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101.
This study examined the effect of leader-member exchange (LMX) on the relationship between employee performance (measured objectively) and the supervisor's rating of that performance. To date, no field study has tested whether high and low LMX members receive differential ratings based on their LMX relationship, beyond their actual performance. Data were collected from employees (directory assistants, cable technicians, and dispatch clerks) and their supervisors in a telephone company. The objective measures of performance which were available for these jobs were related to supervisory ratings of performance for high and low LMX employees. The results showed that poorly performing high LMX employees were given high performance ratings, regardless of their actual performance. The ratings of low LMX employees were consistent with their actual performance. The effect of LMX was more pronounced with more general task and relationship rating categories. Alternative explanations of the results, as well as the theoretical and practical implications for performance appraisal and LMX research, were discussed. 相似文献
102.
Agricultural and recreational impacts of the conservation reserve program in rural North Dakota, USA 总被引:1,自引:0,他引:1
The Conservation Reserve Program (CRP), created in 1985, provides conservation benefits and agricultural supply control through voluntary, long-term retirement of crop land. While the effects of the CRP on the agricultural sector are well understood, the implications of its conservation benefits for rural economies remain largely undocumented. To quantify the effects on rural economies, this study addressed the net economic effects of decreased agricultural activity and increased recreational activity associated with the CRP in six rural areas of North Dakota from 1996 to 2000. Based on the level of economic activity that would have occurred in the absence of the program, net revenues from CRP land if returned to agricultural production in the six study areas were estimated at $50.2 million annually or $37 per acre of land currently enrolled in the CRP. Recreational (hunting) revenues as a result of the CRP in the study areas were estimated at $12.8 million annually or $9.45 per CRP-acre. The net economic effect of the CRP (lost agricultural revenues and gains in recreational expenditures) indicated that several areas of the state are not as economically burdened by the CRP as previous research has suggested. In addition, the net economic effects of the program would appear more favourable if revenues from all CRP-based recreation were included. The degree that recreational revenues offset agricultural losses might be further enhanced by enterprises that capitalize on the economic opportunities associated with expanded recreational activities on CRP lands. 相似文献
103.
A conceptual model for N sequestration into the terrestrial nitrogen(N) sink is presented. The model uses foliar litter-fall data, limit values for litter decomposition, and calculated N concentration at the limit value (Nlimit), giving the N concentration in the hypothesized stable remains. The Nlimit values were determined extrapolating a linear relationship between accumulated litter mass loss and the increasing litter N concentration to the limit value. Thesequestration rates for N in boreal forest humus were calculated and validated for a Scots pine (Pinus sylvestris L.) monocultural stand and mixed stands with Scots pine, Norway spruce (Picea abies L.), and silver birch (Betula pendula L.). The calculated stable N fraction was compared to actually measured amounts of N in humus layers that started to accumulate 2984, 2081, 1106, and 120 yr BP. Sequestration rates of N were measured to be 0.255, 0.221, 0.147, and 0.168 g m-2 yr-1 and modeled to be 0.204, 0.207, 0.190, and 0.190 g m-2 yr-1, respectively, with missing fractions being 11.0, 1.5, 30.8, and 13.3%, respectively. The more N-rich the litter, the larger was the N fraction sequestered. This was found for experimental Scots pine needle litter (n = 6) and for 53 decomposition studies, encompassing seven litter species. The amounts of N sequestered annually ranged from ca. 1–2 kg ha-1 yr-1 under nutrient-poor boreal conditions to about 30 kgha-1 yr-1 in temperate, more nutrient-rich forests. 相似文献
104.
Arbaugh M Bytnerowicz A Grulke N Fenn M Poth M Temple P Miller P 《Environment international》2003,29(2-3):401-406
Toxic effects of photochemical smog on ponderosa and Jeffrey pines in the San Bernardino Mountains were discovered in the 1950s. It was revealed that ozone is the main cause of foliar injury manifested as chlorotic mottle and premature needle senescence. Various morphological, physiological and biochemical alterations in the affected plants have been reported over a period of about 40 years of multidisciplinary research. Recently, the focus of research has shifted from studying the effects of ozone to multiple pollutant effects. Recent studies have indicated that the combination of ozone and nitrogen may alter biomass allocation in pines towards that of deciduous trees, accelerate litter accumulation, and increase carbon sequestration rates in heavily polluted forests. Further study of the effects of multiple pollutants, and their long-term consequences on the mixed conifer ecosystem, cannot be adequately done using the original San Bernardino Mountains Air Pollution Gradient network. To correct deficiencies in the design, the new site network is being configured for long-term studies on multiple air pollutant concentrations and deposition, physiological and biochemical changes in trees, growth and composition of over-story species, biogeochemical cycling including carbon cycling and sequestration, water quality, and biodiversity of forest ecosystems. Eleven sites have been re-established. A comparison of 1974 stand composition with data from 2000 stand composition indicate that significant changes in species composition have occurred at some sites with less change at other sites. Moist, high-pollution sites have experienced the greatest amount of forest change, while dryer low-pollution sites have experienced the least amount of stand change. In general, ponderosa pine had the lowest basal area increases and the highest mortality across the San Bernardino Mountains. 相似文献
105.
106.
107.
Color and chemical oxygen demand (COD) in bleach plant effluents are of concern. Acidified flyash can effectively remove both color and COD from caustic bleach plant effluents. Equally effective, but quicker and easier, is to acidify the effluent to approximately pH 1 and use untreated flyash. Based on maximum color removal, the required contact time is short, about 10 min, and the optimum ash dosage is that amount which raises the pH of the final effluent to about 5. Sufficient color removal is obtained to easily meet Maine's color regulations. Preliminary tests on samples of deionized water spiked with two arochlors of PCB showed high removal efficiency.The major cost of implementing and operating the cleanup procedure will be the cost of the required acid. This might be minimized by using some of the acidic (chlorine) effluent to lower the pH of the caustic effluent. This will, however, lead to less color reduction, and an unknown effect on the COD. 相似文献
108.
This study addressed some conceptual issues central to understanding human reactions to dangerous settings and empirically explored the meaning of physically dangerous work in three different occupational groups (street patrol officers, n=96; investigators, n=21; and clerical and support service workers, n=60) practicing in the same organizational setting (city police department). Objective hazards, estimated with occupational risk statistics, explained 56 per cent of the variation in experienced physical danger which, in turn, significantly heightened emotional exhaustion, dissatisfaction with pay, and disaffection from the employing organization, in the street patrol officer group only, perceived physical danger significantly correlated with task variety, task significance and feedback. The data are interpreted to mean that for street patrol officers, experienced physical danger adds a modicum of enrichment and significance to the work itself. One theme of the analysis is that potentially stigmatic features of the work can be transformed into socially meaningful illusions that enhance the personal dignity of the performer (cf. Hughes, 1958). However, the dominant theme is that physically dangerous work produces fear and related affective distress. Further research on this topic is recommended because of the affective and behavioral consequences of perceived physical danger and also because definitions and meanings of dangerous work are socially, politically and morally important. 相似文献
109.
Gary D. Tasker Nancy E. Driver 《Journal of the American Water Resources Association》1988,24(5):1091-1101
ABSTRACT: Regression models are presented that can be used to estimate mean loads for chemical oxygen demand, suspended solids, dissolved solids, total nitrogen, total ammonia plus nitrogen, total phosphorous, dissolved phosphorous, total copper, total lead, and total zinc at unmonitored sites in urban areas. Explanatory variables include drainage area, imperviousness of drainage basin to infiltration, mean annual rainfall, a land-use indicator variable, and mean minimum January temperature. Model parameters are estimated by a generalized-least-squares regression method that accounts for cross correlation and differences in reliability of sample estimates between sites. The regression models account for 20 to 65 percent of the total variation in observed loads. 相似文献
110.
The Development and Implementation of Indicators of Ecosystem Health in the Great Lakes Basin 总被引:2,自引:0,他引:2
Shear H Stadler-Salt N Bertram P Horvatin P 《Environmental monitoring and assessment》2003,88(1-3):119-151
This paper describes a process for the selection of a suite of ecosystem health indicators for the Great Lakes, as called for in the Great Lakes Water Quality Agreement. The paper also presents some preliminary data on status and trends in ecosystem components based on those indicators. The indicator selection process was carried out by over 150 scientists and managers from both Canada and the USA, and involved the presentation of the proposed indicators at the State of the Lakes Ecosystem Conferences (SOLECs). An open period for comment followed the conferences where input from scientists involved in Great Lakes programs was received. The suite of indicators will, over time, present information in an understandable format that will allow for more informed management decisions. 相似文献