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291.
292.
Ted S. Kornecki George J. Sabbagh Daniel E. Storm 《Journal of the American Water Resources Association》1999,35(4):807-820
ABSTRACT: The purpose of this study was to evaluate the performance of Spatially Integrated Models for Phosphorus Loading and Erosion (SIMPLE) in predicting runoff volume, sediment loss, and phosphorus loading from two watersheds. The modeling system was applied to the 334 ha QOD subwatershed, part of the Owl Run watershed, located in Fauquier County, Virginia, and to the 2240 ha watershed, Battle Branch, located in Delaware County, Oklahoma. Simulation runs were conducted at cell and field scales, and simulation results were compared with observed data. Runoff volume and dissolved phosphorus loading were measured at the Battle Branch watershed. Runoff volume, sediment yield, and total phosphorus loading were measured at the QOD site. SIMPLE tended to underestimate runoff volumes during the dormant period, from November to March. The comparison between observed and predicted dissolved phosphorus showed better correlation than for observed and predicted total phosphorus loading. Cell level simulations provided similar estimates of runoff volume and phosphorus loading when compared to field level simulations for both watersheds. However, observed sediment yields better compared with the values predicted from the cell level simulation when compared to field level simulation. Finally, results of model evaluation indicated that SIMPLE's predictive ability is acceptable for screening applications but not for site-specific quantitative predictions. 相似文献
293.
Daniel Mittler 《Local Environment》1999,4(3):353-365
This paper steps into the minefield that is urban sustainability studies. It defends a rigorous definition of sustainable development called Environmental Space. This approach starts from the assumption that (1) there are limits to the biophysical capacity of the ecosystem and (2) that — within these limits — each individual has equal access rights to natural capital. On this basis, per capita sustainable consumption targets are calculated which can be (and are being) used as policy objectives. The paper explores how environmental space has influenced local sustainability politics in Edinburgh, Scotland. By doing so, it finds that environmental space targets are still far from being achieved. Reasons for this failure are investigated and Edinburgh's continued commitment to the material growth of her economy is identified as one key barrier. This point is illustrated through the investigation of recent policy decisions in Edinburgh which were justified as being necessary for growth, but which clearly contradict the aims of sustainable development. 相似文献
294.
Contradictory findings in studies of sex ratio variation in roe deer (Capreolus capreolus) 总被引:3,自引:0,他引:3
A. J. Mark Hewison Reidar Andersen Jean-Michel Gaillard John D. C. Linnell Daniel Delorme 《Behavioral ecology and sociobiology》1999,45(5):339-348
Patterns of sex ratio variation and maternal investment reported in the literature are often inconsistent. This could be
due to intra- and inter-specific variation in social systems, but may also be a result of the a posteriori nature of much
of this type of analysis or the testing of models which are inappropriate. Two recent papers reported directly opposed results
concerning variation in offspring sex ratios in relation to maternal condition in roe deer, interpreting the results as support
for the Trivers and Willard model and for the local resource competition hypothesis, respectively. In this paper, we present
data on offspring sex ratios and early juvenile body weight from two long-term studies of this species to test predictions
arising from these two models concerning sex biases in litter composition and maternal care. First, we observed no consistent
pattern of sex differences in an index of weaning weight or body weight at 1 month old in either population, indicating a
lack of sex bias in maternal care. However, in one population, higher maternal body weight was associated with higher juvenile
body weight of daughters, but not of sons. Secondly, we found a negative, but not statistically significant, relationship
between maternal body weight and litter sex ratio such that heavier females tended to produce more daughters and lighter females
to produce more sons. These results indicate that roe females which have additional investment potential available do not
invest it in sons, as predicted by the Trivers and Willard model. Our results may provide some support that roe deer are subject
to local resource competition acting at the level of the individual mother; however, the fact that particular trends in sex
ratio data can be explained in functional terms provides no indication that they are actually adaptive.
Received: 9 December 1997 / Accepted after revision: 11 November 1998 相似文献
295.
Alexandrine Daniel Paul Savary Jean-Christophe Foltête Aurélie Khimoun Bruno Faivre Anthony Ollivier Cyril Éraud Hervé Moal Gilles Vuidel Stéphane Garnier 《Conservation biology》2023,37(3):e14047
Habitat connectivity is a key objective of current conservation policies and is commonly modeled by landscape graphs (i.e., sets of habitat patches [nodes] connected by potential dispersal paths [links]). These graphs are often built based on expert opinion or species distribution models (SDMs) and therefore lack empirical validation from data more closely reflecting functional connectivity. Accordingly, we tested whether landscape graphs reflect how habitat connectivity influences gene flow, which is one of the main ecoevolutionary processes. To that purpose, we modeled the habitat network of a forest bird (plumbeous warbler [Setophaga plumbea]) on Guadeloupe with graphs based on expert opinion, Jacobs’ specialization indices, and an SDM. We used genetic data (712 birds from 27 populations) to compute local genetic indices and pairwise genetic distances. Finally, we assessed the relationships between genetic distances or indices and cost distances or connectivity metrics with maximum-likelihood population-effects distance models and Spearman correlations between metrics. Overall, the landscape graphs reliably reflected the influence of connectivity on population genetic structure; validation R2 was up to 0.30 and correlation coefficients were up to 0.71. Yet, the relationship among graph ecological relevance, data requirements, and construction and analysis methods was not straightforward because the graph based on the most complex construction method (species distribution modeling) sometimes had less ecological relevance than the others. Cross-validation methods and sensitivity analyzes allowed us to make the advantages and limitations of each construction method spatially explicit. We confirmed the relevance of landscape graphs for conservation modeling but recommend a case-specific consideration of the cost-effectiveness of their construction methods. We hope the replication of independent validation approaches across species and landscapes will strengthen the ecological relevance of connectivity models. 相似文献
296.
There is extensive research on employee attitudes regarding employers and unions, but these studies have underemphasized social and affective forces. Most studies also examine attitudes toward either the union or the employer without considering how these attitudes might relate to one another. The present study of faculty (N = 306) at a large public research university demonstrated that perceptions of union support were positively related to union participation and perceptions of administration support were negatively related to union participation. Subjective norms and general union attitudes were related to perceptions of union support, and subjective norms were related to perceived organizational support. Taken together, an individual's participation in a union recognition effort depends not only on union instrumentality, but also upon social relationships with the union and administration. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
297.
This research examines the willingness of employees to follow their organization when the entire business unit is geographically relocating. The site for the study was a large government defense agency moving from a major U.S. northeastern metropolitan area to a rural area south of Washington, D.C. The study participants were 380 employees who were deciding within the next 6 months if they would relocate, too. Attachment to the present community, attachment to the current organization, and availability of job market alternatives are the factors most significantly associated with willingness to move during corporate relocation. © 1998 John Wiley & Sons, Ltd. 相似文献
298.
This research examines demographic diversity between mentors and proteges on international internships. Using a sample of 138 interns on six‐month overseas assignments, the results indicate that interns who are different in nationality and gender from their mentors are much less likely to receive task‐related, social‐related, and career‐related support from them. Moreover, this deficit in mentoring is associated with poorer socialization to internship assignments, lower levels of learning about international business, lower likelihoods of receiving and accepting job offers from internship employers, and lower perceived career instrumentality of the internships. The implications of the results for future research on mentor–protege diversity and the design of international internships are discussed as well. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
299.
Haifa RAJHI Daniel PUYOL Mirna C. MARTÍNEZ Emiliano E. DÍAZ José L. SANZ 《Frontiers of Environmental Science & Engineering》2016,10(3):513-521
The successful operation of any type of hydrogen-producing bioreactor depends on the performance of the microorganisms present in the system. Both substrate and partial gas pressures are crucial factors affecting dark fermentation metabolic pathways. The main objective of this study was to evaluate the impact of both factors on hydrogen production using anaerobic granular sludge as inoculum and, secondly, to study the metabolic shifts of an anaerobic community subjected to low partial gas pressures. With this goal in mind, seven different wastewater (four synthetic media, two industrial wastewater, and one domestic effluent) and the effect of applying vacuum on the systems were analyzed. The application of vacuum promoted an increase in the diversity of hydrogenproducing bacteria, such as Clostridium, and promoted the dominance of acetoclastic- over hydrogenotrophic methanogens. The application of different media promoted a wide variety of metabolic pathways. Nevertheless, reduction of the hydrogen partial pressure by application of vacuum lead to further oxidation of reaction intermediates irrespective of the medium used, which resulted in higher hydrogen and methane production, and improved the COD removal. Interestingly, vacuum greatly promoted biogenic hydrogen production from a real wastewater, which opens possibilities for future application of dark fermentation systems to enhance biohydrogen yields. 相似文献
300.
2010年4月~2011年4月,在九寨沟连续监测了总悬浮颗粒物(TSP)和水溶性无机离子的浓度.结果表明:旅游活动显著增加了空气中TSP、SO42-、Ca2+、K+、NH4+和NO3-的含量,而Na+、Mg2+和Cl-则主要来自自然源;旅游强度最高时期(6~10月),降水对空气的清洗作用最强,气溶胶污染程度为全年最低;旅游强度较低时期(1~3、4~5和11~12月),降水量较低且西北沙尘易在春季抵达九寨沟,所以气溶胶污染程度较高;区域燃煤可能是气溶胶[SO42-]:[NO3-]比值较高的原因;生物质燃烧可能是K+在秋末至次年初春较高的原因之一.九寨沟大气环境已明显受当地旅游活动和污染物长距离传输的影响. 相似文献