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141.
The succession of a mixed species stand of the Acadian Forest was simulated by adopting an approach taken by Botkin et al. (1972) (JABOWA) and later modified by Shugart and West (1977) (FORET). The model simulates the dynamic aspects of successional behaviour of the stand by projecting the current stage of vegetation composition (size of each individual of each species present on a 1/12 ha plot) with an element of randomness. The growth of each tree is modeled as a function of its size (represented by its diameter at breast height (dbh), height and leaf area index), the climate, the tree's tolerance to shade and the competition for available resources and space. Stand aboveground biomass (metric ton/ha), leaf area index, number of trees/ha and species composition of the stand were simulated under seven different conditions: (a) normal treatment, (b) increasing biomass maximum 30%, (c) decreasing biomass maximum 30%, (d) increasing degree-days 30%, (e) decreasing degree-days 30%, (f) increasing light extinction coefficient 30% and (g) decreasing light extinction coefficient 30%. Under the first set of conditions (normal treatment), the aboveground biomass reached a maximum value during the first hundred years, decreased during the second, and remained stable for the rest of the 500-year simulation period. The leaf area showed a similar pattern. The total number of trees/ha decreased sharply during the first fifty years and reached a stable value by the end of the first hundred years. Successional patterns and species competitive abilities were interpreted from the accumulated biomass of each species over the simulation period under the different treatments.Species composition of the stand under the normal treatment showed dominance of deciduous species at early stages of succession, with conifer species being increased and becoming dominant at the end of the simulation period. When the climate was raised 30% (warmer) over the average, the deciduous species continued their dominance over the course of the simulation period. Other simulated species dynamics also appeared to follow what is known about their successional behaviour in the field. 相似文献
142.
Wang-Hsien Ding Herman Valente David Spink Kenneth Aldous David Hilker Steven Connor 《Chemosphere》1989,18(9-10):1935-1942
Total concentrations of PCDDs and PCDFs were predicted from the concentrations of specifically identified dioxin and furan isomers of each congener group by partial least-squares (PLS). The accuracy of this prediction can be used to evaluate results from different data sets or different sources which were calculated by an automatic identification and quantification program-TASQR. 相似文献
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Helsen L Van den Bulck E Cooreman H Vandecasteele C 《Journal of environmental monitoring : JEM》2003,5(5):758-765
In the present study a sampling and analysis method for arsenic emissions during pyrolysis of arsenic containing wood, such as chromated copper arsenate (CCA) treated wood, has been developed. The procedure is based on the NIOSH (National Institute for Occupational Safety and Health) standard for arsenic trioxide sampling. Validation for this specific application is needed since pyrolysis of arsenic containing wood leads to a gas stream containing sticky tar compounds and aerosols. Validation was carried out through tube furnace experiments using both CCA treated wood and arsenic trioxide powder as input. The outlet of the tube furnace was coupled to a cooling section and sampling train. The sampling train consisted of one or more filter sections and impingers. Different combinations of filters (untreated or impregnated) and impingers, as well as different combinations of washing solutions were tested. The different units of the sampling train were analysed by inductively coupled plasma mass spectrometry (ICP-MS) in order to determine the distribution of arsenic over the different units. For the working conditions considered (pyrolysis at 350 degrees C for 20 minutes with a nitrogen flow rate of 100 Nl h(-1)) the combination of a quartz cooling tube and a cellulose ester membrane filter impregnated with a Na2CO3-glycerol solution was sufficient to capture the arsenic. Two extra impingers (the first one containing 50 ml HNO3 1 M in the case of CCA treated wood and 50 ml NaOH 0.1 M in the case of As2O3 and the second one containing 50 ml NaOH 0.1 M) were added downstream of the filter section as backup either in case of filter failure or to check whether all the arsenic released is captured by the cooling tube and filter. 相似文献
146.
Charles T. Schick Leonard A. Brennan Joseph B. Buchanan Michael A. Finger Tod M. Johnson Steven G. Herman 《Environmental monitoring and assessment》1987,9(2):115-131
Arctic-breeding shorebirds collected in western Washington state during winter and spring, and a comparative sample collected in coastal California during the winter were analyzed for organochlorine contaminants to determine the potential impact of these residues on populations of peregrine falcons (Falco peregrinus) and merlins (F. columbarius) which prey upon shorebirds in western Washington. Dunlins (Calidris alpina), an important winter prey for falcons in western Washington, were collected between 1975 and 1981. During winter 1980–81, dunlins carried low organochlorine residues; DDE levels ranged from 0.01 to 1.2 ppm, and PCB levels ranged from 0.02 to 0.82 ppm (wet weight). Levels of other organochlorine contaminants (HCB, Chlordane compounds, Dieldrin, and Heptachlor Epoxide), analyzed in a subsample of dunlins, were consistently lower than DDE and PCB levels, and ranged from 0.001 to 0.22 ppm (wet weight). Dunlins in western Washington did not significantly increase their DDE or PCB burdens over the 1980–81 winter. A decline in DDE residues between 1978 and 1981 was noted, and declines in PCB residues from both 1975 and 1978 to 1980–81 were noted. Residues in other wintering shorebirds from western Washington were similar. Wintering sanderlings (Calidris alba) from California, revealed much higher DDE contamination than in Washington (up to 32 ppm, wet weight). Spring migrant shorebirds in western Washington contained both low and very high DDE residues (up to 417 ppm, wet weight). There is evidence suggesting these high DDE concentrations are accumulated along the Pacific coast of North America. 相似文献
147.
Kifayatullah Khan Yonglong Lu Mian Abdal Saee Hazrat Bilal Hassan Sher Hizbullah Khan Jafar Ali Pei Wang Herman Uwizeyiman Yvette Baninl Qifeng Li Zhaoyang Liu Javed Nawa Yunqiao Zhou Chao Su Ruoyu Liang 《环境科学学报(英文版)》2018,30(10):1-12
Fecal bacteria contaminate water resources and result in associated waterborne diseases.This study assessed drinking water quality and evaluated their potential health risks in Swat, Pakistan. Ground and surface drinking water were randomly collected from upstream to downstream in the River Swat watershed and analyzed for fecal contamination using fecal indicator bacteria(Escherichia coli) and physiochemical parameters(potential of hydrogen, turbidity, temperature, electrical conductivity, total dissolved solid, color, odor and taste). The physiochemical parameters were within their safe limits except in a few locations, whereas, the fecal contaminations in drinking water resources exceeded the drinking water quality standards of Pakistan Environmental Protection Agency(Pak-EPA),2008 and World Health Organization(WHO), 2011. Multivariate and univariate analyses revealed that downstream urbanization trend, minimum distance between water sources and pit latrines/sewerage systems, raw sewage deep well injection and amplified urban,pastures and agricultural runoffs having human and animal excreta were the possible sources of contamination. The questionnaire survey revealed that majority of the local people using 10–20 years old drinking water supply schemes at the rate of 73% well supply,13% hand pump supply, 11% spring supply and 3% river/streams supply, which spreads high prevalence of water borne diseases including hepatitis, intestinal infections and diarrhea, dysentery, cholera, typhoid fever, jaundice and skin diseases in children followed by older and younger adults. 相似文献
148.
M. Melissa Rojas-Downing A. Pouyan Nejadhashemi Mohammad Abouali Fariborz Daneshvar Sabah Anwer Dawood Al Masraf Matthew R. Herman Timothy Harrigan Zhen Zhang 《Mitigation and Adaptation Strategies for Global Change》2018,23(3):405-431
Among livestock systems, grazing is likely to be most impacted by climate change because of its dependency to feed quality and availability. In order to reduce the impact of climate change on grazing livestock systems, adaptation measures should be implemented. The goal of this study is to identify the best pasture composition for a representative grazing dairy farm in Michigan in order to reduce the impacts of climate change on production. In order to achieve the goal of this study, three objectives were sought: (1) identify the best pasture composition, (2) assess economic and resource use impacts of pasture compositions under future climate scenarios, and (3) evaluate the resiliency of pasture compositions. A representative farm was developed based on a livestock practices survey and incorporated into the Integrated Farm System Model (IFSM). For the pasture compositions, four cool-season grass species and two legumes were evaluated under both current and future climate scenarios. The effectiveness of adaptation measures based on economic and resource use criteria was evaluated. Overall, the pasture composition with 50% perennial ryegrass (Lolium multiflorum) and 50% red clover (Trifolium pratense) was identified as the best. In addition, the increase in precipitation and temperature of the most intensive climate scenario could significantly improve farm net return per cow (Bos taurus) and whole farm profit while no significant impact was observed on resource use criteria. Finally, the overall sensitivity assessment showed that the most resilient pasture composition under future climate scenarios was ryegrass with red clover and the least resilient was orchardgrass (Dactylis glomerata) with white clover (Trifolium repens). 相似文献
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Louis M. Herman Adam A. Pack Scott S. Spitz Elia Y. K. Herman Kathryn Rose Siri Hakala Mark H. Deakos 《Behavioral ecology and sociobiology》2013,67(10):1653-1663
While on their winter breeding grounds, male humpback whales (Megaptera novaeangliae) produce long sequences of structured vocalizations called song, whose function within the mating system is still unresolved. Here we ask which males sing. Is it only those sexually mature, as typifies songbirds and some lekking ungulates in which vocalizations during the rut are restricted to mature males? Or do immature males join in the chorus? Using an underwater videogrammetric technique, we measured the body lengths of 87 humpback singers in the Hawaiian winter grounds. Applying length and sexual maturity relationships for North Pacific humpbacks as determined by biologists aboard twentieth century Japanese whaling vessels, we found that singer lengths ranged from 10.7 to 13.6 m, with 15 % of lengths indicative of probable sexual immaturity (length?<?11.3 m, p [maturity]?<?0.5). We interpret this broad participation of males as a lekking aggregation and the asynchronous singing chorus as an instance of by-product mutualism. The participation of many singers yields a heightened signal level that may attract more females to the singing area. Sexually mature males can benefit through access to more females. Immature males may gain deferred benefits through increased opportunities to learn and practice the social, behavioral, and acoustical skills and conventions of the winter grounds that they can apply usefully in later years. 相似文献