Stable isotopes in tree rings are the important approaches in climate reconstruction and in studies on tree response to environmental factors in the past,such as the maximum latewood density,tree ring width and other tree ring parameters.In this paper,the tree-ring samples of Larix sibirica Ledeb.collected in south slope of the Altay Mountains in 2009 were used to develop the tree-ring width chronology and stable carbon isotope series based on the standard Dendrochronology methods and stable carbon isotope research achievements.It can establish the de-trend series(DS) of stable carbon isotope of tree rings to eliminate atmospheric CO2 effect from original δ13C.The stable carbon isotope series values of L.sibirica tree rings varied in a range of-22.8‰——25.4‰,The average value was-24.0‰,and the coefficient of variation was-0.017.Width chronology and stable carbon isotope de-trend series were compared with monthly climatic factors(mean temperature,mean maximum temperature,mean minimum temperature,precipitation,relative humidity and sunshine duration) at Fuyun Meteorological Station.Correlation analysis revealed that there was a strong positive correlation between the stable carbon isotope de-trend series and the mean temperature and mean maximum temperature but a negative one between it and the relative humidity in growing season.The correlation coefficient between the de-trend series of stable carbon isotope and the monthly maximum temperature in June and July was as high as 0.611(P0.000 001),that between it and the monthly relative humidity in June and July was-0.493(P0.001),and that between it and monthly precipitation in July was-0.459(P0.01).The response of stable carbon isotope of L.sibirica tree rings to temperature and relative humidity in growing season was the most sensitive.The main factor affecting stable carbon isotope of L.sibirica was the monthly maximum temperature in June and July.
In this paper,the tree-ring samples of Picea schrenkiana Fisch.et Mey,which were collected from five sites in Aksu River basin on the south slopes of Tianshan Mountains in 2005,are used to develop tree-ring width chronolgies based on standard dendrochronological and dendrohydrology methods.Single correlation calculation indicated that the correlation coefficient is 0.611(degree of confidence is much greater than the 99.9 percent)between ZDH standard width chronologies and annual runoff of Aksu River.The result has distinct physiological significance,based on which a runoff series of 300 years is well reconstructed.It is verified that the reconstructed runoff is reliable by leave-one-out.The following results are obtained by analyzing the 300 a reconstructed runoff series: 1) there were significant change cycles of 2.65 a,4.98 a and 51a;with 4 abrupt changes in 1722,1753,1799,1829;2) the runoff of Aksu River has distinctly increased in the past 45 year along with global warming,but the increasing speed has not been the fastest and the annual runoff has not reached the maximum in the past 300 year.Annual runoff averaged over the past 300 year is 109.47×108 m3·a-1,with the maximum of 109.47×108 m3·a-1 and the minimum of 43.28×108 m3·a-1;the coefficient of variation of the reconstructed runoff series is 0.16,which demonstrates that the primary supply sources of the Aksu River is snow-ice meltwater.The frequency of extreme high flow year is less than that of low flow year;consequently the flood-waterlogging damage is few;3) research on the decadal change of runoff and coefficient of variation during the last 100 years revealed that there were a partial high flow period in the 1900s,a partial low flow period in the 1910s,a normal flow period from the 1920s to the 1960s,a partial low flow period from the 1970s to the 1980s and a high flow period after the 1990s.Flood-waterlogging damages were most frequent in the 1950s;4) lag cross correlation analysis indicates that there is high correlation between annual runoff and Arctic Oscillation(AO) and the annual runoff has pronounced lag response to AO.
Abstract Revealing hydrologic variations in the past is helpful to understand the dynamic changes and evolution of a given water body. The widespread long-lived spruce forests growing in the mountainous area around Issyk Lake in Central Asia provide a good opportunity for dendrohydrologic studies about that lake. A regional tree-ring width chronology developed for Picea schrenkiana was used to reconstruct 345-year annual runoff for Issyk Lake. Based on frequency of the wettest/driest years and decades, the 20th century was identified as having the most frequent hydrologic fluctuations among the last three centuries. After applying a 21-year moving average, seven wet and six dry periods were found in the runoff reconstruction. The 10- and 2.1–5.4-year cycles of this reconstruction revealed that annual runoff variability of Issyk Lake may be influenced by solar activity and the atmosphere–ocean system. Spatial correlation proves that the runoff reconstruction contains climatic signals representative of a large area, including the western Tien Shan Mountains and Junggar Basin. A comparison between the annual runoff reconstruction and other hydroclimatic reconstructions reveals similar variations, particularly in the high-frequency domain. The annual runoff reconstruction also accurately captures some flood/drought events noted in the meteorological records and hydroclimatic reconstructions of Central Asia.
Forty-one living larch (<i>Larix principis</i>-<i>rupprechtii</i>) trees collected from two sampling sites in 1310–1530 m a.s.l. in the southern Greater Higgnan Mountains in the northeastern China are used to develop a regional tree-ring width chronology. The credible chronology spans 185 years from 1830 to 2014. The results of correlation analyses indicate that moisture is the main climatic factor controlling radial growth of larch trees in this mountainous area. Spatial correlation proves that the regional tree-ring width chronology contains climatic signals representative for a large area including the eastern Mongolian Plateau and Nuluerhu Mountains. A comparison between the newly developed chronology and a May–July Palmer Drought Severity Index (PDSI) reconstruction for the Ortindag Sand Land reveals similar variations, particularly in the low-frequency domain. The tree-ring records also capture a severe and sustained drying trend recorded in the 1920s across a wide area of northern China.
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