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361.
Access and Local Government Research: Methodological Reflections 总被引:1,自引:0,他引:1
This methodological paper draws on research from Australia to examine the question of gaining access to local governments in undertaking work on natural resource management. It is argued that a range of macro-level changes have impacted on the local government sector in Australia, and these changes have rendered access problematic for researchers. These changes include an expansion of local government roles, an increase in financial pressure within the sector, a proliferation of audit measures across local governments and a low level of respect amongst local government personnel for academics and academic work. The paper concludes by identifying the reasons why understanding access in qualitative research on local government and environmental sustainability is important. 相似文献
362.
Amanda H. Bell Barbara C. Scudder 《Journal of the American Water Resources Association》2007,43(4):957-968
Abstract: In 2003, the U.S. Geological Survey (USGS) National Water‐Quality Assessment (NAWQA) program and U.S. Environmental Protection Agency studied total mercury (THg) and methylmercury (MeHg) concentrations in periphyton at eight rivers in the United States in coordination with a larger USGS study on mercury cycling in rivers. Periphyton samples were collected using trace element clean techniques and NAWQA sampling protocols in spring and fall from targeted habitats (streambed surface‐sediment, cobble, or woody snags) at each river site. A positive correlation was observed between concentrations of THg and MeHg in periphyton (r2 = 0.88, in log‐log space). Mean MeHg and THg concentrations in surface‐sediment periphyton were significantly higher (1,333 ng/m2 for MeHg and 53,980 ng/m2 for THg) than cobble (64 ng/m2 for MeHg and 1,192 ng/m2 for THg) or woody snag (71 ng/m2 for MeHg and 1,089 ng/m2 for THg) periphyton. Concentrations of THg in surface‐sediment periphyton had a strong positive correlation with concentrations of THg in sediment (dry weight). The ratio of MeHg:THg in surface‐sediment periphyton increased with the ratio of MeHg:THg in sediment. These data suggest periphyton may play a key role in mercury bioaccumulation in river ecosystems. 相似文献
363.
Summary This paper analyzes the flexibility of maternal care in wild house mice (Mus domesticus) under different reproductive conditions in the laboratory. All maternal activities were both qualitatively and quantitatively analyzed over a period of 28 days after birth of a litter. The standard behavior of a lactating house mouse with 7–8 young can be described as follows: During days 1–16 the offspring fully depend on the mother for nutrition. Due to rapid growth of the litter, the energetic demands of lactation reach a peak for the female during days 13–16. During days 17–22, the weaning period, the young begin to eat solid food. This period is characterized by behaviors that indicate different interests of the mother and offspring, and thus the existence of a parent-offspring conflict sensu Trivers (1974). Resting alone and remaining far from the litter indicate the female's interest in avoiding the offspring's demands, which are expressed in frequent attempts to initiate sucking. There is no aggression towards the young during weaning. House mice are weaned at 23 days. The relationship between mother and young appears free of conflict after weaning. Nursing is replaced by resting with body contact, but the offspring do not try to suck. The following results suggest that during the weaning period the offspring do not get more milk than corresponds to the maternal optimum—despite their frequent sucking attempts:(a) When the mother is simultaneously lactating and pregnant, offspring are smaller at weaning than under standard conditions. (b) Small litters are weaned earlier than large ones. Despite a longer nursing period, offspring from large litters are lighter at weaning than those from small ones. (c) Under high energy demand, as after postpartum mating and with large litters, females wean their young at a body weight which corresponds to the earliest physiologically possible state of independence.Parity of the female has no effect on maternal activities, nor has the presence of the father. In the latter case, however, offspring are less often left alone and unprotected.Females seem to adjust their investment according to the body weight of the progeny by delaying or advancing the date of weaning (Table 2). This behavior allows the production of the largest possible number of offspring that can be raised to a minimal physiological threshold corresponding to a body weight of approximately 9 g. Such flexibility in parental care may enhance maternal fitness under different and unpredictable environmental conditions. 相似文献
364.
Editorial Introduction
>List of Referees 相似文献365.
Barbara Farinelli Colin A. Carter C.-Y. Cynthia Lin Daniel A. Sumner 《Journal of Cleaner Production》2009
This study presents an empirical analysis of the import demand for Brazilian ethanol by its six major foreign buyers. The primary objectives of this study were to identify the economic factors affecting the demand for ethanol imports and to derive long-run price and income elasticities of import demand. These elasticities could be used to analyze the impact of government policies such as mandatory gasoline/ethanol blends and import tariffs. Import demand models were estimated with ordinary least squares (OLS), using quarterly time series data for the 1997–2007 time period. The results suggest that the factors influencing the import demand for ethanol vary across countries. Markets adopting mandatory blends of renewable fuels tend to have less price elastic import demand schedules. Ethanol imports were found to be price elastic and statistically significant in the Caribbean region (?1.66), Mexico (?2.08), Japan (?1.44) and Nigeria (?1.38), while import demand was price inelastic and not statistically different from zero in the US (?0.76) and Europe (?0.21). The regression results could not determine the impacts of import tariffs for the United States, Mexico and Nigeria on the quantity of imports because tariffs did not vary during the time period studied. Results show that mandatory gasoline/ethanol blends have been an important determinant of ethanol imports. 相似文献
366.
Consequences of organic and non-organic farming practices for field,farm and landscape complexity 总被引:1,自引:0,他引:1
367.
Water soluble organic carbon (WSOC) is considered the most mobile and reactive soil carbon source and its characterization is an important issue for soil ecology study. A biodegradability test was set up to study WSOC extracted from 7 soils differently managed. WSOC was extracted from soil with water (soil/water ratio of 1:2, W/V) for 30 min, and then tested for biodegradability by a liquid state respirometric test. Result obtained confirmed the finding that WSOC biodegradability depended on both land use and management practice. These results suggested the biodegradability test as suitable method to characterize WSOC, adding useful information to soil fertility. 相似文献
368.
Kraaijeveld K Reumer BM Mouton L Kremer N Vavre F van Alphen JJ 《Die Naturwissenschaften》2011,98(3):175-180
Wolbachia is a maternally inherited bacterium that manipulates the reproduction of its host. Recent studies have shown that male-killing
strains can induce cytoplasmic incompatibility (CI) when introgressed into a resistant host. Phylogenetic studies suggest
that transitions between CI and other Wolbachia phenotypes have also occurred frequently, raising the possibility that latent CI may be widespread among Wolbachia. Here, we investigate whether a parthenogenesis-inducing Wolbachia strain can also induce CI. Parthenogenetic females of the parasitoid wasp Asobara japonica regularly produce a small number of males that may be either infected or not. Uninfected males were further obtained through
removal of the Wolbachia using antibiotics and from a naturally uninfected strain. Uninfected females that had mated with infected males produced
a slightly, but significantly more male-biased sex ratio than uninfected females that had mated with uninfected males. This
effect was strongest in females that mated with males that had a relatively high Wolbachia titer. Quantitative PCR indicated that infected males did not show higher ratios of nuclear versus mitochondrial DNA content.
Wolbachia therefore does not cause diploidization of cells in infected males. While these results are consistent with CI, other alternatives
such as production of abnormal sperm by infected males cannot be completely ruled out. Overall, the effect was very small
(9%), suggesting that if CI is involved it may have degenerated through the accumulation of mutations. 相似文献
369.
Evaluating the Eco‐Geomorphological Condition of Restored Streams Using Visual Assessment and Macroinvertebrate Metrics
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Barbara A. Doll Gregory D. Jennings Jean Spooner David L. Penrose Joseph L. Usset 《Journal of the American Water Resources Association》2015,51(1):68-83
The Stream Performance Assessment (SPA), a new rapid assessment method, was applied to 93 restored, 21 impaired, 29 reference, and 13 reference streams with some incision throughout North Carolina. Principal component analysis (PCA) indicated restored streams align more closely with reference streams rather than impaired streams. Further, PCA‐based factor analysis revealed restored streams were similar to reference streams in terms of morphologic condition, but exhibited a greater range of scores relative to aquatic habitat and bedform. Macroinvertebrate sampling and GIS watershed analyses were conducted on 84 restored streams. SPA and watershed data were compared to Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa to determine which factors indicate stream health. SPA and watershed factors were used in least squares, ridge, and principal component regression (PCR) to develop a prediction model for EPT taxa. All three methods produced reasonable predictions for EPT taxa. Cross‐validation indicated ridge regression resulted in the lowest prediction error. The ridge model was then used to predict EPT taxa numbers for 21 impaired and 25 reference streams in addition to the 84 restored streams. Statistical comparisons of the predicted scores indicated urban streams (>10% impervious watershed cover) have lower expected numbers of EPT taxa. Rural restored streams have macroinvertebrate metric scores similar to those predicted for rural reference streams. 相似文献
370.
Carol A Johnston Dana M Ghioca Mirela Tulbure Barbara L Bedford Michael Bourdaghs Christin B Frieswyk Lynn Vaccaro Joy B Zedler 《Ecological applications》2008,18(4):983-1001
Emergent plants can be suitable indicators of anthropogenic stress in coastal wetlands if their responses to natural environmental variation can be parsed from their responses to human activities in and around wetlands. We used hierarchical partitioning to evaluate the independent influence of geomorphology, geography, and anthropogenic stress on common wetland plants of the U.S. Great Lakes coast and developed multi-taxa models indicating wetland condition. A seven-taxon model predicted condition relative to watershed-derived anthropogenic stress, and a four-taxon model predicted condition relative to within-wetland anthropogenic stressors that modified hydrology. The Great Lake on which the wetlands occurred explained an average of about half the variation in species cover, and subdividing the data by lake allowed us to remove that source of variation. We developed lake-specific multi-taxa models for all of the Great Lakes except Lake Ontario, which had no plant species with significant independent effects of anthropogenic stress. Plant responses were both positive (increasing cover with stress) and negative (decreasing cover with stress), and plant taxa incorporated into the lake-specific models differed by Great Lake. The resulting models require information on only a few taxa, rather than all plant species within a wetland, making them easier to implement than existing indicators. 相似文献