Covariance structure modeling in organizational research: Problems with the method versus applications of the method

Brannick (1995) offers several criticisms of how covariance structure analysis techniques (CSA—also known as causal modeling methods) are being used by organizational researchers, as well as some suggestions for improving organizational research. This article responds to some of the issues raised by Brannick (1995), points out areas of agreement and disagreement, and offers some reactions to his suggestions for how future use of CSA methods can be improved.     

Large-scale constructed wetlands for nutrient removal from stormwater runoff: An everglades restoration project

The South Florida Water Management District (SFWMD) constructed a wetland south of Lake Okeechobee to begin the process of removing nutrients (especially phosphorus) from agricultural stormwater runoff entering the Everglades. The project, called the Everglades Nutrient Removal (ENR) project, is a prototype for larger, similarly constructed wetlands that the SFWMD will build as part of the Everglades restoration program. This innovative project is believed to be one of the largest agricultural stormwater cleanup projects in the United States, if not in the world. This publication describes the ENR project's design, construction, and proposed operation, as well as the proposed research program to be implemented over the next few years.     

PHOSPHORUS MANAGEMENT TO PROTECT LAKE WATER QUALITY1

ABSTRACT: The Hallett Quarry gravel pit lakes are an active sand and gravel extraction operation located 0.4 km north of the City of Ames, Iowa. During periods of drought, these lakes serve as a supplemental water supply for Ames. A modified version of the Vollenweider input-output model was used to predict future water quality under various watershed land use, drainage, and lake configurations. The dominant factor controlling the future water quality of the lakes was found to be the nutrient input. It is recommended that a management plan to protect the future water quality should be oriented towards reducing the sources of phosphorus to the lakes.     

APPLICATION OF AN ENVIRONMENTAL AND ECONOMIC MODELING SYSTEM FOR WATERSHED ASSESSMENTS1

ABSTRACT: A National Pilot Project (NPP) on Livestock and the Environment was initiated in 1992 to help provide solutions to environmental problems associated with livestock production. A major development of the NPP was the Comprehensive Economic and Environmental Optimization Tool‐Livestock and Poultry (CEEOT‐LP), an integrated modeling system designed to produce economic and environmental indicators for alternative policy scenarios applied to intensive livestock production watersheds. The system consists of a farm‐level economic model (FEM) and two environmental models: the field‐scale APEX model and the watershed‐level SWAT model. To date, CEEOT‐LP has been applied to two watersheds in Texas and one in Iowa. Predicted reductions in P losses for two P‐based manure application rate scenarios, relative to baseline conditions, ranged from ?4 to ?54 percent across the three watersheds; however, N loss impacts ranged from a decrease of 34 percent to an increase of 79 percent. For five other alternative scenarios that were simulated for only one watershed, N and P loss impacts ranged between a reduction of 78 percent to an increase of 20 percent. Aggregate watershed‐level economic impacts of the seven scenarios spanned a spectrum of a 27 percent decrease to a 25 percent increase in profit, relative to the baseline.     

Advancing the use of an innovative cleanup technology: Case study of Lasagna™

Originated from a recognized need for significantly more effective technologies for soil cleanup, the Lasagna^TM project provides an interesting case study in which industry, government, and academia successfully collaborated to rapidly advance the technology from the laboratory to the field. Called Lasagna^TM because of its layered configurations, the technology combines electrically induced contaminant transport in soils, treatment in place, and geotechnical methods to achieve completely in situ clean-up of contaminated soils. Experiences with respect to the partnership, the development of technology and its current commercialization status are described.     

Regional investigations of soil and overburden analysis and plant uptake of metals

Regional studies on the bioavailability of metals at native and disturbed sites were conducted over the past seven years by the USGS. The work was concentrated in the Fort Union, Powder River, and Green River coal resource regions where measures of extractable metals in soils were found to have limited use in predicting metal levels in plants.Correlations between Cu, Fe, and Zn in plants and extractable (DTPA, EDTA, and oxalate) or total levels in native A- and C-horizons of soil were occasionally significant. A simple linear model is generally not adequate, however, in estimating element uptake by plants. Prediction capabilities were improved when a number of soil chemical and physical parameters were included as independent variables in a stepwise linear multiple regression analysis; however, never more than 54% of the total variability in the data was explained by the equations for these metals. Soil pH was the most important variable relating soil chemistry to plant chemistry. This relation was always positive and apparently a response to soil levels of metal carbonates and not Fe and Mn oxides. Studies that compared the metal uptake by rehabilitation species to extractable (DTPA) metal levels in mice soils produced similar results.     

Manure history and long-term tillage effects on soil properties and phosphorus losses in runoff

Manure additions to cropland can reduce total P losses in runoff on well-drained soils due to increased infiltration and reduced soil erosion. Surface residue management in subsequent years may influence the long-term risk of P losses as the manure-supplied organic matter decomposes. The effects of manure history and long-term (8-yr) tillage [chisel plow (CP) and no-till (NT)] on P levels in runoff in continuous corn (Zea mays L.) were investigated on well-drained silt loam soils of southern and southwestern Wisconsin. Soil P levels (0-15 cm) increased with the frequency of manure applications and P stratification was greater near the surface (0-5 cm) in NT than CP. In CP, soil test P level was linearly related to dissolved P (24-105 g ha(-1)) and bioavailable P (64-272 g ha(-1)) loads in runoff, but not total P (653-1893 g ha(-1)). In NT, P loads were reduced by an average of 57% for dissolved P, 70% for bioavailable P, and 91% for total P compared with CP. This reduction was due to lower sediment concentrations and/or lower runoff volumes in NT. There was no relationship between soil test P levels and runoff P concentrations or loads in NT. Long-term manure P applications in excess of P removal by corn in CP systems ultimately increased the potential for greater dissolved and bioavailable P losses in runoff by increasing soil P levels. Maintaining high surface residue cover such as those found in long-term NT corn production systems can mitigate this risk in addition to reducing sediment and particulate P losses.     

Impact of selective herbicide right-of-way vegetation treatment on birds

Power line rights-of-way provide a major portion of the shrub habitat in New York. Since this habitat type is on the decline, many of the birds dependent on shrub habitat are also declining. The methods used to control right-of-way vegetation could therefore have serious impacts on several birds of conservation concern. Since New York is increasingly using selective herbicide treatments in vegetation management, we sought to investigate the potential impacts of these treatments on nesting birds. The study looked at plots in two adjacent rights-of-way before and after a selective herbicide treatment in one of the rights-of-way. We investigated three bird species: alder flycatcher (Empidonax alnorum), chestnut-sided warbler (Dendroica pensylvanica), and gray catbird (Dumetella carolinensis). All three species exhibited a preference for shrub vegetation around nest sites. The selective herbicide treatment did not significantly decrease that shrub vegetation, and neither the density nor the nesting success of the three species declined following the treatment. We conclude that selective herbicide vegetation management encourages the development of shrub habitat without negatively impacting the birds nesting in the habitat.     

WATER HARVESTING TREATMENT EVALUATION AT GRANITE REEF1

ABSTRACT: Yearly runoff efficiencies (total runoff/total precipitation), threshold retentions (precipitation needed to initiate runoff), and runoff-efficiencies-after-thresholds were determined for several water-harvesting catchment treatments at the Granite Reef test site. This information was found to be useful for showing (1) overall performance of catchments with time; (2) the distribution of the precipitation among runoff, surface retention, and infiltration; (3) why, how, and when certain treatments weathered and failed; (4) when to repair treatments; and (5) how to design catchments (size, site preparation, material selection, etc.). New impermeable membranes with smooth surfaces yielded nearly 100% of the precipitation. An asphalt-fiberglass treatment continues this high efficiency after 10 years of weathering – polyethylene after 8; efficiency of butyl sheeting was high initially but decreased rapidly after 9 years weathering. A standard roofing treatment retained up to 30% of the precipitation in the gravel covering. A concrete catchment lost as much as 50% of the total precipitation through micropores and surface cracks. Silicone treatments rapidly lost repellancy and efficiency, while paraffin treatments have weathered 5 years with little loss of efficiency.