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To assess whether the biochemical characteristics of peat can provide clues for past ecosystem changes or not, a study was carried out combining elemental analysis, micro-morphological counts and neutral monosaccharide determination of peat organic matter (OM) and the dominant living plants from a formerly cut-over peat bog in the Jura Mountains. Peat profiles (up to 50 cm depth) from two distinctive zones (bare peat, FRA and a regenerating stage, FRC) were compared with the reference profile (FRD) taken from an unexploited area of the bog. The results show contrasting OM composition along the profiles. In the upper sections of the FRD and FRC profiles, high C/N ratios and sugar contents (in the same range as in the source plants) and the large predominance of well preserved plant tissues indicate good preservation of primary biological inputs. In contrast, in peat from the FRA profile and deeper levels of the FRC profile, lower C/N ratios, lower amounts of sugars and a predominance of amorphous OM and mucilage suggest more extensive OM degradation. These features delineate a clear threshold between an uppermost “new” regenerating peat section and an “old” catotelm peat below. Nevertheless, even in the latter, the sugar contents remain relatively high (>80 mg/g) compared with other organic and mineral soils. Analysis of typical peat-forming plants and of bulk peat and fine grained fractions allowed identification of the following source indicators: xylose and arabinose for Cyperaceae; rhamnose, galactose and mannose for mosses; and ribose (and to a lesser extent, hemicellulosic glucose) possibly for microbial synthesis. 相似文献
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Pavel E. Tarasov Rachid Cheddadi Joel Guiot Sytze Bottema Odile Peyron Jordina Belmonte Vittoria Ruiz-Sanchez Fatima Saadi Simon Brewer 《第四纪科学杂志》1998,13(4):335-344
An objective method for the assignment of pollen spectra to appropriate biomes has been published recently. The aim of this paper is to improve the distinction between warm and cool steppes, thus refining vegetation and climate reconstruction, particularly during the Last Glacial Maximum. A set of modern pollen spectra from the Mediterranean and Kazakhstan regions, dominated today by open vegetation types, has been analysed statistically in order to relate pollen taxa abundances to warm and cool grass/shrub plant functional types (PFTs). A statistical test using modern pollen data shows that the method is able to distinguish between cool and warm steppe biomes with a high degree of confidence. The method has been applied to two fossil pollen records. The results of this exercise showed that cool steppe dominated in central Greece between 18 000 and 13 000 yr BP, while in western Iran the vegetation was at the boundary between cool and warm steppes. These vegetation types were replaced by warm mixed forest in Greece and warm steppe in Iran after that time span. © 1998 John Wiley & Sons, Ltd. 相似文献
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Frédéric Delarue Fatima Laggoun-Défarge Alexandre Buttler Sébastien Gogo Vincent E.J. Jassey Jean-Robert Disnar 《Organic Geochemistry》2011,42(9):1016-1024
In a future warmer world, peatlands may change from a carbon sink function to a carbon source function. This study tracks changes in water-extractable organic matter (WEOM) after 1 year of in situ experimental warming using open top chambers (OTCs). WEOM was studied in the upper peat layers (0–10 cm) through analysis of water-extractable organic carbon (WEOC), stable C isotopic composition (δ13C), specific UV absorbance at 280 nm and sugar composition of cores taken from an open bog (DRY sites) and a transitional poor fen (WET sites). At the DRY sites, the impact of OTCs was weak with respect to WEOM parameters, whereas at the WET sites, the air warming treatment led to a decrease in peat water content, suggesting that the supply of heat by OTCs was used mainly for evapotranspiration. OTCs at the WET sites also induced a relative enrichment at the surface (0–5 cm depth) of aliphatic and/or aromatic compounds with concomitant decrease in WEOC, as a result of decomposition. On the contrary, WEOC and sugar content increased in the deeper peat layer (7.5–10 cm depth) probably as a result of increased leaching of phenolic compounds by roots, which then inhibits microbial activity. The different response to experimental warming at DRY and WET sites suggests that the spatial variability of moisture is critical for understanding of the impact of global warming on the fate of OM and the carbon cycle in peatlands. 相似文献
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Yves Missenard Omar Saddiqi Jocelyn Barbarand Pascale Leturmy Geoffrey Ruiz Fatima‐Zahra El Haimer Dominique Frizon de Lamotte 《地学学报》2008,20(3):221-228
In North Africa, the High Atlas belt culminates at more than 4000 m. In Morocco, recent work shows that a lithospheric thinning explains about 1000 m of the mean topography, the remaining topography being related to crustal shortening. We combine regional geology with new apatite fission‐track (AFT) ages to constrain the timing of these events in the Marrakech High Atlas (MHA). In the inner belt, 10 AFT ages are comprised between 9 ± 1 and 27 ± 3 Ma. These Neogene ages indicate that the MHA underwent significant denudation during that time. In the southern foreland domain of the belt, three samples give scattered AFT ages between 27 ± 2 and 87 ±5 Ma. Geological evidences allow us to constrain the age of a major denudation event during Middle Miocene age. We propose that it is linked to the thermal doming highlighted in the whole Moroccan Atlas domain. 相似文献
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Numerical simulation of the probability distribution function of precipitation over Morocco 总被引：1，自引：0，他引：1
A variable resolution version of the global GCM ARPEGE is constructed, so that Morocco has maximum resolution. A 30-year simulation, driven by observed sea surface temperature 1971–2000, is carried out. This paper examines the precipitation over northern Morocco during the extended winter season (from October to March), comparing model simulations with daily values at 14 stations. An approach utilising weather regimes has been adopted. The model is successful in representing the frequency and the interannual variability of the regimes. The precipitation over Morocco differs from one regime to another, but the model is not enough rainy along the Atlantic coast in general. The model is too persistent with too long dry spells, but is able to produce heavy rainfall as well as long dry periods in the centre of the area. 相似文献
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Fniguire Fatima Laftouhi Nour-Eddine Saidi Mohamed Elmehdi Zamrane Zineb El Himer Hicham Khalil Nourddine 《Theoretical and Applied Climatology》2017,129(1-2):321-339
Theoretical and Applied Climatology - The multiple downscaled scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future... 相似文献
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Toxic hexavalent chromium reduction by Bacillus pumilis,Cellulosimicrobium cellulans and Exiguobacterium 总被引：1，自引：0，他引：1
Three bacterial strains B acillus pumilis,Cellulosimicrobium cellulans and Exiguobacterium were investigated when grown in Luria-Bertani(LB) medium at 500 μg/m L Cr(VI). The hexavalent chromium reduction was measured by growing the strains in De Leo and Ehrlich(1994) medium at 200 and 400 μg/m L K 2 Cr O 4. The optimal Cr(VI) reduction by strains B. pumilis,Exigubacterium and C. cellulans was 51%,39%,and 41%,respectively,at an initial K2 Cr O 4 concentration of 200 μg/m L at p H 3 and temperature 37°C. At an initial chromate concentration of 400 μg/m L,the Cr(VI) reduction by strains B. pumilis,Exigubacterium and C. cellulans was 24%,19%,and 18%,respectively at p H 3 at 37°C after 24 h. These strains have ability to reduce toxic hexavalent chromium to the less mobile trivalent chromium at a wide range of different environmental conditions and can be useful for the treatment of contaminated wastewater and soils. 相似文献
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Ahmad Hammad Ali Asad Fatima Syeda Hira Zaidi Farrah Khisroon Muhammad Rasheed Syed Basit Ullah Ihsan Ullah Saleem Shakir Muhammad 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(7):1023-1036
Stochastic Environmental Research and Risk Assessment - During the span of August–October, 2017 a major outbreak of Dengue fever happened in Khyber Pakhtunkhwa province of Pakistan. Cases... 相似文献