Quantitative estimates of recent environmental changes in the Canadian High Arctic inferred from diatoms in lake and pond sediments   总被引：4，自引：0，他引：4  

Antoniades  Dermot  Douglas  Marianne S. V.  Smol  John P. 《Journal of Paleolimnology》2005,33(3):349-360

Diatoms were examined in three lacustrine sediment records from Alert, northern Ellesmere Island, and from Isachsen, Ellef Ringnes Island. Diatom assemblages changed markedly since the mid-19th century following relatively stable community composition that spanned centuries to millennia. Three different assemblages, primarily composed of Fragilaria pinnata, Diadesmis spp., or Pinnularia spp., dominated the pre-1850 period at the three sites, but were replaced with different, more diverse assemblages in recent sediments. These species shifts occurred in the mid- to late-19th century in the Isachsen sites, and in the mid- to late-20th century in our Alert site. This difference in timing appears to be a result of the different sensitivities of lakes and ponds to environmental change, rather than of site-specific chemical properties. Reconstructions of pH using diatom inference models indicated increases from 0.5 to 0.8 pH units at these sites over this period of assemblage change. The diatom-inferred pH record from Alert showed agreement with measured climate data from Alert over the last 30 years. These marked community changes suggest that these sensitive high arctic sites have recently crossed important ecological thresholds due to environmental change, most likely related to recent warming.  相似文献   

Cows versus rubber: Changing livelihoods among Amazonian extractivists     

David S. Salisbury  Marianne Schmink   《Geoforum》2007,38(6):1233-1249

The livelihood strategies of former rubber tappers in the Amazon region are rapidly shifting from extraction of non-timber forest products to mixed systems based on agriculture and small scale cattle ranching. Using a combination of participatory methods and Geographical Information Systems, a case study in western Acre, Brazil explores how rubber tapper livelihood strategies may be changing, and the implications of these changes for land use and forest cover. Field (cattle pasture and agriculture) expansion and the decline of forest extractivism present challenges to many regional conservation and development projects such as sustainable settlement projects and extractive reserves seeking to develop forest-based livelihood alternatives to limit deforestation. Sustainability goals require researchers and policy makers to address the still experimental status of these forest-based organizational units, the heterogeneity and dynamism of extractivist livelihoods, and the necessary importance of small-scale cattle ranching for insurance and income generation among many former and current extractivists.  相似文献   

Gas-Phase OH Oxidation of Monoterpenes: Gaseous and Particulate Products     

Bo. R. Larsen  Dario Di Bella  Marianne Glasius  Richard Winterhalter  Niels R. Jensen  Jens Hjorth 《Journal of Atmospheric Chemistry》2001,38(3):231-276

Smog chamber experiments have beenconducted in which cyclic monoterpenes were oxidisedin the gas phase by OH. The evolved secondary organicaerosol (SOA) was analysed by LC-MSⁿ and thegas-phase products were analysed by FT-IR. Theconcentrations of the identified compoundscorresponded to carbon mass balances in the range of40%–90%. The identified compounds in the particularphase corresponded to 0.5%–4.2% of the reactedcarbon. The most abundant compounds in SOA fromterpenes with an endocyclic C=C double bond wereC₁₀-keto-aldehydes, C₁₀-keto-carboxylicacids, C₁₀-hydroxy-keto-carboxylic acids, andC₁₀-hydroxy-keto-aldehydes (pinonaldehyde,pinonic acid, hydroxy-pinonic acid isomers, andhydroxy-pinonaldehyde isomers from -pinene;3-caronaldehyde, 3-caronic acid, hydroxy-3-caronicacid isomers, and hydroxy-3-caronaldehyde isomers from3-carene). The most abundant compounds in SOA fromterpenes with an exocyclic C=C double bond wereC₉-ketones, C₉-dicarboxylic acids, andC₁₀-hydroxy-keto-carboxylic acids (nopinone,pinic acid, and hydroxy-pinonic acid isomers from-pinene; sabinaketone, sabinic acid andhydroxy-sabinonic acid isomers from sabinene).Decarboxylated analogues of most of the compounds werepresent in SOA in minor concentrations, such asC₉-keto-carboxylic acids (norpinonic acid,nor-3-caronic acid) and C₈-dicarboxylic acids(norpinic acid, nor-3-caric acid, norsabinic acid). InSOA from limonene, which contains an endocyclic aswell as an exocyclic C=C double bond, the mostabundant compounds were a C₁₀-keto-aldehyde andits oxo-derivative (limononaldehyde and keto-limononaldehyde) together with hydroxy-derivatives of aC₁₀-keto-carboxylic acid (isomers ofhydroxy-limononic acid). Also aC₁₀-keto-carboxylic acid (limononic acid) waspresent together with minor concentrations of aC₉-dicarboxylic acids (limonic acid), itsoxo-derivative (keto-limonic acid), and itsdecarboxylated analogue (norlimonic acid). Mechanisticpathways for the formation of these products, some ofwhich are identified here for the first time, areproposed.  相似文献   

Ergebnisse der limnologischen Untersuchungen der Oberengadiner Seen     

Frau Dr. Marianne Bosli-Pavoni 《Aquatic Sciences - Research Across Boundaries》1971,33(1):386-409

Ohne Zusammenfassung  相似文献   

Active tectonics,seismicity and geomorphology with special reference to Normandy (France)     

Jean‐Louis Lagarde  Stphane Baize  Daniel Amorese  Bernard Delcaillau  Marianne Font  Philippe Volant 《第四纪科学杂志》2000,15(7):745-758

Integrated studies based on tectonic, seismotectonic and geomorphological analyses indicate that Normandy (northwest France) has been an active area during the Quaternary. Topography and landform discontinuities reflect the dislocation and differential uplift of a late Cenozoic platform. The tectonic activity is represented by (i) active faults, indicated by linear scarps and seismic activity, (ii) offsetting of pre‐existing surfaces, (iii) Plio‐Pleistocene sedimentation restricted within narrow subsiding zones, and (iv) morphometric properties of drainage basins that indicate zones of differential uplift. The inferred strain pattern involves (i) a shortening direction that strikes NW–SE as expected in the European context of Alpine compression, and (ii) a NE–SW trending extension accommodated by NW–SE normal faults. The geomorphological systems encountered in Normandy preferentially record differential vertical displacements. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献