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101.
Frederick Amon-Armah Emmanuel K. Yiridoe Nafees H. M. Ahmad Dale Hebb Rob Jamieson David Burton Ali Madani 《Environmental management》2013,52(5):1177-1191
Government priorities on provincial Nutrient Management Planning (NMP) programs include improving the program effectiveness for environmental quality protection, and promoting more widespread adoption. Understanding the effect of NMP on both crop yield and key water-quality parameters in agricultural watersheds requires a comprehensive evaluation that takes into consideration important NMP attributes and location-specific farming conditions. This study applied the Soil and Water Assessment Tool (SWAT) to investigate the effects of crop and rotation sequence, tillage type, and nutrient N application rate on crop yield and the associated groundwater ${\text{NO}_{3}}^{ - } {\text{-N }}$ leaching and sediment loss. The SWAT model was applied to the Thomas Brook Watershed, located in the most intensively managed agricultural region of Nova Scotia, Canada. Cropping systems evaluated included seven fertilizer application rates and two tillage systems (i.e., conventional tillage and no-till). The analysis reflected cropping systems commonly managed by farmers in the Annapolis Valley region, including grain corn-based and potato-based cropping systems, and a vegetable-horticulture system. ANOVA models were developed and used to assess the effects of crop management choices on crop yield and two water-quality parameters (i.e., ${\text{NO}_{3}}^{ - } {\text{-N }}$ leaching and sediment loading). Results suggest that existing recommended N-fertilizer rate can be reduced by 10–25 %, for grain crop production, to significantly lower ${\text{NO}_{3}}^{ - } {\text{-N }}$ leaching (P > 0.05) while optimizing the crop yield. The analysis identified the nutrient N rates in combination with specific crops and rotation systems that can be used to manage ${\text{NO}_{3}}^{ - } {\text{-N }}$ leaching while balancing impacts on crop yields within the watershed. 相似文献
102.
Abstract A local sustainable development initiative to establish a temporary pedestrian zone within a Canadian urban community served as a research study into the efficacy of social capital in the development of a network for community action. This community-based initiative used social capital to overcome campaign obstacles and the campaign itself generated new social capital within the neighbourhood through the creation of adaptive networks of participants. The campaign succeeded in creating a part-time pedestrian-only space that serves as an educational example of change for sustainable community development that is replicable in other communities, and provides an example of alternative occupation of community space. Contrary to other literature, little evidence of “core burnout” was found although the network does continue to expend a large amount of effort and time on fundraising. While social capital is a powerful tool for local grassroots action, the availability of a critical source of economic capital may prove vital to the long-term success and sustainability of the network. 相似文献
103.
A commercially available thermal-infrared scanning system was used to survey populations of several wildlife species. The
system's ability to detect species of different sizes in varying habitats relative to conventional survey methods, to differentiate
between species in the same habitat, and the influence of environtmental factors on operational aspects of employing this
technology in the field were evaluated. Total costs for the surveys were approximately $0.36/ha. There were marked discrepancies
in the counts of untrained observers and those from trained analysis. Computer-assisted analysis of infrared imagery recorded
52% fewer deer than were estimated from drive counts, and densities of moose were five times those estimated from conventional
aerial methods. By flying concentric circles and using telephoto, detailed counts of turkeys and deer were possible. With
the aid of computer-assisted analysis, infrared thermography may become a useful wildlife population survey tool. More research
is needed to verify the actual efficiency of detection by combining aerial scans with ground truthing for a variely of species
and habitals. 相似文献
104.
105.
106.
Does female aggression prevent polygyny? An experiment with pied flycatchers (Ficedula hypoleuca) 总被引:1,自引:0,他引:1
The female aggression hypothesis states that resident females may be able to prevent polygyny by behaving aggressively towards
intruding females. A critical test of the hypothesis is to provide prospecting females with a choice between displaying mated
males some of which have initial mates with artificially reduced levels of aggressiveness. Here we present a mate choice experiment
on pied flycatchers Ficedula hypoleuca. The species is a cavity nester, and resident females were prevented from behaving aggressively by enclosing them within
their own nestboxes: narrowing the entrance hole so that they could not escape but could still let their head out and have
some contact with their mate. This treament had only a minor influence on male behaviour. We studied whether the experimental
males were better able to attract a new female than a control group of mated males. Four predictions from the female aggression
hypothesis were supported. (1) Mating success of control males was positively related to the distance between their primary
and secondary territory. (2) For experimental males, mating success was unrelated to interterritorial distance. (3) Experimental
males had higher mating success than control males when the interterritorial distance was short but (4) not when it was long.
Experimental males had much lower mating success than unmated males, as would be expected if prospecting females are able
to discover male mating status from cues other than visits by primary females to their mates' secondary nest sites.
Received: 5 January 1998 / Accepted after revision: 30 December 1998 相似文献
107.
Dale Toetz Letong Tang Daniel E. Storm Timothy Mihuc Michael D. Smolen 《Journal of the American Water Resources Association》1999,35(4):853-865
ABSTRACT: Predicting stream eutrophication potential from non-point source nutrient loading across large temporal and spatial scales is a significant problem. In this paper we describe how two physiological indicators of P stress of stream bioflims, alkaline phosphatase activity (APA) and stored (surplus) P relate to two predictors of P loading: annual P loading predicted by the watershed model SIMPLE, and stream concentrations of soluble reactive P (SRP) in eight subbasins in the illinois River basin in Oklahoma. Data for APA, surplus P, nutrients and water chemistry were obtained at watershed outlets once during the cold season and twice during the warm season. There was a negative curvilinear relationship between APA and both predictors. Best fit was achieved by APA vs. annual predicted P loading. Both SRP and P. load are potentially useful to identify subbasins requiring no pollution abatement and to establish a regional target for P-load reduction. Surplus P is not as useful as APA in establishing these thresholds. 相似文献
108.
Landscape Planning for Agricultural Nonpoint Source Pollution Reduction III: Assessing Phosphorus and Sediment Reduction Potential 总被引:2,自引:0,他引:2
Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in
response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical
land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable
following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds
(average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin
streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage
density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel
erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot
attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from
streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction
in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately
20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales,
including the watershed scale. 相似文献
109.
Urbanisation significantly impacts water environments with increased runoff and the degradation of water quality. The management of quantity impacts are straight forward, but quality impacts are far more complex. Current approaches to safeguard water quality are largely ineffective and guided by entrenched misconceptions with a primary focus on 'end-of-pipe' solutions. The outcomes of a research study presented in the paper, which investigated relationships between water quality and six different land uses offer practical guidance in the planning of future urban developments. In terms of safeguarding water quality, high-density residential development which results in a relatively smaller footprint would be the preferred option. The research study outcomes bring into question a number of fundamental concepts and misconceptions routinely accepted in stormwater quality management. The research findings confirmed the need to move beyond customary structural measures and identified the key role that urban planning can play in safeguarding urban water environments. 相似文献
110.
Source profiles for industrial, mobile, and area sources in the Big Bend Regional Aerosol Visibility and Observational study 总被引:20,自引:0,他引:20
Chow JC Watson JG Kuhns H Etyemezian V Lowenthal DH Crow D Kohl SD Engelbrecht JP Green MC 《Chemosphere》2004,54(2):185-208
Representative PM2.5 and PM10 source emissions were sampled in Texas during the Big Bend Regional Aerosol Visibility and Observa (BRAVO) study. Chemical source profiles for elements, ions, and carbon fractions of 145 samples are reported for paved and unpaved road dust, soil dust, motor vehicle exhaust, vegetative burning, four coal-fired power stations, an oil refinery catalytic cracker, two cement kilns, and residential meat cooking. Several samples were taken from each emitter and source type, and these were averaged by source type, and in source subgroups based on commonality of chemical composition. The standard deviation represents the variability of the chemical mass fractions. BRAVO profiles differed in some respects from profiles measured elsewhere. High calcium abundances in geological dust, high selenium abundances in coal-fired power stations, and high antimony abundances in oil refinery catalytic cracker emissions were found. Abundances of eight thermally evolved carbon fractions [Atmos. Environ. 28 (15) (1994) 2493] differ among combustion sources, and a Monte Carlo simulation demonstrates that these differences are sufficient to differentiate among several carbon-emitters. 相似文献