The climate of the past 1000 years is an important context for evaluating the recent climate warming.However,there are few 1000-year-long climate reconstructions with annual resolution in the Qing-hai-Tibet Plateau.In...The climate of the past 1000 years is an important context for evaluating the recent climate warming.However,there are few 1000-year-long climate reconstructions with annual resolution in the Qing-hai-Tibet Plateau.In this paper,a dendroclimatic analysis was conducted for the radial growth of Qilian juniper from the upper forest limit in Wulan,Qinghai Province.The results of correlation analysis between the tree-ring widths and the climate variables indicate that the growth of junipers at the upper forest limit is mainly limited by low temperatures of September,November and February of the pregrowth season,and July of the current growth season.There is no significant correlation between the tree-ring widths and precipitation.A mean temperature from the previous year's September to the current year's April was reconstructed for the Wulan area since A.D.1000.The reconstruction can explain 40.8% of the instrumental variance in the calibration period(1856―2002).The reconstruction shows that the 20th century is the warmest 100 years,and the 1990s is the warmest decade during the past 1000 years,while the coldest 100 years and decade occur at 1600―1699 and 1642―1651,respectively.The variations are verified well by the temperature reconstruction of the middle Qilian Mountain(QL) and the total organic carbon(TOC) in the Qinghai Lake sediments.The comparison of our reconstruction with the annual temperature reconstruction of extra-tropical Northern Hemisphere suggests that the climate of Wulan during the Medieval Warm Period is of obvious regional specialty,but there was a good response to the climate of hemispheric scales during the recent 400 years.展开更多
epartment of Wood Science, University of Hamburg, Hamburg D-21031, GermanyBased on three Chinese pine (Pinus tabulaeformis Carr.) and one Meyer spruce (Picea meyeri Rehd. et Wils.) ring-width chronologies, a 163-year ...epartment of Wood Science, University of Hamburg, Hamburg D-21031, GermanyBased on three Chinese pine (Pinus tabulaeformis Carr.) and one Meyer spruce (Picea meyeri Rehd. et Wils.) ring-width chronologies, a 163-year drought history was reconstructed in the eastern Ortindag Sand Land. All tree-ring chronologies show large inter-annual variations and strong common signals and fairly consistent variation between different chronologies, indicating that they are excellent proxy of regional climate. A regional chronology (RC) was established by averaging the four standard chronologies and further employed for the analysis and climatic reconstruction. The analysis revealed that tree growth is primarily limited by low precipitation in February-March and June-July and high temperature in May-July. In addition, RC has high correlations with the monthly Palmer drought severity index (PDSI) prior to and during the growing season because the PDSI considers the accumulation of the droughts. Response function analysis revealed that RC only exhibits significant correlations with the PDSI in June and July (close to the 95% significance level in May). Because May―July is a critical period for tree growth, the average May-July PDSI (PDSI5-7) was reconstructed back to 1842 using RC in the Ortindag Sand Land. The reconstruction can explain 52% of the PDSI variance and the equation was rather stable over time. It agrees well with the variation of the average dryness/wetness indices in North China,and captures the decline process of the East Asian summer monsoon since the mid-1960s. It is worth noting that the Ortindag Sand Land has experienced the most severe drought in the recent 40 years based on the 163-year drought reconstruction. Like summer precipitation in North China the reconstructed PDSI5-7 also displays a 20-year oscillation.展开更多
基金Supported by National Basic Research Program of China (Grant No. 2005 CB422002)National Natural Science Foundation of China (Grant Nos. 40671194 and 40371118)the Knowledge Innovation Program of Institute of Geographic Sciences and Natural Resources Research (Grant No.CXIOG-A05-12)
文摘The climate of the past 1000 years is an important context for evaluating the recent climate warming.However,there are few 1000-year-long climate reconstructions with annual resolution in the Qing-hai-Tibet Plateau.In this paper,a dendroclimatic analysis was conducted for the radial growth of Qilian juniper from the upper forest limit in Wulan,Qinghai Province.The results of correlation analysis between the tree-ring widths and the climate variables indicate that the growth of junipers at the upper forest limit is mainly limited by low temperatures of September,November and February of the pregrowth season,and July of the current growth season.There is no significant correlation between the tree-ring widths and precipitation.A mean temperature from the previous year's September to the current year's April was reconstructed for the Wulan area since A.D.1000.The reconstruction can explain 40.8% of the instrumental variance in the calibration period(1856―2002).The reconstruction shows that the 20th century is the warmest 100 years,and the 1990s is the warmest decade during the past 1000 years,while the coldest 100 years and decade occur at 1600―1699 and 1642―1651,respectively.The variations are verified well by the temperature reconstruction of the middle Qilian Mountain(QL) and the total organic carbon(TOC) in the Qinghai Lake sediments.The comparison of our reconstruction with the annual temperature reconstruction of extra-tropical Northern Hemisphere suggests that the climate of Wulan during the Medieval Warm Period is of obvious regional specialty,but there was a good response to the climate of hemispheric scales during the recent 400 years.
基金the International Foundation for Science (D/3681-1) (Sweden)the Humboldt Research Foundation (Germany) the National Natural Science Foundation of China (Grant No. 40471123)
文摘epartment of Wood Science, University of Hamburg, Hamburg D-21031, GermanyBased on three Chinese pine (Pinus tabulaeformis Carr.) and one Meyer spruce (Picea meyeri Rehd. et Wils.) ring-width chronologies, a 163-year drought history was reconstructed in the eastern Ortindag Sand Land. All tree-ring chronologies show large inter-annual variations and strong common signals and fairly consistent variation between different chronologies, indicating that they are excellent proxy of regional climate. A regional chronology (RC) was established by averaging the four standard chronologies and further employed for the analysis and climatic reconstruction. The analysis revealed that tree growth is primarily limited by low precipitation in February-March and June-July and high temperature in May-July. In addition, RC has high correlations with the monthly Palmer drought severity index (PDSI) prior to and during the growing season because the PDSI considers the accumulation of the droughts. Response function analysis revealed that RC only exhibits significant correlations with the PDSI in June and July (close to the 95% significance level in May). Because May―July is a critical period for tree growth, the average May-July PDSI (PDSI5-7) was reconstructed back to 1842 using RC in the Ortindag Sand Land. The reconstruction can explain 52% of the PDSI variance and the equation was rather stable over time. It agrees well with the variation of the average dryness/wetness indices in North China,and captures the decline process of the East Asian summer monsoon since the mid-1960s. It is worth noting that the Ortindag Sand Land has experienced the most severe drought in the recent 40 years based on the 163-year drought reconstruction. Like summer precipitation in North China the reconstructed PDSI5-7 also displays a 20-year oscillation.
