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Seasonal variability in CDOM absorption and fluorescence properties in the Barataria Basin,Louisiana,USA

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Journal of Environmental Sciences 2010年第10期22卷 1481-1490页

作者： Shatrughan Singh Eurico D'Sa Erick swenson Department of Oceanography and Coastal Sciences Louisiana State University

Absorption and fluorescence properties of chromophoric dissolved organic matter （CDOM） along a 124 km transect in the Barataria Basin, a large estuary located in Louisiana, USA, were investigated during high and low flow periods of the Mississippi River in the spring and winter of 2008-2009. Mean CDOM absorption at 355 nm from the marine to the freshwater end member stations ranged from （3.25 ± 0.56） to （20.76 ± 2.43） m^-1 for the three month high flow period whereas it varied from （1.48 ± 1.08） to （25.45 ± 7.03） m^-1 for the same stations during low flow period. Corresponding salinity values at these stations indicated the influence of river and shelf exchanges in the lower basin and precipitation and runoff in the upper basin. An inverse relationship of CDOM absorbance and fluorescence with salinity observed in the basin could he a useful indicator of salinity. CDOM fluorescence also varied over a large range showing an approximately 8 to 12-fold increase between the marine and freshwater end members for the two flow seasons. Excitation-emission matrix spectral plots indicated the presence of various fluorescence components with highest being the A-peak, lowest the T-peak, and the C and M-peaks showing similar trends along the transect. During low flow season the A/C ratio were well correlated with station locations indicating increased terrestrial influence towards the upper basin. CDOM absorption and fluorescence at 355 nm were highly correlated and independent of CDOM sources suggesting that fluorescence could be used to characterize CDOM in the basin.

关键词： Barataria Basin chromophoric dissolved organic matter CDOM fluorescence excitation-emission matrix

Functional perspectives on tropical tree demography and forest dynamics

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Ecological Processes 2019年第1期8卷 1-11页

作者： Samantha J.Worthy Nathan G.swenson Department of Biology University of MarylandCollege ParkMD 20742USA

Disentangling the processes that drive population,community and whole forest structure and dynamics is a *** becomes a grand challenge in the tropics where there are a large number of species,small population sizes,less research infrastructure,and a relatively smaller number of researchers compared to the temperate *** this grand challenge,we argue,requires detailed knowledge of the functioning of individuals and *** this end,researchers frequently employ plant functional traits to study tree populations and ***,we review this approach by first providing a basic background regarding the major trait axes generally of *** then discuss how these axes may be or have been applied from ecosystem to community and population *** doing so,we highlight where the functional trait research program has failed in tropical tree ecology and where it can be improved or ***,we provide a perspective regarding how functional trait and emerging‘omics approaches can be integrated to address large questions facing the *** intention throughout is to provide an entryway into this literature for an early career researcher rather than a comprehensive review of all possible studies that have taken place in tropical forests.

关键词： Demographic rate Functional diversity Functional trait Transcriptome Tropical forest Tropical rain forest

Phylofloristics:an example from the Lesser Antilles

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Journal of Plant Ecology 2014年第2期7卷 166-175页

作者： Nathan G.swenson María N.Umaña Department of Plant Biology Michigan State UniversityEast LansingMichigan 48824USA

Aims The last decade has seen many plant ecologists integrating phylogenetic analysis into ecology to explain patterns of species cooccurrence and compositional similarity across *** the advances in this area,there are still some challenges that need to be *** challenge is that most of the phylogenetic studies of plant assemblages have focused only on a small proportion of all of the vascular plants that co-occur(*** plants),while much of the remaining co-occurring flora has been *** Here we introduce an analytical approach that we term phylofloristics that analyzes the compositional similarity of floras in relation to spatial and environmental gradients to understand their *** an illustration,we assembled a large phylogenetic tree for the flora of the Lesser Antilles and evaluated the patterns of floristic and phylofloristic similarity among the island-specific *** analyzed the relationship of these similarities with spatial and environmental distance and compared the results for non-endemic and endemic *** Findings The results show a major influence of environmental heterogeneity on the assembly of island floras and far less evidence for the importance of dispersal limitation of lineages and *** study highlights the importance of incorporating broader taxonomic sampling to improve our understanding of assembly processes in *** expect future phylofloristic studies will improve the approach we have taken by generating more refined phylogenetic trees and by incorporating phylogeographic information.

关键词： biogeography Caribbean flora phylogeny plant geography

The past,present,and future of the Siberian Grouse(Falcipennis falcipennis)under glacial oscillations and global warming

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Avian Research 2022年第1期13卷 57-63页

作者： Wendong Xie Kai Song Siegfried Klaus Jon E.swenson Yue-Hua Sun Key Laboratory of Animal Ecology and Conservation Biology Institute of ZoologyChinese Academy of SciencesBeijing100101China College of Life Science Hebei UniversityBaoding071002China Lindenhöhe 5 D-07749JenaGermany Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life SciencesPO Box 5003NO-1432ÅsNorway

Global climate change has a significant effect on species,as environment conditions change,causing many species'distributions to *** the last three million years,the earth has experienced glacial oscillations,forcing some species to survive in ice-free refugia during glacial periods and then disperse *** this study,by assessing the potential distribution of Siberian Grouse(Falcipennis falcipennis),we used Global Circular Models and Representative Concentration Pathways to model their pattern of range changes during glacial oscillations and the potential impact of present global *** used 158 location records of Siberian Grouse to generate a full climate model using 19 bioclimate variables in *** discarded variables with a correlation coefficient larger than 0.8 and relatively lower modeling contributions between each pair of correlated *** the remaining variables,we created a normally uncorrelated simple climate model to predict the possible distribution of Siberian Grouse from the most recent Ice Age to present and to *** we added geographical data and the human interference index to construct a multiple factor full model to evaluate which were important in explaining the distribution of Siberian *** Total Suitability Zone(P≥0.33)of Siberian Grouse is about 243,000km^(2) and the Maximum Suitability Zone(P≥0.66)is 36,000km^(2) and is confined to the Russian Far *** habitat modeling suggested that annual precipitation,annual mean temperature,and the distance from lakes are the most explanatory variables for the current distribution of Siberian *** distribution center moved to the southeast during the Last Glacial Maximum and spread back to the northwest after the ice melted and temperatures *** total area range of Siberian Grouse experienced a dramatic loss during the Last Glacial *** warming is presently forcing the Siberian Grouse to migrate northward with a contraction of

关键词： Climate change Falcipennis falcipennis Ice age refugia Last glacial maximum

Egg laying and incubation rhythm of the Chinese Grouse(Tetrastes sewerzowi)at Lianhuashan,Gansu,China

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Avian Research 2019年第3期10卷 357-365页

作者： Mei Shi Yun Fang Jin-ming Zhao Siegfried Klaus Yingxin Jiang Jon E.swenson Yue-Hua Sun Key Laboratory of Animal Ecology and Conservation Biology Institute of ZoologyChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China School of Life Science Huaibei Normal UniversityHuaibei 235000China Jena Germany Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life SciencesBox 50031432 AsNorway

Background:Incubating birds must balance the conflict between thermal needs of the developing embryos and their self?maintenance needs for *** Chinese Grouse (Tetrastes sewerzowi) lives in high mountain conifer forests and faces energy stress,cold environment,and predation *** might adjust incubation rhythm to adapt to these constraints. Methods:Two methods were used to investigate egg laying and incubation pattern of the Chinese Grouse;25 nests were monitored by data loggers and 12 nests by infrared video cameras. Results:Female Chinese Grouses usually laid an egg every 2 *** incubation period was 28-31 days. Overall incubation constancy for Chinese Grouse was 93%. The females took 5.0 recesses per day and 34% of all 1696 recesses were taken in the crepuscular period. The average recess duration was 20.3 min. Females took more and shorter recesses in the latter part of *** females who allocated more time to foraging had a higher reproductive success. Conclusions:Probably due to its high egg/body mass ratio,the Chinese Grouse has a long laying interval of 49 h. We suggest that,due to energy stress,females have relatively more recesses and they increase the number of recesses as incubation *** compensate for the embryos'thermal needs, they extend the incubation period and shorten the recess duration in this cold environment.

关键词： Body mass Chinese Grouse Environment temperature Incubation pattern Nest attentiveness

The Conditions for Se-Enzymes, NO, cGMP and LDL to be Formed and How They are Connected with Each Other

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Journal of Chemistry and Chemical Engineering 2014年第3期8卷 278-285页

作者： Birgit Elisabeth swenson Chalmers Technical University Molnda143136 Sweden

Transportation of energy and substances is fundamental for the conditions of life. The energy from metabolised food is yielded at the reduction of oxygen by the assistance of Se-enzymes. Activated Se-enzymes contain an electron conducting Se-link with elemental Se bounded to Se-cys （Se-cystein） that prevents electron transferring （autoxidable） agents, as arginine, from oxidations. NO is formed from e.g. arginine during the passive state of a Se-enzyme. With NO, instead of O2, bounded to a hem group, destroying oxidations are avoided. This is the role of NO. A nerve signal is activated by the GTP （guanosine triphosphate）-induced triggered transformation of cGMP （cyclic guanosine monophosphate） into GMP, closing the sodium channels. When GTP is consumed, the opposite reaction takes place. The direct influence of the GMP/cGMP quote on a nerve signal makes GMP/cGMP equal to EDHF （endothelium-derived hyperpolarizing factor）. Part of the energy from food is stored and transported in the form of acetyl groups, building up many important molecules of which LDL （low density lipoprotein） is one, containing cholesteryl esters. These are brought in to the cell, decomposed to acetyl groups generating hydrogen, H, making LDL to an essential substance. High levels are connected to impaired energy yielding reactions, perhaps related to low levels of some substances, especially to one or both forms of Se. The necessity of a Se-link and NO induced protection against oxidations by reducible oxygen can no longer be neglected.

关键词： Se-enzymes Se-toxicity formation of NO formation of cGMP EDHF cholesteryl esters from LDI. .

A Method and a Surface Treatment Agent for Preventing Biofouling on Surfaces under Water

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Journal of Chemistry and Chemical Engineering 2012年第3期6卷 227-232页

作者： Birgit Elisabeth swenson

This paper presents an environm centally friendly method of inhibiting biofouling especially acorn barnacles on surfaces under water by using nicotine and selenium in the form of Se（0）, or such a substance which can be converted into them. Both of the substances are necessary to oxygen dependent organisms and will be used after conversion, but are toxic in high doses. By adding the substances to paint or other surface treatment agent which marine surfaces are treated with, organisms which are trying to establish themselves on the surfaces will be exposed to so high doses, the reactions which the settling is based on are disturbed. When the substances leak out into the seas, they will act as environment protectors, as they promote the development of organisms. Nicotine is transformed to nicotine amid which is the reactive part in NADH and one of the most important substances for the transference of hydrogen. Selenite is reduced to Se（0）, also involved in the transport chain of hydrogen to reducible oxygen. However, large quantities Se（0） may disturb the reactions of sulphur b＇./binding to it and impairing the formation of S-S-bridges.

关键词： Marine biofouling environment protection crustaceans catemines nicotine selenite.

Injections of Substances Inducing Apoptosis to Cancer Cells but Stimulation of Normal Cells May Prevent Cancer

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Journal of Chemistry and Chemical Engineering 2011年第5期5卷 393-403页

作者： Birgit Elisabeth swenson Tegelformsgatan 4 Moelnda143136 Sweden

Selenium（Se） compounds have prevented and Se-deficiency has induced the initiation of cancer. Se（0）-forming compounds and hydroxy-xanthones have killed cancer ceils but shown beneficial effects to normal cells. They may together be effective in the treatment of cancer. Many enzymes which contain selenocysteine （Secys） can catalyze reactions with reducible oxygen （O2~ 02 or H202）. Experiments strongly support that Se-enzymes are activated by Se（0）, from e.g. selenite, selenodiglutathione, binding to Se（-II） in Secys, forming an electron conducting Se-link to reducible oxygen as a protection against oxidations. Cancer cells, which are energy supported only from fermentation, are not dependent on Se which is why they are more sensitive to toxic effects of Se than normal cells. The energy from fermentation is insufficient for normal cell functions. High doses of Se（0）-containing compounds are toxic in that they form links with thiols （R-S-Se） reducing their reaction rate. The reaction of an SH-enzyme, necessary in fermentation, is impaired. Mangostins （hydroxy-xanthones） induce apoptosis in human cancer ceils but stimulate respiration. The OH-groups are responsible for the effects and the reduction of NADP＋ into NADPH. Fermentation is inhibited as NADP＋ is necessary for the process. Cancer may be treated by injections of Se（0）-forming compounds and hydroxy-xanthones into cancer cells in doses causing apoptosis. However, in diluted form, when meting normal cells, the substances promote the yield of energy by stimulating the electron transference to reducible oxygen. Se（0）-activated Se-links and hydrogen from hydroxy-xanthones hopefully prevent the initiation of cancer.

关键词： Cancer prevention Se-enzymes Se-link selenite nicotine hydroxy-xanthones.

Phylogenetic alpha and beta diversity in tropical tree assemblages along regionalscale environmental gradients in northwest South America

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Journal of Plant Ecology 2014年第2期7卷 145-153页

作者： Sebastián González-Caro María Natalia Umaña Esteban Álvarez Pablo R.Stevenson Nathan G.swenson Ecosystem Services&Climate Change Lab Botanical Garden of MedellínMedellínAntioquia 050001Colombia Department of Plant Biology Michigan State UniversityEast LansingMI 48824USA Department of Ecology Universidad de AlcaláAlcaláMadrid 28801Spain Department of Biological Sciences Universidad de Los AndesBogotá7495Colombia

Aims Environmental gradients are drivers of species diversity;however,we know relatively little about the evolutionary processes underlying these relationships.A potentially powerful approach to studying diversity gradients is to quantify the phylogenetic structure within and between assemblages arrayed along broad spatial and environmental ***,we evaluate the phylogenetic structure of plant assemblages along an environmental gradient with the expectation that the habitat specialization of entire lineages is an important evolutionary pattern influencing the structure of tree communities along environmental *** We evaluated the effect of several environmental variables on the phylogenetic structure of plant assemblages in 145 plots distributed in northwestern South America that cover a broad environmental *** phylogenetic alpha diversity was quantified for each plot and the phylogenetic beta diversity between each pair of plots was also *** the alpha and beta diversity measures were then related to spatial and environmental gradients in the study *** Findings We found that gradients in temperature and potential evapotranspiration have a strong relationship with the phylogenetic alpha diversity in our study system,with phylogenetic overdispersion in low temperatures and phylogenetic clustering at higher ***,the phylogenetic beta diversity between two plots increases with an increasing difference in temperature,whereas annual precipitation was not a significant predictor of community phylogenetic *** also found that the phylogenetic structure of the plots in our study system was related to the degree of seasonal flooding and seasonality in *** particular,more stressful environments such as dry forests and flooded forests showed phylogenetic ***,in contrast with previous studies,we find that phylogenetic beta diversity was not strongly related to the spatial d

关键词： phylogenetic conservatism habitat filtering immigration environmental gradient