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排序方式: 共有334条查询结果,搜索用时 31 毫秒
21.
Patrick C. Tobin Julie Van Stappen Laura M. Blackburn 《Journal of environmental management》2010,91(10):1991-1996
The introduction of non-native species has accelerated due to increasing levels of global trade and travel, threatening the composition and function of ecosystems. Upon arrival and successful establishment, biological invaders begin to spread and often do so with considerable assistance from humans. Recreational areas can be especially prone to the problem of accidental non-native species transport given the number of visitors that arrive from geographically diverse areas. In this paper, we examine camping permit data to the Apostle Islands National Lakeshore in northwestern Wisconsin, USA, from 1999 to 2007 relative to gypsy moth distribution, phenology and outbreak data. During this time, gypsy moth populations became established in this area ahead of the moving population front of the gypsy moth, suggesting anthropogenic introduction. The permit data revealed that the majority of visitors arrived from outside of the gypsy moth established area. However, there was a consistent yearly trend of visitors that arrived from areas of high gypsy moth populations and who arrived during the gypsy moth life stage (egg masses) most likely to be successfully introduced. Using available data on the gypsy moth and its relationship to camping permit data, we describe how recreational managers could optimize park strategies to mitigate unwanted introductions of the gypsy moth as well as develop analogous strategies for managing other biological invaders in recreational areas. 相似文献
22.
Azotobacter vinelandii UWD, ATCC 53799, an engineered strain derived from Azotobacter vinelandii UW was used in the poly(ethylene glycol) (PEG)-modulated synthesis of poly(-hydroxybutyrate) (PHB). To the best of our knowledge, this is the first report on modulating the production of PHB by amending the fermentation broth with PEG using A. vinelandii UWD. It was determined that A. vinelandii UWD is prone to back-mutation to the parent strain; hence fermentation experiments require the use of the antibiotic rifampicin. Diethylene glycol (DEG) and PEGs with molecular weights of 400, 2000, and 3400 Da and pentaerythritol ethoxylate (PEE) were used in the modulated fermentation experiments in a concentration of 2% (w/v). The molecular weight of the resulting polymers was reduced by up to 78%. No impact on the productivity of the strain was observed. Spectroscopic evidence showed that PEG-modulated synthesis resulted in the covalent attachment of the ethylene glycol moiety only when a small molecule, DEG, was used. PEGs had the same effects on the polymer formation in terms of molecular weight reduction as DEG, but no spectroscopic evidence was found for the formation of a covalent linkage between PHB and higher molecular weight PEGs. 相似文献
23.
Agricultural Land Use Effects on Sediment Loading and Fish Assemblages in Two Minnesota (USA) Watersheds 总被引:1,自引:1,他引:0
We examined the relationship between water quality and fish communities within two agricultural areas using a computer simulation model. Our analyses focused on a coolwater stream, Wells Creek in southeastern Minnesota, and a warmwater stream, the Chippewa River in western Minnesota. We used the Agricultural Drainage and Pesticide Transport (ADAPT) model in relation to land use to calculate instream suspended sediment concentrations using estimates of sediment delivery, runoff, baseflow and streambank erosion, and quantified the effects of suspended sediment exposure on fish communities. We predicted the effects of agricultural practices on stream fish communities under several possible land use scenarios, with reference to current conditions. Land use changes led to reductions in sediment loading of up to 84% in Wells Creek and 49% in the Chippewa River. The reduction in sediment loading across scenarios may be directly related to a reduction in runoff by about 35% in both study areas. We found a 98% decrease in lethal concentrations of suspended sediment on fish in Wells Creek with an increase in conservation tillage, riparian buffers, and permanent vegetative cover. However, the effects of suspended sediment did not significantly decrease in the Chippewa River. This difference between study areas was likely due to differences in tolerance to suspended sediment between coolwater and warmwater fish communities and differences in topography, runoff and bank erosion between the two streams.
The Minnesota Cooperative Fish and Wildlife Research Unit is jointly sponsored by the US Geological Survey, the University of Minnesota, the Minnesota Department of Natural Resources, and the Wildlife Management Institute. 相似文献
24.
Julie?Gros-LouisEmail author David?J.?White Andrew?P.?King Meredith?J.?West 《Behavioral ecology and sociobiology》2003,53(3):163-173
In many species, females' behavior appears to be influenced by that of other females, particularly regarding mate choice. Females theoretically can reduce the costs associated with independent male assessment by observing conspecifics. Studies of brown-headed cowbirds suggest that females pay attention to other females' behavior. Group-housed females modify their song preferences, whereas females housed in pairs do not. What information is available to females in a group environment? To address this question, we studied two groups of juvenile (i.e. hatch-year birds) and adult female cowbirds in a naturalistic group setting. We used a longitudinal ABA design, consecutively introducing and removing males that differed in age, amount of song production and stage of song development, to isolate the male characteristics that related to changes in female behavior. Juvenile and adult females assorted by age class when singing adult males were in the aviary, but not when singing juveniles or silent males of any age class were in the aviary. Results from playback tests confirmed that adult male song alone influenced female age class assortment. Videotape analysis from playback tests revealed that females also wing stroked in response to male song. Other females sometimes approached females who wing stroked and observed them. We hypothesize that group-level changes in social organization and individual females' responses can serve as visual signals for other individuals. 相似文献
25.
Phleum pratense and Poa pratensis were significantly lower (P ≤ 0.001) on plots with more than 250 ppm copper. Above-ground biomass of Phleum pratense was also significantly lower on plots with copper levels above 250 ppm. Decreased mean grass density was found on plots with
pH < 6.4, but the only statistically significant difference was for Juncus balticus, which had increased density on plots with pH < 6.4. In contrast to the clear impacts of trace metals and pH on vegetation,
other site characteristics did not alter measured vegetation characteristics. 相似文献
26.
27.
Julie Wallace Pavlos Kanaroglou 《Atmospheric environment (Oxford, England : 1994)》2009,43(22-23):3596-3604
We assess the sensitivity of tropospheric nitrogen dioxide (NO2) derived from the Ozone Monitoring Instrument (OMI), to episodes of temperature inversion in the lower boundary layer. Vertical temperature data were obtained from a 91-m meteorological tower located in the study area, which is centered on the Hamilton Census Metropolitan Area, Ontario, Canada. Hamilton is an industrial city with high traffic volumes, and is therefore subjected to high levels of pollution. Pollution buildup is amplified by frequent temperature inversions which are commonly radiative, but are also induced by local physiography, proximity to Lake Ontario, and regional meteorology. The four-year period from January 2005 to December 2008 was investigated. Ground-level data for validation were obtained from in situ air quality monitors located in the study area. The results indicate that OMI is sensitive to changes in the NO2 levels during temperature inversions, and exhibits changes which roughly parallel those of in situ monitors. Overall, an 11% increase in NO2 was identified by OMI on inversion days, compared to a 44% increase measured by in situ monitors. The weekend effect was clearly exhibited under both normal and inversion scenarios with OMI. Seasonal and wind direction patterns also correlated fairly well with ground-level data. Temperature inversions have resulted in poor air quality episodes which have severely compromised the health of susceptible populations, sometime leading to premature death. The rationale for this study is to further assess the usefulness of OMI for population exposure studies in areas with sparse resources for ground-level monitoring. 相似文献
28.
Joke Muys Yves Jacquemyn Bettina Blaumeiser Laura Bourlard Nathalie Brison Saskia Bulk Patrizia Chiarappa Anne De Leener Marjan De Rademaeker Julie Désir Anne Destrée Koenraad Devriendt Annelies Dheedene Armelle Duquenne Annelies Fieuw Erik Fransen Jean-Stéphane Gatot Mauricette Jamar Sandra Janssens Jorien Kerstjens Kathelijn Keymolen Damien Lederer Björn Menten Bruno Pichon Sonia Rombout Yves Sznajer Ann Van Den Bogaert Kris Van Den Bogaert Joris Vermeesch Katrien Janssens 《黑龙江环境通报》2020,40(10):1272-1283
29.
Chris Pratt Adrian S. Walcroft Julie Deslippe Kevin R. Tate 《Waste management (New York, N.Y.)》2013,33(2):412-419
Landfills that generate too little biogas for economic energy recovery can potentially offset methane (CH4) emissions through biological oxidation by methanotrophic bacteria in cover soils. This study reports on the CH4 oxidation efficiency of a 10-year old landfill cap comprising a volcanic pumice soil. Surface CH4 and CO2 fluxes were measured using field chambers during three sampling intervals over winter and summer. Methane fluxes were temporally and spatially variable (?0.36 to 3044 mg CH4 m?2 h?1); but were at least 15 times lower than typical literature CH4 fluxes reported for older landfills in 45 of the 46 chambers tested. Exposure of soil from this landfill cover to variable CH4 fluxes in laboratory microcosms revealed a very strong correlation between CH4 oxidation efficiency and CH4/CO2 ratios, confirming the utility of this relationship for approximating CH4 oxidation efficiency. CH4/CO2 ratios were applied to gas concentrations from the surface flux chambers and indicated a mean CH4 oxidation efficiency of 72%. To examine CH4 oxidation with soil depth, we collected 10 soil depth profiles at random locations across the landfill. Seven profiles exhibited CH4 removal rates of 70–100% at depths <60 cm, supporting the high oxidation rates observed in the chambers. Based on a conservative 70% CH4 oxidation efficiency occurring at the site, this cover soil is clearly offsetting far greater CH4 quantities than the 10% default value currently adopted by the IPCC. 相似文献