An axenic plant culture system for optimal growth in long-term studies

The symbiotic co-evolution of plants and microbes leads to difficulties in understanding which of the two components is responsible for a given environmental response. Plant-microbe studies greatly benefit from the ability to grow plants in axenic (sterile) culture. Several studies have used axenic plant culture systems, but experimental procedures are often poorly documented, the plant growth environment is not optimal, and axenic conditions are not rigorously verified. We developed a unique axenic system using inert components that promotes plant health and can be kept sterile for at least 70 d. Crested wheatgrass (Agropyron cristatum cv. CDII) plants were grown in sand within flow-through glass columns that were positively pressured with filtered air. Plant health was optimized by regulating temperature, light level, CO2 concentration, humidity, and nutrients. The design incorporates several novel aspects, such as pretreatment of the sand with Fe, graduated sand layers to optimize the air-water balance of the root zone, and modification of a laminar flow hood to serve as a plant growth chamber. Adaptations of several sterile techniques were necessary for maintenance of axenic conditions. Axenic conditions were verified by plating and staining leachates as well as a rhizoplane stain. This system was designed to study nutrient and water stress effects on root exudates, but is useful for assessing a broad range of plant-microbe-environment interactions. Based on total organic C analysis, 74% of exudates was recovered in the leachate, 6% was recovered in the bulk sand, and 17% was recovered in the rhizosphere sand. Carbon in the leachate after 70 d reached 255 microg d(-1). Fumaric, malic, malonic, oxalic, and succinic acids were measured as components of the root exudates.     

Poultry litter application to loblolly pine forests: growth and nutrient containment

Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8-yr-old stands at 0, 4.6, and 18.6 dry Mg ha-1, supplying 0, 200, and 800 kg N ha-1 and 0, 92, and 370 kg P ha-1, respectively. Levels of nitrate in soil water, monitored at a 50-cm depth with porous cup tension lysimeters, exceeded 10 mg N L-1 during the first two years after application in the 18.6 Mg ha-1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha-1 rate. Mehlich III-extractable phosphate peaked in excess of 100 microg P g-1 soil during the third year of the study for the 18.6 Mg ha-1 rate. The 4.6 Mg ha-1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross-sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha-1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha-1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.     

Merit pay raises and organization‐based self‐esteem

We developed and tested a theory of the relationship between merit pay raises and organization‐based self‐esteem (OBSE) in a longitudinal study of hospital employees. We predicted that the positive relationship between merit pay raise size and OBSE would be stronger when pay‐for‐performance (PFP) perceptions were high and predicted further that this interaction would be stronger among older employees. As predicted, merit pay raises were not related to OBSE levels for younger employees, but, among older employees, larger merit raises increased OBSE when PFP perceptions were high and decreased OBSE when PFP perceptions were low. Implications of the study for merit pay theory and practice are addressed. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydrologic Calibration and Validation of SWAT in a Snow‐Dominated Rocky Mountain Watershed,Montana, U.S.A.1

Abstract: The Soil and Water Assessment Tool (SWAT) has been applied successfully in temperate environments but little is known about its performance in the snow‐dominated, forested, mountainous watersheds that provide much of the water supply in western North America. To address this knowledge gap, we configured SWAT to simulate the streamflow of Tenderfoot Creek (TCSWAT). Located in central Montana, TCSWAT represents a high‐elevation watershed with ～85% coniferous forest cover where more than 70% of the annual precipitation falls as snow, and runoff comes primarily from spring snowmelt. Model calibration using four years of measured daily streamflow, temperature, and precipitation data resulted in a relative error (RE) of 2% for annual water yield estimates, and mean paired deviations (Dv) of 36 and 31% and Nash‐Sutcliffe (NS) efficiencies of 0.90 and 0.86 for monthly and daily streamflow, respectively. Model validation was conducted using an additional four years of data and the performance was similar to the calibration period, with RE of 4% for annual water yields, Dv of 43% and 32%, and NS efficiencies of 0.90 and 0.76 for monthly and daily streamflow, respectively. An objective, regression‐based model invalidation procedure also indicated that the model was validated for the overall simulation period. Seasonally, SWAT performed well during the spring and early summer snowmelt runoff period, but was a poor predictor of late summer and winter base flow. The calibrated model was most sensitive to snowmelt parameters, followed in decreasing order of influence by the surface runoff lag, ground water, soil, and SCS Curve Number parameter sets. Model sensitivity to the surface runoff lag parameter reflected the influence of frozen soils on runoff processes. Results indicated that SWAT can provide reasonable predictions of annual, monthly, and daily streamflow from forested montane watersheds, but further model refinements could improve representation of snowmelt runoff processes and performance during the base flow period in this environment.     

Reducing Nonpoint Source Pollution Through Collaboration: Policies and Programs Across the U.S. States

Nonpoint source (NPS) pollution has emerged as the largest threat to water quality in the United States, influencing policy makers and resource managers to direct more attention toward NPS prevention and remediation. In response, the United States Environmental Protection Agency (USEPA) spent more than $204 million in fiscal year (FY) 2006 on the Clean Water Act’s Section 319 program to combat NPS pollution, much of it on the development and implementation of watershed-based plans. State governments have also increasingly allocated financial and technical resources to collaborative watershed efforts within their own borders to fight NPS pollution. With increased collaboration among the federal government, states, and citizens to combat NPS pollution, more information is needed to understand how public resources are being used, by whom, and for what, and what policy changes might improve effectiveness. Analysis from a 50-state study suggests that, in addition to the average 35% of all Section 319 funds per state that are passed on to collaborative watershed groups, 35 states have provided financial assistance beyond Section 319 funding to support collaborative watershed initiatives. State programs frequently provide technical assistance and training, in addition to financial resources, to encourage collaborative partnerships. Such assistance is typically granted in exchange for requirements to generate a watershed action plan and/or follow a mutually agreed upon work plan to address NPS pollution. Program managers indicated a need for greater fiscal resources and flexibility to achieve water quality goals.     

Approach for extrapolating in vitro metabolism data to refine bioconcentration factor estimates

National and international chemical management programs are assessing thousands of chemicals for their persistence, bioaccumulative and environmental toxic properties; however, data for evaluating the bioaccumulation potential for fish are limited. Computer based models that account for the uptake and elimination processes that contribute to bioaccumulation may help to meet the need for reliable estimates. One critical elimination process of chemicals is metabolic transformation. It has been suggested that in vitro metabolic transformation tests using fish liver hepatocytes or S9 fractions can provide rapid and cost-effective measurements of fish metabolic potential, which could be used to refine bioconcentration factor (BCF) computer model estimates. Therefore, recent activity has focused on developing in vitro methods to measure metabolic transformation in cellular and subcellular fish liver fractions. A method to extrapolate in vitro test data to the whole body metabolic transformation rates is presented that could be used to refine BCF computer model estimates. This extrapolation approach is based on concepts used to determine the fate and distribution of drugs within the human body which have successfully supported the development of new pharmaceuticals for years. In addition, this approach has already been applied in physiologically-based toxicokinetic models for fish. The validity of the in vitro to in vivo extrapolation is illustrated using the rate of loss of parent chemical measured in two independent in vitro test systems: (1) subcellular enzymatic test using the trout liver S9 fraction, and (2) primary hepatocytes isolated from the common carp. The test chemicals evaluated have high quality in vivo BCF values and a range of logK(ow) from 3.5 to 6.7. The results show very good agreement between the measured BCF and estimated BCF values when the extrapolated whole body metabolism rates are included, thus suggesting that in vitro biotransformation data could effectively be used to reduce in vivo BCF testing and refine BCF model estimates. However, additional fish physiological data for parameterization and validation for a wider range of chemicals are needed.     

Climate Change Adaptation for the US National Wildlife Refuge System

Since its establishment in 1903, the National Wildlife Refuge System (NWRS) has grown to 635 units and 37 Wetland Management Districts in the United States and its territories. These units provide the seasonal habitats necessary for migratory waterfowl and other species to complete their annual life cycles. Habitat conversion and fragmentation, invasive species, pollution, and competition for water have stressed refuges for decades, but the interaction of climate change with these stressors presents the most recent, pervasive, and complex conservation challenge to the NWRS. Geographic isolation and small unit size compound the challenges of climate change, but a combined emphasis on species that refuges were established to conserve and on maintaining biological integrity, diversity, and environmental health provides the NWRS with substantial latitude to respond. Individual symptoms of climate change can be addressed at the refuge level, but the strategic response requires system-wide planning. A dynamic vision of the NWRS in a changing climate, an explicit national strategic plan to implement that vision, and an assessment of representation, redundancy, size, and total number of units in relation to conservation targets are the first steps toward adaptation. This adaptation must begin immediately and be built on more closely integrated research and management. Rigorous projections of possible futures are required to facilitate adaptation to change. Furthermore, the effective conservation footprint of the NWRS must be increased through land acquisition, creative partnerships, and educational programs in order for the NWRS to meet its legal mandate to maintain the biological integrity, diversity, and environmental health of the system and the species and ecosystems that it supports.     

Sustainability versus liveability: an investigation of neighbourhood satisfaction

Recent years have witnessed an increasing emphasis placed on planning systems in most advanced capitalist societies to develop a more sustainable urban development pattern, resulting in policies to increase residential densities. Although belief in the virtues of the compact city approach is now widespread among the policy community, questions remain relating to the ‘sustainability versus liveability’ implications of compact city environments. In this regard, while the public may support sustainability principles, there is a perception that high-density development poses too great a cost on individuals' quality of life. Combining both quantitative and qualitative research data, this paper evaluates the relationship between high-density living and neighbourhood satisfaction within the central city. Findings suggest that, in many instances, it is not high density per se that is the source of dissatisfaction for respondents, but rather other related factors such as environmental quality, noise, lack of community involvement, traffic and lack of services and facilities.     

Greenhouse gas balance for composting operations

The greenhouse gas (GHG) impact of composting a range of potential feedstocks was evaluated through a review of the existing literature with a focus on methane (CH(4)) avoidance by composting and GHG emissions during composting. The primary carbon credits associated with composting are through CH(4) avoidance when feedstocks are composted instead of landfilled (municipal solid waste and biosolids) or lagooned (animal manures). Methane generation potential is given based on total volatile solids, expected volatile solids destruction, and CH(4) generation from lab and field incubations. For example, a facility that composts an equal mixture of manure, newsprint, and food waste could conserve the equivalent of 3.1 Mg CO(2) per 1 dry Mg of feedstocks composted if feedstocks were diverted from anaerobic storage lagoons and landfills with no gas collection mechanisms. The composting process is a source of GHG emissions from the use of electricity and fossil fuels and through GHG emissions during composting. Greenhouse gas emissions during composting are highest for high-nitrogen materials with high moisture contents. These debits are minimal in comparison to avoidance credits and can be further minimized through the use of higher carbon:nitrogen feedstock mixtures and lower-moisture-content mixtures. Compost end use has the potential to generate carbon credits through avoidance and sequestration of carbon; however, these are highly project specific and need to be quantified on an individual project basis.