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Bao Yang Dmitry M. Sonechkin Nina M. Datsenko Nadezda N. Ivashchenko Jingjing Liu Chun Qin 《Theoretical and Applied Climatology》2011,106(3-4):489-497
Based on a set of very long-living (2,000?years) Qilian junipers (Sabina przewalskii Kom.) from the north-eastern part of the Tibetan Plateau (the region of Dulan), we carefully consider the regional curve standardization (RCS) technique. For this goal, we correlate deviations of individual tree-ring width records from their regional mean age-dependent curve (RC). It turns out that these correlations keep their positivity for almost all shifts between ages compared (up to 500?years and even more) evidencing each Dulan juniper to be a unique ??thermometer??. Just the unification of these ??thermometers?? in the form RC creates a spurious positive trend in the Dulan chronology. We modify the RCS technique to closer attach RC to these ??thermometers?? in order to construct a new chronology in which the trend is absent. 相似文献
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Amber J. Soja Nadezda M. Tchebakova Nancy H.F. French Michael D. Flannigan Herman H. Shugart Brian J. Stocks Anatoly I. Sukhinin E.I. Parfenova F. Stuart Chapin III Paul W. Stackhouse Jr. 《Global and Planetary Change》2007,56(3-4):274
For about three decades, there have been many predictions of the potential ecological response in boreal regions to the currently warmer conditions. In essence, a widespread, naturally occurring experiment has been conducted over time. In this paper, we describe previously modeled predictions of ecological change in boreal Alaska, Canada and Russia, and then we investigate potential evidence of current climate-induced change. For instance, ecological models have suggested that warming will induce the northern and upslope migration of the treeline and an alteration in the current mosaic structure of boreal forests. We present evidence of the migration of keystone ecosystems in the upland and lowland treeline of mountainous regions across southern Siberia. Ecological models have also predicted a moisture-stress-related dieback in white spruce trees in Alaska, and current investigations show that as temperatures increase, white spruce tree growth is declining. Additionally, it was suggested that increases in infestation and wildfire disturbance would be catalysts that precipitate the alteration of the current mosaic forest composition. In Siberia, 7 of the last 9 yr have resulted in extreme fire seasons, and extreme fire years have also been more frequent in both Alaska and Canada. In addition, Alaska has experienced extreme and geographically expansive multi-year outbreaks of the spruce beetle, which had been previously limited by the cold, moist environment. We suggest that there is substantial evidence throughout the circumboreal region to conclude that the biosphere within the boreal terrestrial environment has already responded to the transient effects of climate change. Additionally, temperature increases and warming-induced change are progressing faster than had been predicted in some regions, suggesting a potential non-linear rapid response to changes in climate, as opposed to the predicted slow linear response to climate change. 相似文献
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Bao Yang Dmitry M. Sonechkin Nina M. Datsenko Nadezda N. Ivashchenko Jingjing Liu Chun Qin 《Theoretical and Applied Climatology》2012,107(1-2):131-141
The technique of expanding meteorological fields on eigenvectors of the field covariation matrix is popular. In this paper, we propose for the first time to use a mathematically similar technique to solve the main problem of dendrochronology: classifying variations in tree-ring records as either age- and microenvironment-dependent or climate-induced. Applying this technique to a sample of very long-lived Qilian junipers (Sabina przewalskii Kom.) from the Dulan region in western China, we demonstrate that the ring-width variations projected on the first eigenvector are age-dependent, but those projected on several of the first subsequent vectors are mainly climate-induced. In particular, the second and third projections capture multi-centennial climatic variations, and the variations projected on the fourth through seventh eigenvectors show periodic variations that are probably induced by the 178-year solar cycle. The projections on the smallest eigenvectors seem to be negligible. 相似文献
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Nadezda Degermendzhy 《湖泊科学》1998,10(S1):411-419
The ecological forecasting of microorganisms and water quality dynamics in Krasnoyarsk Reservoir is based on knowledge of dependence of specific growth rate (SGR) on limiting substrata. It investigated the influence of soil extract on the growth autochtonic (bacterioplankton of Krasnoyarsk Reservoir. The maximum SGR and Michaelis-Menten constant (on chemical oxidation decomposition (COD)-permanganate) is determined. These parameters are used in eco-model of Krasnoyarsk Reservoir and the Yenisei River to estimate the payojf of self-purification. 相似文献
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Vladimir Pinsky Tatiana Meirova Anatoli Levshin Abraham Hofstetter Nadezda Kraeva Mikhail Barmin 《Journal of Seismology》2013,17(2):385-397
For the purpose of studying the Earth’s crust by means of tomography, we investigated cross-correlation functions emerging from long-term observations of propagating ambient seismic noise at pairs of broadband stations in Israel and Jordan. The data was provided by the eight permanent broadband stations of the Israel Seismic Network evenly distributed over Israel and the 30 stations of the DESERT2000 experiment distributed across the Arava Fault (South of the Dead Sea basin). To eliminate the influence of earthquakes and explosions, we have applied the methodology of Bensen et al. (Geophys J Int 169:1239–1260, 2007), including bandpass filtering and amplitude normalization in time and frequency domain. The cross-correlation functions estimated from continuous recordings of a few months were used to extract Rayleigh waves group velocity dispersion curves using automatic version of the frequency–time analysis procedure. Subsequently, these curves have been converted into the Rayleigh wave group velocity maps in the period range 5–20 s and S waves velocity maps in the depth range 5–15 km. In these maps, four velocity anomalies are prominent. Two of them are outlined by the previous reflection-refraction profiles and body wave tomography studies, i.e. a low velocity anomaly corresponds to the area of the extremely deep (down to 14 km) sedimentary infill in the Southern Dead Sea Basin and a high velocity anomaly in the Southern Jordan corresponds to the area of the Precambrian crystalline rocks of the Nubian Shield on the flanks of the Red Sea. The two other anomalies have not been reported before - the high velocity zone close to the Beersheba city and the low velocity anomaly in the region of Samaria-Carmel mountains - Southern Galilee. They have relatively low resolution and hence need further investigations for approving and contouring. The highest contrast between the average Rayleigh wave group velocity (2.7 km/s) and the anomalies is 10–13 %, comparable, however, to the level of noise in the data. The results have been verified by modeling the revealed anomalies which showed that all the four zones mentioned above could be detected by the tomography study. 相似文献
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Bao Yang Dmitry M. Sonechkin Nina M. Datsenko Nadezda N. Ivashchenko Jingjing Liu Chun Qin 《Theoretical and Applied Climatology》2012,107(3-4):519-530
This paper reports on the further development of a new technique for standardization of tree-ring records called the eigen analysis of tree-ring records. The data are from the same sample set of 56 long-lived Qilian junipers (Sabina przewalskii Kom.) from the Dulan region in western China as was used in our previous paper (Yang et al. 2011b). To assess the heteroscedasticity of individual record deviations from the sample set regional curve (RC), we tested five different definitions of those deviations. Direct computations of eigenvectors of all relevant intrarecord covariation matrices turned out to be greatly affected by observational and computational noise; an analytic approximation of these vectors was therefore desirable. The Bessel function of the first kind and the zero order proved suitable for such an approximation, especially because the deviations were defined via subtraction of the RC from raw ring width records. Exclusion of the contributions of the first segment of the Bessel approximation, corresponding to the extremely large first eigenvalue, rendered individual record deviations from RC homoscedastic. Therefore, the routine Fourier basis became applicable to extract climate-dependent components of the residual deviations. A Fourier expansion of the Dulan chronology revealed the quasi-200-year-long solar activity cycle to be the main factor affecting Dulan tree growth. 相似文献
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