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71.
Virginia Wittrock Suren N. Kulshreshtha Elaine Wheaton 《Mitigation and Adaptation Strategies for Global Change》2011,16(3):267-290
Droughts can have severe negative effects on the environment, society and economy. The drought of 2001–2002 caused severe
strain on economic and social activities in western Canada, particularly on rural communities through changes in water resources.
This paper examines physical and social vulnerabilities and associated adaptation measures undertaken and the adaptive capacity
in communities in the South Saskatchewan River Basin, Canada. Although all of these communities were exposed to the 2001–2002
drought, they had different levels of impacts, resulting in different types of drought adaptation measures, some due to experience
with previous droughts and some in response to the 2001–2002 drought. Communities with unreliable water supply were the most
vulnerable to these droughts. This vulnerability resulted in historic adaptations being implemented (e.g., Hanna, Alberta)
and re-active adaptations (e.g., Cabri, Saskatchewan). It is important to examine the effectiveness of the current adaptive
strategies to cope with more extensive and extended drought situations. First Nation communities, such as the Kainai Blood
Indian Reserve, have many social and environmental issues but the impacts from the drought were minor. The Reserve had implemented
economic changes in the late 1980s to make it less vulnerable to drought but resulted in negative impacts to the Reserve’s
social health. It is imperative to determine how vulnerable First Nation communities are and will to improve future adaptive
capacity. This paper provides a snap shot view of how Canadian Prairie Communities have adapted to drought and how vulnerable
they are to future drought situations. 相似文献
72.
73.
Female nutritional state affects the rate of male incubation feeding in the pied flycatcher Ficedula hypoleuca 总被引:2,自引:0,他引:2
Smith H. G. Källander H. Hultman J. Sanzén B. 《Behavioral ecology and sociobiology》1989,24(6):417-420
Summary Male pied flycatches Ficedula hypoleuca regularly feed their mates during incubation. By experimentally supplying some females with extra food we studied how the female's nutritional state affected her incubation schedule and the rate at which her mate fed her. Females that received extra food spent more time on the nest and shorter periods away from it, compared with control females. This suggests that nest attentiveness is governed by the amount of energy available to the female. When females reccived extra food, males decreased their rate of incubation feeding. They also did so in response to increasing ambient temperatures, whereas incubation schedules were unaffected. We, therefore, conclude that our results support the female nutrition hypothesis, i.e., that the food provided by the male constitutes a significant nutritional contribution to the incubating female. 相似文献
74.
Virginia E. Villafañe Paul J. Janknegt Marco de Graaff Ronald J. W. Visser Willem H. van de Poll Anita G. J. Buma E. Walter Helbling 《Marine Biology》2008,154(6):1021-1029
During austral summer 2006, experiments were carried out to evaluate the effects of ultraviolet radiation (UVR, 280–400 nm)
on carbon fixation of natural phytoplankton assemblages from Patagonia (Argentina). Surface water samples were collected (ca.
100 m offshore) at mid morning using an acid-cleaned (1 N HCl) dark container. The short-term impact of UVR (measured as radiocarbon
incorporation) was immediately assessed by exposing samples to three artificial illumination treatments: PAR (400–700 nm),
PAR + UV-A (320–700 nm), and PAR + UV-A + UV-B (280–700 nm). Pico-nanoplankton characterized the assemblages, and taxon-specific
pigment fingerprinting combined with CHEMTAX and supplemented with microscopic observations showed varied proportions of diatoms,
chlorophytes, and cyanobacteria throughout January–February 2006. Photosynthetic efficiency, as assessed through assimilation
numbers, was high [between 4.4 and 10.4 μg C (μg chl-a)−1 h−1], and it was probably favored by the supply of inorganic nutrients from the Chubut River. UVR-induced photoinhibition appeared
to be related to the taxonomic composition: in general, higher photoinhibition was observed when diatoms dominated, whereas
this was lower when samples were dominated by chlorophytes. Our data suggest that xanthophyll pigments might have provided
only limited protection in these already highlighted acclimated assemblages. 相似文献
75.
76.
Defining and measuring sustainability of bioenergy systems are difficult because the systems are complex, the science is in early stages of development, and there is a need to generalize what are inherently context-specific enterprises. These challenges, and the fact that decisions are being made now, create a need for improved communications among scientists as well as between scientists and decision makers. In order for scientists to provide information that is useful to decision makers, they need to come to an agreement on how to measure and report potential risks and benefits of diverse energy alternatives in a way that allows decision makers to compare options. Scientists also need to develop approaches that contribute information about problems and opportunities relevant to policy and decision making. The need for clear communication is especially important at this time when there is a plethora of scientific papers and reports and it is difficult for the public or decision makers to assess the merits of each analysis. We propose three communication guidelines for scientists whose work can contribute to decision making: (1) relationships between the question and the analytical approach should be clearly defined and make common sense; (2) the information should be presented in a manner that non-scientists can understand; and (3) the implications of methods, assumptions, and limitations should be clear. The scientists’ job is to analyze information to build a better understanding of environmental, cultural, and socioeconomic aspects of the sustainability of energy alternatives. The scientific process requires transparency, debate, review, and collaboration across disciplines and time. This paper serves as an introduction to the papers in the special issue on “Sustainability of Bioenergy Systems: Cradle to Grave” because scientific communication is essential to developing more sustainable energy systems. Together these four papers provide a framework under which the effects of bioenergy can be assessed and compared to other energy alternatives to foster sustainability. 相似文献
77.
78.
79.
Effective coordination of behaviors such as foraging and avoiding predators requires an assessment of cues provided by other
organisms. Integrating cues from multiple sensory modalities may enhance the assessment. We studied cue integration by tadpoles
of Oophaga pumilio, which live in small arboreal water pools. In this species, mothers periodically visit their tadpoles and feed them with
unfertilized eggs. When mothers visit, tadpoles beg conspicuously by vibrating until fed. However, animals other than mother
frogs including potential predators may visit water pools. Thus, when a visitor appears, tadpoles must use visitor cues to
decide whether to beg or to remain inactive to avoid predation. To elucidate the cues that prompt these behaviors, we videotaped
behavior of O. pumilio tadpoles in response to isolated and multimodal cues. Tadpoles swam more when exposed to visual or visual and chemical cues
of adult O. pumilio but only exhibited begging when exposed to visual, chemical, and tactile cues together. Visual, chemical, and tactile cues
from either male or female adult O. pumilio stimulated swimming and begging, but the same cues from similarly sized heterospecific frogs did not. Lastly, tadpoles exposed
to a potential predator did not beg and swam less than tadpoles with no stimulus. Together, these findings suggest that O. pumilio tadpoles use multimodal cues to modulate swimming behavior accordingly in the presence of egg provisioners, predators, and
other visitors and that tadpole begging is induced by multimodal cues of conspecific frogs such that tactile and perhaps chemical
cues supplement visual cues. 相似文献
80.
In the environmental health sciences, measurements of toxic exposures are often constrained by a lower limit called the limit of detection (LOD), with observations below this limit called non-detects. Although valid inference may be obtained by excluding non-detects in the estimation of exposure effects, this practice can lead to substantial reduction in power to detect a significant effect, depending on the proportion of censoring and the closeness of the effect size to the null value. Therefore, a variety of methods have been commonly used in the environmental science literature to substitute values for the non-detects for the purpose of estimating exposure effects, including ad hoc values such as ${LOD/2, LOD/\sqrt{2}}$ and LOD. Another method substitutes the expected value of the non-detects, i.e., E[X|X ≤?LOD] but this requires that the inference be robust to mild miss-specifications in the distribution of the exposure variable. In this paper, we demonstrate that the estimate of the exposure effect is extremely sensitive to ad-hoc substitutions and moderate distribution miss-specifications under the conditions of large sample sizes and moderate effect size, potentially leading to biased estimates. We propose instead the use of the generalized gamma distribution to estimate imputed values for the non-detects, and show that this method avoids the risk of distribution miss-specification among the class of distributions represented by the generalized gamma distribution. A multiple imputation-based procedure is employed to estimate the regression parameters. Compared to the method of excluding non-detects, the proposed method can substantially increase the power to detect a significant effect when the effect size is close to the null value in small samples with moderate levels of censoring (?≤ 50%), without compromising the coverage and relative bias of the estimates. 相似文献