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81.
Arild?Johnsen Kim?L.?Carter Kaspar?Delhey Jan?T.?Lifjeld Raleigh?J.?Robertson Bart?KempenaersEmail author 《Behavioral ecology and sociobiology》2012,66(2):181-190
In birds, the number of sperm trapped between the perivitelline membranes around the ovum is an estimate of sperm numbers
present at the time and place of fertilisation in the female reproductive tract. Sperm numbers may vary among species and
between eggs in a clutch and can provide information about sperm utilisation and mechanisms of sperm competition. Here, we
describe patterns of variation in sperm numbers through the egg-laying sequence in three passerines in which extra-pair paternity
is common, but copulation behaviour differs. Sperm numbers showed no systematic change across the laying sequence in blue
tits (Cyanistes caeruleus), but decreased significantly with laying order in bluethroat (Luscinia svecica) and tree swallow (Tachycineta bicolor) clutches. This is consistent with observations that blue tits regularly copulate throughout the laying sequence, while bluethroats
stop mate guarding and tree swallows reduce their copulation frequency once the first egg is laid. Nevertheless, cases of
a sudden increase in sperm numbers in clutches of bluethroats and tree swallows suggest that successful inseminations also
occurred after laying started. In blue tits and bluethroats, sperm numbers were not higher on extra-pair sired eggs than on
eggs sired by the social male, suggesting that extra-pair copulations are not timed to the period of peak fertility for each
egg. More extra-pair offspring originated from eggs laid early in the sequence in blue tits, while there was no systematic
bias in bluethroats. Our results suggest that copulations during the laying sequence are predominantly performed by within-pair
males in our study species. 相似文献
82.
Changes in leaf chlorophyll content can serve as relative indicators of plant vigor and environmental quality. This study identified reflectance, transmittance, and absorptance wavebands and band ratios within the 400- to 850-nm range for intact leaves that could be used to estimate extracted leaf chlorophyll per unit leaf area (areal concentration) with minimal error. Leaf optical properties along with chlorophyll a, b, and a + b concentrations were measured for the planar-leaved sweetgum (Liquidambar styraciflua L.), red maple (Acer rubrum L.), wild grape (Vitis rotundifolia Michx.), and switchcane [Arundinaria gigantea (Walter) Muhl.], and for needles of longleaf pine (Pinus palustris Miller). Generally, reflectance, transmittance, and absorptance corresponded most precisely with chlorophyll concentrations at wavelengths near 700 nm, although regressions were also strong in the 550- to 625-nm range. A power function was superior to a simple linear function in yielding low standard deviations of the estimate (s). When data were combined among the planar-leaved species, s values were low at approximately 50 mumol/m2 out of a 940 mumol/m2 range in chlorophyll a + b at best-fit wavelengths of 707 to 709 nm. Minimal s values for chlorophyll a + b ranged from 32 to 62 mumol/m2 across species when band ratios having numerator wavelengths of 693 to 720 nm were used with the application of a power function. Optimal denominator wavelengths for the band ratios were 850 nm for reflectance and transmittance and 400 nm for absorptance. This information can be applied in designing field portable chlorophyll meters and in the landscape-scale remote sensing of plant responses to the environment. 相似文献
83.
Streets DG Chang YS Tompkins M Ghim YS Carter LD 《Journal of environmental management》2001,61(4):345-365
When environmental regulatory bodies formulate control plans, it is incumbent upon them to try to achieve the stated goals in an economically efficient manner. The US Environmental Protection Agency (EPA) is presently developing regulations to limit the influence of transported ozone on areas that are having difficulty meeting the ambient air quality standard. EPA has proposed stringent control measures for emissions of nitrogen oxides (NOx) in 22 states of the eastern US. The strategy would necessitate the use of selective catalytic reduction or similar high-performance technology on almost all major power plants in the region, as well as extensive controls on industrial sources. This paper suggests several alternative approaches that would achieve equal or better environmental improvement at lower cost. These include focusing control efforts on sources closer to the North-east Corridor, pushing controls on close-in sources to a higher level of technology performance, and relaxing the stringency of requirements for states remote from ozone problem areas. All the approaches examined are two to three times more cost-effective than EPA's proposed approach in the North-east Corridor. 相似文献
84.
Virginia Carter Mary Keith Garrett Lurie Shima Patricia Gammon 《Journal of the American Water Resources Association》1977,13(1):1-12
ABSTRACT: Both color infrared aerial photography and Landsat data are being used to provide information to meet present and future management goals for the Great Dismal Swamp National Wildlife Refuge. High and low altitude color infrared photographs are being used to study the hydrology and map the present vegetation of the swamp. A variety of significant ecologic units have been identified using these photographs. The completed maps will be used to evaluate analyses of landsat digital data. Once the present data base is compiled, it is hoped that routine analysis of Landsat data can be used for updating or to indicate areas where low altitude coverage or ground checking is desirable. The data base will also aid in identifying and evaluating trends that may provide guidelines for wetland management. 相似文献
85.
Ted L. Napier Michael V. Carter Elizabeth G. Bryant 《Journal of the American Water Resources Association》1982,18(2):211-237
ABSTRACT: The purpose of this paper is to examine the correlates of attitudes toward alternative uses which could have been made of public resources employed to construct a multipurpose reservoir. A sample of 303 adult residents of a rural community impacted by lake construction was asked to evaluate several alternative development options which could have been implemented in lieu of the lake project. The alternative options evaluated were: rural industrialization, keeping land in agriculture and forests, improving public services, building a state or national park, drilling water wells for urban water supply, aid to small business, helping poor people, building several smaller impoundments, and private recreation development. The findings revealed the local people preferred the lake project to every option except keeping the land in agriculture and forest. Even this option was not strongly supported when compared with the lake project. Socio-demographic, attitude, and cost assessment factors were investigated using a “vested interest” perspective for hypotheses development. These findings demonstrated that costs and benefits were relatively good predictors of attitudes toward alternative development options and were supportive of the theoretical perspective advanced in this paper. 相似文献
86.
Sherman R. Ellis Gary W. Levings Lisa F. Carter Steven F. Richey Mary Jo Radell 《Journal of the American Water Resources Association》1993,29(4):617-646
ABSTRACT: The Rio Grande Valley National Water-Quality Assessment study unit encompasses about 45,700 square miles in Colorado, New Mexico, and Texas upstream from the gaging station Rio Grande at El Paso, Texas, and includes surface-water closed basins east of the Continental Divide in New Mexico, and the San Luis Closed Basin in Colorado. The mean annual precipitation ranges from less than 6 to more than 50 inches; potential evapo-transpiration ranges from less than 35 to more than 80 inches per year. Land use is mainly rangeland, forest land, and cropland. Total irrigated acreage in 1990 was about 914,000 acres and water use was about 3,410,000 acre-feet. Two structural settings are found in the study unit: alluvial basins and bedrock basins. The alluvial basins can have through-flowing surface water or be closed basins. The discussion of streamflow and water quality for the surface-water system is based on four river reaches for the 750 miles of the main stem. The quality of the ground water is affected by both natural process and human activities and by nonpoint and point sources. Nonpoint sources for surface water include agriculture, hydromodification, and mining operations; point sources are mainly discharge from wastewater treatment plants. Nonpoint sources for ground water include agriculture and septic tanks and cesspools; point sources include leaking underground storage tanks, unlined or manure-lined holding ponds used for disposal of dairy wastes, landfills, and mining operations. 相似文献
87.
Virginia Carter Mary Keith Garrett Patricia T. Gammon 《Journal of the American Water Resources Association》1988,24(2):297-306
ABSTRACT: A weighted average method was used to analyze transition zone vegetation in the Great Dismal Swamp to determine if a more uniform determination of wetland boundaries can be made nationwide. The method was applied to vegetation data collected on four transects and three vertical layers across the wetland-to-upland transition zone of the swamp. Ecological index values based on water tolerance were either taken from the literature or derived from local species tolerances. Wetland index values were calculated for 25-m increments using species cover and rankings based on the ecological indices. Wetland index values were used to designate increments as either wetland, transitional, or upland, and to examine the usefulness of a provisional wetland-upland break-point. Most increments were designated wetland or transitional when all species were used. Removal of three or five ubiquitous species either gave a wider range of wetland index values with a more variable designation of increments or caused designation of increments to be similar for all layers. The use of locally-derived rankings showed the sensitivity of the weighted averages method to ecological indices of species with large importance values. The weighted average method did not provide for an objective placement of an absolute wetland boundary, but did serve to focus attention on the transitional boundary zone where supplementary information is necessary to select a wetland-upland breakpoint. 相似文献
88.
Barbara Farinelli Colin A. Carter C.-Y. Cynthia Lin Daniel A. Sumner 《Journal of Cleaner Production》2009
This study presents an empirical analysis of the import demand for Brazilian ethanol by its six major foreign buyers. The primary objectives of this study were to identify the economic factors affecting the demand for ethanol imports and to derive long-run price and income elasticities of import demand. These elasticities could be used to analyze the impact of government policies such as mandatory gasoline/ethanol blends and import tariffs. Import demand models were estimated with ordinary least squares (OLS), using quarterly time series data for the 1997–2007 time period. The results suggest that the factors influencing the import demand for ethanol vary across countries. Markets adopting mandatory blends of renewable fuels tend to have less price elastic import demand schedules. Ethanol imports were found to be price elastic and statistically significant in the Caribbean region (?1.66), Mexico (?2.08), Japan (?1.44) and Nigeria (?1.38), while import demand was price inelastic and not statistically different from zero in the US (?0.76) and Europe (?0.21). The regression results could not determine the impacts of import tariffs for the United States, Mexico and Nigeria on the quantity of imports because tariffs did not vary during the time period studied. Results show that mandatory gasoline/ethanol blends have been an important determinant of ethanol imports. 相似文献
89.
The relationship between epilithic periphyton (biofilm) bound metals and metals bound to sediments in freshwater systems 总被引:1,自引:0,他引:1
Surficial sediments and epilithic periphyton (biofilm) were sampled from six sites on the River Churnet and five sites on the River Manifold in Staffordshire and analysed for cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). The sites demonstrated a wide range of sediment trace metal concentrations determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorbtion spectroscopy (AAS). Biofilm was removed from the substrate using physical abrasion and 0.005 M ethylenediaminoethanetetra-acetic acid (EDTA) extractant. The European Standards, Measurements and Testing Programmes (BCR) operationally defined geochemical speciation scheme was used to determine the exchangeable, acid soluble fraction of the sediments. Significant positive correlations were determined between the EDTA extractable biofilm and the exchangeable sediment fraction for Cd, Cu and Zn but not for Pb. Natural epilithic periphyton may be a potential metal biomonitor particularly of Cu, Cd and Zn in aquatic systems and provide supporting information in relation to potential sediment toxicity. 相似文献
90.
Julia Wynn Jennifer Hoskovec Rebecca D. Carter Meredith J. Ross Sriram C. Perni 《黑龙江环境通报》2023,43(10):1344-1354