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621.
Jonathan W.Moore Daniel E.Schindler Mark D.Scheuerell Danielle Smith Jonathan Frodge 《Ambio-人类环境杂志》2003,32(1):13-18
引言 近50年来美国住宅开发大量增加.所增住宅很多集中在市区,美国几乎80%的人口现今居住在城里[1].当人们从农村地区和市中心向城市边缘和郊区迁移时,城市变得越来越大,人口增加、地区扩大[1].在城市扩建时,开发商把农业用地和林区的土地转变成城市和城郊[2,3].于是,在城市的边缘、在城乡结合部常常夹杂着被建筑工地、新开发的住宅和商业网点所分割的小块农田和林地以及现在被城市扩建所吞噬的过去十分偏僻的住宅[1,2]. 相似文献
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Swati Mookherji Gregory W. McCarty Jonathan T. Angier 《Journal of the American Water Resources Association》2003,39(2):381-387
ABSTRACT: Dissolved gas analysis permits direct detection of ground water denitrification, a technique we used in this study to assess the fate of nitrate in a riparian wetland. Dissolved argon (Ar) and dinitrogen (N2) were measured in transects of nested piezometers installed at different depths within upwelling regions of a riparian wetland. The method uses the Ar content in the water as a natural inert tracer for assessing background content of N2 from the previous air/water equilibrium. Within the wetland under study, anoxic to suboxic ground water became more oxic in piezometers close to the aquifer layer, indicating upwelling of oxic ground water. Assessment of loss of nitrate and Ar in ground water within an upwelling zone indicated that shallow piezometers had significant N2 loss through degassing. Most of the measured nitrate‐nitrogen (NO3?‐N) loss of 205 μM in a piezometer nest could be accounted for by total N2‐N produced (169 μM N), calculated from changes in dissolved N2 and estimated N2 degassed. Degassing due to methane (CH4) production was also detected in some shallow piezometers within nests. This technique for analysis of dissolved gases in ground water can be applied to detect small changes in N gas concentration and aids in assessing the fate of nitrate along a ground water flow path. 相似文献
626.
Timothy P. Munyon Matthew T. Jenkins T. Russell Crook Jonathan Edwards N. Paul Harvey 《组织行为杂志》2019,40(5):587-602
It is unclear why some firms suffer greater negative consequences than others following a product recall. To shed light on this question, we extend attribution theory to the firm level to explore how consumers engage in an attributional process following product recalls that shapes their responses to firms. Integrating attribution theory and the demand side theoretical perspective, we assert that consumer judgments of responsibility toward manufacturers are shaped by causal data regarding the locus of causality (i.e., manufacturer or supplier) and controllability (i.e., prior knowledge or awareness) of a recalled product's potential for harm. We then examine the impact of product recall characteristics on judgments of responsibility and firm‐level outcomes using an experimental test involving responses from 320 subjects. Our findings suggest that judgments of responsibility are attributed to the manufacturing firm more when consumers are given causal information indicating that the firm is the source of, or is aware of, a product's defects. The results also indicate that judgments of responsibility can have costly firm‐level consequences in the form of reputational damage, diminished consumer purchase intentions, and increased legal damage recommendations. We discuss theoretical contributions, practical implications, and opportunities for further research. 相似文献
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Saumya Sarkar Hillary N. Yonce Ann Keeley Timothy J. Canfield Jonathan B. Butcher Michael J. Paul 《Journal of the American Water Resources Association》2019,55(2):497-510
A total maximum daily load for the Chesapeake Bay requires reduction in pollutant load from sources within the Bay watersheds. The Conestoga River watershed has been identified as a major source of sediment load to the Bay. Upland loads of sediment from agriculture are a concern; however, a large proportion of the sediment load in the Conestoga River has been linked to scour of legacy sediment associated with historic millpond sites. Clarifying this distinction and identifying specific segments associated with upland vs. channel sources has important implications for future management. In order to address this important question, we combined the strengths of two widely accepted watershed management models — Soil and Water Assessment Tool (SWAT) for upland agricultural processes, and Hydrologic Simulation Program FORTRAN (HSPF) for instream fate and transport — to create a novel linked modeling system to predict sediment loading from critical sources in the watershed including upland and channel sources, and to aid in targeted implementation of management practices. The model indicates approximately 66% of the total sediment load is derived from instream sources, in agreement with other studies in the region and can be used to support identification of these channel source segments vs. upland source segments, further improving targeted management. The innovated linked SWAT‐HSPF model implemented in this study is useful for other watersheds where both upland agriculture and instream processes are important sources of sediment load. 相似文献
629.
We used variance decomposition to explore the importance of body size, sex, location, and sampling period as predictors of intrapopulation variation in δ15N and δ13C values in spiny dogfish Squalus suckleyi from the Puget Sound–Strait of Georgia basin. Isotopes in two tissues with long (dorsal white muscle) and short (liver) isotopic turnover rates (~1 year and ~3–4 months, respectively) were sampled to evaluate whether the relative importance of each variable differed depending on the time span over which diet information was integrated. Significant spatial variation was observed in both muscle and liver isotopic composition, whereby location uniquely explained 25 and 17 % of the total variance, respectively. The remaining variables explained considerably less variation in both tissue types. Furthermore, evidence of seasonal isotopic shifts in δ15N and δ13C values was apparent, but differed widely in direction and magnitude among groups. These findings suggest that members of spiny dogfish schools may share a common feeding history, possibly by spending extended time periods (weeks to months) foraging in a spatially fixed region. Another explanation is that individuals may move and feed in aggregations that exist for extended periods. These complex group-level patterns suggest that even for large-bodied, motile predators such as sharks, population-level diet estimates derived from averaging isotope ratios of individuals collected from only a few locations may poorly reflect the true population mean. 相似文献
630.
Jonathan Z. Shik 《Behavioral ecology and sociobiology》2010,64(12):1981-1990
Ant colonies are superorganisms with emergent traits that, for some species, reflect the combined activity of physically distinct
worker castes. Although larger castes have high production costs, they are thought to save their colonies energy by efficiently
performing specialized tasks. However, because workers are generally idle until sensing specific stimuli, their maintenance
costs may be an important component of colony-level investment. I used metabolic scaling to examine the maintenance costs
of dimorphic major and minor Pheidole castes across levels of colony organization (e.g., individual, group, and colony). Majors from three species had lower mass-specific
metabolic rates than minors because of allometries at both individual and group levels and subsequently lived longer when
starved. Thus, large major castes may offset their production costs in both their idle and active states. The slope scaling
metabolic rate from incipient to reproductive colonies of Pheidole dentata (∼colony mass0.89) fell between the slopes for minor groups (∼group mass1.04) and major groups (∼group mass0.79) and appears to reflect developmental shifts in subunit mass and number and their offsetting effects on per capita energy
demands. These results highlight how metabolic scaling may help visualize the energetic correlates of emergent behavior and
unravel the mechanisms governing colony organization. 相似文献