David Daniel

Problems with detecting moderators in leadership research using moderated multiple regression

Abstract A number of recent leadership studies have questioned whether situational variables are important moderators of leadership effectiveness. Pessimistic conclusions from these studies regarding situational modifiers challenge the foundations of path–goal and substitutes for leadership theories. However, analysis of this research reveals questionable methodological practices that cast doubt on the validity of these conclusions. This article discusses two methodological issues, elucidates specific flaws in methods used in recent leadership studies, and makes recommendations for the use of moderated multiple regression (MMR) in leadership studies. We argue that low power to detect moderators and inappropriate use of regression methods can account for the lack of confirmatory findings regarding moderators. Comparative analysis using a previously published data set provides strong support for major arguments presented in this article. We conclude that situational variables are important moderators of leadership effectiveness and are detectable using appropriate procedures.

Community College Leadership Preparation: Needs, perceptions, and Recommendations

This research provides the results of a random survey, administered in 2001, of 128 community college instructional leaders. Respondents rated 48 skills and areas of expertise in effectively fulfilling community college instructional leadership roles. Survey results also suggest respondents recommend a different emphasis in doctoral coursework than they experienced in their doctoral programs of study.

Gender-Role Conflict and Self-Esteem: Factors Associated With Partner Abuse in Court-Referred Men.

This study investigated the relationship between gender-role conflict, self-esteem, and domestic violence. Seventy-four men entering a domestic violence treatment program completed self-report measures of gender-role conflict, self-esteem, and abusive and controlling behavior. Regression analysis revealed that high gender-role conflict with respect to success, power, and competition was positively related to physical abuse. Restrictive emotionality and self-esteem both negatively related to use of intimidation and threats. Finally, restrictive affectionate behavior between men was positively related to using isolation.

Chemical and Physical Properties of Chihuahuan Desert Soils Irrigated with Industrial Effluent

Land application of secondary industrial effluent to Chihuahuan Desert upland near Las Cruces, New Mexico, was designed to meet the water demand of creosote and mesquite shrubs. The major objective of this study was to assess changes in chemical and physical properties of desert soils after 4 years (2002–2005) of irrigation with secondary industrial effluent. Soil texture and bulk density (pb) did not differ between irrigated and control plots, but did so between bare ground and mesquite sites in the control and irrigated plots. Reductions in saturated hydraulic conductivity (K s ), drainable porosity (θd), and effective porosity (θe) in the upper 0–15 cm of irrigated plot soils were attributed to decline of soil structure and dispersion of clays resulting from the addition of highly sodic and alkaline effluent to irrigated plots. Although rarely significant, consistently higher electrical conductivity, sodium adsorption ratio, chloride, exchangeable sodium percentage, and Na+ in the soil profile (between 30 cm and 210 cm) at creosote and mesquite sites compared to the bare ground site suggested deeper leaching of wastewater constituents at shrub sites. Deeper leaching of wastewater constituents beneath shrubs compared to bare ground areas may be attributed to higher water inputs caused by sprinkler spray interception, and higher Ks, θd, and θe of soils beneath creosote and mesquite canopies. Continued application of industrial effluent to a Chihuahuan Desert ecosystem over the long term should consider the relative importance of canopy and intercanopy areas.

Provenance determination of sapphires and rubies using laser-induced breakdown spectroscopy and multivariate analysis

Abstract Determination of gem provenance is a topic of research in the gemological community for financial, security, and societal reasons. Laser-induced breakdown spectroscopy (LIBS) and multivariate analysis have the potential to revolutionize the field of gem provenance. This study acquired LIBS spectra from 569 rough sapphire and ruby specimens from 21 localities in 11 countries. The spectra were analyzed using the multivariate technique partial least-squares regression (PLSR) in separate algorithms for sapphires and rubies. Each algorithm consists of a series of PLS models. Each model compares the spectra from a locality of interest to the spectra from all other localities in the database. Success rates, as determined by the percent of correct provenance identifications, are 98.9% (sapphire) and 96.0% (ruby) for country of origin and 97.9% (sapphire) and 95.4% (ruby) for deposit of origin. Individual deposits are not recognized by the concentrations of a few elements; rather, the unique compositional signature of each deposit consists of the ratios of many elements, primarily Ca, Zr, Fe, Ba, Mt, Ti, Sr, Si, Cr, H, C, and Li, some of which may reside in inclusions. This work demonstrates that determination of country or deposit of origin may be related to a quantitative measure with a high level of success.

A Case Study Perspective on Working with ProUCL and a State Environmental Agency in Determining Background Threshold Values

ProUCL is a software package made available by the Environmental Protection Agency (EPA) to provide environmental scientists with better tools with which to conduct statistical analyses. ProUCL has been in production for over ten years and is in its fifth major version. In time, it has included more sophisticated and appropriate analysis tools. However, there is still substantial criticism of it among statisticians for its various omissions and even its philosophical approach. Due to limited resources, some state agencies have set ProUCL as a standard by which all state-mandated environmental analyses are compared, despite the EPA’s more open acceptance of other software products and methodologies. As such, it can be difficult for state-supervised sites to convince the state to allow the use of more appropriate methodologies or different software. In the current case study, several such instances arose and substantial resources were invested to demonstrate the appropriateness of alternative methodologies, sometimes without acquiring acceptance by the state despite sound statistical demonstration. In particular, efforts were made to address: inappropriate outlier detection, upper tolerance limit (UTL) calculations based on gamma distributions when non-detects were present, and inappropriate use of nonparametric UTL formulas.

Irrigation with Treated Wastewater: Quantification of Changes in Soil Physical and Chemical Properties

Land application of treated wastewater is increasing particularly in areas where water stress is a major concern. The primary objective of this study was to quantify the effect of irrigation with aerated lagoon treated wastewater on soil properties. Core and bulk soil samples were collected from areas under the canopies of mesquite and creosote and intercanopy areas from each of the three plots. Irrigation water quality from 2006 to 2008 showed that average sodium adsorption ratio (SAR), electrical conductivity (EC) and pH of irrigation water were 37.16, 5.32 dS m-1 and 9.7, respectively. The sprinkler uniformity coefficients of irrigated plot-I was 49.34 ± 2.23 % and irrigated plot-II was 61.57 ± 2.11 %. Within irrigated and between irrigated and un-irrigated plots, most soil physical properties remained similar except saturated hydraulic conductivity (Ks) which was significantly higher under mesquite canopies than in the intercanopy areas. Chloride (Cl-) concentrations below 60 cm depth were higher under creosote than mesquite canopies in irrigated plots indicating deeper leaching of Cl-. Nitrate (NO3 -) concentrations below 20 cm depth under canopy and intercanopy areas were low indicating no leaching of NO3 -.The average SAR to 100 cm depth under shrub canopies was 18.46 ± 2.56 in irrigated plots compared to 2.94 ± 0.79 in the un-irrigated plot. The Na+ content of creosote was eleven times higher un-irrigated than un-irrigated plot and Na+ content of herbaceous vegetation was three times higher in the irrigated than unirrigated. Thus irrigation with high sodium wastewater has exacerbated the soil sodicity and plant Na+ content. Since the majority of mesquite roots are found within 100 cm, and creosote and herbaceous vegetation roots are found within 25 cm from soil surface, a further increase in sodicity may threaten the survival of woody and perennial herbaceous vegetation of the study site.

Physiologic response of six plant species grown in two contrasting soils and irrigated with brackish groundwater and RO concentrate

ABSTRACT With declining availability of fresh surface water, brackish groundwater is increasingly used for irrigation in the arid and semi-arid southwestern United States. Brackish water can be desalinated by reverse osmosis (RO) but RO results in a highly saline concentrate. Disposal of concentrate is a major problem hindering augmentation of inland desalination in arid areas. The objective of this study was to determine the effect of texture and saline water irrigation on the physiology of six species (Atriplex canescens (Pursh) Nutt., Hordeum vulgare L., Lepidium alyssoides A. Gray, Distichlis stricta (L.) Greene, Panicum virgatum L., and ×Triticosecale Wittm. ex A. Camus [Secale × Triticum]). All species were grown in two contrasting soils and irrigated with the same volume of control water (EC 0.9 dS/m), brackish groundwater (4.1 dS/m), RO concentrate (EC 8.0 dS/m). Several plant physiological measurements were made during the growing season including height, number of stem nodes, average internodal length, number of leaves, leaf length, photosynthetic rates, stomatal conductance rates, transpiration rates, leaf temperatures, stem water potential, and osmotic potential. P. virgatum was the only species that showed significant decrease in plant height and growth with texture and irrigation water salinity. Except for A. canescens and L. alyssoides, number and length of leaves decreased with increasing salinity for all species. No significant differences were observed for photosynthetic, stomatal conductance, and transpiration rates by soil texture or irrigation water salinity. Stem water potential and osmotic potential did show some significant influence by soil texture and irrigation water salinity. Based on the results, RO concentrate can be reused to grow all six species in sand; however, growth of all species showed some limitations in clay. Local reuse of RO concentrate along desert margins with regular soil and environmental quality monitoring can accelerate implementation of inland desalination for sustaining food security.

Land Application of Treated Industrial Wastewater on a Chihuahuan Desert Shrubland: Impacts on the Natural Vegetation

Impacts of wastewater land application on desert vegetation are not adequately known. In a 4-yr field study, we evaluated the effects of treated, saline−sodic industrial effluent application on the aboveground vegetation biomass and mineral accumulation of a Chihuahuan Desert shrubland. The vegetation included two shrubs, Larrea tridentata (DC.) Coville and Prosopis glandulosa Torr. var. glandulosa, and seven herbaceous species in the intershrub spaces. Early summer fruit dry weights on terminal branches of the irrigated shrubs were 3 to 14 times higher than those on the non-irrigated shrubs. The combined irrigated vegetation produced 2 Mg of additional dried biomass per ha above that of the non-irrigated plot, and contained excesses of total Kjeldahl-N (TKN) and Ca2+ equivalent to 18% of effluent N deposition and 12% of effluent Ca2+ deposition. Under irrigated and highly sodic conditions (soil sodium adsorption ratio up to 35), the herbaceous Lepidium alyssoides A. Gray var. alyssoides produced the highest biomass of all plant species. However, there was a decline in plant species diversity as L. alyssoides became dominant in the irrigated intershrub spaces. While the findings demonstrate the natural attenuation of effluent minerals by native Chihuahuan Desert vegetation, highly sodic conditions may alter the composition of the vegetation community.

Salinity an Environmental “Filter” Selecting for Plant Invasiveness? Evidence from Indigenous Lepidium alyssoides on Chihuahuan Desert Shrublands☆

ABSTRACT A better understanding of site-specific factors such as soil salinity that regulate plant invasions is needed. We conducted a 3-mo greenhouse study to evaluate the salinity responses of three local maternal sources of Lepidium alyssoides, which is an indigenous species shown to aggressively colonize disturbed shrubland sites in the southwestern United States, including those affected by high salinity and sodicity. Results indicated that there were little or no population effects on plant evapotranspiration (ET), growth, and tissue Na and Cl concentrations. Significant reductions in seedling growth and ET were largely independent of various isosmotic saline irrigation solutions that included NaCl, Na2SO4, and CaCl2, each at-0.1MPa and-0.2MPa, suggesting that ET and growth were controlled by solution osmotic potential. The combined Na and Cl concentrations in leaves were 9–10% of dry weight with no visible sign of injury. However, increasing leaf mortality and abscission as a proportion of total leaf production was observed in the high-salt treatments (-0.2 MPa), with a combined Na and Cl concentration reaching 16% with high NaCl. Under saline conditions, considerable foliage salt loads of this species could deposit high-salt litter to potentially alter a landscape to its own favor and to the detriment of other salt-sensitive species. Results of this study add to a limited quantitative database on site-specific salinity factors governing plant invasions by showing the potential for these populations to behave invasively under saline conditions and, thus, potential for soil salinity assessment to predict incipient populations. However, due to its halophytic traits and indigenous status, L. alyssoides may alternatively provide ecosystem services to salinized shrublands of the arid and semiarid southwestern United States.