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201.
Becky L. Williams Charles T. Hanifin Edmund D. Brodie Jr Edmund D. Brodie III 《Chemoecology》2010,20(4):285-290
Lethal chemical defenses in prey species can have profound effects on interactions with predators. The presence of lethal defenses in prey can correct the selective imbalance suggested by the life-dinner principle in which the fitness consequences of an encounter between predator and prey should be much greater for the prey species than the predator. Despite the apparent adaptive advantages of lethality the evolution of deadly prey presents a fundamental dilemma. How might lethal defenses confer an individual fitness advantage if both predators and prey die during interactions? We examined the interaction between the rough-skinned newt (Taricha granulosa), which contains a powerful neurotoxin called tetrodotoxin (TTX), and the common garter snake (Thamnophis sirtalis). In some sympatric populations, Th. sirtalis have evolved physiological resistance to TTX. Whether the newts’ toxin confers protection from snake predators or has been disarmed by the snakes’ physiological resistance has not yet been directly tested. In predator–prey trials, newts that were rejected by snakes had greater concentrations of TTX in their skin (4.52 ± 3.49 mg TTX/g skin) than those that were eaten (1.72 ± 1.53 mg TTX/g skin). Despite the plethora of taxa that appear to use TTX defensively, this is the first direct and quantitative demonstration of the antipredator efficacy of TTX. Because the survival probability of a newt (and thus fitness) is affected by individual TTX concentration, selection can drive the escalation of toxin levels in newts. The variable fitness consequences associated with both TTX levels of newts and resistance to TTX in snakes that may promote a strong and symmetrical coevolutionary relationship have now been demonstrated. 相似文献
202.
Andrew Charles 《Local Environment》2013,18(3):209-221
Abstract This paper contributes to discussions of procedural aspects of environmental justice, understood as having procedural and substantive dimensions. It argues that the struggle for environmental justice must recognize the oppression of disabled people as part of the essential broadening of the notion of citizenship, which continues to be the focus for struggle for the international disability movement. Its case study of an area of South Wales suggests that at present disabled people, and the struggles of the disability movement, do not really feature in the way environmental activists (inside and outside government) see the world. This huge omission must be addressed, but in a way that avoids interpreting disability as an administrative category, and must engage with disablement as a political and contested notion. The paper develops the significance of this contention by considering the case of Deafness, which is entirely different from hearing impairment. The paper's case study, presented as an illustration of its arguments, shows that to regard Deaf people in South Wales as part of some generic category of ‘disabled people’ would be to ignore their self-identification as a distinctive linguistic community. Moreover, there is some evidence that Deaf people have a distinctive view of, and set of concerns about, quality of life, reflecting their distinctive experience of social injustice and marginalization. This underlines the necessity for a serious engagement with disablement as a political category, and the disability movement as a struggle for social justice, within the promotion of environmental justice. 相似文献
203.
Ian Calder Ashvin Gosain M. S. Rama Mohan Rao Charles Batchelor M. Snehalatha Emma Bishop 《Environment, Development and Sustainability》2008,10(4):537-557
This paper recommends a revision of watershed development policy in India in relation to the planning of development interventions
involving agricultural intensification and rainwater harvesting following biophysical and societal impact studies carried
out on two watershed development projects in Karnataka. A need for changes in policy has arisen in response to progressive
catchments closure at the basin level and declining volumes of water flowing into village level reservoirs (known locally
as tanks). Flow reductions have occurred largely as a result of increased agricultural intensification over the past 10–15 years.
Field levelling, field bund construction, soil water conservation measures, farm ponds, the increase in areas under horticulture
and forestry and the increased abstraction and use of groundwater for irrigation are all contributing factors to reduced flows.
Planning methodologies and approaches, which may have been appropriate 20 years ago for planning water harvesting within watershed
development projects, are no longer appropriate today. New planning approaches are required which (1) take account of these
changed flow conditions and (2) are also able to take account of externalities, which occur when actions of some affect the
livelihoods of others who have no control or influence over such activities and which (3) contribute to the maintenance of
agreed minimum downstream flows for environmental and other purposes.
相似文献
Ian CalderEmail: |
204.
Stephen D. Preston Richard B. Alexander Gregory E. Schwarz Charles G. Crawford 《Journal of the American Water Resources Association》2011,47(5):891-915
Preston, Stephen D., Richard B. Alexander, Gregory E. Schwarz, and Charles G. Crawford, 2011. Factors Affecting Stream Nutrient Loads: A Synthesis of Regional SPARROW Model Results for the Continental United States. Journal of the American Water Resources Association (JAWRA) 47(5):891‐915. DOI: 10.1111/j.1752‐1688.2011.00577.x Abstract: We compared the results of 12 recently calibrated regional SPARROW (SPAtially Referenced Regressions On Watershed attributes) models covering most of the continental United States to evaluate the consistency and regional differences in factors affecting stream nutrient loads. The models – 6 for total nitrogen and 6 for total phosphorus – all provide similar levels of prediction accuracy, but those for major river basins in the eastern half of the country were somewhat more accurate. The models simulate long‐term mean annual stream nutrient loads as a function of a wide range of known sources and climatic (precipitation, temperature), landscape (e.g., soils, geology), and aquatic factors affecting nutrient fate and transport. The results confirm the dominant effects of urban and agricultural sources on stream nutrient loads nationally and regionally, but reveal considerable spatial variability in the specific types of sources that control water quality. These include regional differences in the relative importance of different types of urban (municipal and industrial point vs. diffuse urban runoff) and agriculture (crop cultivation vs. animal waste) sources, as well as the effects of atmospheric deposition, mining, and background (e.g., soil phosphorus) sources on stream nutrients. Overall, we found that the SPARROW model results provide a consistent set of information for identifying the major sources and environmental factors affecting nutrient fate and transport in United States watersheds at regional and subregional scales. 相似文献
205.
Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments
on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three different diatom strains (9B, 1G, and 7J) induced widely different effects on Acartia tonsa physiology, and the 9B strain induced different effects for the three copepods. In contrast, different strains induced no
or small alterations in the distribution, swimming behavior, and turning frequency of the copepods. 22:6(n-3) fatty acid (DHA)
and sterol content of the diet typically showed a positive effect on either egg production (A. tonsa) or hatching success (P. elongatus), while other measured compounds (PUA, other long-chain polyunsaturated fatty acids) of the algae had no obvious effects.
Our results demonstrate that differences between strains of a given diatom species can generate effects on copepod physiology,
which are as large as those induced by different algae species or groups. This emphasizes the need to identify the specific
characteristics of local diatoms together with the interacting effects of different mineral, biochemical, and toxic compounds
and their potential implications on different copepod species. 相似文献
206.
Omo O. Omo-Irabor Samuel B. Olobaniyi Joe Akunna Valentijn Venus Joseph M. Maina Charles Paradzayi 《Environmental monitoring and assessment》2011,178(1-4):39-51
Mangroves are known for their global environmental and socioeconomic value. Despite their importance, mangrove like other ecosystems is now being threatened by natural and human-induced processes that damage them at alarming rates, thereby diminishing the limited number of existing mangrove vegetation. The development of a spatial vulnerability assessment model that takes into consideration environmental and socioeconomic criteria, in spatial and non-spatial formats has been attempted in this study. According to the model, 11 different input parameters are required in modelling mangrove vulnerability. These parameters and their effects on mangrove vulnerability were selected and weighted by experts in the related fields. Criteria identification and selection were mainly based on effects of environmental and socioeconomic changes associated with mangrove survival. The results obtained revealed the dominance of socioeconomic criteria such as population pressure and deforestation, with high vulnerability index of 0.75. The environmental criteria was broadly dispersed in the study area and represents vulnerability indices ranging from 0.00?C0.75. This category reflects the greater influence of pollutant input from oil wells and pipelines and minimal contribution from climatic factors. This project has integrated spatial management framework for mangrove vulnerability assessment that utilises information technology in conjunction with expert knowledge and multi-criteria analysis to aid planners and policy/ decision makers in the protection of this very fragile ecosystem. 相似文献
207.
A Method for Ensemble Wildland Fire Simulation 总被引:1,自引:0,他引:1
Mark A. Finney Isaac C. Grenfell Charles W. McHugh Robert C. Seli Diane Trethewey Richard D. Stratton Stuart Brittain 《Environmental Modeling and Assessment》2011,16(2):153-167
An ensemble simulation system that accounts for uncertainty in long-range weather conditions and two-dimensional wildland
fire spread is described. Fuel moisture is expressed based on the energy release component, a US fire danger rating index,
and its variation throughout the fire season is modeled using time series analysis of historical weather data. This analysis
is used to characterize the seasonal trend in ERC, autocorrelation of residuals, and daily standard deviation and stochastically
generate artificial time series of afternoon fuel moisture. Daily wind speed and direction are sampled stochastically from
joint probabilities of historical wind speed and direction for the date range of the fire simulation period. Hundreds or thousands
of fire growth simulations are then performed using the synthetic fire weather sequences. The performance of these methods
is evaluated in terms of the number of ensemble member simulations, one- versus two-dimensional fire spread simulations, and
comparison with results from 91 fires occurring from 2007 to 2009. Simulations were found to be in consistent agreement with
observations, but trends indicate that the ensemble average of simulated fire sizes were consistently larger than actual fires
whereas the farthest extent burned by fires was underestimated. 相似文献
208.
Johnson BJ Melde BJ Leska IA Charles PT Hewitt AD 《Journal of environmental monitoring : JEM》2011,13(5):1404-1409
A novel porous organosilicate material was evaluated for application as a solid phase extraction sorbent for preconcentration of nitroenergetic targets from aqueous solution prior to HPLC analysis. The performance of the sorbent in spiked deionized water, groundwater, and surface water was evaluated. Targets considered included 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, RDX, HMX, and nitroglycerin. The sorbent was shown to provide improved performance over Sep-Pak RDX. The impact of complex matrices on target preconcentration by the sorbent was also found to be less dramatic than that observed for LiChrolut EN. The impact of changes in pH on target preconcentration was considered. Aqueous soil extracts generated from samples collected at sites of ordnance testing were also used to evaluate the materials. The results presented here demonstrate the potential of this novel sorbent for application as a solid phase extraction material for the preconcentration of nitroenergetic targets from aqueous solutions. 相似文献
209.
Charles T. Garten Deanne J. Brice Hector F. Castro Robin L. Graham Melanie A. Mayes Jana R. Phillips Wilfred M. Post Christopher W. Schadt Stan D. Wullschleger Donald D. Tyler Phillip M. Jardine Julie D. Jastrow Roser Matamala R. Michael Miller Kelly K. Moran Timothy W. Vugteveen R. Cesar Izaurralde Allison M. Thomson Tristram O. West James E. Amonette Jeffrey L. Smith 《Agriculture, ecosystems & environment》2011,140(1-2):289-297
Switchgrass (Panicum virgatum) is a perennial, warm-season grass that has been identified as a potential biofuel feedstock over a large part of North America. We examined above- and belowground responses to nitrogen fertilization in “Alamo” switchgrass grown in West Tennessee, USA. The fertilizer study included a spring and fall sampling of 5-year old switchgrass grown under annual applications of 0, 67, and 202 kg N ha?1 (as ammonium nitrate). Fertilization changed switchgrass biomass allocation as indicated by root:shoot ratios. End-of-growing season root:shoot ratios (mean ± SE) declined significantly (P ≤ 0.05) at the highest fertilizer nitrogen treatment (2.16 ± 0.08, 2.02 ± 0.18, and 0.88 ± 0.14, respectively, at 0, 67, and 202 kg N ha?1). Fertilization also significantly increased above- and belowground nitrogen concentrations and decreased plant C:N ratios. Data are presented for coarse live roots, fine live roots, coarse dead roots, fine dead roots, and rhizomes. At the end of the growing season, there was more carbon and nitrogen stored in belowground biomass than aboveground biomass. Fertilization impacted switchgrass tissue chemistry and biomass allocation in ways that potentially impact soil carbon cycle processes and soil carbon storage. 相似文献
210.
Forest productivity increases in response to carbon dioxide (CO2) enrichment of the atmosphere. However, in nitrogen-limited ecosystems, increased productivity may cause a decline in soil nitrogen (N) availability and induce a negative feedback on further enhancement of forest production. In a free-air CO2 enrichment (FACE) experiment, the response of sweetgum (Liquidambar styraciflua L.) productivity to elevated CO2 concentrations [CO2] has declined over time, but documenting an associated change in soil N availability has been difficult. Here we assess the time history of soil N availability through analysis of natural 15N abundance in archived samples of freshly fallen leaf litterfall. Litterfall delta15N declined from 1998 to 2005, and the rate of decline was significantly faster in elevated [CO2]. Declining leaf litterfall delta15N is indicative of a tighter ecosystem N cycle and more limited soil N availability. By integrating N availability over time and throughout the soil profile, temporal dynamics in leaf litterfall delta15N provide a powerful tool for documenting changes in N availability and the critical feedbacks between C and N cycles that will control forest response to elevated atmospheric CO2 concentrations. 相似文献