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501.
Pre‐Development Groundwater Conditions Surrounding Memphis,Tennessee: Controversy and Unexpected Outcomes 下载免费PDF全文
Reliance on groundwater resources by differing governing bodies can create transboundary disputes raising questions of ownership and apportionment as the resource becomes strained through overuse or threatened by contamination. Transboundary disputes exist at varying scales, from conflicts between countries to smaller disputes between intrastate jurisdictions. In 2005 within the United States, the State of Mississippi filed a lawsuit against its political neighbor and their utility, the City of Memphis and Memphis Light, Gas, and Water, for groundwater deemed owned by the State of Mississippi to be wrongfully diverted across the state line and into Tennessee by the defendants. The basis of the lawsuit was potentiometric maps of groundwater levels for the Memphis aquifer that showed under suggested pre‐development conditions no flow occurring across the Mississippi‐Tennessee state line, but subsequent historic potentiometric maps show a cone of depression under the City of Memphis with a clear northwesterly gradient from Mississippi into Tennessee. The suggested pre‐development conditions were derived from limited groundwater level observations between 41 and 74 years post‐development. A new pre‐development map is constructed using historic records that range 0‐17 years post‐development that shows the natural flow is northwesterly from Mississippi into Tennessee and transboundary groundwater quantities have actually decreased since pre‐development conditions. 相似文献
502.
J. Antonio Baeza 《Behavioral ecology and sociobiology》2007,61(3):365-370
Sex allocation theory predicts phenotypic adjustments by individuals in their investments into the male and female reproductive function in response to environmental conditions. I tested for phenotypically plastic shifts in sex allocation in a protandric simultaneous hermaphrodite, in which individuals mature and reproduce as males first, and later in life, as simultaneous hermaphrodites. I predicted that initially maturing males should adjust the timing of maturation as hermaphrodites according to male mating opportunities mediated by population size of hermaphrodites. In a first experiment, males maintained with only one hermaphrodite reduced the time they spent as males in comparison to males maintained with no conspecifics, presumably because total reproductive output is maximized by two individuals being simultaneous hermaphrodites when the mating system is a pair. Conversely, males maintained in groups with two or more hermaphrodites increased the time they spent as males in comparison to single males. This delay in maturation was not an effect of resource depletion with increasing shrimp density because the growth rate of males did not differ among most of the experimental treatments. One hypothesis to explain this social mediation of sex allocation is that the smaller males are more successful in mating as males than are the larger hermaphrodites: it will pay reproductively for males to delay maturation as hermaphrodites in large but not in small groups. In agreement with this notion, a second experiment demonstrated that smaller males were four times more successful than were larger hermaphrodites in inseminating shrimps reproducing as females. The informative cue that males may use to perceive different group sizes deserves further attention. 相似文献
503.
Elise D. Ferree 《Behavioral ecology and sociobiology》2007,62(1):109-117
Theory, empirical examples, and recently, proximate mechanisms point to the possibility of adaptive sex ratio adjustment in
various organisms. General predictions state that a female should adjust her offspring sex ratio to maximize the benefits
or minimize the costs of reproduction given her physical condition or current social and environmental conditions. I tested
for an influence of male attractiveness on brood sex ratio in a population of dark-eyed juncos (Junco hyemalis thurberi) by manipulating a male’s white outer tail feathers (“tail white”). Experimentally increasing male tail white did not significantly
affect sex ratio, nor was premanipulated male tail white significantly related to brood sex ratio. However, the amount of
white on the female’s outer tail feathers, independently of female condition, was positively related to the number of sons
in a brood. Determining how a female’s potential genetic contribution to her sons’ attractiveness influences offspring sex
ratio should be a priority for future research. 相似文献
504.
Wei Yang 《Ecological modelling》2011,222(2):261-267
In this paper, a multi-objective optimization model has been developed for allocating freshwater to meet the environmental flow requirements of the restored wetlands in the Yellow River Delta, China. The model seeks a rational balance among appropriate water allocation for the wetlands, a healthy ecosystem, and optimum economic returns for the humans that use the wetlands to earn their livelihood, with the degree of ecosystem health represented by the difference between actual and ideal water levels. And then a holistic method has been used for satisfying multiple objectives to avoid the problem of decision-maker subjectivity, and then solved the resulting optimal allocation model for environmental flows of the wetlands using a genetic algorithm. With water from the Yellow River as the source, the model shows how the optimal monthly water release into the restored wetlands can be achieved in dry, average, and wet years. Using the model, 20-56% reductions in water use could be achieved compared with the current pattern of water release, and the optimal water level in each month would coincide better with the ideal value based on an indicator plant community (reeds). The results of the study demonstrate the capability of the multi-objective programming model to optimize ecological water allocation and management for the wetlands of the Yellow River Delta. 相似文献
505.
Based on comprehensive analysis of the status, major characteristics and regulation of regional differentiation of water pollution in China, the following counter measures for control water pollution were suggested: Overall planning and rational allocation; Comprehensive utilization and technical reform; Strengthening environmental management and the legal system. 相似文献
506.
507.
Wyness K Mills G Jones L Barnes JD Jones DL 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2493-2499
The combined impacts of simulated increased nitrogen (N) deposition (75 kg N ha−1 yr−1) and increasing background ozone (O3) were studied using two mesotrophic grassland species (Dactylis glomerata and Ranunculus acris) in solardomes, by means of eight O3 treatments ranging from 15.5 ppb to 92.7 ppb (24 h average mean). A-Ci curves were constructed for each species to gauge effects on photosynthetic efficiency and capacity, and effects on biomass partitioning were determined after 14 weeks. Increasing the background concentration of O3 reduced the healthy above ground and root biomass of both species, and increased senesced biomass. N fertilisation increased biomass production in D. glomerata, and a significantly greater than additive effect of O3 and N on root biomass was evident. In contrast, R. acris biomass was not affected by high N. The study shows the combined effects of these pollutants have differential implications for carbon allocation patterns in common grassland species. 相似文献
508.
Stefanie Hellweg Thomas B. Hofstetter Konrad Hungerbühler 《Environmental Modeling and Assessment》2001,6(4):219-235
This paper proposes a mathematical model for life-cycle inventory analysis (LCI) of waste incineration in Switzerland. In order to model conventional and new incineration technologies adequately, fundamental aspects of the different technologies relevant for the LCI are discussed. The environmental impact of these technologies strongly depends on the assessment of the long-term emissions of the solid incineration residues and is therefore related to value based decisions about the time horizon considered. The article illustrates that the choice of the landfill model has a significant influence on the results of life-cycle assessment of waste incineration. 相似文献
509.
510.
甘肃马先蒿(Pedicularis kansuensis)作为高寒草甸退化进程中的一种入侵毒杂草,其生长状况和繁殖特征为草地退化状况的重要指标,也是衡量高寒草甸演替进程的重要指示植物。通过比较重度退化和未退化高寒草甸的群落特征,甘肃马先蒿的生长状况与花期资源分配,结果表明:退化的高寒草甸土壤-植被系统变化明显,高寒草甸退化显著影响了甘肃马先蒿的生长状况和资源分配特征。在重度退化的黑土滩样地中,甘肃马先蒿个体形态特征如株高、根长、分叉数、叶片数、花数、总生物量都显著高于未退化高寒矮嵩草草甸样地;重度退化草甸中甘肃马先蒿花期各器官的资源投资状况,如根系投资、茎叶投资、繁殖投资分别为7.46%、48.76%、43.78%,未退化样地中甘肃马先蒿的根系投资、茎叶投资、繁殖投资分别为10.12%、54.34%、35.54%。在重度退化高寒草甸中甘肃马先蒿占据较大的生态位,长势良好,且将资源更多地用于繁殖投入。而未退化草甸中甘肃马先蒿优势度不大,更多的是将资源分配到根系和茎叶等营养器官,以期获得较多的水分、无机盐、光照等资源,增强个体竞争力。甘肃马先蒿在不同生境下资源分配的显著差异实质反映了草地退化的影响,亦是植物对外部环境改变的一种适应机制,同时也是植物可塑性的重要表现形式。 相似文献