The effects of acid precipitation-long term ecological measurements in loch vale watershed,Rocky Mountain National Park

Contribution from Fourth World Wilderness Congress-Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.     

Citizenship and sustainability in dependent island communities: the case of the Huon Valley region in southern Tasmania

In Western democracies, rising levels of political alienation have prompted concerned political authorities to improve the quality of citizenship by such means as civic education. As well, the several international conventions underpinning the sustainable development discourse mandate participation to empower people in their own development. Active citizenship and the participation fundamental to it can be problematic for island communities with a history of economic and political dependence, since there exist a number of structural and agentic barriers to its practice and to the exercise of ecological responsibility through participation. Both the barriers to and the prospects for ecological sustainability are elaborated in this study of aspects of community, participation, citizenship and ecological literacy among the communities of the Huon Valley region of southern Tasmania.     

Managing employee perceptions of the psychological contract over time: the role of employer social accounts and contract fulfillment

This study proposed and tested relationships pertaining to employee perceptions of psychological contract type over time. Using a longitudinal design, we examined the mediated role that adequacy of social accounts and psychological contract fulfillment play in determining the development of contract perceptions. More specifically, our model posits that perceptions of contract type will influence employee perceptions of the adequacy of social accounts that are offered by the organization and its agents to explain job‐related decisions. These initial perceptions of social accounts at Time 1 were expected to impact perceptions of psychological contract fulfillment at Time 2 (6 months later) and psychological contract fulfillment was proposed to be positively associated with perceptions of a relational psychological contract. Results support the mediating roles of social accounts and psychological contract fulfillment in determining perceptions of contract type over time. Practical implications of these findings and directions for future research are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Cystic hygroma and congenital diaphragmatic hernia: Early prenatal sonographic evaluation of Fryns' syndrome

We report a case of cystic hygroma and diffuse lymphangiectasia detected by sonogram at 12 weeks' gestation. Fetal karyotype was normal. At 20 weeks' gestation, herniation of the bowel into the chest was noted. At delivery, the infant was diagnosed as having Fryns' syndrome. This is the first reported case of Fryns' syndrome presenting with cystic hygroma.     

A misdiagnosis of X-linked adrenoleucodystrophy in cultured chorionic villus cells by the measurement of very long chain fatty acids

A case is reported of a male fetus at risk of X-linked adrenoleucodystrophy who showed a normal cultured chorionic villus cell very long chain fatty acid (VLCFA) profile but at birth exhibited grossly abnormal plasma and cultured fibroblast VLCFAs. Maternal contamination or a sample mix-up was excluded by chromosome analysis and analysis of polymorphic markers. This is the second report of a fetus affected with this disorder who showed normal cultured chorionic villus cell VLCFAs. It highlights the importance of a proper audit of all prenatal diagnoses to evaluate method reliability.     

Nutrient and mercury variations in soils from family farms of the Tapajós region (Brazilian Amazon): Recommendations for better farming

In the Brazilian Amazon, colonization is modifying the landscape at an exceedingly fast pace. Recently established households practice slash-and-burn agriculture and participate in the overall deforestation of the Amazon. Near the Transamazon highway, these family agricultural practices are the main cause of deforestation. The study presented here is oriented toward a better understanding of the impacts of farming practices on soil chemical composition. This study used a sampling design based on soil samples taken on farm plots, which had been submitted to a wide range of spatial and temporal sequential land-uses, including soils that were only recently denuded. The data shows that soil responses (organic matter (OM) content, fertility and mercury (Hg) retention) to these varied land-uses were relatively similar, suggesting that the most important event determining the responses was deforestation itself. This is well illustrated by the Hg content of soils, which changed immediately after deforestation and then only slightly thereafter. This phenomenon could also be seen in the base cation (calcium (Ca), potassium (K) and magnesium (Mg)) content which rose drastically after deforestation and tended to stay high for a period up to 10 years of cropping and pasture. This lasting cation rise is reflected by ammonium (NH₄) displacement from surface soils. Indeed, inorganic nitrogen (N) is the most important nutrient loss upon deforestation. Nonetheless, when time spent in fallow was greater than 15 years, base cations (Ca, Mg, K), available N and phosphorus (P) contents tended to go back to initial forest soil values and in some cases to exceed them. Soil type was seen to mediate responses to land-use. Clay-sandy soils showed a lower content of available N and carbon (C) than clayey soils at the soil surface, a difference that was accentuated by deforestation. Conversely, the higher initial content of Hg in clayey soils was associated with a more important Hg loss from the soil's surface. By shedding light on the consequences of family practices for OM, nutrient status and Hg depletion, this paper gives a new perspective on soil responses to agricultural practices. These conclusions need to be addressed in a strategy plan to limit family land-use impacts on soils and the surrounding ecosystems. Recommendations for more sustainable land uses are proposed based on what has been learned about soil responses to local agricultural practices.     

Multiple stressors and amphibian declines: dual impacts of pesticides and fish on yellow-legged frogs.

More than 40% of Earth's 5700+ amphibian species have undergone recent declines. Despite the likely involvement of multiple factors in driving these declines, most studies continue to focus on single stressors. In California (USA), separate studies have implicated either introduced fish or pesticides as causal agents. To date, however, no study has simultaneously evaluated the respective roles of these two potential stressors nor attempted to assess their relative importance, information critical for the development of effective conservation efforts and environmental policies. We examined the role and relative effect of fish and pesticides on the mountain yellow-legged frog (Rana muscosa) using unusually detailed data sets for a large portion of R. muscosa's historic range in California's Sierra Nevada. Habitat characteristics and presence/absence of R. muscosa and fish were quantified at each of 6831 sites during field surveys. Pesticide use upwind of each site was calculated from pesticide application records and predominant wind directions. Using generalized additive models, we found that, after accounting for habitat effects, the probability of R. muscosa presence was significantly reduced by both fish and pesticides, with the landscape-scale effect of pesticides much stronger than that of fish. The degree to which a site was sheltered from the predominant wind (and associated pesticides) was also a significant predictor of R. muscosa presence. Taken together, these results represent the strongest evidence to date that windborne pesticides are contributing to amphibian declines in pristine locations. Our results suggest that amphibian declines may have complex multi-factorial causes, and caution that single-factor studies that demonstrate the importance of one factor should not be used as evidence against the importance of other factors.     

Effects of UV-B irradiation on growth and survival of Antarctic marine diatoms

Growth rate, survival, and stimulation of the production of UV-B (280 to 320 nm) absorbing compounds were investigated in cultures of five commonly occurring Antarctic marine diatoms exposed to a range of UV-B irradiances. Experimental UV-B exposures ranged from 20 to 650% of the measured peak surface irradiance at an Antarctic coastal site (0.533 J m^-2 s^-1). The five diatom species (Nitzschia lecointei, Proboscia alata, P. inermis, Thalassiosira tumida and Stellarima microtrias) appear capable of surviving two to four times this irradiance. In contrast to Phaeocystis cf. pouchetii, another major component of the Antarctic phytoplankton, the concentrations of pigments with discrete UV absorption peaks in diatoms were low and did not change significantly under increasing UV-B irradiance. Absorbance of UV-B by cells from which pigments had been extracted commonly greatly exceeded that of the pigments themselves. Most of this absorbance was due to oxidisable cell contents, with the frustule providing the remainder. Survival of diatoms did not correlate with absorption by either pigments, frustules or oxidisable cell contents, indicating that their survival under elevated UV-B irradiances results from processes other than screening mechanisms.