Canopy and leaf composition drive patterns of nutrient release from pruning residues in a coffee agroforest

In a coffee agroforest, the crop is cultivated under the shade of fruit-bearing and nitrogen (N)-fixing trees. These trees are periodically pruned to promote flowering and fruiting as well as to make nutrients stored in tree biomass available to plants. We investigated the effect of canopy composition and substrate quality on decomposition rates and patterns of nutrient release from pruning residues in a coffee agroforest located in Costa Rica's Central Valley. Initial phosphorus (P) release was enhanced under a canopy composed solely of N-fixing, Erythrina poeppigiana compared to a mixed canopy of Erythrina and Musa acuminata (banana). Both initial and final N release were similar under the two canopy types. However, after five months of decomposition, a higher proportion of initial N had been released under the single canopy. Although patterns of decomposition and nutrient release were not predicted by initial substrate quality, mass loss in leaf mixtures rates were well predicted by mean mass loss of their component species. This study identifies specific pruning regimes that may regulate N and P release during crucial growth periods, and it suggests that strategic pruning can enhance nutrient availability. For example, during the onset of rapid fruit growth, a two-species mixture may release more P than a three-species mixture. However, by the time of the harvest, the two- and three-species mixtures have released roughly the same amount of N and P. These nutrients do not always follow the same pattern, as N release can be maximized in single-species substrates, while P release is often facilitated in species mixtures. Our study indicates the importance of management practices in mediating patterns of nutrient release. Future research should investigate how canopy composition and farm management can also mediate on-farm nutrient losses.     

Simulation of flow and mercury transport in Upper East Fork Poplar Creek,Oak Ridge,Tennessee

As a result of nuclear processing activities started back in the 1950s, the environment in the vicinity of the Y‐12 National Security Complex (Y‐12 NSC) in Oak Ridge, Tennessee, and surrounding watersheds has been contaminated by nearly 1,000 tons of elementary mercury. To comply with the state and federal surface water quality standards, a significant reduction in mercury concentration to parts‐per‐trillion levels has been proposed. In order to analyze the mercury cycle in the environment and provide forecasting capabilities for the flow and transport of mercury within the Upper East Fork Poplar Creek (UEFPC) watershed, an integrated surface and subsurface flow and transport model has been developed using the hydrodynamic and transport numerical package, MIKE, developed by the Danish Hydraulic Institute. The model has been constructed and calibrated using an extensive collection of historical records (i.e., hydrological data, and mercury concentration measurements in groundwater, soil, and sediment) obtained from the Oak Ridge Environmental Information System database. Daily fluctuations in stream flow, as a result of scattered rainfall, flooding, and flow augmentation, resuspend the contaminated streambed sediments and/or erode the polluted streambank soil and provide a secondary source of mercury to the creek. In order to investigate the significance of sediment‐mercury interactions on the fate and transport of mercury within the UEFPC study domain, simulations were performed for two different cases (i.e., with and without consideration of sediment‐mercury interactions). Computed total suspended solids and mercury concentrations at the integration point of the creek are compared with the corresponding historical records in both cases. As confirmed by the numerical simulations, a substantial portion of the mercury detected in the river is likely in the form of sediment particle–bound mercury (i.e., mercury particulates). © 2012 Wiley Periodicals, Inc.     

Part-time versus full-time employment status differences: A replication and extension

Two groups of part-time employees were compared to full-time employees on several organizationally relevant reactions and behaviours in order to replicate and extend research on potential employment status differences. After controlling for demographics, it was found that there were mean differences between the groups; however, no evidence was found for differences in how the various groups ‘process’ organizational experience. Based on the results, implications for managing part-versus full-time employees are discussed.     

Mathematical models of dissolved oxygen concentration in fresh water

An adequate reserve of dissolved oxygen in a receiving stream is extremely important for protecting aquatic plants and animals, and for conserving our water resources. This paper briefly describes the environmental engineering significance of the stream self-purification, the current stream quality standards on dissolved oxygen concentration, and the solubility of dissolved oxygen in water. Special emphasis is placed on the modelling of the biological reactions and the dissolved oxygen saturation concentration in fresh water. The model can be used for calculating the dissolved oxygen saturation concentration, in turn, for determining the dissolved oxygen deficits, the critical dissolved oxygen concentration, and the allowable dissolved oxygen drop in a stream into which the waste water is discharged.     

Challenges of meeting ISO 14000 auditing guidelines: Audit program gaps

At long last, the ISO 14000 environmental auditing guidelines have been issued in final form and have been accepted in the United States and elsewhere as official national standards. The auditing guidelines consist of: Guidelines for environmental auditing—General principles (ISO 14010: 1996(E)) Guidelines for environmental auditing—Audit procedures—Auditing of environmental management systems (ISO 14011: 1996(E)) Guidelines for environmental auditing—Qualification criteria for environmental auditors (ISO 14012: 1996(E)) Unlike the environmental management system (EMS) standard (ISO 14001), the auditing guidelines are just that, guidelines. The ISO 14000 auditing guidelines are not long documents: ISO 14010 is three pages, ISO 14011 is five pages and ISO 14012 is three pages.     

Simulated interior floods and the flood experience in urban communities

The Hydrologic Engineering Center (HEC-1) model was used to construct synthetic hydrographs for isolated interior urban floods. Flood peak and lag time were very well preserved in simulated flows. Total volume was not adequately expressed. Lag time varied inversely with both urban development and storm intensity. Peak discharge varied with storm intensity, but this variability was well defined only at very high urbanization levels. An 175% increase in storm intensity produced a change of about 15% in peak discharge. Claims for flood damage correlated well with estimates of peak flow and lag time combined. Other measures of flood experience also correlated with the two features. Within the range of storms utilized, urban development factors consistently outranked storm intensity as a determining factor in flood damage.     

Can developing countries benefit from innovative pricing in the power sector?

This study explores electricity pricing as a demand-side management (DSM) strategy, looking to the developed country experience for insights into the types of approaches currently used, their effects, and the direction in which electricity pricing is headed. The discussion should be especially useful for electric utilities in developing countries that are exploring alternatives to capacity expansion to meet current and future electric power demand. For these electric utilities, demand-side options are especially important under today's conditions in which the capital cost of new generating capacity is increasing rapidly, international funds for expanding power sectors are not expected to be sufficient for meeting projected capacity needs and environmental concerns over fossil fuel emissions have raised new questions about constructing thermal power plants.     

POTENTIAL,ACTUAL, AND EQUILIBRIUM EVAPOTRANSPIRATION IN A WHEAT FIELD 1

ABSTRACT: This paper examines the relationship between both potential (E*) and nonpotential evapotranspiration and equilibrium evapotranspiration (EQ) in an irrigated wheat field in southcentral Alberta, Canada. The control exercised by surface wetness and root reservoir moisture content in determining the value of the Priestley-Taylor constant a is explored. Also investigated is the relationship between a and the vapor flux fraction ET/(R-G) where ET is the actual evapotranspiration, R the net radiation, and G the soil heat flux. It is shown that evapotranspiration occurred at the potential rate (E*) when the available soil moisture (ASM) within the root zone was ≥3 percent. a varied from 0.84 for a dry soil to 1.49 for a saturated soil. The mean a for E* was 1.24. Surface wetness sustained evapotranspiration at the potential rate when such wetting exceeded 2mm d^?1 following a period of prolonged drawdown of soil moisture, α and ET/(R-G) were positively correlated and this correlation strengthened with increasing soil moisture for constant values of the energy partitioning factor s+γ/s where s is the slope of the saturation humidity-temperature curve and γ is the psychrometric constant. ET=EQ when ETI(R-G) lay within the range of 0.59 to 0.82 corresponding to Bowen ratio (β) values of 0.22 and 0.69, respectively.