FLOW PERSISTENCE AS A MODIFIER OF SEASONAL RUNOFF PATTERNS1

ABSTRACT: The effect of flow persistence on seasonal patterns of watershed runoff was modeled by using runoff of the immediate antecedent month as an index. Monthly runoff was expressed as a function of monthly rainfall, season of the year, and runoff of the antecedent month. The three independent variables were expressed functionally as sliding polynomials, thus producing a piece-wise, form-free, three-dimensional causative structure. A model form allowing complete interactivity of the three independent variables could not be optimized because of insufficient data with high values of both antecedent runoff and monthly rainfall. A model with reduced interactivity was successfully optimized. Data sets from five watersheds ranging from 0.14 to 398 square miles were analyzed. Results were presented as a series of contour maps that showed contours of monthly runoff in the data space of season and monthly rain. In the series of maps, the patterns of the runoff contours changed with changing values of antecedent runoff. During the wet season of the year the contours changed significantly with antecedent runoff, but changes in the dry season were minimal. The quantitative change of runoff was more readily portrayed with cross-sections through the contoured surfaces.     

The Kirton Adaption - Innovation Inventory: A re-examination of the factor structure

Although the Kirton Adaption - Innovation Inventory (KAI) has almost always been used as a single scale purporting to measure a dimension of cognitive style, the KAI Manual characterizes three factors. This paper provides further confirmatory evidence of the structure of the three-factor model and of the high reliability coefficients of the three subscales. However, it questions whether three factors are sufficient and examines four- and five-factor models. Evidence is provided that the ‘O’ subscale in the orthodox three-factor model contains two conceptual elements, a major component concerned with idea generation and a minor component concerned with preference for stability/change. A four-factor model of KAI is proposed and an argument is advanced which leads to concern about the idea generation element of the ‘O’ subscale as a measure purely of cognitive style. Some implications for the development of the KAI are outlined.     

Pathways of arsenic uptake and incorporation in estuarine phytoplankton and the filter-feeding invertebrates Eurytemora affinis,Balanus improvisus and Crassostrea virginica

Arsenic uptake from water and from phytoplankton was followed in the copepod Eurytemora affinis and the barnacle Balanus improvisus collected from the Patuxent River estuary, Chesapeake Bay, eastern coast of the USA in 1987, and in the oyster Crassostrea virginica obtained from a hatchery on the shore of Chesapeake Bay in 1987. Dissolved arsenic was readily taken up by phytoplankton and by shell material of B. improvisus and C. virginica; however, no dissolved arsenic was incorporated into the invertebrate tissues. When E. affinis, B. improvisus and C. virginica were fed phytoplankton containing elevated arsenic contents, significant arsenic incorporation occurred. Juvenile B. improvisus incorporated relatively more arsenic than adults of all three species. Compared to the 100 to 200% increase in arsenic content by phytoplankton exposed to dissolved arsenic, the 25 to 50% increase in these invertebrate species via trophic transfer is relatively small. Even though the trophic pathway for arsenic transfer is the major one for higher trophic levels within an ecosystem, the potential for direct arsenic impact to trophic levels other than phytoplankton appears to be minimal.     

Role stress,physical symptomatology,and turnover intentions: A causal analysis of three alternative specifications

Causal relationships involving role stressors, physical symptomatology, and turnover intentions were examined within three alternative specifications. These specifications stemmed from Beehr and Newman's (1978) and Schuler's (1982) models of role stress and Locke's (1976) theory of job satisfaction. The results, derived from LISREL VI analyses, indicate that a revised Schuler model is the most plausible specification. Findings are discussed in terms of implications for understanding role stress and employee withdrawal.     

The Impact of Brown-Headed Cowbird Parasitism on Populations of the White-Crowned Sparrow

Brown-headed Cowbirds, Molothrus ater , are brood parasites on many species of North American Passerines. Cowbird parasitism is frequently cited as a contributing factor in the decline of United States passerine populations, based on three lines of evidence. First, range expansion and population increases by Cowbirds in this century are dramatic and well documented. Second, increasing rates of parasitism have been discovered in a variety of host species populations. Finally, direct negative effects of parasitism on certain vulnerable species notably Kirtland's Warbler, Dendroica kirtlandii , have been demonstrated. It remains unproven, however, that Cowbirds have significant negative effects on more abundant and widely-distributed hosts.
We report here on the impact of Cowbird parasitism on populations of Nuttall's White-crowned Sparrow, Zonotrichia leucophrys nuttalli , in the San Francisco Bay Area. This widespread songbird is now subject to a 40–50% rate of parasitism in San Francisco, an increase from 5% only 15 years ago. Using known mortality and fecundity values, we calculate that this population of White-crowns cannot maintain its numbers when the parasitism rate exceeds approximately 20%. Present levels of parasitism thus appear to threaten the longevity survival of this adaptable Songbird in the San Francisco Bay Area.