Relationships between tree-ring cell features of Pinus koraiensis and climate factors in the Changbai Mountains,Northeastern China

Anatomical characteristics have been proven useful for extracting climatic signals. To examine the climatic signals recorded by tree-ring cell features in the Changbai Mountains, we measured cell number and cell lumen diameter, in addition to ring widths, of Korean pine （Pinus koraiensis） tree rings at sites of varied elevation, and we developed chronologies of cell number （CN）, mean lumen diameter （MLD）, maximum lumen diameter （MAXLD） and tree-ring width （TRW）. The chronologies were correlated with climatic factors monthly mean tem- perature and the sum of precipitation. As shown by our analysis, the cell parameter chronologies were suitable for dendroclimatology studies. CN and TRW shared relatively similar climatic signals which differed from MLD and MAXLD, and growth-climate relationships were elevation- dependent, as shown by the following findings： （1） at each elevation, MLD and MAXLD recorded different monthly climatic signals from those recorded by TRW for the same climatic factors; and （2） MLD and MAXLD recorded cli- matic factors that were absent middle elevations. Cell lumen effective archive for improving for this study area. from TRW at lower and diameter proved to be an the climate reconstruction

Spatiotemporal variability in tree ring's δ^(13)C of Picea crassifolia in the Qilian Mountains:climatic significance and responses to rising CO_2

Abstract：The carbon isotopic composition （δ13C） of tree rings was used to assess changes in intrinsic water-use efficiency （Wi） to increasing atmospheric CO2 and climate change during the period of 1891–2003. Five Qinghai spruce （Picea crassifolia） stands were selected in the Qilian Mountains, growing along a precipitation gradient. All five δ13C were correlated to each other, but two sites （DDS and CLS）, which are far from the main body of the mountains, show relative weak connections to other sites. Although trees at all sites had improved their Wi in response to increasing atmospheric CO2 concentration, spruce growing in the regions far away from the main body of the mountains were less sensitive to improved Wi than those of other sites. Based on the correlation between carbon isotope discrimination （Δ） and Palmer Drought Severity Index （PDSI）, the drought history covering the period of 1891–2003 was reconstructed in the study region. The two most severe drought epochs of the late 1920s and the last decade were caused by reduced precipitation and climate warming, respectively. Our results will be useful in assessing any further spatial climate-related bioclimatic information.

High-resolution reconstruction of April-September precipitation and major extreme droughts in China over the past∼530 years

Extreme drought events have increased,causing serious losses and damage to the social economy under current warming conditions.However,short-term meteorological data limit our understanding and projection of these extremes.With the accumulation of proxy data,especially tree-ring data,large-scale precipitation field reconstruction has provided opportunities to explore underlying mechanisms further.Using point-by-point regression,we reconstructed the April-September precipitation field in China for the past~530 years on the basis of 590 proxy records,including 470 tree-ring width chronologies and 120 drought/flood indices.Our regression models explained average 50%of the variance in precipitation.In the statistical test on calibration and verification,our models passed the significance level that assured reconstruction quality.The reconstruction data performed well,showing consistency and better quality than previously reported reconstructions.The first three leading modes of variability in the reconstruction revealed the main distribution modes of precipitation over China.Wet/drought and extremely wet/drought years accounted for 12.81%/10.92%(68 years/58 years)and 1.69%/3.20%(9 years/17 years)of the past~530 years in China,respectively.Major extreme drought events can be identified explicitly in our reconstruction.The detailed features of the Chongzhen Great Drought(1637-1643),the Wanli Great Drought(1585-1590),and the Ding-Wu Great Famine(1874-1879),indicated the existence of potentially different underlying mechanisms that need further exploration.Although further improvements can be made for remote uninhabited areas and large deserts,our gridded reconstruction of April-September precipitation in China over the past~530 years can provide a solid database for studies on the attribution of climate change and the mechanism of extreme drought events.

Tree Rings and Ecology The 7th International Conference on Dendrochronology

Tree rings have long been recognized as a useful indicator of past environmental changes. Besides traditional applications in studies of climate change and archaeology, the technique of dendrochronology has been widely used in answering ecological questions. This has been partly reflected by the broad topics on tree rings and ecology presented at the 7th International Conference on Dendrochronology （ICD）, which was held in Beijing, June 11-17 2006. At this conference, Dr Henri Grissono-Mayer, the plenary speaker for the theme, defined dendroecology as the science that uses tree rings, dated to their exact year of formation, to analyze temporal and spatial relationships between living organisms and their environment.