Kang 2013 QI Extreme drought events

Extreme drought events in the years 1877e 1878,and 1928,in the southeast Qilian Mountains and the air e sea coupling system

Shuyuan Kang,Bao Yang *,Chun Qin,Jianglin Wang,Feng Shi,Jingjing Liu

Key Laboratory of Desert and Deserti ?cation,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences,Gansu Province,Lanzhou 730000,China

a r t i c l e i n f o

Article history:

Available online 13March 2012

a b s t r a c t

Droughts events have long-lasting effects on economic and social activities,particularly in the semi-arid region of northern China.In this study,four tree ring-width chronologies were developed based on lived Qilian Juniper (Sabina przewalskii Kom.)trees in the southeast Qilian Mountains,China.The four chro-nologies were developed from 164cores (82trees)for the northern marginal of the Asian summer monsoon in China.Tree growth of this area is sensitive to moisture variability of the growth season.During the last 260years,there had been extreme growth depressions in the years 1877e 1878and 1928,indicating large-scale droughts had occurred in the study area.These extreme drought events had a devastating effect not only on hydrology and agriculture,but also on society and economics.Extreme droughts in 1877e 1878and in 1928occurring in the study region and most of China were triggered by different climate regimes.The former drought distribution pattern was probably attributable to El Ni?o events,while the latter was associated with warm and cold air masses.

ó2012Elsevier Ltd and INQUA.All rights reserved.

1.Introduction

The East Asian summer monsoon climate exerts a large impact on ecosystems,human society,and moisture conditions in China (Shen et al.,2007).The strength of East Asian monsoon can lead to moisture variability of transitional regions,such as severe droughts in north China.In extreme cases,a drought disaster can cause ?ourishing societies and highly developed civilizations to collapse abruptly (Bryson and Swain,1981;Fang,1999;deMenocal,2001;Weiss and Bradley,2001;Huang et al.,2003).The deep under-standing of these problems will help to reasonably utilize water resource and provide some insight for the development of regional economy and society.

In recent years,tree rings have been employed worldwide to study climate extremes (Liu et al.,2004,2005,2010a ;Gou et al.,2007,2008;Yang et al.,2009a,b ,2010a,b ),such as droughts (Stahle et al.,1998;Liang et al.,2006;Gou et al.,2007;Liu et al.,2009;Cheng et al.,2011),hurricanes (Drew,1998),and tropical cyclone activities (Miller et al.,2006;Rodgers et al.,2006).Radial growth of trees integrates the effects of climate conditions,local site conditions,and physiological mechanisms of tree species (Fritts,1976).In the semi-arid regions of China,radial growth has

a strong correlation to the Palmer Drought Severity Index (PDSI;Palmer,1965),which was used to investigate the combined effects of temperature,precipitation and soil moisture on tree growth.PDSI is used in tree-ring based drought reconstructions in the western United States (Cook et al.,2004),in East Asia (Cook et al.,2010)and in China in the Xionglong Mountains (Fang et al.,2009)and the Qilian Mountains (Tian et al.,2007).

This paper presents four new tree ring-width chronologies from the southeast Qilian Mountains at the northern fringe of the Asian summer monsoon in China.The relationship between the tree-growth reduction and extreme drought events and the air e sea coupling system was analyzed to attempt to understand the climate forces that might cause droughts during the past 260years.2.Materials and methods 2.1.Sampling sites and climate data

The Qilian Mountains run northwest to southeast for 800km,and the range ’s highest peak is 5808m above sea level (a.s.l.).Ring-width chronologies were developed in Tianzhu County of Gansu Province in the southeast part of the Qilian Mountains of China.From northwest to southeast of Tianzhu County,the three forest sites were selected for increment core sampling at the Qilian forest farm (hereafter QL),Haxi forest farm (hereafter HX),and Gucheng forest farm (hereafter GC)(Fig.1,Table 1).The trees are all of the

*Corresponding author.

E-mail address:yangbao@https://www.360docs.net/doc/ea8479855.html, (B.

Yang).

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Quaternary International 283(2013)85e 92

species of Qilian Juniper (Sabina przewalskii Kom.),which are grown in open stands on steep and south-facing slopes of the mountains.The soils are generally shallow and poor in organic matter (Sheppard et al.,2004).A variety of xeric shrubs and grasses,for example,elm (Fructus Ulmi Macrocarpae Preparatus )and lilac (Syringa oblata )are in the understory of the forests.The source of water supply to tree growth depends solely on precipitation,and the trees have no access to groundwater.

In China,precipitation variations are markedly in ?uenced by the intensity variations of the East Asian summer monsoon (EASM).Generally,in summer,the Westerlies is to the north of the Tibetan Plateau,and the southerly monsoon ?ow over eastern China converges in the lee side,forming a subtropical front that gradually moves from southern China to the Yangtze River basin and reaches northern China in late July (Hu and Qian,2007).In some cases,the monsoon can lead to severe droughts or ?oods in different regions and produce climate events such as the severe droughts in north-west China (Qian et al.,2007).Precipitation also strongly depends up whether the warm e humid air mass coming from the summer

monsoon can meet with the cold e dry air mass coming from the northern China and forming frontal precipitation,especially in the north of China,because the north of China is in the northern limit of the EASM.

The study region is located close to the current boundary of the Asian summer monsoon.Therefore it could be sensitive to varia-tions in the strength of the EASM,although the study region is presently characterized by continental arid climate.The closest available meteorological station is located near the sampling site at Wushaoling (37 120N,102 520E,3045m a.s.l;Fig.1).At Wushaoling,the mean January and July temperatures are à11.8 C and 11.5 C,respectively.Mean annual precipitation amounts to 410.5mm for the period 1951e 2008.Precipitation is concentrated from May to September,being coincident with the highest temperature.

The correlation between tree-ring chronologies and meteoro-logical station records of temperature,precipitation,and regional moisture conditions (PDSI)were assessed using the software DendroClim 2002(Biondi and Waikul,2004)for the common period from May of the previous year to October of current year.The monthly PDSI dataset from the nearest Dai PDSI (Dai et al.,2004)grid points (41.25 N,103.75 E),which was designed for global coverage based on a 2.5 ?2.5 gridding system and showed the highest correlations with these chronologies.In China,Li et al.(2006)and Liang et al.(2007)reconstructed PDSI series spanning the last centuries based on tree-ring data in semi-arid regions.The drought and ?ood grades of the central part of Gansu Province were derived from historical documentary records and climate descriptions relevant to agriculture and living conditions from year 1750e 2010(Institute of arid meteorology,Lanzhou,1992).The ?ve grades were categorized for each year,namely extremely wet (grade 1),wet (grade 2),normal (grade 3),dry (grade 4),and extremely dry (grade 5).A dry-wet index value

for

Fig.1.Location of tree sampling sites.

Table 1

Basic information and statistics of the four chronologies developed.

Chronology Latitude Longitude Elevation (m)Core/tree no.Time span (A.D.)QL 37.07 N 102.52 E 3252e 344072/361809e 2009HX 37.48 N 102.30 E 3137e 352648/241765e 2009GC

37.68 N 102.20 E 3192e 350044/221810e 2009TZ-regional

_

_

_

164/82

1750e

2009

Fig.2.Standard chronologies of ring-width for the study https://www.360docs.net/doc/ea8479855.html,mon periods are indicated by shaded bars.

Table 2

Statistical characteristics of the four standard chronologies.

ML SD MS AC1QL 1840.1810.1270.465HX 2260.2110.1770.322GC 2110.2780.1720.689TZ

197

0.177

0.128

0.473

ML:mean segment length;SD:standard deviation;MS:mean sensitivity;AC1:?rst-order autocorrelation.

S.Kang et al./Quaternary International 283(2013)85e 92

86

the central Gansu Province during the extreme drought years (1877e 1878and 1928as discussed below)was determined by combining the drought/?ood grades from six stations of Lanzhou,Jingyuan,Lintao,Linxia,Huajialing and Hezuo (Fig.1).

The global surface sea temperature (SST)anomaly ?elds throughout the drought events were analyzed using the HadISST (Rayner et al.,2003)data-sets of the United Kingdom Meteoro-logical Of ?ce Hadley Centre.

2.2.Tree-ring data and chronology development

In April 2010,a total of 164cores were extracted with increment borers at breast height from 82living trees along an altitude ranging from 3137to 3500m.All the cores were air dried and mounted on grooved sticks with transverse surfaces facing up (Phipps,1985).Cores were prepared with razor blades to expose ring details to cellular level (Stokes and Smiley,1968).A LINTAB 6measuring system was used to register ring widths at a resolution of 0.01mm,and visual inspection facilitated crossdating of all series using the software package TSAP-Win (Rinn,2003).The quality of visual crossdating was further checked by the COFECHA program (Holmes,1983).These methods ensure the exact dating for each ring-width series.

The program ARSTAN (Cook,1985)was used to develop ring-width chronologies,and a data-adaptive power transformation was applied prior to standardization in order to remove bias caused by so-called heteroscedasticity (Cook and Peters,1997).There is a biological trend inherent in the raw data series,which is removed by a cubic spline function,subject to a 50percent frequency e response cutoff equal to 67percent of the series length.The residual (or difference)between the transformed ring-width measurements and the ?tted spline functions allows calculation of the ?nal tree-ring chronology.

The biweight robust mean is computed for each of the detrended series,which can then be averaged to chronologies (Cook and Kairiukstis,1990).To account for changes in variance attributable to the decline in sample size with time,variance stabilization (Osborn et al.,1997)was applied.The sample size was smaller for the early portion of the tree-ring chronology;thus the subsample signal strength statistic (SSS;Wigley et al.,1984)was calculated using a 30-year moving window with 15-year overlaps to determine the most reliable time span of the chronology.

As a result,the STD version was chosen for further analysis (Fig.2)based on the SSS threshold value exceeding 0.85,and several descriptive statistics were calculated for the standard chronologies (Table 2).3.Results and discussion

3.1.The growth depression in the 1877e 1878and 1928and climate signals recorded in tree rings

Some common patterns were observed from the tree-ring chronologies shown in Fig.2over the last 260years.The most signi ?cant growth decline in 1878and 1928is found compared with other periods in QL and HX chronologies.For the GC

Table 3

Inter-correlations of the four chronologies for the common period 1809e 2009.

QL

HX GC

TZ

QL 1.00HX 0.41 1.00GC 0.400.39 1.00TZ

0.83

0.75

0.73

1.00

Fig.3.Correlation function analysis of region ’s TZ chronology:to temperature (solid bars)and precipitation (light bars)measure at the Wushaoling meteorological station.The asterisks indicate the correlations at or over 95%con ?dence

levels.

Fig.4.Relationship of four chronologies and monthly PDSI of current year during 1951e 2004.

Table 4

Calculated lengths of non-soaking rain days in 1877e 1878recorded by historical documents (Zhang,2004b ;Zhang and Liang,2010).County,province

Length (1877)/days Length

(1877e 1878)/days Historical records

(in the lunar calendar)

Gaoping,Shanxi z 160>330No rain from June 1877to May 1878

Linyi,Shanxi >250e No rain after March

Kaifeng,Henan 170285No rain from June 1877to March 1878

Fangcheng,Henan >200>300No rain from May to following March

Mianchi,Henan 240>300No rain from spring to following March

Huayin,Shaanxi

250340No rain from April 1877to March 1878

Tianshui,Gansu

e

>200

No rain from May to the end of the year

S.Kang et al./Quaternary International 283(2013)85e 92

87

chronology,the growth depression is exhibited in 1877,which is earlier than that in QL and HX chronologies,and growth depression in 1928is not more signi ?cant than that two sites.

Inter-correlations among these chronologies are all signi ?cant at 0.01levels (Table 3),further suggesting strong coherence of large-scale tree growth in the Qilian Mountains.Among these common growth anomaly signals,chronologies of three sites were combined into one regional chronology by simple average and named TZ chronology (Fig.2,Table 3).The TZ chronology also has a signi ?cant correlation with the other three chronologies.The most striking feature is the tree-growth reductions in 1878and 1928.There is no doubt that the extremely narrow rings occurred in 1877e 1878and 1928in the study region.

As shown in Fig.3,signi ?cant correlations (at 95%con ?dent level)with temperature at Wushaoling were found in May of the previous year (r ?à0.242),March (r ?0.243)and May (r ?à0.32)

Table 5

Instrumental precipitation data from eight stations in western China for the year 1928(Tang et al.,2007).Stations

Xi ’an Lanzhou Tianshui Xifeng Wudu Wuwei Zhangye Jiuquan Annual precipitation in the 1928(mm)100100138112194231912Mean annual precipitation (mm)580.4326.6536.4555.3485.6115.3130.386.5Departures (%)

à83

à69

à74

à80

à60

à80

à85

à

86

Fig.5.Spatial drought patterns in 1877,1878(a)and 1928(b)of Asia,negative PDSI values indicate dry conditions and positive values indicate wet conditions.The black rectangle indicates the sampling area.

S.Kang et al./Quaternary International 283(2013)85e 92

88

of current year for the period 1951e 2008.The precipitation at Wushaoling in early growing season is positively correlated with tree growth,especially in February (r ?0.379),March (r ?0.314)and April (r ?0.34)for the time period 1951e 2004.The PDSI integrates rainfall and temperature records from prior to current growing seasons.

Moisture variation is the major limiting factor of tree growth in the study region.Tree rings showed a little stronger correlation with the PDSI than with meteorological records.The regional moisture availability and chronologies have signi ?cant correlations at the 95%con ?dent level (Fig.4).Relatively high correlations with the TZ chronology were found in May (r ?0.426)and April (r ?0.357)of current year,which indicate that early growing season moisture is signi ?cant impact factor on tree growth in the study area,while late growth season moisture availability is less

important.

Fig.6.SST anomalies in drought years,December e February of 1877e 1878(a)and 1928(b).Anomalies were calculated with respect to the 1870e 2009mean values,from the HadISST with 1 latitude e longitude grids.

S.Kang et al./Quaternary International 283(2013)85e 9289

https://www.360docs.net/doc/ea8479855.html,rge-scale severe droughts occurring in the1877e1878and 1928in northern China

Dry-wet grade values of the central part of Gansu Province are grade5,3and5in years1877,1878and in1928,respectively.In particular,a signi?cant correlation(r?à0.365,n?252,p<0.01) was found between the TZ chronology and the?rst principal component(PC1)derived from seven moisture-sensitive ring-width chronologies(Yang et al.,2010b).This PC1series was regarded as an indicator of regional precipitation variations on the northeastern Tibetan Plateau.Higher PC1values indicate dry conditions whereas lower values re?ect wet conditions.This signi?cant correlation suggests that the drought variations between these two regions have been closely connected over the past centuries.Evidence for these drought events in1877e1878 and1928has also been found in the Great Bend of the Yellow River region(Qian et al.,2011),North China area(Liang et al.,2003; Zhang,2004a;Hao et al.,2010;Liu et al.,2010),and Jiang-Huai area (Zheng et al.,2006).Therefore,the tree-growth anomalies of the study region are likely representative of the large-scale moisture change.

Statistically,abundant historical records are available in China. During the period1876e1878,13provinces were affected by drought,including Gansu Province(Zhang and Liang,2010).There are some descriptions of long-lasting non-soaking rainfall days during this period in Shanxi,Henan,Shaanxi and Gansu provinces (Zhang,2004b;Zhang and Liang,2010),as shown in Table4.These records represented the extreme drought event occurring in the northern China during1877e1878.The population decreased in Shanxi,Shaanxi,Henan,Zhili and Shandong provinces by more than22million people(Hao et al.,2010).

The sustained drought of the1920s(Yuan,1984;Liang et al., 2003,2006;Zhang et al.,2005)and simultaneous plague of locusts caused repeated crop failures,leading to a severe famine from1927through1929in northern China;34million people suffered,and10million died as a direct consequence of this event (Deng,1937).The hydrological records of Gansu Province showed that the stream?ow had a decline of64percent compared with the mean(The Editing Committee for“The Flood/Drought Hazards in Gansu Province”,1996),and the severe drought caused the drying up of wells and springs in1928(Deng,1937).In Gansu Province,the unprecedented drought took place in the spring and summer of 1928,with a spring loss of seeds,and crops not harvested in1929 (Liu,2010).As a consequence,the repeated crop failures occurred in Shaanxi,Ningxia,Gansu and Inner Mongolia(Liang et al.,2006).In particular,the1920s mega-drought was associated with two to three million deaths and low water levels in the Yellow River Basin (Xu et al.,1997).There are no available instrumental observations for the years1877e1878in China.However,some valuable precipitation data with respect to the year1928were recorded in several stations of northwestern China(Tang et al.,2007),as shown in Table5.These stations witnessed a large-scale drought event occurring in the year1928.Especially,annual total precipitation in Lanzhou station(capital of Gansu Province,close to the study region)was100mm in1928(Table5),which is69%less than mean annual precipitation(326.6mm).

3.3.Mechanism of regional drought regimes

Fig.5was derived based on PDSI gridded data-sets(Cook et al., 2010).Negative PDSI values indicate dry conditions and positive values indicate wet conditions.The patterns of these two drought events(1877e1878and1928)are not similar.The drought of 1877e1878was widely distributed in Asia,including the study region,most of China,India,and Southeast Asia near the tropics.It is interesting to note that this drought event had a considerable impact on almost all Asia,not only the study region and northern China.In contrast,the spatial extent of the year1928drought was not larger than that of the year1877e1878drought.The most obvious difference was that Southeast Asia near the tropic was in the wet condition,whereas most of China(especially northern China)and the study region had dry conditions.The drought of 1877e1878was more severe than that of1928within the study region.Similarly,the annual ring is narrower in1877and1878than that in1928in the GC and QL sites.

The SST anomalies of the tropical Paci?c Ocean for the two drought events in the years1877e1878and1928are shown in Fig.6.Positive SST anomalies spread and intensi?ed throughout the east tropical Paci?c during1877e1878(Fig.6a).In1877e1878,the major El Ni?o events occurred(Quinn and Neal,1992).In these two years,the event strengths and El Ni?o con?dence ratings are“very strong”and5(most credible),respectively.The most dramatic impacts of this typical El Ni?o event were associated with intense and long-lasting droughts in Asia,America,and other regions.Davis (2001)estimated that some15to25million people,mostly peas-ants and rural workers,died in India and northern China during 1876e1879as a result of famine and drought-related diseases. Jakarta(Indonesia)received less than one-third of its normal rainfall from May1877through February1878(Kiladis and Diaz, 1986).Droughts also plagued Americans,as the anomalously mild 1877e1878winter in the upper Midwest and south-central Canada is another feature typical of major El Ni?o episodes(Aceituno et al., 2009).Comparing the spatial drought patterns of Asia(Fig.5a)with SST anomalies of the tropical Paci?c Ocean in1877e1878(Fig.6a),it appears that the El Ni?o event resulted in the drought condition in Asia during1877and1878.

However,in1928,the SST anomalies of Middle East Paci?c were low(Fig.6b).In this non-El Ni?o year,there was also a drought event in the study region,as well as in northern China;conversely, there was a wet condition in the tropics of Southeast Asia.This indicates that the drought event of1928in the study region was not induced by an El Ni?o event.This drought event was probably the result of the air mass coming from the summer monsoon being unable to meet with the cold e dry air mass coming from northern China and,therefore,not forming frontal precipitation.

4.Conclusions

The tree-ring chronologies spanning the last260years were established in the semi-arid areas of the northern fringe of the Asian summer monsoon in China.Analysis showed that tree rings are sensitive records of extreme drought and tree growth reduced in the years1877e1878and1928.Tree-ring analysis with reference to historical records indicated that these periods were synchronous with natural and social disruptions in China.Paci?c SST was likely a factor driving the drought pattern in monsoon Asia in years 1877e1878,and the air mass frontal activity in?uenced the drought in northern China in year1928.This research provides new insights into the extreme drought events and the atmospheric circulation patterns over the northern fringe of the Asian summer monsoon in China.Thus,it is important to further study and extend the tree-ring network in China to assess characteristics of extreme drought events and others.

Acknowledgments

The authors extend many thanks to Guest Editor Eryuan Liang and two anonymous reviewers for their valuable comments and suggestions.The study was jointly funded by the Chinese Academy of Sciences(CAS)100Talents Project(29082762),the National Basic

S.Kang et al./Quaternary International283(2013)85e92 90

Research Program of China(973Program)(No.2010CB950104),the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(Grant No.2010T1Z31,2009S1-388),and the NSFC(Grant no.41071130,41002050).

References

Aceituno,P.,Prieto,M.R.,Solari,M.E.,2009.The1877e1878El Ni?o episode: associated impacts in south America.Climatic Change92,389e416.

Biondi, F.,Waikul,K.,2004.DENDROCLIM2002:a Cttprogram for statistical calibration of climate signals in tree-ring https://www.360docs.net/doc/ea8479855.html,puters&Geo-sciences30,303e311.

Bryson,R.A.,Swain,A.M.,1981.Holocene variations of monsoon rainfall in Rajas-than.Quaternary Research16,135e145.

Cheng,F.,Yuan,Y.J.,Wei,W.S.,Yu,S.L.,Zhao,Y.,2011.Variations of long-term palmer drought index in recent354year in yili based on tree-ring record.Plateau Meteorology30,355e362.

Cook,E.R.,Kairiukstis,A.,1990.Methods of Dendrochronology:Applications in the Environmental Sciences.Kluwer Academic Press,Dordrecht.

Cook,E.R.,Peters,K.,1997.Calculating unbiased tree-ring indices for the study of climatic and environmental change.The Holocene7,361e370.

Cook,E.R.,Woodhouse,C.A.,Eakin,C.M.,Meko,D.M.,Stahle,D.W.,2004.Long-term aridity changes in the western United States.Science306,1015.

Cook,E.R.,Anchukaitis,K.J.,Buckley,B.M.,D’Arrigo,R.D.,Jacoby,G.C.,Wright,W.E., https://www.360docs.net/doc/ea8479855.html,n monsoon failure and megadrought during the last millennium.

Science328,486e489.

Cook,E.R.,1985.A time-series analysis approach to tree-ring standardization.Ph.D.

Dissertation.The University of Arizona Press,Tucson.

Dai,A.,Trenberth,K.E.,Qian,T.,2004.A global dataset of palmer drought severity index for1870e2002:relationship with soil moisture and effects of surface warming.Journal of Hydrometeorology5,1117e1130.

Davis,M.,https://www.360docs.net/doc/ea8479855.html,te Victorian Holocausts:El Ni?o Famines and the Making of the Third World.Ed.Verso,London.

deMenocal,P.B.,2001.Culture responses to climate change during the late Holo-cene.Science292,667e673.

Deng,Y.T.,1937.History of Famine Relief in https://www.360docs.net/doc/ea8479855.html,mercial Press,China. Drew,A.P.,1998.Growth rings,phenology,hurricane disturbance and climate in Cyrilla racemi?ora L.,a rain forest tree of the Luquillo Mountains.Puerto Rico.

Biotropica30,35e49.

Fang,K.Y.,Gou,X.H.,Chen,F.H.,Yang,M.X.,2009.Drought variations in the eastern part of northwest China over the past two centuries:evidence from tree rings.

Climate Research38,129e135.

Fang,X.Q.,1999.Decline of pre-historical agriculture and formation of farming-grazing transitional zone in north China:a view from climatic changes.

Journal of Natural Resources14,212e218(In Chinese with English abstract).

Fritts,H.C.,1976.Tree Rings and Climate.Academic Press,London.

Gou,X.H.,Chen,F.H.,Cook,E.R.,Jacoby,G.C.,Yang,M.X.,Li,J.B.,2007.Stream?ow variations of the Yellow River over the past593years in western China reconstructed from tree rings.Water Resources Research43(6),W06434. Gou,X.H.,Chen, F.H.,Yang,M.X.,Jacoby,G.C.,Fang,K.Y.,Tian,Q.H.,Zang,Y., 2008.Asymmetric variability between maximum and minimum tempera-tures in northeastern Tibetan Plateau:evidence from tree rings.Science in China Series D:Earth Sciences51,41e55.

Hao,Z.X.,Zheng,J.Y.,Wu,G.F.,Zhang,X.Z.,Ge,Q.S.,2010.1876e1878severe drought in North China:facts,impacts and climatic background.Chinese Science Bulletin55,3001e3007.

Holmes,R.L.,https://www.360docs.net/doc/ea8479855.html,puter-assisted quality control in tree-ring dating and measurement.Tree Ring Bulletin43,69e95.

Hu,H.R.,Qian,W.H.,2007.Identi?cation of the northernmost boundary of East Asia summer monsoon.Progress in Natural Sciences17,812e820.

Huang,C.C.,Zhao,S.C.,Pang,J.L.,Zhou,Q.Y.,Chen,S.,Li,P.H.,Mao,L.J.,Ding,M., 2003.Climatic aridity and the relocations of the Zhou culture in the southern loess plateau of China.Climatic Change61,361e378.

Institute of arid meteorology of Lanzhou,1992.Historical Climate Drought Data of Gansu Province in Year1470e1990.

Kiladis,G.,Diaz,H.F.,1986.An analysis of the1877e78ENSO episode and comparison with1982e83.Monthly Weather Review114,1035e1047.

Li,J.B.,Gou,X.H.,Cook,E.R.,2006.Tree-ring based drought reconstruction for the central Tien Shan area in northwest China.Geophysical Research Letters33, L07715.doi:10.1029/2006GL025803.

Liang,E.Y.,Shao,X.M.,Kong,Z.C.,Lin,J.X.,2003.The extreme drought in the1920s and its effect on tree growth deduced from tree ring analysis:a case study in North China.Annals of Forest Science60,145e152.

Liang,E.Y.,Liu,X.H.,Yuan,Y.J.,Qin,N.S.,Fang,X.Q.,Huang,L.,Zhu,H.F.,Wang,L.L., Shao,X.M.,2006.The1920s drought recorded by tree rings and historical documents in the semi-arid and arid areas of northern China.Climatic Change 79,403e432.

Liang,E.Y.,Shao,X.M.,Liu,H.Y.,Eckstein,D.,2007.Tree-ring based PDSI recon-struction since AD1842in the Ortindag Sand Land,east Inner Mongolia.

Chinese Science Bulletin52,2715e2721.

Liu,Y.,Shi,J.F.,Shishov,V.,Vaganov,E.,Yang,Y.K.,Cai,Q.F.,Sun,H.M.,Wang,L., Djanseitov,I.,2004.Reconstruction of May e July precipitation in the north

Helan Mountain,Inner Mongolia since AD1726from tree-ring late-wood widths.Chinese Science Bulletin49,405e409.

Liu,Y.,Cai,Q.F.,Shi,J.F.,2005.Seasonal precipitation in the south-central Helan Mountain region,China,reconstructed from tree-ring width for the past224 years.Canadian Journal of Forest Research35,2403e2412.

Liu,Y.,Bao,G.,Song,H.M.,Cai,Q.F.,Sun,J.Y.,2009.Precipitation reconstruction from Hailar pine(Pinus sylvestris var.mongolica)tree rings in the Hailar region,Inner Mongolia,China back to1865AD.Palaeogeography,Palaeoclimatology,Palae-oecology282,81e87.

Liu,Y.,Tian,H.,Song,H.M.,Liang,J.M.,2010.Tree ring precipitation reconstruction in the Chifeng e Weichang region,China,and East Asian summer monsoon variation since A.D.1777.Journal of Geophysical Research115,D06103.

doi:10.1029/2009JD012330.

Liu,J.J.,Yang,B.,Qin,C.,2010a.Tree-ring based annual precipitation reconstruction since AD1480in south central Tibet.Quaternary International236,75e81. Liu,G.H.,2010.History of Gansu(in Chinese).The People’s Publishing company of Gansu province.

Miller,D.L.,Mora,C.I.,Grissino-Mayer,H.D.,Mock,C.J.,Uhle,M.E.,Sharp,Z.,2006.

Tree-ring isotope records of tropical cyclone activity.Proceedings of the National Academy of Sciences of the United States of America103, 4294e14297.

Osborn,T.J.,Briffa,K.R.,Jones,P.D.,1997.Adjusting variance for sample-size in tree-ring chronologies and other regional mean time series.Dendrochronologia15, 89e99.

Palmer,W.C.,1965.Meteorological Drought.Weather Bureau Res.Paper45.U.S.

Department of Commerce,Washington,DC,58pp.

Phipps,R.L.,1985.Collecting,Preparing,Crossdating,and Measuring Tree Incre-ment Cores,U.S.Geological Survey Water-Resources Investigations Report, 85e4148pp.

Qian,W.H.,Lin,X.,Zhu,Y.F.,Xu,Y.,Fu,J.L.,2007.Climatic regime shift and decadal anomalous events in China.Climatic Change84,167e189.doi:10.1007/s10584-006-9234-z.

Qian,W.H.,Shan,X.L.,Chen,D.L.,2011.Droughts near the northern fringe of the East Asian summer monsoon in China during1740e2003.Climate Change.

doi:10.1007/s10584-011-0096-7.

Quinn,W.H.,Neal,V.T.,1992.The historical record of El Ni?o events.In: Bradley,R.S.,Jones,P.D.(Eds.),Climate Since1500AD.Routledge,London, pp.623e648.

Rayner,N.A.,Parker,D.E.,Horton,E.B.,2003.Global analyses of SST,sea ice,and night marine air temperature since the late nineteenth century.Journal of Geophysical Research108,4407.doi:10.1029/2002JD002670.

Rinn,F.,2003.TSAP-Win:Time Series Analysis and Presentation for Dendrochro-nology and Related Applications.Version0.55User reference.Heidelberg, Germany.https://www.360docs.net/doc/ea8479855.html,.

Rodgers,J.C.,Gamble,D.W.,McCay,D.H.,Phipps,S.,2006.Tropical cyclone signals within tree-ring chronologies from Weeks Bay national estuary and research reserve,Alabama.Journal of Coastal Research22,1320e1329.

Shen,C.M.,Wang,W.C.,Hao,Z.X.,Gong,W.,2007.Exceptional drought events over eastern China during the last?ve centuries.Climatic Change85, 453e471.

Sheppard,P.R.,Tarasov,P.,Graumlich,L.,Heussner,K.,Wagner,M.,?sterle,H., 2004.Annual precipitation since515BC reconstructed from living and fossil juniper growth of Northeast Qinghai Province,China.Climate Dynamics23, 869e881.

Stahle,D.W.,Cleaveland,M.K.,Blanton,D.B.,Therell,M.D.,Gay,D.A.,1998.The lost colony and Jamestown droughts.Science280,564e567.

Stokes,M.A.,Smiley,T.L.,1968.An Introduction to Tree-Ring Dating.The University of Chicago Press,Chicago,London.

Tang,X.,Sun,G.W.,Qian,W.H.,2007.The Research of the Northern Fringe of Asian Summer Monsoon.China Meteorological Press,Beijing.

The Editing Committee for“The Flood/Drought Hazards in Gansu Province”,1996.

The Flood/Drought Hazards in Gansu Province.Yellow River Conservancy Press, Zhengzhou.

Tian,Q.H.,Gou,X.H.,Zang,Y.,Peng,J.F.,Wang,J.S.,2007.Tree-ring based drought reconstruction(A.D.1855e2001)for the Qilian Mountains,northwestern China.

Tree-ring Research63(1),27e36.

Weiss,H.,Bradley,R.S.,2001.Archaeology-what drives societal collapse?Science 291,609e610.

Wigley,T.,Briffa,K.R.,Jones,P.D.,1984.On the average value of correlated time series,with applications in dendroclimatology and hydrometeorology.Journal of Applied Meteorology23,201e213.

Xu,G.C.,Yao,H.,Li,X.M.,1997.Climate Change in Arid and Semiarid Regions of China.China Meteorological Press,Beijing.

Yang,B.,Kan,X.C.,Liu,J.J.,Br?uning,A.,Qin,C.,2009a.Annual temperature history in southwest Tibet during the last400years recorded by tree rings.Interna-tional Journal of Climatology30,962e971.doi:10.1002/joc.1956.

Yang,B.,Kang,X.C.,Br?uning,A.,Liu,J.,Qin,C.,Liu,J.J.,2009b.A622-year regional temperature history of southeast Tibet derived from tree rings.The Holocene 20,181e190.

Yang,B.,Qin,C.,Br?uning,A.,Burchardt,I.,Liu,J.J.,2010a.Rainfall history for the Hexi Corridor in the arid northwest China during the past620years derived from tree rings.International Journal of Climatology31,1166e1176.

Yang,B.,Qin,C.,Huang,K.,Fan,Z.X.,Liu,J.J.,2010b.Spatial and temporal patterns of variations in tree growth over the northeastern Tibetan Plateau during the period AD1450e2001.The Holocene20,1235e1245.

S.Kang et al./Quaternary International283(2013)85e9291

Yuan,L.,1984.The Northwestern Drought and History of the Famine(in Chinese).

The People’s Publishing Company of Gansu Province.

Zhang, D.E.,Liang,Y.Y.,2010.A long lasting and extensive drought event over China in1876e1878.Advances in Climate Change Research1, 91e99.

Zhang,Y.,Gou,X.H.,Hu,W.,Peng,J.,Liu,P.,2005.The drought events recorded in tree ring width in Helan Mountain over past100years.Acta Ecologica Sinica25, 2121e2125.Zhang,D.E.,2004a.Variation of dry-wet climate and severe drought events as revealed in the climate records of China over the past1000years.Science and Technology Review(in Chinese)22,47e49.

Zhang,D.E.,2004b.A Compendium of Chinese Meteorological Records of the Last 3,000Years(in Chinese).Jiangsu Education Press.

Zheng,J.Y.,Wang,W.,Ge,Q.S.,2006.Precipitation variability and extreme events in eastern China during the past1500years.Terrestrial Atmospheric and Oceanic Sciences17,579e592.

S.Kang et al./Quaternary International283(2013)85e92 92