》2014,38(2):351-374
During the 1997–98 El Niño, Tumbes, Peru received 16 times the annual average rainfall. This study explores how Tumbes residents perceived the impact of the El Niño event on basic necessities, transport, health care, jobs and migration. Forty‐five individuals from five rural communities, some of which were isolated from the rest of Tumbes during the event, participated in five focus groups; six of these individuals constructed nutrition diaries. When asked about events in the past 20 years, participants identified the 1997–98 El Niño as a major negative event. The El Niño disaster situation induced a decrease in access to transport and health care and the rise in infectious diseases was swiftly contained. Residents needed more time to rebuild housing; recover agriculture, livestock and income stability; and return to eating sufficient animal protein. Although large‐scale assistance minimized effects of the disaster, residents needed more support. Residents' perspectives on their risk of flooding should be considered in generating effective assistance policies and programmes. 相似文献
74.
In the eastern United States, land-use and climate change have likely contributed to declines in the abundance of Neotropical migrant birds that occupy forest interiors, but the mechanisms are not well understood. We conducted a nest-predation experiment in southern Appalachian Mountain forests (North Carolina, U.S.A.) during the 2009 and 2010 breeding seasons to determine the effects of exurban development and temperature on predator presence and the average number of days until eggs in an artificial nest were disturbed by predators. We baited artificial nests with quail (Excalfactoria chinensi) eggs and monitored them for 18 days. We used clay eggs, track plates, and motion-triggered cameras to detect and identify nest predators. The average number of days a nest was undisturbed decreased as mean temperature increased and, to a lesser extent, as the density of buildings increased. Nests on the ground were more often depredated than those in trees, likely due to increased predation by opossum (Didelphis virginiana) and other carnivores. Raccoons (Procyon lotor), opossums, corvids (Corvus brachyrhynchos and Cyanocitta cristata), chipmunks (Tamias striatus), black bears (Ursus americanus), and domestic cats (Felis catus) were the most commonly detected predators. Presence of these predators did not vary as a function of mean temperature. Domestic cats and corvids were detected more frequently in plots with high rather than low densities of buildings. Forest-interior specialists and Neotropical migrants often nest in cool, high-elevation areas with low housing density. These bird species, especially those that nest on the ground, may be most vulnerable to increased nest predation if temperature and exurban development increase at higher elevations as anticipated. 相似文献
75.
Henrik Brumm Sue Anne Zollinger Peter J. B. Slater 《Behavioral ecology and sociobiology》2009,63(9):1387-1395
Several recent studies have tested the hypothesis that song quality in adult birds may reflect early developmental conditions,
specifically nutritional stress during the nestling period. Whilst all of these earlier studies found apparent links between
early nutritional stress and song quality, their results disagree as to which aspects of song learning or production were
affected. In this study, we attempted to reconcile these apparently inconsistent results. Our study also provides the first
assessment of song amplitude in relation to early developmental stress and as a potential cue to male quality. We used an
experimental manipulation in which the seeds on which the birds were reared were mixed with husks, making them more difficult
for the parents to obtain. Compared with controls, such chicks were lighter at fledging; they were thereafter placed on a
normal diet and had caught up by 100 days. We show that nutritional stress during the first 30 days of life reduced the birds’
accuracy of song syntax learning, resulting in poorer copies of tutor songs. Our experimental manipulations did not lead to
significant changes in song amplitude, song duration or repertoire size. Thus, individual differences observed in song performance
features probably reflect differences in current condition or motivation rather than past condition. 相似文献
76.
Francis H. Chapelle Lashun K. Thomas Paul M. Bradley Heather V. Rectanus Mark A. Widdowson 《补救:环境净化治理成本、技术与工艺杂志》2012,22(3):19-28
Aquifer sediment and groundwater chemistry data from 15 Department of Defense facilities located throughout the United States were collected and analyzed with the goal of estimating the amount of natural organic carbon needed to initiate reductive dechlorination in groundwater systems. Aquifer sediments were analyzed for hydroxylamine and NaOH‐extractable organic carbon, yielding a probable underestimate of potentially bioavailable organic carbon (PBOC). Aquifer sediments were also analyzed for total organic carbon (TOC) using an elemental combustion analyzer, yielding a probable overestimate of bioavailable carbon. Concentrations of PBOC correlated linearly with TOC with a slope near one. However, concentrations of PBOC were consistently five to ten times lower than TOC. When mean concentrations of dissolved oxygen observed at each site were plotted versus PBOC, it showed that anoxic conditions were initiated at approximately 200 mg/kg of PBOC. Similarly, the accumulation of reductive dechlorination daughter products relative to parent compounds increased at a PBOC concentration of approximately 200 mg/kg. Concentrations of total hydrolysable amino acids (THAA) in sediments also increased at approximately 200 mg/kg, and bioassays showed that sediment CO2 production correlated positively with THAA. The results of this study provide an estimate for threshold amounts of bioavailable carbon present in aquifer sediments (approximately 200 mg/kg of PBOC; approximately 1,000 to 2,000 mg/kg of TOC) needed to support reductive dechlorination in groundwater systems. © 2012 Wiley Periodicals, Inc. 相似文献
77.
Gagnon PR Passmore HA Platt WJ Myers JA Paine CE Harms KE 《Ecology》2010,91(12):3481-6; discussion 3503-14
Pyrogenic plants dominate many fire-prone ecosystems. Their prevalence suggests some advantage to their enhanced flammability, but researchers have had difficulty tying pyrogenicity to individual-level advantages. Based on our review, we propose that enhanced flammability in fire-prone ecosystems should protect the belowground organs and nearby propagules of certain individual plants during fires. We base this hypothesis on five points: (1) organs and propagules by which many fire-adapted plants survive fires are vulnerable to elevated soil temperatures during fires; (2) the degree to which burning plant fuels heat the soil depends mainly on residence times of fires and on fuel location relative to the soil; (3) fires and fire effects are locally heterogeneous, meaning that individual plants can affect local soil heating via their fuels; (4) how a plant burns can thus affect its fitness; and (5) in many cases, natural selection in fire-prone habitats should therefore favor plants that burn rapidly and retain fuels off the ground. We predict an advantage of enhanced flammability for plants whose fuels influence local fire characteristics and whose regenerative tissues or propagules are affected by local variation in fires. Our "pyrogenicity as protection" hypothesis has the potential to apply to a range of life histories. We discuss implications for ecological and evolutionary theory and suggest considerations for testing the hypothesis. 相似文献
78.
Promiscuous honeybee queens generate colonies with a critical minority of waggle-dancing foragers 总被引:1,自引:1,他引:0
Honeybees present a paradox that is unusual among the social Hymenoptera: extremely promiscuous queens generate colonies of
nonreproducing workers who cooperate to rear reproductives with whom they share limited kinship. Extreme polyandry, which
lowers relatedness but creates within-colony genetic diversity, produces substantial fitness benefits for honeybee queens
and their colonies because of increased disease resistance and workforce productivity. However, the way that these increases
are generated by individuals in genetically diverse colonies remains a mystery. We assayed the foraging and dancing performances
of workers in multiple-patriline and single-patriline colonies to discover how within-colony genetic diversity, conferred
to colonies by polyandrous queens, gives rise to a more productive foraging effort. We also determined whether the initiation
by foragers of waggle-dance signaling in response to an increasing sucrose stimulus (their dance response thresholds) was
linked to patriline membership. Per capita, foragers in multiple-patriline colonies visited a food source more often and advertised
it with more waggle-dance signals than foragers from single-patriline colonies, although there was variability among multiple-patriline
colonies in the strength of this difference. High-participation patrilines emerged within multiple-patriline colonies, but
their more numerous foragers and dancers were neither more active per capita nor lower-threshold dancers than their counterparts
from low-participation patrilines. Our results demonstrate that extreme polyandry does not enhance recruitment effort through
the introduction of low-dance-threshold, high-activity workers into a colony’s population. Rather, genetic diversity is critical
for injecting into a colony’s workforce social facilitators who are more likely to become engaged in foraging-related activities,
so boosting the production of dance signals and a colony’s responsiveness to profitable food sources. 相似文献
79.
Ruchira Sen Heather D. Ishak Trevor R. Kniffin Ulrich G. Mueller 《Behavioral ecology and sociobiology》2010,64(7):1125-1133
Interspecies or intraspecies cooperation can be stabilized evolutionarily if choosing partners favor beneficial partners and
discriminate against non-beneficial partners. We quantified such partner choice (symbiont choice) in the leafcutter ant Atta texana (Attini, Formicidae) by presenting the ants in a cafeteria-style preference assay with genotypically distinct fungal cultivars
from A. texana and Acromyrmex versicolor. Symbiont choice was measured as the ants' tendency to choose one or more cultivar(s) from several pure (axenic) cultivar
fragments and convert a given fungal fragment into a garden. Microsatellite DNA fingerprinting enabled us to identify the
cultivars chosen by the ants for their gardens. In 91% of the choice tests, A. texana workers combined multiple cultivars into a single intercropped, chimaeric garden, and the cultivars coexisted in such chimaeric
gardens for as long as 4 months. Coexistence of distinct fungal genotypes in chimaeric gardens appears to contradict a recent
model of cultivar competition postulating that each cultivar secretes incompatibility compounds harming other cultivars, which
presumably would preclude the intercropped polyculture observed in our experiments. Although we found no clear evidence of
novel, recombinant genotypes in the experimental chimaeric gardens, the intercropping of cultivar genotypes may occasionally
lead under natural conditions to exchange of genetic material between coexisting cultivars, thus introducing novel cultivar
genotypes into the leafcutter symbiosis. Symbiont choice by ants and any competition between coexisting cultivar strains in
chimaeric gardens do not appear to operate fast enough in our laboratory assay to convert chimaeric gardens into the monocultures
observed for A. texana under natural conditions. 相似文献
80.
Simon H Allen DT Wittig AE 《Journal of the Air & Waste Management Association (1995)》2008,58(2):320-343
Emissions inventories of fine particulate matter (PM2.5) were compared with estimates of emissions based on data emerging from U.S. Environment Protection Agency Particulate Matter Supersites and other field programs. Six source categories for PM2.5 emissions were reviewed: on-road mobile sources, nonroad mobile sources, cooking, biomass combustion, fugitive dust, and stationary sources. Ammonia emissions from all of the source categories were also examined. Regional emissions inventories of PM in the exhaust from on-road and nonroad sources were generally consistent with ambient observations, though uncertainties in some emission factors were twice as large as the emission factors. In contrast, emissions inventories of road dust were up to an order of magnitude larger than ambient observations, and estimated brake wear and tire dust emissions were half as large as ambient observations in urban areas. Although comprehensive nationwide emissions inventories of PM2.5 from cooking sources and biomass burning are not yet available, observational data in urban areas suggest that cooking sources account for approximately 5-20% of total primary emissions (excluding dust), and biomass burning sources are highly dependent on region. Finally, relatively few observational data were available to assess the accuracy of emission estimates for stationary sources. Overall, the uncertainties in primary emissions for PM2.s are substantial. Similar uncertainties exist for ammonia emissions. Because of these uncertainties, the design of PM2.5 control strategies should be based on inventories that have been refined by a combination of bottom-up and top-down methods. 相似文献