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1.
Holocene pine tree-line evolution in the Swedish Scandes: Recent tree-line rise and climate change in a long-term perspective 总被引：1，自引：0，他引：1
LEIF KULLMAN LENA KJÄLLGREN 《Boreas: An International Journal of Quaternary Research》2006,35(1):159-168
This article focuses on the Holocene tree line (Pinus sylvestris) and climate change in the Swedish Scandes. A composite of three previously independently published data sets of megafossil tree remains (trunks, stumps and roots) from sites above today's tree line is analysed. Calibration of ages, adjustment for glacio-isostatic land uplift and a larger sample provide new and more conclusive insights. The tree-line altitude peaked about 11 200 cal. yr BP, 425 m higher than the position about a century ago, when it was at its Holocene low. At the millennial-centennial scale, tree-line retraction has been a smooth process, following a linear trend, which largely conforms to the Milankovitch model of orbital forcing of summer temperature evolution. Shorter excursions from this trend cannot be ruled out, as these are beyond the resolution of the analytical approach. During the earliest Holocene, summers may have been about 2.5°C warmer than by the late-19th century. Projection of the 20th-century maximum tree-line rise by 150-190 m upon the entire Holocene tree-line chronology indicates that present-day tree lines may be higher than ever during the past 5000 or even 7000 years. Indirectly, this might reflect an anomalous modern climatic regime for which there is supporting evidence from retreating mountain glaciers and recent evolution of the alpine plant cover and its zonation patterns. With this background, the evolution of the tree-line ecotone in the case of continued warming is considered. Pine is likely to regain the dominant position held in the early Holocene. Its tree line may shift at least 400 m above its present position. Small outlier stands of mountain birch will establish in sheltered, moderately snow-rich habitats high above the new pine tree line, but an overall alpine character of the landscape will prevail above the tree line of pine. Exotic tree species, mainly belonging to the genus Pinus may profit from a new climatic regime and establish in the tree-line ecotone. 相似文献
2.
ABSTRACT Standard hydrological methods have been used to evaluate the water balance of a Central American river basin located in Costa Rica, for the purpose of appraising its water resources potential. Estimates are made of the present utilization of water by each major sectorial user, and a comparison of demand and supply is presented that enables the determination of the degree of present utilisation of water resources. 相似文献
3.
G. J. ROELOFS P. KASIBHATLA L. BARRIE D. BERGMANN C. BRIDGEMAN M. CHIN J. CHRISTENSEN R. EASTER J. FEICHTER A. JEUKEN E. KJELLSTRÖM D. KOCH C. LAND U. LOHMANN P. RASCH 《Tellus. Series B, Chemical and physical meteorology》2001,53(5):673-694
The COSAM intercomparison exercise (comparison of large‐scale sulfur models) was organized to compare and evaluate the performance of global sulfur cycle models. Eleven models participated, and from these models the simulated surface concentrations, vertical profiles and budget terms were submitted. This study focuses on simulated budget terms for the sources and sinks of SO2 and sulfate in three polluted regions in the Northern Hemisphere, i.e., eastern North America, Europe, and Southeast Asia. Qualitatively, features of the sulfur cycle are modeled quite consistently between models, such as the relative importance of dry deposition as a removal mechanism for SO2 , the importance of aqueous phase oxidation over gas phase oxidation for SO2 , and the importance of wet over dry deposition for removal of sulfate aerosol. Quantitatively, however, models may show large differences, especially for cloud‐related processes, i.e., aqueous phase oxidation of SO2 and sulfate wet deposition. In some cases a specific behavior can be related to the treatment of oxidants for aqueous phase SO2 oxidation, or the vertical resolution applied in models. Generally, however, the differences between models appear to be related to simulated cloud (micro‐)physics and distributions, whereas differences in vertical transport efficiencies related to convection play an additional rôle. The estimated sulfur column burdens, lifetimes and export budgets vary between models by about a factor of 2 or 3. It can be expected that uncertainties in related effects which are derived from global sulfur model calculations, such as direct and indirect climate forcing estimates by sulfate aerosol, are at least of similar magnitude. 相似文献
4.
Deglaciation of western Central Norway 总被引：4，自引：0，他引：4
JOHAN LUDVIG SOLLID LEIF SØRBEL 《Boreas: An International Journal of Quaternary Research》1979,8(2):233-239
The glacier movements and corresponding ice margins in Central Norway during Younger Dryas and Preboreal are reconstructed. Scattered, older marginal deposits are difficult to correlate. Raised beach features indicate that the deep fjords became ice-free at an early stage due to calving. In Møre og Romsdal county the glacier front lay at the fjord heads during Younger Dryas, with extensive local glaciation in the intervening mountain areas, and a limit of glaciation 500–600 m lower than the present. In certain places local moraines older than Younger Dryas have been preserved. Autochthonous block fields are widespread in the mountains of Møre og Romsdal. The lower limit of block fields lies at c. 500 m above sea level on the outermost coast and rises to c. 1500 m above sea level in the interior fjord country. No erratics, striation or lateral moraines from the inland ice have been found above this limit. Its gradient, which in outer fjord districts is about 1%, seems to indicate the ice surface at the last maximum of Weichsel glaciation. 相似文献
5.
LEIF KULLMAN 《Boreas: An International Journal of Quaternary Research》1998,27(3):153-161
Early-Holocene occurrences of broad-leaved temperate tree species at a site now within the subalpine belt of the Swedish Scandes are reported and analysed. Macrofossil remains (fruits and leaves) of Alnus glutinosa, Corylus avellana, Quercus robur and Ulmu.s glahra were recovered in a peat deposit far beyond and above their modern distributional limits. A previous nearby finding of Tilia cantata adds to this group of Hemiboreal lowland species, the regional presence of which in high-elevation northern Scandinavia has gone entirely unrecognized by pollen stratigraphical studies. Radiocarbon dates (AMS) range between 8500 and 8000 BP, indicating early and rapid spread, closely following the ice recession. Maximum tree species richness and distributional limits (latitude and altitude) were attained during the earliest part of the Holocene. In a regional perspective, the temperate trees coexisted with a dominant boreal (cold-climate) element, viz. Pinus sylvestris, Bclulu pubescens ssp. tortuosa, Betula pendula, Alnus incana, Picea ahies and Larix sibirica, which are all identified and dated from macrofossils. This climatically seemingly incompatible assemblage is without modern analogues. Presumably, this diverse tree flora owed its existence to a unique (Holocene perspective) climatic regime, ultimately forced by the Milankovitch cycles of insolation. The results strengthen previous palaeoclimatic inferences based on past tree-limit positions (Pinus sylvestris) and imply that Holocene summer warmth peaked fairly soon after the regional deglaciation, practically concurrently with the solar radiation maximum. Important questions are raised concerning several palynologically derived postulates within general palaeobiogeography. For example, rates of geographic tree spread are not necessarily individualistic, despite fundamentally different dispersal modes. The emergent efficiency of dispersal suggests that distribution patterns relate to climate and soil factors rather than time. Dispersal steps may have been fairly large, and the resultant geographic spread was epidemic, resulting in a sparse pattern of outlying stands, rather than sequentially following certain routes in the landscape. Rapid geographic expansion is likely to have been relatively unrestrained by physical barriers, e.g. mountain ranges, seas and large lakes. Even in Central Europe, close to the ice margin, there may have been more trees during the latest glaciation than previously realized. 相似文献
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7.
Jutta ZIPFEL Bradley L. JOLLIFF Ralf GELLERT Kenneth E. HERKENHOFF Rudolf RIEDER Robert ANDERSON James F. BELL III Johannes BRÜCKNER Joy A. CRISP Philip R. CHRISTENSEN Benton C. CLARK Paulo A.
De SOUZA Jr. Gerlind DREIBUS Claude
D’USTON Thanasis ECONOMOU Steven P. GOREVAN Brian C. HAHN Göstar KLINGELHÖFER Timothy J. McCOY Harry Y. McSWEEN Jr. Douglas W. MING Richard V. MORRIS Daniel S. RODIONOV Steven W. SQUYRES Heinrich WÄNKE Shawn P. WRIGHT Michael B. WYATT Albert S. YEN 《Meteoritics & planetary science》2011,46(1):1-20
Abstract– The Opportunity rover of the Mars Exploration Rover mission encountered an isolated rock fragment with textural, mineralogical, and chemical properties similar to basaltic shergottites. This finding was confirmed by all rover instruments, and a comprehensive study of these results is reported here. Spectra from the miniature thermal emission spectrometer and the Panoramic Camera reveal a pyroxene‐rich mineralogy, which is also evident in Mössbauer spectra and in normative mineralogy derived from bulk chemistry measured by the alpha particle X‐ray spectrometer. The correspondence of Bounce Rock’s chemical composition with the composition of certain basaltic shergottites, especially Elephant Moraine (EET) 79001 lithology B and Queen Alexandra Range (QUE) 94201, is very close, with only Cl, Fe, and Ti exhibiting deviations. Chemical analyses further demonstrate characteristics typical of Mars such as the Fe/Mn ratio and P concentrations. Possible shock features support the idea that Bounce Rock was ejected from an impact crater, most likely in the Meridiani Planum region. Bopolu crater, 19.3 km in diameter, located 75 km to the southwest could be the source crater. To date, no other rocks of this composition have been encountered by any of the rovers on Mars. The finding of Bounce Rock by the Opportunity rover provides further direct evidence for an origin of basaltic shergottite meteorites from Mars. 相似文献
8.
L. A. BARRIE Y. YI W. R. LEAITCH U. LOHMANN P. KASIBHATLA G.&#;J. ROELOFS J. WILSON F. McGOVERN C. BENKOVITZ M. A. MÉLIÈRES K. LAW J. PROSPERO M. KRITZ D. BERGMANN C. BRIDGEMAN M. CHIN J. CHRISTENSEN R. EASTER J. FEICHTER C. LAND A. JEUKEN E. KJELLSTRÖM D. KOCH P. RASCH 《Tellus. Series B, Chemical and physical meteorology》2001,53(5):615-645
9.
ANDERS LINDROTH FREDRIK LAGERGREN MIKA AURELA BRYNHILDUR BJARNADOTTIR TORBEN CHRISTENSEN EBBA DELLWIK ACHIM GRELLE REAS IBROM TORBJÖRN JOHANSSON HARRY LANKREIJER SAMULI LAUNIAINEN TUOMAS LAURILA MEELIS MÖLDER EERO NIKINMAA KIM PILEGAARD BJARNI D. SIGURDSSON TIMO VESALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(2):129-142
10.
Relaxation of soil variables in a regional climate model 总被引：2，自引：0，他引：2
OLE BØSSING CHRISTENSEN 《地球，A辑:动力气象学与海洋学》1999,51(5):674-685