Carbon Stores, Sinks, and Sources in Forests of Northwestern Russia: Can We Reconcile Forest Inventories with Remote Sensing Results?     

Olga N. Krankina  Mark E. Harmon  Warren B. Cohen  Doug R. Oetter  Zyrina Olga  Maureen V. Duane 《Climatic change》2004,67(2):257-272

Forest inventories and remote sensing are the two principal data sources used to estimate carbon (C) stocks and fluxes for large forest regions. National governments have historically relied on forest inventories for assessments but developments in remote sensing technology provide additional opportunities for operational C monitoring. The estimate of total C stock in live forest biomass modeled from Landsat imagery for the St. Petersburg region was consistent with estimates derived from forest inventory data for the early 1990s (272 and 269 TgC, respectively). The estimates of mean C sink in live forest biomass also agreed well (0.36 and 0.34 Mg C ha^–1 yr^–1). Virtually all forest lands were accumulating C in live biomass, however when the net change in total ecosystem C stock was considered, 19% of the forest area were a net source of C. The average net C sink in total ecosystem biomass is quite weak (0.08 MgC ha^–1 yr^–1 and could be reversed by minor increases in harvest rates or a small decline in biomass growth rates.  相似文献   

Geomorphic Effects of the Extreme Rainfall Event of 20–21 July, 2004 in the Latnjavagge Catchment, Northern Swedish Lapland     

Achim A. Beylich  Olga Sandberg 《Geografiska Annaler: Series A, Physical Geography》2005,87(3):409-419

Mass transfers triggered by a rare rainfall event on 20–21 July, 2004, with 58.4 mm of rain within 24 h and 71.7 mm of rain within 48 h in the Latnjavagge catchment (9 km² , 950–1440 m a.s.l.; 68°20'N, 18°30'E) in the higher Abisko mountain region (Swedish Lapland), are quantified and analysed in direct comparison with mean annual mass transfers in this drainage basin. In years without rare rainfall events the Latnjavagge catchment is characterized by restricted sediment availability resulting in low mechanical denudation and mass transfers. During the rare rainfall event of 20–21 July, 2004, major stability thresholds on the slope systems (triggering debris flows and slides) and in the channel systems (break‐up of channel debris pavements and step–pool systems) in the Latnjavagge catchment were passed and mass transfers by debris flows, slides and fluvial debris transport in creeks and channels were several times higher than the mean annual mass transfers in Latnjavagge. In the calculation of longer‐term mass transfers and sediment budgets, rare events like the 20–21 July, 2004 rainfall event have to be considered as essential components. A reliable estimation of the recurrence intervals of such rare events is especially problematic. The general problem of defining an adequate length of process monitoring programmes is pointed out.  相似文献   

The Retreat of Tien Shan Glaciers (Kyrgyzstan) Since the Little Ice Age Estimated from Aerial Photographs, Lichenometric and Historical Data   总被引：2，自引：0，他引：2  

Olga Solomina  Roger Barry  Maria Bodnya 《Geografiska Annaler: Series A, Physical Geography》2004,86(2):205-215

The retreat of 293 glaciers in the Tien Shan Mountains (Kyrgyz Republic) from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25000, constructed during period 1956–1990. Two indices of changes are used: the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s to the 1930s was used as an indirect control of remote sensing data. The age of moraines in key regions was estimated by lichenometry. On average, Tien Shan glaciers have retreated by 989 ± 540 m since the LIA maximum. Their front elevations (dh) rose by 151 ± 105 m. These changes are similar to changes observed in the Alps and western Norway, Pamir‐Alay and Koryak plateau, but greater than in east Siberia over the same interval. Differences between four regions in Tien Shan (northern, western, inner, central) are generally small, though in the northern Tien Shan the glacier retreat and frontal rise are more prominent (1065 ± 479 m and 215 ± 140 m, respectively).  相似文献   

Comments about the drag laws used in hail growth simulations     

Nesvit E. Castellano  Olga B. Nasello 《Atmospheric Research》1997,43(4):315-323

The values of the drag coefficient (C_D), experimentally obtained by different authors for graupels and hailstones, are carefully analyzed, in order to investigate how the numerical simulations of hail trajectories, which markedly depend on the C_D values assigned to the growing particle, can be improved. It is found that new measurements of C_D should be performed in the whole range of the Reynolds number (Re) of the cloud ice particles. These measurements should be carried out applying the same criterion to define the characteristic variables (particle cross section and dimensions) used to calculate C_D and Re. Furthermore, it is found that the C_D fitting curves should be expressed as a function not only of Re but also of other parameters which represent the particle surface roughness and the departure from the spherical form. Based on this finding, a plausible definition of these variables and the way to introduce them in a hail trajectory calculation are proposed.  相似文献   

Haute cuisine versus healthy nutrition: cultural gradients in Europe and the geography of baby food     

Olga Gritsai 《GeoJournal》2001,53(1):71-80

The article deals with the problem, how the geography of baby food in Europe may be explained by cultural patterns, differences in healthcare systems and standards of living. A survey, conducted in 12 European countries, revealed differences and similarities in gastronomic preferences and healthcare attitudes. National food markets and dietary targets reflect the pressure of internationalization on cultural traditions. Special attention is paid to the adaptation strategies of multinationals, operating in different cultural environments. The requirements to the qualities of baby food (the emphasis on being healthy or rather tasty, the choice of producers, etc.) reflect the whole variety of lifestyles in European countries, their economic opportunities, stability of cultural traditions, innovative potential.  相似文献   

Composition,properties and radiocarbon age of humus in paleosols     

Olga A. Chichagova 《GeoJournal》1995,36(2-3):207-212

The paper presents methods for the study of the organic matter content (OM) of Pleistocene and Holocene paleosols. Paleosols of various age from the Russian Plain and Western Siberia were studied for their humus composition and physico-chemical properties. The permanent features of humus in paleosols useful for paleogeographical reconstruction and geoecological monitoring are separated from those criteria which are typical of the natural evolution of OM on the geological timescale.  相似文献   

Thermodynamic data for phases in the FeO-MgO-SiO2 system and phase relations in the mantle transition zone     

Olga B. Fabrichnaya 《Physics and Chemistry of Minerals》1995,22(5):323-332

Based on the available experimental data on phase equilibria in the FeO -MgO -SiO₂ system the mixing properties of the solid solutions (olivine, β- and γ-spinel, pyroxene, majorite, ilmenite and perovskite and magnesiowustite), the enthalpies of FeO and fictive FeSiO₃ phases with ilmenite and majorite structures have been assessed. The entropies, temperature dependance of heat capacities for fictive FeSiO₃ end-members were estimated from structural analogies. The calculated phase diagrams for Mg₂SiO₄-Fe₂SiO₄ and MgSiO₃ — FeSiO₃ systems at pressures up to 30 GPa and temperatures between 1000 and 2100 K are quite consistent with the available experimental determinations except for the fine features of the phase diagram at 2073 K.  相似文献   

Einsatzmöglichkeiten von Membranprozessen zur Beseitigung organischer Substanzen aus natürlichen Wässern     

I. Dobrevski  V. Mavrov  S. Pavlova 《洁净——土壤、空气、水》1986,14(5):551-554

Membrane-filtration or dialysis techniques are increasingly used for the partial desalting of waters, e.g. brackish waters. By the use of Bulgarian PAN and acetate-cellulose separating membranes there are eliminated also organic substances – inclusive of humic matter – from natural waters to different degrees. The experimental arrangement is described and the measured results for COD-Mn, concentrations of humic acid and specific electrolytic conductivity are summarized in tables. The humic acid concentration (2.8 mg/l) was reduced by about 79 % by ultrafiltration, 82 % by reverse osmosis and 62 % by electrodialysis. The efficiency of the investigated techniques could be increased under certain conditions.  相似文献   

Removal of trace elements from landfill leachate by calcite precipitation   总被引：1，自引：0，他引：1  

Vojtch Ettler  Olga Zelen  Martin Mihaljevi   Ond&#x;ej &#x;ebek  Ladislav Strnad  Pavel Coufal  Petr Bezdi ka 《Journal of Geochemical Exploration》2006,88(1-3):28

Spontaneous precipitation of secondary calcite (CaCO₃) has been observed in 25 samples of landfill leachate-polluted stream waters. During the 6-month precipitation experiment, the formation of calcite acts as a principal trace-element scavenging process. The concentrations of Fe, Sr, Ba and Mn and other trace elements in solution significantly decreased as calcite formed during the experiments. The PHREEQC-2 geochemical code indicated high supersaturation of the initial leachate-polluted waters with respect to calcite. The chemical/mineralogical study (SEM/EDS, XRD, ICP MS) revealed that this newly formed calcite contains considerable amounts of metals and metalloids removed from solution. Such a geochemical process can be considered to be important for spontaneous decontamination in landfill-affected environments (stream sediments, soils) or landfill technical facilities (settling basins). This removal takes place especially during dry periods with low rain precipitation, when the landfill waters exhibit both higher alkalinity and higher trace element concentrations.  相似文献   

Crustal microdeformations and tides in the coastal zone of the Sea of Japan     

V. V. Navrotsky  E. D. Kholodkevich  E. P. Pavlova  S. A. Smirnov 《Izvestiya Physics of the Solid Earth》2007,43(6):517-523

Based on experimental data and numerical modeling, the possible mechanisms of the effect of internal gravitational waves within the range of periods from tidal values to a few tens of minutes on crustal microdeformations in the coastal zone of the Sea of Japan are examined. The spectral analysis of oscillations in the sea level and microdeformations recorded in various seasons reveals common maximums of energy at diumal and semidiurnal periods, but the coincidence of the maximums at shorter periods is random and varies with time. The phase shifts between the surface tide and crustal deformations are also unstable in time. To explain the observed interrelations between the processes at sea and in the Earth’s crust, we modeled numerically the generation of internal tides, bores, and packets of short internal waves in terms of a nonlinear model of shallow water. It is shown that the observed effects can be caused (1) by the resonance between the wavelength of the internal tide and the shelf width and (2) by the reflection of bores and internal wave packets from a steep bottom and rocky shores or by their collapse.  相似文献