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31.
The decomposition of the mangrove Rhizophora mangle and the seagrass Thalassia testudinum was examined using litterbags along a natural gradient in nutrient availability. Seagrass leaves had a higher fraction of their biomass in the labile pool (57%), compared to mangrove leaves (36%) and seagrass rhizomes (29%); the overall decomposition rates of the starting material reflected the fractionation into labile and refractory components. There was no relationship between the N or P content of the starting material and the decomposition rate. Nutrient availability had no influence on decomposition rate, and mass was lost at the same rate from litterbags that were buried in the sediment and litterbags that were left on the sediment surface. The dynamics of N and P content during decomposition varied as a function of starting material and burial state. N content of decomposing mangrove leaves increased, but seagrass rhizomes decreased in N content during decomposition while there was no change in seagrass leaf N content. These same general patterns held for P content, but buried seagrass leaves increased in P content while surficial leaves decreased. δ13C and δ15N changed by as much as 2‰ during decomposition. 相似文献
32.
Carol Jill Kambites 《Local Environment》2013,18(9-10):867-878
The possible role of parish and town councils (local councils) in the local implementation of sustainable development has been overlooked both in research and in policy-making. This article is based on research into local councillors' attitudes to sustainability and to their own role within a single county. A “discourse of local council legitimation” is identified, in which local councillors see their communities as living organisms, whose interests they represent with the benefit of local knowledge and holistic thinking – characteristics which they see as absent at other levels of government. Local councillors essentially see their role as local and relatively short-term – a perspective that will have to be addressed if local councils are to make a significant contribution to sustainability. 相似文献
33.
Jill P. Collins Christian A. Vossler 《Journal of Environmental Economics and Management》2009,58(2):226-235
This paper uses laboratory experiments with induced values to address fundamental issues related to the incentive compatibility of choice experiment value elicitation questions. In particular, we compare two- versus three-option choice sets and the effect of using alternative provision rules, including one where the outcome is influenced by both participant and “regulator” votes. We find the overall proportion of choices that are inconsistent with induced preferences is rather low. However, there are more deviations from induced preferences for two-option choice sets, and for alternatives to a simple plurality vote implementation rule. A multinomial probit analysis of choices in tandem with a mixed logit welfare analysis suggests there is a statistically significant but modest degree of bias towards selecting the status quo option. 相似文献
34.
Canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic. Our results indicate expansion
in canopy cover and height of willows on Herschel Island located at 70° north on the western Arctic coast of the Yukon Territory.
We examined historic photographs, repeated vegetation surveys, and conducted monitoring of long-term plots and found evidence
of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century. A simple model of patch initiation indicates that the majority of willow patches for each
of these species became established between 1910 and 1960, with stem ages and maximum growth rates indicating that some patches
could have established as late as the 1980s. Collectively, these results suggest that willow species are increasing in canopy
cover and height on Herschel Island. We did not find evidence that expansion of willow patches is currently limited by herbivory,
disease, or growing conditions. 相似文献
35.
Neufeld HS Peoples SJ Davison AW Chappelka AH Somers GL Thomley JE Booker FL 《Environmental pollution (Barking, Essex : 1987)》2012,160(1):74-81
Ozone-sensitive and -tolerant individuals of cutleaf coneflower (Rudbeckia laciniata L.) were compared for their gas exchange characteristics and total non-structural carbohydrates at Purchase Knob, a high elevation site in Great Smoky Mountains National Park, USA. Photosynthesis and stomatal conductance decreased with increased foliar stipple. Sensitive plants had lower photosynthetic rates for all leaves, except the very youngest and oldest when compared to tolerant plants. Stomatal conductance decreased with increasing leaf age, but no ozone-sensitivity differences were found. Lower leaves had less starch than upper ones, while leaves on sensitive plants had less than those on tolerant plants. These results show that ambient levels of ozone in Great Smoky Mountains National Park can adversely affect gas exchange, water use efficiency and leaf starch content in sensitive coneflower plants. Persistence of sensitive genotypes in the Park may be due to physiological recovery in low ozone years. 相似文献
36.
Jill M. Goldstein Glen E. Woolfenden Jack P. Hailman 《Behavioral ecology and sociobiology》1998,44(1):15-22
Prebreeders of the Florida scrub-jay (Aphelocoma coerulescens) are less likely to be found on their natal territories with a same-sex stepparent than with parents or an opposite-sex stepparent.
We tested two models that had been proposed to account for this sexual asymmetry. The dominance hypothesis states that stepparents
perceive same-sex prebreeders as competitors, primarily for a mate, so behave aggressively toward them. The pair-formation
hypothesis states that prebreeders remain home to pair eventually with the opposite-sex stepparent. Predictions from these
two models were tested by analyses from a quarter-century of records on a study population at Archbold Biological Station
and by new behavioral field observations at the Station. Results clearly rejected the latter and strongly supported the former
hypothesis. No prediction from the pair-formation hypothesis was confirmed: no pairing by a prebreeder of either sex has ever
occurred with a stepparent; remaining home was equally frequent in age-one males with stepmothers and genetic mothers, and
in females with stepfathers and genetic fathers; and the same results were found in age-two prebreeders. By contrast, the
data strongly supported the dominance hypothesis. Field data showed higher aggression rates by stepfathers to male prebreeders
and stepmothers to female prebreeders than by parents to their same-sex genetic offspring. Fewer age-one males remained home
with a stepfather than with the genetic father, and the same was found for age-one females with a stepmother and genetic mother;
at age two, the effect occurred only in female prebreeders. The two hypotheses make different predictions about prebreeders
with two stepparents versus with both parents, thus providing a critical test. The dominance hypothesis correctly predicted
decreased duration at home by age-one males and females; data for age-two females were in the direction of predicted difference
but not significant; and, as in other tests, no effect was found for age-two males. We propose that age-two male prebreeders
remain home despite elevated aggression from stepfathers because these prebreeders retain the possibility of budding from
or inheriting the natal territory.
Received: 16 July 1997 / Accepted after revision: 26 June 1998 相似文献
37.
Adaptive introgression as a resource for management and genetic conservation in a changing climate 下载免费PDF全文
Current rates of climate change require organisms to respond through migration, phenotypic plasticity, or genetic changes via adaptation. We focused on questions regarding species’ and populations’ ability to respond to climate change through adaptation. Specifically, the role adaptive introgression, movement of genetic material from the genome of 1 species into the genome of another through repeated interbreeding, may play in increasing species’ ability to respond to a changing climate. Such interspecific gene flow may mediate extinction risk or consequences of limited adaptive potential that result from standing genetic variation and mutation alone, enabling a quicker demographic recovery in response to changing environments. Despite the near dismissal of the potential benefits of hybridization by conservation practitioners, we examined a number of case studies across different taxa that suggest gene flow between sympatric or parapatric sister species or within species that exhibit strong ecotypic differentiation may represent an underutilized management option to conserve evolutionary potential in a changing environment. This will be particularly true where advanced‐generation hybrids exhibit adaptive traits outside the parental phenotypic range, a phenomenon known as transgressive segregation. The ideas presented in this essay are meant to provoke discussion regarding how we maintain evolutionary potential, the conservation value of natural hybrid zones, and consideration of their important role in adaptation to climate. 相似文献
38.
Jill Whynot Gary Quinn Pamela Perryman Peter Votlucka 《Journal of the Air & Waste Management Association (1995)》2013,63(9):95-99
ABSTRACT This paper describes efforts to reduce particulate matter (PM) emissions from restaurant operations, including application of an existing control method to a new equipment type. Commercial charbroiling in the South Coast Air Basin results in emissions of approximately 10 tons/day of fine particulate matter (PM2.5) and 1.3 tons/day of volatile organic compounds (VOCs). Over a seven-year period, the South Coast Air Quality Management District worked with industry to develop test methods for measuring emissions from various cooking operations, evaluate control technologies, and develop a rule to reduce these emissions. Of the two basic types of charbroilers—chain-driven and underfired—underfired produce four times the emissions when equivalent amounts of product are cooked. Cost-effective control technology is currently available only for chain-driven charbroilers. The application of flameless catalytic oxidizers to chain-driven charbroilers was found to effectively reduce emissions by at least 83% and is cost-effective. The catalysts have been used worldwide at restaurants for several years. Research efforts are underway to identify control options for underfired charbroilers. Implementation of Rule 1138, Control of Emissions from Restaurant Operations, adopted November 14, 1997, will result in reductions of 0.5 tons/day of PM2.5 and 0.2 tons/day of VOCs. Future rules will result in reductions from underfired charbroilers and possibly other restaurant equipment when cost-effective solutions are available. 相似文献
39.
Callaghan TV Tweedie CE Akerman J Andrews C Bergstedt J Butler MG Christensen TR Cooley D Dahlberg U Danby RK Daniëls FJ de Molenaar JG Dick J Mortensen CE Ebert-May D Emanuelsson U Eriksson H Hedenås H Henry H R G Hik DS Hobbie JE Jantze EJ Jaspers C Johansson C Johansson M Johnson DR Johnstone JF Jonasson C Kennedy C Kenney AJ Keuper F Koh S Krebs CJ Lantuit H Lara MJ Lin D Lougheed VL Madsen J Matveyeva N Mcewen DC Myers-Smith IH Narozhniy YK Olsson H Pohjola VA Price LW Rigét F Rundqvist S 《Ambio》2011,40(6):705-716
Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon, and to dramatic increases in shrub and tree density on Herschel Island, and in subarctic Sweden. The population of geese tripled at one site in northeast Greenland where biomass in non-grazed plots doubled. A model parameterized using results from a BTF study forecasts substantial declines in all snowbeds and increases in shrub tundra on Niwot Ridge, Colorado over the next century. In general, results support and provide improved capacities for validating experimental manipulation, remote sensing, and modeling studies. 相似文献
40.
This paper describes the relatively new, university entry level examination offered by the International Baccalaureate Organisation in the subject of Environmental Systems. The programme has an integrated, holistic approach, and a strong international focus. The authors are Chief Examiner and Deputy Chief Examiner for this examination. 相似文献