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Sensitive Regions (sensitive + regions)
Selected AbstractsLate-glacial and Holocene climatic effects on fire and vegetation dynamics at the prairie,forest ecotone in south-central MinnesotaJOURNAL OF ECOLOGY, Issue 5 2003Philip Camill Summary 1Treeline ecotones, such as the prairie,forest boundary, represent climatically sensitive regions where the relative abundance of vegetation types is controlled by complex interactions between climate and local factors. Responses of vegetation and fire to climate change may be tightly linked as a result of strong feedbacks among fuel production, vegetation structure and fire frequency/severity, but the importance of these feedbacks for controlling the stability of this ecotone is unclear. 2In this study, we examined the prairie,forest ecotone in south-central Minnesota using two lake sediment cores to reconstruct independent records of climate, vegetation and fire over the past 12 500 years. Using pollen, charcoal, sediment magnetic analyses and LOI properties, we investigated whether fires were controlled directly by climate or indirectly by fuel production. 3Sediment magnetic and LOI data suggest four broad climatic periods occurring c. 11 350,8250 BP (cool/humid), c. 8250,4250 BP (warm/dry), c. 4250,2450 BP (warm/humid), and c. 2450,0 BP (cool/humid), indicating that, since the mid-Holocene, climate has shifted towards wetter conditions favouring greater in-lake production and fuel production on the landscape. 4The area surrounding both lakes was characterized by boreal forest c. 12 500,10 000 BP, changing to an Ulmus-Ostrya forest c. 10 000,9000 BP, changing to a community dominated by prairie (Poaceae-Ambrosia-Artemisia) and deciduous forest taxa c. 8000,4250 BP, and finally shifting to a Quercus -dominated woodland/savanna beginning c. 4250,3000 BP. 5Charcoal influx increased from an average of 0.11,0.62 mm2 cm,2 year,1 during the early Holocene forest period (c. 11 350,8250 BP) to 1.71,3.36 mm2 cm,2 year,1 during the period of prairie expansion (c. 8250,4250 BP) and again increased to 4.18,4.90 mm2 cm,2 year,1 at the start of the woodland/savanna period (c. 4250 BP). 6As a result of the influence of climate on community composition and fuel productivity, changes in fire severity may be the result and not the cause of shifts in vegetation. [source] Deglacial seasonal and sub-seasonal diatom record from Palmer Deep, Antarctica,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2005Eleanor J. Maddison Abstract The Antarctic Peninsula is one of the most sensitive regions of Antarctica to climate change. Here, ecological and cryospheric systems respond rapidly to climate fluctuations. A 4.4,m thick laminated diatom ooze deposited during the last deglaciation is examined from a marine sediment core (ODP Site 1098) recovered from Basin I, Palmer Deep, western Antarctic Peninsula. This deglacial laminated interval was deposited directly over a glaciomarine diamict, hence during a globally recognised period of rapid climate change. The ultra-high-resolution deglacial record is analysed using SEM backscattered electron imagery and secondary electron imagery. Laminated to thinly bedded orange-brown diatom ooze (near monogeneric Hyalochaete Chaetoceros spp. resting spores) alternates with blue-grey terrigenous sediments (open water diatom species). These discrete laminae are interpreted as austral spring and summer signals respectively, with negligible winter deposition. Sub-seasonal sub-laminae are observed repeatedly through the summer laminae, suggesting variations in shelf waters throughout the summer. Tidal cycles, high storm intensities and/or intrusion of Circumpolar Deep Water onto the continental shelf introduced conditions which enhanced specific species productivity through the season. Copyright © 2005 John Wiley & Sons, Ltd. [source] Denaturant sensitive regions in creatine kinase identified by hydrogen/deuterium exchangeRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2005Hortense Mazon The GdmHCl-induced unfolding of creatine kinase (CK) has been studied by hydrogen/deuterium (H/D) exchange combined with mass spectrometry. MM-CK unfolded for various periods in different denaturant concentrations was pulsed-labeled with deuterium to identify different conformational intermediate states. For all denaturation times or GdmHCl concentrations, we observed variable proportions of only two species. The low-mass envelope of isotope peaks corresponds to a species that has gained about 10 deuteriums more than native CK, and the high-mass envelope to a completely deuterated species. To localize precisely the unfolded regions in the states highly populated during denaturation, the protein was digested with two proteases (pepsin and type XIII protease) after H/D exchange and rapid quenching of the reaction. The two sets of fragments obtained were analyzed by liquid chromatography coupled to mass spectrometry to determine the deuterium level in each fragment. Bimodal distributions of deuterium were found for most peptides, indicating that these regions were either folded or unfolded. This behavior is consistent with cooperative, localized unfolding. However, we observed a monomodal distribution of deuterium in two regions (1,12 and 162,186). We conclude that the increment of mass observed in the low-mass species of the intact protein (+10,Da) has its origin in these two segments. These regions, which are very sensitive to low GdmHCl concentrations, are involved in the monomer,monomer interface of CK and their perturbation is likely to weaken the dimeric structure. At higher denaturant concentration, this would induce dissociation of the dimer. Copyright © 2005 John Wiley & Sons, Ltd. [source] The value of observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 628 2007III: Influence of weather regimes on targeting Abstract This paper assesses the value of targeted observations over the North Atlantic Ocean for different meteorological flow regimes. It shows that during tropical cyclone activity and particularly tropical cyclone transition to extratropical characteristics, removing observations in sensitive regions, indicated by singular vectors optimized on the 2-day forecast over Europe, degrades the skill of a given forecast more so than excluding observations in randomly selected regions. The maximum downstream degradation computed in terms of spatially and temporally averaged root-mean-square error of 500 hPa geopotential height is about 13%, a value which is 6 times larger than when removing observations in randomly selected areas. The forecast impact for these selected periods, resulting from degrading the observational coverage in sensitive areas, was similar to the impact found (elsewhere in other weather forecast systems) for the observational targeting campaigns carried out over recent years, and it was larger than the average impact obtained by considering a larger set of cases covering various seasons. Copyright © 2007 Royal Meteorological Society [source] Modelling the wet deposition of reduced nitrogen over the British Isles using a Lagrangian multi-layer atmospheric transport modelTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 606 2005N. Fournier Abstract Wet deposition of reduced nitrogen is estimated for the United Kingdom using a Lagrangian long-term, long-range atmospheric transport model. Such long-range transport models are used to develop emission-control strategies to combat environmental acidification in the sensitive regions of the United Kingdom and Europe. These models currently consider the wet deposition as a loss term using scavenging rates and a simple seeder,feeder effect. The seeder,feeder effect is assumed to be the main process producing orographic precipitation since the majority of British Isles annual rainfall falls in frontal events. This paper focuses on the analysis of different parametrizations of the removal process by wet deposition. It is shown that the seeder,feeder effect is very dependent on flow direction. Therefore, a model of directional orographic enhancement of precipitation is developed to simulate this effect. A revised formulation of the wet deposition parametrization is suggested, incorporating the directional orographic precipitation produced with this model. This new formulation also takes into account the larger concentrations of ions dissolved in rain water measured in mountainous areas. Moreover, a new representation of the wet deposition process is developed by considering explicitly the mixing layer's depth calculated in the model. The results from the atmospheric model, with these revised parametrizations of the wet deposition, are then compared with measured wet deposition of reduced nitrogen. Firstly, with the new directional orographic rainfall, the modelled United Kingdom reduced nitrogen wet deposition budget is still underestimated but an increased correlation with measurements is obtained. Secondly, the inclusion of the calculated mixing layer's depth leads to a considerable improvement in the modelled reduced nitrogen wet deposition budget compared with measurements. Copyright © 2005 Royal Meteorological Society. [source] Corn ethanol growth in the USA without adverse foreign land-use change: defining limits and devising policiesBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 3 2010Paul W. Gallagher Abstract This study addresses the question: ,How does a 15 billion gallon per year renewable fuel standard (RFS) compare to the capacity of the US corn market to generate necessary input supplies for the ethanol industry?' The analysis accounts for adjustments in world corn and soybean markets, including corn technology improvements (yield increases) that allow substantial production growth on the existing corn area, and byproduct (DDG) replacement of displaced corn-feed demand. Our midpoint estimate suggests that increased production on foreign lands only accounts for a small fraction (6%) of the RFS demand expansion. Further, corn yield response to moderate price increases would likely offset much of the foreign production increase. US policies that could sever any remaining link between US ethanol expansion and environmentally sensitive regions of the world feed economy are discussed. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd [source] | ||||||||||