THE 1920S DROUGHT RECORDED BY TREE RINGS AND ...

THE 1920S DROUGHT RECORDED BY TREE RINGS ANDHISTORICAL DOCUMENTS IN THE SEMI-ARID AND ARID AREASOF NORTHERN CHINAERYUAN LIANG 1,2 , XIAOHONG LIU 1 ,YUJIANG YUAN 3 , NINGSHENG QIN 4 ,XIUQI FANG 5 , LEI HUANG 1 , HAIFENG ZHU 5 , LILY WANG 1,2and XUEMEI SHAO 1,21 Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences,Beijing 100101, P. R. China2 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing100085, P. R. ChinaE-mail: shaoxm@igsnrr.ac.cn3 Institute of Desert Meteorology, China Meteorological Administration, Urumqi 830002, P. R. China4 Climate Date Center of Qinghai, Xining 810001, P. R. China5 Beijing Normal University, Beijing 100875, P. R. ChinaAbstract. Using a network of tree-ring data, we show that there had been significant growth declinein the 1920s and early 1930s throughout a wide area of northern China. This growth depression isindicative of a severe and sustained drought in the 1920s and early 1930s, which was then confirmedwith a variety of historical and instrumental records including hydrological, meteorological, and documentaryevidence. The 1920s drought had a devastating effect not only on agricultural productivity,hydrological resources and society in the affected areas, but also on natural vegetation, as inferredfrom the tree-ring network and historical records. This research offers a picture of the drought calamityduring the 1920s and early 1930s in northern China, and demonstrates the potential to identify spatialanomalies of large-scale drought using tree-ring networks in the semi-arid and arid areas of northernChina.1. IntroductionLarge-scale or regional drought disasters can have significant social, economic andecological impacts (Neumann and Dettwiller, 1990; Ge and Wang, 1995; Xu, 1998;IPCC, 2001). In extreme cases, a drought disaster can cause flourishing societies andhighly developed civilizations to collapse abruptly (Bryson and Swain, 1981; Fang,1999; deMenocal, 2001; Weiss and Bradley, 2001; Huang et al., 2003). Knowledgeof past drought disasters could aid in the evaluation of potential regional hazards inthe future and facilitate the assessment of the links between regional and worldwidedroughts (Wilhite, 2000). As droughts continue to have increasingly costly and devastatingimpacts on our society, economy and environment, it is becoming even moreimportant to put the severe droughts of the 20th century into a long-term perspective(IPCC, 2001). This perspective can be achieved through the use of paleoclimaticrecords of drought. To date, understanding undocumented historical drought disastersis generally dependent on climatic proxies (Woodhouse and Overpeck, 1998),Climatic Change (2006) 79: 403–432DOI: 10.1007/s10584-006-9082-x c○ Springer 2006

404 ERYUAN LIANG ET AL.and of these climatic proxies, trees growing in the arid or semi-arid regions canprovide annual or seasonal records of drought events through the study of theirannual rings (Fritts, 1976; Bradley and Jones, 1992; Schweingruber, 1996). Unlikethe general descriptions of drought disasters in historical records, high-resolutionprecipitation reconstructions using tree rings and other climatic proxies can providequantitative estimates of anomalous rainfall deficiency. In several case studies,tree-ring data has successfully reproduced the severe and sustained drought of the1660s and 1579–1598 in the Upper Colorado River Basin (Meko et al., 1995), themegadrought of the 16th century in North America (Stahle et al., 2000), the LostColony and Jamestown droughts in the southeastern USA (Stahle et al., 1998) andthe prolonged droughts in 1429–1519 and 1634–1741 in the northeastern TibetanPlateau (Shao et al., 2005). In addition, tree-ring networks can provide a pictureof temporal and spatial patterns of past drought events (Fritts, 1974; Hughes andGraumlich, 1996; Villalba and Veblen, 1997; Cook et al., 1999), enabling scientiststo learn more about the characteristics of droughts.China is subject to a strong monsoon climate with precipitation varying greatlyfrom year to year and from season to season (Zhang and Lin, 1992). In some years,rainfall is abundant enough to cause flooding, while in other years there is toolittle rain to support agriculture from region to region (http://www.mwr.gov.cn/english1/20040802/38161.asp). Thus affected by monsoons and topography, Chinais one of the countries with the most frequent drought and flood hazards in theworld (http://w.mwr.gov.cn/english1/20040802/38161.asp). According to the reportof damage in China (1949–1995), among all disasters, droughts lead to thegreatest economic loss (Damage Report, 1995). Based on the dryness/wetness indicesin eastern China over the last 530 years, studies found that the dry and wetanomalies initially appeared in northeastern China and then migrated to affectsouthern China (Hu and Feng, 2001; Qian and Zhu, 2001). The regional characteristicsof interannual and interdecadal variability are also outstanding. A quasi-20aand a quasi-70a oscillation exist in temperature and precipitation series in differentregions over China, but wet and dry spells occur in an opposite phase in the northand the south (Qian et al., 2003). The 1920s was the driest decade in northern Chinaof the past 120 years, and this dryness coincided with elevated temperatures (Xu,1997; Wang et al., 2004a).The identification of links between tree growth and documented drought eventsallows us to determine how accurately tree-ring records reflect drought occurrence.The 1920s drought was the most severe and well-recorded natural hazard in thelast 200 years in the semi-arid and arid areas of northern China (Xu, 1997). Avariety of historical records including newspapers, unpublished reports, and booksabout natural hazards in each province documented the 1920s drought and itssocial impact (Deng, 1937; Li et al., 1994). Based on the historical record, Li et al.(1994) considered the 1928–1930 drought to be one of the top ten natural disastersin modern Chinese history (1840–1949). Also recently, Xu (1997) analyzed thepossible social and natural factors leading to the great famine in the 1920s and early

THE 1920S DROUGHT IN NORTHERN CHINA 4051930s in Northwest China. Based on dryness/wetness indices in the past 500 yearsin Northwest China, Dong et al. (2000) found that severe droughts, including the1920s drought, usually started in South Ningxia and central Gansu (see Figure 1),and then expanded to Northwest China. The hydrological station in the middlereaches of the Yellow River also showed an 11-yr low-flow period from 1922 to1932 (Shi et al., 1991; Liu and Wu, 1996). In comparison with the 1930s DustBowl in the southern plains of the USA (Worster, 1982; Woodhouse and Overpeck,1998), most studies of the 1920s drought have been based on historical records inChinese and have received scant mention in international journals (Hughes et al.,1994; Fu et al., 1999; Qian and Zhu, 2001; Liang et al., 2003). Recently, severalstudies have also reported that the 1920s drought in northern China was recorded intree rings (Hughes et al., 1994; Zhang and Wu, 1997; Liu and Ma, 1999; Liang et al.,2003; Liu et al., 2004). These studies were, however, limited to a few forest standsin North China. Moreover, most dendrochronological studies in China have beenconfined to climatic reconstructions of a single or just a few tree-ring sites, and todate no large-scale drought or precipitation reconstructions have been completed.The development of a tree-ring network in recent years and the availability ofdocumentation of the well-recorded 1920s drought provide a rare opportunity tocapture the links between the growth of drought-sensitive trees and documentedevidence of drought, and to thus examine the possibility of recovering past largescaledrought events using tree rings.In this study, fourteen tree-ring chronologies, four precipitation and two moistureindex series derived from tree rings in the semi-arid and arid areas of northernChina were selected for analysis. The detailed historical records concerning theeffect of the 1920s drought on agriculture, society, and hydrological systems wereemployed to demonstrate the intensity, duration and spatial extent of the 1920sdrought, allowing for a comparison to be made with drought-related informationderived from a large-scale tree-ring network.2. Study Areas, Climate and Tree-Ring Network2.1. STUDY AREAS AND TREE-RING NETWORKThe study areas are the semi-arid and arid regions of northern China (Figure 1).Along an east-west orientation, the drought-prone forest sites were selected from theTaihang and Yinshan Mountains in North China (Region 1), the Qinling Mountains(Region 2), the Qilian Mountains (Region 3), the mountains in the east margin ofthe Qaidam Basin (Region 4), the South Qinghai Plateau (Region 5), the east TianshanMountains (Region 6) and the middle-west Tianshan Mountains (Region 7)(Figure 1). The distance between the most eastern forest site (XWT) in Region 1and the most western forest site (ZL) in Region 7 is about 2825 km. Based on administrativedivisions in China, tree-ring sites are situated in six provinces in North

406 ERYUAN LIANG ET AL.Figure 1. Map of the study area, tree-ring sampling sites (), capital of several provinces (◦ ), meteorological stations and other cities (◦), the rivers andlakes mentioned in the text in the upper and middle reaches of the Yellow River in northern China. Tree-ring sites in the same region are enclosed by acircle. Four forest stands (XWT, HHT, JGB, BT) in North China (Region 1), three in the Huashan Mountains (HS) (Region 2), six (CLS2, HX1, QYG,DDS, QF1, QF2) in the Qilian Mountains (Region 3), eight (HT1, WL4, WL3, DLH1-DLH5) in the east margin of the Qaidam Basin (Region 4), two(ZHD and QYG) in the South Qinghai Plateau (Region 5) and ten (YW1, HM1, JMS, FKA, XGS, BEQ, XBY, TL, TU and ZL) in the Tianshan Mountains(Regions 6 and 7) were indicated. The location of the Daihai, Huangqihai and Hongjiannao Lakes is indicated by an arrow. The dryness/wetness index datain Figure 10 are from fifteen stations including Hohot, Xi’an, Yinchuan, Lanzhou, Xining, Zhangye and others indicated by black squares ().

THE 1920S DROUGHT IN NORTHERN CHINA 407TABLE ISite description and general characteristics of eight new tree-ring width standardized chronologies inthis study. All the chronologies are listed along an east-west direction in northern China. The species(s) include 1, Pinus tabulaeformis; 2,Pinus armandii; 3,Picea crassifolia; 4,Sabina przewalskii.MS, mean sensitivity; CP, calibrating period (years) between tree-ring width chronologies andprecipitation records in the nearby meteorological stations (Figure 4)Chronology Elevation Trees/code S Latitude (N) Longitude (E) m asl Years Cores MS CPXWT 1 39 ◦ 52 ′ 06 ′′ , 114 ◦ 57 ′ 18 ′′ 1600 1888–2002 20/37 0.38 49JGB 1 39 ◦ 29 ′ , 110 ◦ 42 ′ 1347 1850–1998 30/61 0.39 42DDS 3 39 ◦ 02 ′ 54 ′′ , 103 ◦ 48 ′ 42 ′′ 2666 1787–2003 31/92 0.22 53CLS2 1 37 ◦ 26 ′ 41 ′′ , 103 ◦ 41 ′ 25 ′′ 2512 1842–2003 18/54 0.32 52HX1 3 37 ◦ 29 ′ 26 ′′ , 102 ◦ 26 ′ 27 ′′ 2750 1826–2003 30/88 0.17 53HT1 4 37 ◦ 02 ′ 06 ′′ , 98 ◦ 40 ′ 3736 860–2002 12/22 0.37 47QF1 3 39 ◦ 25 ′ 29 ′′ , 98 ◦ 26 ′ 29 ′′ 2783 1816–2003 17/51 0.34 53QF2 4 39 ◦ 25 ′ 18 ′′ , 98 ◦ 26 ′ 10 ′′ 3060 1729–2003 18/52 0.32 53China (Hebei, Inner Mongolia) and Northwest China (Shaanxi, Gansu, Qinghaiand Xinjiang).In Region 1, natural forests have become rare because of long-term humandamage, with the exception of small patches around temples or along steep cliffs(Liang et al., 2003). Four Chinese pine (Pinus tabulaeformis Carr.) forest standsfrom the Xiaowutai Mountain (XWT) on the northwestern edge of the TaihangMountains, Yinshan Mountains (HHT, BT) and Erdos Plateau (JGB) were selectedfor the tree-ring analysis (Figure 1, Table I, II). A standard ring-width chronologyat HHT was taken from Zhang (1994). The BT tree-ring samples were taken byLi et al. (1992) and were re-crossdated later to correct some dating errors (Lianget al., 2003). The JGB and XWT records were developed in this study.Tree ring samples of Huashan pine (Pinus armandii Franch.) were collectedfrom the eastern (HSE), southern (HSS) and western (HSW) peaks of the HuashanMountains (HS) in Region 2 (Figure 1, Table II), and three standard tree-ringchronologies were developed by Shao and Wu (1994).Sixteen forest stands were selected in the northeastern Tibetan Plateau (Regions3–5). In September 2003, five new tree-ring sampling sites were collected from theChanlingshan (CLS2), Haxi (HX1), Dongdashan (DDS), Qifeng (QF1 and QF2)forest centers in Gansu Province in Region 3 (Figure 1, Table I). One Qilian juniper(QYG) tree-ring width chronology in Qilian County of Qinghai Province was developedby Zhang and Wu (1997). In Region 4, eight Qilian juniper (Sabina przewalskiiKom.) forest stands (HT1, WL4, WL3, and DLH1-DLH5) are located in the aridarea (Figure 1, Table II) (Shao et al., 2003, 2005). Several juniper chronologies(WL4, WL3 and DLH1-DLH5) of over 1000 years have been established by Shaoet al. (2003, 2005) and HT1 was developed in this study. In Region 5, two tree-ring

408 ERYUAN LIANG ET AL.TABLE IISite description and general characteristics of twenty-five published tree-ring width standardizedchronologies. The species (s) include 1–4 (see Table I); 5, Sabina tibetica;6,Larix sibirica;7,Piceaschrenkinna var. tianschanica. MI, moisture index; CP, calibrating period (years) between tree-ringchronologies and precipitation records in the nearby meteorological stationsElevation Trees/ PrecipitationCode S Latitude N Longitude E m asl Years Cores MS CP (pre) signal SourceHHT 1 40 ◦ 48 ′ 111 ◦ 17 ′ 1300 1622–1991 19/38 0.33 41 Feb–Jun pre Zhang, 1994BT 1 40 ◦ 50 ′ 110 ◦ 21 ′ 460 1724–1987 30/61 0.42 37 Feb–Jul pre Li et al., 1992; Liuet al., 2001HSE 2 34 ◦ 28 ′ 46 ′′ 110 ◦ 04 ′ 56 ′′ 2050 1458–1992 13/26 0.23 Apr–Jun pre Shao and Wu, 1994HSW 2 34 ◦ 28 ′ 55 ′′ 110 ◦ 04 ′ 45 ′′ 2050 1359–1992 13/26 0.23 40HSS 2 34 ◦ 28 ′ 43 ′′ 110 ◦ 04 ′ 43 ′′ 2100 1512–1992 14/28 0.22QYG 4 38 ◦ 08 ′ 30 ′′ 100 ◦ 32 ′ 50 ′′ 3500 1259–1993 15/24 0.26 37 May–Jul MI Zhang and Wu, 1997WL4 4 36 ◦ 40 ′ 76 ′′ 98 ◦ 24 ′ 97 ′′ 3700 900–2002 21/32 0.52 47 pJul–Jun pre Shao et al., 2005WL3 4 36 ◦ 44 ′ 52 ′′ 98 ◦ 13 ′ 13 ′′ 3720 681–2002 23/43 0.50DLH4 4 37 ◦ 26 ′ 19 ′′ 98 ◦ 03 ′ 23 ′′ 3660 1005–2002 27/46 0.51DLH5 4 37 ◦ 26 ′ 59 ′′ 97 ◦ 47 ′ 06 ′′ 3700 757–2002 24/47 0.62DLH3 4 37 ◦ 27 ′ 08 ′′ 97 ◦ 32 ′ 55 ′′ 3920 404–2002 22/42 0.45DLH1 4 37 ◦ 28 ′ 14 ′′ 97 ◦ 14 ′ 06 ′′ 3730 843–2002 25/41 0.36DLH2 4 37 ◦ 28 ′ 05 ′′ 97 ◦ 13 ′ 44 ′′ 3780 828–2002 25/41 0.45ZHD 5 33 ◦ 43 ′ 96 ◦ 17 ′ 3950 1374–2002 54/27 0.22 46 Apr-Jun MI Qin et al., 2003QML 5 33 ◦ 48 ′ 96 ◦ 08 ′ 4060 1480–2002 57/29 0.27YW1 6 43 ◦ 01 ′ 95 ◦ 02 ′ 2594 1456–1979 18/? 0.31 21 pOct–Jan pre Li, 1989HM1 6 43 ◦ 20 ′ 93 ◦ 18 ′ 3026 1678–1979 25/50 0.14 29 Jul–Sep pre Li, 1989JMS 7 43 ◦ 50 ′ 89 ◦ 07 ′ 1985 1510–1989 49/24 0.19 27 Drought days Zhang et al., 1996FKA 7 43 ◦ 54 ′ , 87 ◦ 59 ′ 2500 1660–1988 15/29 0.20 27 Drought days Zhang et al., 1996XGS 7 43 ◦ 16 ′ 35 ′′ 87 ◦ 14 ′ 05 ′′ 2070 1667–1993 94/47 0.44 34 May pre Yuan et al., 2001BEQ 7 43 ◦ 08 ′ 20 ′′ 87 ◦ 07 ′ 12 ′′ 2440 1630–1993 28/14 0.33 34 pJul–Feb pre Yuan et al., 2001XBY 7 43 ◦ 24 ′ 10 ′′ 87 ◦ 07 ′ 02 ′′ 2270 1752–1993 60/30 0.31 34 Yuan et al., 2001TL 7 42 ◦ 53 ′ 23 ′′ 81 ◦ 59 ′ 50 ′′ 2110 1580–1995 28/14 0.11 36 pJun–May Yuan et al., 2000TU 7 42 ◦ 50 ′ 32 ′′ 81 ◦ 58 ′ 24 ′′ 2724 1682–1995 28/14 0.11 36 pre Yuan et al., 2000ZL 7 42 ◦ 44 ′ 52 ′′ 81 ◦ 05 ′ 45 ′′ 2270 1676–1995 23/15 0.12 36 Yuan et al., 2000width chronologies of Tibet juniper (Sabina tibetica Kom.) in Zhiduo (ZHD) andQumalai (QML) have been developed by Qin et al. (2003).Nine published tree-ring width chronologies (YW1, HM1, JMS, XGS, BEQand XBY) from Regions 6 and 7 were also used in this study (Figure 1, Table II).Among them, two tree-ring chronologies of Siberian larch (Larix sibirica Ledeb)are from Hami (HM1) and Yiwu (YW1) in Region 6 (Li, 1989) and seven Tianshanspruce (Picea schrenkinna var. tianschanica) forest sites are located in Jimusare(JMS) (Zhang et al., 1996), the Urumqi River Basin (BEQ, XBY, XGS) (Yuan et al.,2001) and Yili (ZL, TU and TL) (Yuan et al., 2000) in Region 7 (Figure 1, Table II).2.2. CLIMATE IN THE STUDY AREAThe climate in Regions 1 and 2 is strongly influenced by the East Asian monsoon.Tree-ring sampling sites (XWT, HHT, JGB and BT) in Region 1 are near the

410 ERYUAN LIANG ET AL.TABLE IIIThe meteorological stations closed to the tree-ring sampling sites and their total annual precipitation (TNP) and mean annualtemperature (MAT)Tree ring I.D. Meteorological stations Latitude N Longitude E Elevation m asl Years TNP mm MAT ◦ CXWT Yuxian 39 ◦ 50 ′ 114 ◦ 34 ′ 910 1954–2002 411 6.8HHT Hohot 40 ◦ 49 ′ 111 ◦ 41 ′ 1063 1951–2002 408 6.3HS Huashan 34 ◦ 29 ′ 110 ◦ 05 ′ 2100 1953–2002 702 6.1JGB Dongsheng 39 ◦ 50 ′ 109 ◦ 59 ′ 1460 1957–2002 386 5.9BT Baotou 40 ◦ 40 ′ 109 ◦ 51 ′ , 1067 1951–2002 299 6.9HX1 Tianzhu 37 ◦ 12 ′ 102 ◦ 53 ′ 3045 1951–2002 408 −0.9CLS2 Wuwei 37 ◦ 55 ′ 102 ◦ 40 ′ 1531 1952–2002 164 7.8QYG Qilian 38 ◦ 11 ′ 100 ◦ 15 ′ 2787 1957–2002 401 0.9DDS Zhangye 38 ◦ 56 ′ 100 ◦ 26 ′ 1483 1951–2002 128 7.1QF1, 2 Jiuquan 39 ◦ 46 ′ 98 ◦ 29 ′ 1477 1951–2002 85 7.4HT1 WL3-4 Wulan 36 ◦ 55 ′ 98 ◦ 29 ′ 2950 1981–2002 178 5.6DLH1-5 Delingha 37 ◦ 22 ′ 97 ◦ 22 ′ 2982 1956–2002 161 3.6ZHD Zhiduo 33 ◦ 51 ′ 95 ◦ 36 ′ 4179 1968–1990 404 −1.6QML Qumalai 34 ◦ 33 ′ 95 ◦ 29 ′ 4232 1957–2002 398 −2.3YW1 Yiwu 43 ◦ 16 ′ 94 ◦ 42 ′ 1729 1959–2002 97 3.8HM1 Hami 42 ◦ 49 ′ 93 ◦ 31 ′ 738 1951–2002 38 15.1JMS Jimusare 44 ◦ 01 ′ 89 ◦ 10 ′ 735 1961–1989 171 6.6FKA Urumqi 43 ◦ 47 ′ 87 ◦ 37 ′ 918 1951–2002 262 6.7BEQ, XBY XGS Daxigou 43 ◦ 06 ′ 86 ◦ 50 ′ 3544 1959–1998 543 2.2ZL TU TL Zhaosu 43 ◦ 09 ′ 81 ◦ 08 ′ 1849 1956–2002 505 3.2

THE 1920S DROUGHT IN NORTHERN CHINA 411Feb–July precipitation in Baotou (Liu et al., 2001) can be explained by the HHT andBT chronologies, respectively. Tree-ring chronologies (ring width and maximumdensity) of Huashan pine account for about 55% of May–June precipitation at onesite (Hughes et al., 1994). In addition, 66% and 64% of the variance of April–Juneprecipitation (Shao and Wu, 1996) and May–June drought indices (Liu et al., 2002)can be captured by the HS tree-ring chronologies, respectively.In Regions 3 and 4, precipitation, especially in May and June, is the most dominantlimiting factor for tree growth. The QYG tree-ring width chronology in Region3 explains 60% of the variance of May–July moisture indices, as defined by theratio of monthly precipitation to monthly mean temperature (Zhang and Wu, 1997).The first principal component series extracted from these seven millennial lengthchronologies (DLH1 to DLH5, WL3 and WL4) explains 63% of the annual precipitation(from July to June) variance in Delingha in Region 4 (Shao et al., 2005)and captures the transition from the dry spell to the wet spell in the past 20 yearsin Northwest China (Shi, 2003). In Region 5, Qin et al. (2003) reported that theQML and ZHD chronologies together account for 30% of the variance of May–Junemoisture indices.In Regions 6 and 7, tree growth is also primarily influenced by seasonal precipitation(Table II). HM1 and YW1 of Region 6 show a significant and positiveresponse to May–September and December–January precipitation, respectively (Li,1989). In Region 7, BEQ and XBY explain 62% of the total variance of observedprecipitation from July through February (Yuan et al., 2001). In addition, Zhanget al. (1996) reported that the mean tree-ring series of six chronologies includingJMS and FKA had a strong and negative correlation with regional drought days.Three chronologies (ZL, TU and TL) together can explain 75% of the variance inannual (June–May) precipitation (Yuan et al., 2000).2.4.2. Climatic Signals Recorded in the New Tree-Ring ChronologiesAll eight new tree-ring chronologies in Regions 1 and 3 contain strong precipitationsignals. They show a high correlation with precipitation in July, August andSeptember (or one of these months) of the previous year, and May–June of thegrowth year (Figure 2). At the XWT, JGB and HX1 stands, precipitation duringthe early spring also has a significant impact on tree growth (Figure 2). In addition,a strong negative relationship was found between tree growth and monthly meantemperature in May and June at XWT, and June at CLS2, DDS, QF1 and QF2, andApril and June at HT1.Precipitation is a pronounced limiting factor for tree growth in these semi-aridand arid regions, where the annual precipitation ranges from 89 to 400 mm. Basedon annual temperature variation, cambial activity starts in May at most forest sites(Zhang et al., 1982). During the early growing season, sufficient soil moisture isnecessary for tree growth. However, the recharge of soil water prior to tree growthand precipitation in the early growing season in these semi-arid and arid regionsof northern China is often not sufficient to meet the needs of biological processes;

412 ERYUAN LIANG ET AL.Figure 2. Correlation coefficients between eight new tree-ring width chronologies with monthlyprecipitation and monthly mean temperature at nearby meteorological stations (Table III). Blackcircles indicate positive correlations and empty circles indicate negative correlations. The shadingrepresents the data significance at the p < 0.05 level. The circle size shows the strength of correlation,in which the smallest circle denotes r ≤ 0.15 and the largest circle denotes r ≥ 0.50 with the intervalof 0.05. For calibrating periods see Table I.therefore, precipitation in the previous August–September and May–June of thegrowth year has a significant correlation to tree growth. In those years when theclimate was extremely dry, such as 1928 and 1929, cambial activity was so inhibitedthat a locally absent ring occurred. Several studies in the semi-arid and arid areasof northern China all revealed that precipitation in the early growing season inMay and June and soil water storage prior to tree growth is critical for tree growth(Liang et al., 2001; Liu and Ma, 1999; Zhang et al., 2003; Shao et al., 2005).A negative correlation between tree growth and temperature is also indicative ofmoisture limitation on tree growth in the study area (Liang et al., 2001; Shaoet al., 2005). The analysis suggests that these tree-ring chronologies are sensitiveto precipitation and are thus excellent records of past moisture variation. Togetherwith the published tree-ring chronologies, the tree-ring network described in thisstudy is an important resource for examining large-scale drought events in northernChina.2.5. CORRELATIONS AMONG THE TREE-RING CHRONOLOGIESMultiple analyses revealed the similarity in magnitude and trend of ring-widthvariation between the chronologies within the same regions (Figures 3 and 4). In

THE 1920S DROUGHT IN NORTHERN CHINA 413Figure 3. The strength of correlation between the tree-ring standard chronologies during their overlappingperiod (1852–1979) (left). The correlation coefficients derived from the chronologies afterthe first order difference (1853–1979) is shown on the right side. The common interval between XWTwith other chronologies is from 1890 to 1979. Black circles indicate positive correlations and emptycircles indicate negative correlations. The shading represents the data significance at the p < 0.001level. The circle size shows the strength of correlation, in which the smallest circle denotes r ≤ 0.10and the largest circle denotes r ≥ 0.90 with the interval of 0.10.Region 1, significant correlations (P< 0.001) exist among four adjacent Chinesepine standard chronologies (XWT, HHT, JGB and BT), which also exhibit a highcorrelation with HX1 (P< 0.001), CLS2 and DDS (P< 0.05 or 0.01) in Region 3.The mean HS chronology in Region 2 only demonstrates a significant correlationwith HHT and XWT in Region 1 at the P < 0.05 level. Despite the great distancebetween some forest sites (more than 500 km), the correlation between the fourteenchronologies in Regions 3 and 4 is high and most correlations are at the P< 0.001 or0.01 level (Figure 3). The chronologies (ZHD and QML) in Region 5 also exhibit ahigh correlation with the ones in Region 4. Significant correlations at the p < 0.001level also exist among YW1, HM1 and JMS in Regions 6 and 7 and among XGS,

414 ERYUAN LIANG ET AL.BEQ and XBY in Region 7. Aside from the high correlation among TL, TU and ZLin the western part of Region 7, ZL also shows a significant correlation (P < 0.001)with the chronologies (FKA, XGS, BEQ and XBY) in the eastern part of Region 7.In addition, a significant correlation is evident among the remote chronologies inRegions 1 and 3.After the first-order difference, the correlation between the chronologies in differentregions was partly altered (Figure 3). Apart from the strong correlationbetween HX1, DDS and QYG in Region 3 and HT1 and WL4 in Region 4, thelinkage between the chronologies in these two regions decreases. The ZHD andQML chronologies in Region 5 display a weaker correlation to the chronologiesin Region 4. In addition, the correlation between YW1 with HM1 and with JMS isalso lower.The parallel behavior of relatively nearby chronologies indicates a regional synchronizationof tree-ring variations. The highest correlation between the chronologieswas found in the arid region (Region 4), where tree growth is strongly linked toseasonal precipitation (Shao et al., 2005). According to the correlation between thechronologies (after the first-order difference), the tree-ring network in this studycan be divided into seven major dendrochronological regions (Figure 1). Such dendrochronologicalregions are closely related to the difference in regional climate.The climate in Region 3 is influenced by the East Asian monsoon and the Westerlies,which may result in the high correlation between the chronologies in this regionwith the ones in Regions 1 and 4. The frequency-dependent tree-ring correlationbetween regions also revealed the effect of regional climate change on tree growth.3. The 1920s Drought Recorded by Tree Rings3.1. TREE GROWTH DECLINE IN THE 1920SThe smoothed ring-width chronologies show rather similar patterns of variationwithin the regions (Figure 4). The growth development differed more among distantforest sites, although some common patterns were also observed. Within theperiod of the last 200 years, pronounced and abnormal growth depression occurredduring the 1920s and early 1930s in Regions 1–4 (Figure 4). In Region 5, treegrowth decline was also evident in the 1920s, as indicated by the QML and ZHDchronologies (Qin et al., 2003, 2004). In Regions 6 and 7, the most significantgrowth decline in the 1920s and early 1930s is found in HM1 and YW1 in eastXinjiang (Figure 4). For the JMS, XGS, XBY and WLL chronologies in Region 7(Figure 4), the growth depression is also observed, but its magnitude is lesser thanthat in other regions. A significant growth decline in Chinese pine in the 1920s wasalso evident in the Helan Mountains (39 ◦ 05 ′ N, 106 ◦ 05 ′ E) (Liu et al., 2004) and inHuangling (35 ◦ 35 ′ N, 180 ◦ 41E ′ ) in central Shaanxi Province (Liu et al., 1997).

THE 1920S DROUGHT IN NORTHERN CHINA 415Figure 4. Tree-ring width patterns for the standardized chronologies with 5-year moving averages(thick line) in the last 200 years. The period from 1922 to 1932 is delineated by two vertical lines.The sites in the same regions are identified by a bracket on the left side.3.2. THE OCCURRENCE OF MISSING RINGS IN THE 1920S AND EARLY 1930SFrequently missing rings were observed in the late 1920s and the early 1930sin several regions (Figure 5). In Region 1, a high percentage of missing ringsoccurred in 1928, 1929 and 1931. Over the entire period of study (113–200 years)

416 ERYUAN LIANG ET AL.Figure 5. The percent of missing rings from 1922 to 1932 in 20 east-west oriented stands in northernChina. The period from 1922 to 1932 is delineated by two vertical lines. At HHT, only missing ringsfrom 1922 to 1932 were plotted. The sites in the same regions are identified by a bracket on the left side.(Figures 4 and 5), the highest percentage of missing rings occurs in 1928 at XWTand in 1929 at the other stands. In Region 2, extremely narrow rings occurred in 1928and 1929 and a few missing rings were found in 1929 (Shao and Wu, 1994). Theincidence of missing rings in Chinese pine in 1929 was also reported in Huangling in

THE 1920S DROUGHT IN NORTHERN CHINA 417Shaanxi Province (Liu et al., 1997). In Region 3, the highest occurrence of missingrings in the past 200 years occurs in 1928 at CLS2, HX1 and DDS. Missing ringsdid occur in 1926 and 1927 at QF1 and QF2, but their frequency is lower thanthat of 1962 and 1995 (QF2), in the context of the 200-year period. In Region 4,there is a high occurrence of missing rings in 1929 and 1931 at HT1, WL3 andWL4, and in 1930 at DLH1-DLH5. However, the frequency of missing rings inthe 1920s is much lower than that of 1824, 1861 and 1918 in the past 200 years.Missing rings were also found at QML and ZHD in Region 5, but they did not occurwith the greatest frequency over the past 200 years. No detailed information aboutthe occurrence of missing rings in the 1920s was available in the research reportsfrom Regions 6 and 7 (Li, 1989; Yuan et al., 2000, 2001). Frequently missing ringsand dramatic tree growth decline in these forest stands are indicative of large andextensive growth depressions in the 1920s and early 1930s.The occurrence of missing rings implies that extreme climatic conditions cannotmeet the various species’ ecological requirements (Fritts, 1976). As mentionedabove, tree growth is primarily limited by precipitation in the semi-arid and aridareas of northern China. Thus, the comparatively synchronized growth shocks exhibitedby trees in northern China in the 1920s and early 1930s were probably theresult of the large-scale, severe, and sustained drought of this period. This droughtappears to have been the most severe and most persistent in (at least) the last 150 to200 years in Regions 1, 2 and 3. As inferred from the frequency of missing rings,peak drought disaster in the 1920s may have occurred in 1928–1929 in Region 1,in 1928 in the eastern segment of Region 3, in 1926–1927 in the western segmentof Region 3 and in 1929–1931 in Region 4. As shown in Figure 6, the HHT, JGBand BT stands of Region 1 experienced a long-lasting drought from 1926 to 1929,of which an extreme drought with a dryness/wetness index of 5 occurred in 1928and 1929. However, the XWT site was not subject to extreme drought in 1927and 1929. No summer drought occurred in 1930 in Region 1 (Figure 6). The dryness/wetnessindices in Figure 6 supported the highest percentage of missing ringsin 1928 at XWT and other sites in 1929 in Region 1 in the 1920s and early 1930s.The sustained drought from 1922 to 1932 hit the eastern part of Region 3 and thedrought in 1928 was extremely severe (with a dryness/wetness index of 5). In theother regions, the peak drought inferred from high percentage of missing rings cannot be validated by the dryness/wetness index because of a data deficit.3.3. THE SPATIO-TEMPORAL OCCURRENCE OF THE 1920S DROUGHT DERIVEDFROM TREE RINGSThe spatio-temporal distribution of the 1920s drought can be partly inferred fromtree-ring analysis of drought-sensitive forest stands. Although there is a generalspatial synchronicity of tree growth decline associated with drought, the tree-ringnetwork also shows intra-regional variations in drought intensity. Based on the

418 ERYUAN LIANG ET AL.Figure 6. Dry distributions derived from the dryness/wetness indices from 1922 to 1932 in China(Xu, 1997). The dryness/wetness indices are derived from historical records and are classified into 5grades: 1-very wet, 2-wet, 3-normal, 4-dry and 5-very dry. The single lines show dry (grade 4) areas,and cross lines shows very dry (grade 5) areas. The first figure shows the study area and forest sitesin Figure 1.tree-ring network in this study, the 1920s drought may have occurred in NorthChina, and in Ningxia, east Qinghai, Gansu and east Xinjiang in Northwest China.The reconstruction of April-August and May-June precipitation in Baekdam-Jang(38 ◦ 9 ′ 30 ′′ N, 128 ◦ 22 ′ 30E) and Dae-Seung (38 ◦ 9 ′ 28 ′′ N, 128 ◦ 22 ′ 30 ′′ E) in northeasternKorea shows that the strongest precipitation deficiency over the past 100–150years occurred in the 1920s and 1930s (Park et al., 2001 a, b). As indicated bytree-ring analysis (Pederson et al., 2001; Jacoby et al., 2003) and historical reconstruction(Mijiddor and Namhay, 1983), the central-eastern part of Mongolia alsoexperienced the severe 1920s drought. However, no significant growth decline wasfound in forest sites in western Mongolia (Jacoby et al., 2003). The lowest growth

THE 1920S DROUGHT IN NORTHERN CHINA 419also occurred in 1922 and 1930 in eastern Inner Mongolia (Zhang, 1994; Lianget al., 2003), where the amplitude of tree growth decline was weaker than that inRegion 1. At the XWT stand of Region 1, the number of missing rings is significantlylower than that in other Chinese pine stands, indicating that the drought wasless severe in northern Hebei Province (Li et al., 1994). The XWT stand only hada dryness/wetness index of 4 in 1926, 1928 and 1931 (Figure 6), a milder droughtcondition relative to other stands of Region 1 in the 1920s and early 1930s. Thegrowth decline from 1922 to 1932 is more pronounced at the JGB stand of Region1 (Figure 4). At the BT and HHT stands, the growth decline was significantbeginning in 1926 (Figure 4). Although the HHT and BT stands are close to theJGB stand, the onset of tree growth at these stands capture the spatial variation ofthe 1920s drought (Figure 6). The HS tree-ring series of Region 2 also shows adramatic growth decline in the 1920s, which was the most severe drought (culminatingin 1929) over the 389-yr period, as indicated by a reconstruction of regionalMay–June (Hughes et al., 1994) and April–June precipitation (Figure 7a). The reconstructionof April–June precipitation (1890–1989), based on tree ring densityand stable isotopes in Huangling in central Shaanxi Province, indicated that themost severe drought occurred in the late 1920s in the past 100 years (Liu et al.,1997). Similarly, the May-June precipitation reconstruction using latewood widthsof Chinese pine in the north Helan Mountains also showed a significant droughtinterval in the 1920s (Liu et al., 2004). In the west, Region 3 experienced the severeand sustained drought in the 1920s, as reflected by the dramatic growth decline ofdrought-sensitive trees (Figure 4). In the context of the past 700 years, the lowestmoisture indices in the middle part of Region 3 occurred in the 1920s, which isindicative of dry and warm conditions (Zhang and Wu, 1997) (Figure 7b). The1920s drought was more severe in the eastern part of Region 4, such as HT1, WL3and WL4, compared with DLH1-DLH5 at the western part of Region 4 (Figure7c). However, it is not the most severe drought in the past 200 years in this region.Significant tree growth decline (QML and ZHD) was also observed in Region 5(Figure 7d) (Qin et al., 2003), which was then confirmed with historical records(Chen and Cheng, 1997). The drought was also severe in Region 6 (HM1 andYW1), but weaker in Region 7 (Figure 7e,f). In Regions 4, 6 and 7, few historicalrecords are available to validate the spatial variance of the 1920s drought. Insummary, tree-ring analysis and tree-ring based precipitation reconstructions showthat the 1920s drought was a rare and geographically extensive event. However,more tree-ring sites are needed to fully capture the spatio-temporal occurrence ofthe 1920s drought over northern China.4. Instrumental and Historical Records of the 1920s DroughtA variety of historical records provide a frame of reference for assessing climaticextremes in the 1920s and early 1930s in northern China. The monthly

420 ERYUAN LIANG ET AL.Figure 7. The reconstruction of (a) April–June precipitation based on two chronologies (HSE andHSW) in Region 2 (Shao and Wu, 1996), (b) May–July moisture indices based on the QYG chronologyin Region 3 (Zhang and Wu, 1997), (c) July–June precipitation based on the first principal componentof the seven chronologies (WL4, WL3, DLH1-DLH5) in Region 4 (Shao et al., 2005), (d) May–Junemoisture indices based on the ZHD and QML chronologies in Region 5 (Qin et al., 2004), (e) July–February precipitation based on the BEQ and XBY chronologies in Region 7 (Yuan et al., 2001)and (f) June–May precipitation based on the ZL, TU and TL chronologies in Yili of Region 7 (Yuanet al., 2000). Each reconstruction is based on the linear regression. The period from 1922 to 1932 isdelineated by two vertical lines.

422 ERYUAN LIANG ET AL.Figure 8. The annual precipitation (mm) in 1928 and 1929 in (a) Pingyao (37 ◦ 11 ′ N, 112 ◦ 13 ′ E,767.4 m asl) of Shanxi Province, (b) Shanxian (34 ◦ 48 ′ N, 111 ◦ 12 ′ E, 410 m asl) of Henan Province(Chu, 1936), (c) The annual precipitation series in Taiyuan of Shanxi Province, 1926–2000.

424 ERYUAN LIANG ET AL.TABLE IVThe hydrological records about the 1920s drought derived from historical documentsItems Hydrological records SourceRiver runoff in1928 in GansuProvinceOther rivers innorthernChina andMongoliaInland lakesIt was estimated that the stream flowin 1928 in Gansu Province had adecrease of 64% compared withthe mean (2.99 × 10 10 m 3 )The low-flow period of the HeiheRiver in the late 1920s and early1930s (derived from tree rings)The Taohe and Jialingjiang riverswere exhausted in 1928. Boats cangenerally cross the Jinghe,Hanjiang and Baohe rivers, butthese rivers stopped flowing in thesummer of 1928The severe drought caused thedrying up of wells and springs in1928Low runoff in the Yongding river(1926–1932) and Hutuo river(1925–1932) in North China.Shallow water in the Weihe river ofShaanxi ProvinceRunoff decline in the Tongtian river,as indicated by tree-ring analysisin the source region of theYangtze RiverThe lowest stream flow of theKherlen river over the past 345years occurred from 1925 to 1929,as derived from tree-ring widthdata in northeastern MongoliaHuangqihai Lake in central InnerMongolia desiccated in 1929Daihai Lake only had a surface areaof 50 km 2 from 1927 to 1929,compared to an area of 169 km 2 inthe 1960sHongjiannao Lake in north Shaanxilost all the water in 1929, while ithad an average of 60 km 2 in the1960s and 1970sThe editing committee for “Theflood/drought Hazards in GansuProvince”, 1996Kang et al., 2002; Wang et al., 2004bSummary documents of disaster relief,1928Deng, 1937Summary documents of disaster relief,1928Takung Newspaper, October 24, 1928Qin et al., 2004Pederson et al., 2001Archives of hydrological department inChayouqian Banner, Inner Mongolia,1989, unpublished reportWang et al., 1990Tang et al., 2003

THE 1920S DROUGHT IN NORTHERN CHINA 425Figure 10. The average dryness/wetness indices from fifteen stations (see Figure 1) in central InnerMongolia, Shaanxi, Gansu and Qinghai Provinces (Chinese Academy of Meteorological Science,1981).the drought occurrence (Chinese Academy of Meteorological Science, 1981). Asdemonstrated in Figure 10, sustained and severe droughts in the last 500 years occurredin 1484–1486, 1528–1529, 1586–1587, 1638–1640, 1720–1722 and 1877–1878, and 1928–1929. Of these, the drought occurrence in the 1920s was the mostsevere in the past 200 years. It was reported that the 1920s drought may havebeen the most severe in the past 700 years in the middle Qilian Mountains (Zhangand Wu, 1997) where no dryness/wetness index was available. The early droughts,however, in 1484–1486 and 1638–1640, appear to have been more severe than the1920s drought based on fifteen stations in northern China.4.4. THE EFFECTS OF THE 1920S DROUGHT ON SOCIOECONOMIC CONDITIONSThe severe drought in the 1920s had a catastrophic effect on socioeconomic conditionsin northern China (Table V). After sustained drought and repeated cropfailures, severe famine ensued in 1928 and 1929 and the number of people affectedreached approximately 34 million (Deng, 1937). The toll of the famine is difficult toaccurately determine. It is generally accepted that at least four million people died(Xu, 1997). Edgar Snow, an American journalist, reported that the famine led to thedeaths of about five million people in northern China (Snow, 1981). Deng (1937)estimated at least ten million deaths due to starvation and associated diseases in1927–1929 in northern China. Owing to a dramatic decline in the birth and survival

426 ERYUAN LIANG ET AL.TABLE VThe historical records about the 1920s droughtYear Historical record Source1928 In Shaanxi, Ningxia and Gansu, the summer grain only has20–30% of the average annual yield and the autumn grain hadno harvest at all in 1928.The winter wheat could not be sown because of the persistentdrought. The corn price was 5 times higher than normal in thewinter of 1928.The extraordinary drought in 1928 also caused a heavy mortalityof old trees in Shaanxi and Gansu.No precipitation during the spring and summer in 1928 inwestern Inner Mongolia; no grass could survive in thegrassland region, leading to a substantial loss of livestock.Since 1925, Chihli, including eastern Inner Mongolia andnorthern Hebei Provinces, has suffered from the drought, andthe nomadic area in Xilin Gol Banner lost most livestock.As a consequence of the repeated crop failures in Shaanxi,Ningxia, Gansu, Inner Mongolia, the overwhelming majorityof the population had to live on an unwholesome diet,including grasses and their roots, tree bark, and chaff. Theeating of grass and tree bark mixed with ground clay resultedin sickness and usually hastened death.1929 There were 2.21 million victims of drought calamity in fourteencounties including Guanzhong, Weinan, Pucheng, Huaxian andLintong, et al., in Shaanxi by the end of January 1929; grainstorage was only about 12.5 million kg. Thus, each person inthese counties had only an average of six kg of grain in a year.No single grain was harvested among all the 88 counties ofShaanxi Province in the summer and autumn of 1929.In the worst affected area in Gansu, Ningxia and Shaanxi, thechaff, seeds and roots of grasses and tree bark were notavailable in 1929. Most livestock starved to death and wereeaten. About 70% of the trees have been killed throughanthropogenic removal of tree bark and leaves.Severe hunger has led to some cases of cannibalism in Shaanxiand Gansu Provinces.In Shaanxi, three million perished from starvation, disease andviolence and six million people became utterly destitute andhomeless, which accounted for 70% of the entire population(13 million).Out of a population of 5.5 million, 4.57 million were affected bythe famine in Gansu. The death of people in Gansu was about2.3 million, of which 1.4 million people perished of starvation,0.6 million died of epidemics and 0.3 million lost their lives inthe violence.Ningxia Province lost one third of its entire population (0.7million).Takung Newspaper,September 21 1928;Shanghai Daily, June 26,1929Summary documents ofdisaster relief, 1928Takung Newspaper, July16Takung Newspaper, July14, 1929Takung Newspaper onJuly 16 and September8, 1928The report of “Lvpingassociation for disasterrelief in Shaanxi” inFebruary 1929Summary documents offamine relief inShaanxi, 1932Takung NewspaperFebruary 15, May 6,1929 Takung,Newspaper, May 61929Shanghai Daily, April28, 1929 and March16, 1931Guowen WeeklyNewspaper, 7 (19),page 8Summary documents ofdisasters in eachcounty of Gansu in1929Deng, 1937

THE 1920S DROUGHT IN NORTHERN CHINA 427rate from 1928–1930, the population age structure developed a corresponding agegap in Gansu (Su, 1988).The heavy effect of the 1920s drought was due to multiple factors. The prolongedsevere drought, combined with high temperatures and widespread crop failure,contributed to catastrophic famine and millions of deaths (Xu, 1997). This madethe period a crucial point in the country’s history. The disastrous results of the 1920sdrought were also closely related to the socioeconomic situation and poor humandecisions. Lower productivity in the 1920s increased the vulnerability of societyto natural disasters. In the semi-arid regions, agricultural yield is more dependenton the weather than in other parts of China and is usually low. With such a largepopulation (millions live along the Yellow River), the loss of even one crop wouldhave ensured widespread starvation (Mallory, 1926). Because of the misguidanceof local government, a large area of opium was planted on fertile land, which hadpreviously been used for agriculture (Snow, 1937). Furthermore, the planting ofopium in a large area (70–80% of the fertile land in Shaanxi) had a great effecton agricultural production, making Northwest China highly vulnerable to naturaldisasters (Shanghai Daily, June 30, 1931). In addition, frequent civil wars led to asharp food demand for soldiers, and farms were consequently overburdened (Deng,1937). Deterioration in the economic situation of the country was thus aggravatedby the severe drought conditions through most of the 1920s. Swarms of locustsfollowing the sustained drought gave rise to further hardships (Shanghai Daily,August 14, 1930). In addition, the government could not organize effective reliefactivity or control of epidemics during the drought, exacerbating conditions evenfurther (Deng, 1937). Thus, the natural and social factors together had direct anddevastating effects on socio-economic conditions and resulted in unimaginable loss.5. ConclusionTree ring chronologies in the semi-arid and arid areas of northern China are sensitiverecords of extreme drought. Analysis of tree-ring records spanning the last 200 yearsshows an abnormal growth decline in the 1920s and early 1930s, and a variety ofhistorical records provide substantial evidence of the severity of the 1920s droughtin northern China. In the upper and middle reaches of the Yellow River, the low-flowin the 1920s was coincident with dramatic tree growth decline. The high incidence ofmissing rings in 1928 and 1929 was synchronous with extremely low precipitationrecorded at several meteorological stations, the dramatic runoff decline or dryingup of river courses and desiccation of lakes, catastrophic agricultural failure, greatfamines and merciless decimation of the population in North China and the easternpart of Northwest China. This study demonstrates that tree rings in the semi-aridand arid regions of northern China are excellent indicators of severe and sustaineddrought.Tree-ring networks across the arid and semi-arid areas of northern China havethe potential to reflect the severity, extent and duration of historical megadroughts.

428 ERYUAN LIANG ET AL.Tree growth decline exhibited a regionally synchronous and coherent pattern innorthern China, which is a reflection of drought variability. Based on the studiedtree-ring sites, the 1920s drought extended across North China, southern Ningxia,eastern Qinghai, Gansu and eastern Xinjiang in Northwest China. Dendroclimaticevidence is clearly supported by a variety of historical records. This research alsoshows the need to extend the tree-ring network, to enable a more detailed assessmentof the spatio-temporal characteristics of extreme drought events. Ultimately, thelarge-scale spatio-temporal climate anomalies recovered from an extensive treeringnetwork would provide insights into the atmospheric circulation patterns thatinfluenced precipitation patterns over the semi-arid areas in northern China.AcknowledgementsThis research was supported by the Knowledge Innovation Project of CAS (KZCX3-SW-321) and the National Natural Science Foundation of China (30300053 and90102005). We gratefully acknowledge Professor Raymond S. Bradley for encouragingus to write this paper, and for insightful comments and suggestions on anearlier version of the manuscript. Thanks to Dr. Jürg Luterbacher for many usefulsuggestions and Tom Cannavino for helpful English corrections. We sincerelythank Jingyun Zheng and Hongbin Liu for their suggestions, and Zhaochen Kong,Xudong Chen, Kejun Che, Hu Hao, Tianyu Li, Jicheng He, Lusan Liu and Pu Wufor their help with the fieldwork. The authors also wish to thank to the anonymousreviewers and the editor whose comments and suggestions were helpful inthe improvement of the quality of this paper.ReferencesBradley, R. S. and Jones, P. D.: 1992, Climate Since A.D. 1500, Routledge, London, p. 679.Bryson, R. A. and Swain, A. M.: 1981, ‘Holocene variations of monsoon rainfall in Rajasthan’, Quat.Res. 16, 135–145.Chen, G. R. and Cheng, G. W.: 1997, ‘Drought analysis in the upper basin of changjiang riverand disaster prevention/abatement’, Resources and Environment in the Yangtze Valley 6, 74–79.(in Chinese with English abstract)Chinese Academy of Meteorological Science: 1981, Yearly Charts of Dryness/Wetness in China forthe Last 500-Year Period, China Map Press, Beijing, p. 332. (in Chinese with English abstract)Chu, K. Z., Tu, C. W., and Chang, P. K.: 1936, The Chinese Rainfall, The National Research Instituteof Meteorology, Academic Sinica, Beijing, p. 536. (in Chinese with English abstract)Cook, E. R.: 1992, ‘Using tree rings to study past El Niño/Southern oscillation influences on climate’,in Diaz, H. F. and Markgraf, V. (eds), El Niño: Historical and Paleoclimatic Aspects of the SouthernOscillation, Cambridge University Press, Cambridge, pp. 203–214.Cook, E. R. and Kairiukstis, L.: 1990, Methods of Dendrochronology: Applications in the EnvironmentalSciences, Kluwer Academic Publishers, Dordrecht, pp. 23–217.Cook, E. R., Meko, D. M., Stahle, D. W., and Cleaveland, M. K.: 1999, ‘Drought reconstructions forthe continental united states’, J. Clim. 12, 1145–1162.

THE 1920S DROUGHT IN NORTHERN CHINA 429Damage Report: 1995, Report of the Damage Caused by Disaster in China, China Statistical Press,Beijing, pp. 1–406. (in Chinese)deMenocal, P. B.: 2001, ‘Culture responses to climate change during the late holocene’, Science 292,667–673.Deng, Y. T.: 1937, History of Famine Relief in China, Commercial Press, Beijing, p. 376. (in Chinese)Dong, A. X., Hao, H. L. and Xiang, J.: 2000, ‘The analysis of several severe dry damages in historicaltime in northwest China’, in Xie, J. N. (ed.), The Research on Change and Prediction of DroughtClimate in northwest China, China Meterological Press, Beijing, pp. 93–96. (in Chinese withEnglish abstract)Fang, X. Q.: 1999, ‘Decline of pre-historical agriculture and formation of farming-grazing transitionalzone in north China : A view from climatic changes’, J. Nat. Resour. 14, 212–218. (in Chinesewith English abstract)Feng, J. X. and Ke, X. X.: 2000, ‘The variation features of the runoff in the upper reaches of the yellowriver for 260 years’, in Xie, J. N. (ed.), The Research on Change and Prediction of Drought Climatein Northwest China, China Meterological Press, Beijing, pp. 166–170. (in Chinese with Englishabstract)Fritts, H. C.: 1974, ‘Relationships of ring widths in arid-site conifers to variations in monthly temperatureand precipitation’, Ecol. Monograph. 44, 411–440.Fritts, H. C.: 1976, Tree Ring and Climate, Academic Press, London, p. 567.Fu, C. B., Diaz, H. F., Dong, D. F. and Fletcher, J. O.: 1999, ‘Changes in atmospheric circulation overnorthern hemisphere oceans associated with the rapid warming of the 1920s’, Int. J. Climatol. 19,581–606.Ge, Q. S. and Wang, W. Q.: 1995, ‘Population pressure, climate change and tai-ping rebellion’, Geog.Res. 14, 32–41. (in Chinese with English abstract)Grissino-Mayer, H. D.: 2001, ‘Assessing crossdating accuracy: A manual and tutorial for the computerprogram COFECHA’, Tree-ring Res. 57, 205–221.Hu, Q. and Feng, S.: 2001, ‘A southward migration of centennial-scale variations of drought/flood ineastern China and the Western United States’, J. Clim. 14, 1323–1328.Huang, C. C., Zhao, S. C., Pang, J. L., Zhou, Q. Y., Chen, S., Li, P. H., Mao, L. J. and Ding, M.: 2003,‘Climatic aridity and the relocations of the zhou culture in the southern loess plateau of China’,Clim. Change 61, 361–378.Hughes, M. K., Wu, X. D., Shao, X. M. and Garfin, G. M.: 1994, ‘A preliminary reconstruction ofrainfall in north-central China since A.D. 1600 from tree-ring density and width’, Quat. Res. 42,88–99.Hughes, M. K. and Graumlich, L. J.: 1996, ‘Multimillennial dendroclimatic studies from the WesternUnited States’, in Jones, P. D., Bradley, R. S. and Jouzel, J. (eds.), Climatic Variations and ForcingMechanisms of the Last 2000 Years. NATO ASI Series I41, 109–124.IPCC.: 2001, Climate Change 2001: Impact, Adaptation, and Vulnerability. Contribution of WorkingGroup II to the Third Assessment Report of the Intergovernmental Panel on Climate Change,Cambridge University Press, Cambridge, p. 1031.Jacoby, G., Pederson, N. and D’Arrigo, R.: 2003, ‘Temperature and precipitation in mongolia basedon dendroclimatic investigations’, Chin. Sci. Bull. 48, 1474–1479.Kang, X. C., Cheng, G. D., Kang, E. S. and Zhang, Q. H.: 2002, ‘Mountain pass runoff reconstructionof the Heihe river during the past 1000 years using tree rings’, Sci. China (D) 32, 675–685.(in Chinese)Li, J. F.: 1989, Xinjiang Dendroclimatological and Dendrohydrological Studies, China MeteorologicalPress, Beijing, p. 268. (in Chinese with English abstract)Li, X., Zhan, X. Z. and Wu, X. D.: 1992, ‘Preliminary study on drought/wet variation over Last 250years in baotou area using tree-ring data’, Sin. Geog. Sin. 12, 143–152. (in Chinese with Englishabstract)

430 ERYUAN LIANG ET AL.Li, W. H., Cheng, X., Liu, Y. D. and Xia, M. F.: 1994 The Top Ten Natural Disasters in ModernChinese History (1840-1949), Shanghai People’s Press, Shanghai, p. 350. (in Chinese)Liang, E. Y., Shao, X. M., Hu, Y. X. and Lin, J. X.: 2001, ‘Dendroclimatic evaluation of climategrowthrelationships of meyer spruce (Picea meyeri) on a sandy substrate in semi-arid grassland,North China’, Trees 15, 230–235.Liang, E. Y., Shao, X. M., Kong, Z. C. and Lin, J. X.: 2003, ‘The extreme drought in the 1920s andits effect on tree growth deduced from tree ring analysis: A case study in north China’, Ann. For.Sci. 60, 145–152.Liu, H. B. and Wu, X. D.: 1996, ‘Spatio-temporal characteristics of the low-flow period from 1922to 1932 in the middle reaches of the yellow river’, Shaanxi Meteorol. 6, 12–15. (in Chinese)Liu, H. B., Shao, X. M., and Huang, L.: 2002, ‘Reconstruction of early-summer drought indices inmid-north region of China after 1500 using tree ring chronologies’, Quat. Sci. 22.Liu, Y. and Ma, L. M.: 1999, ‘Tree-ring seasonal precipitation reconstruction for Mt. Da Qing area,inner Mongolia, China for the last 376 years’, Chin. Sci. Bull. 44, 1986–1992 (in Chinese).Liu, Y., Cai, Q. F., Ma, L. M. and An, Z. S.: 2001, ‘Tree ring precipitation records from Baotou andthe east Asian summer monsoon variation for the last 254 years’, Earth Sci. Frontiers 8, 91–97(in Chinese).Liu, Y., Shao, X. M., Wu, X. D. and Liu, H. B.: 1997, ‘Seasonal temperature and rainfall reconstructionin north-central China from tree-ring density and stable carbon isotope for the last 100 years’,Sci. in China (D) 27, 271–277. (in Chinese)Liu, Y., Shi, J. F., Shishov, V., Vaganov, E., Yang., Y. K., Cai, Q. F., Sun, J. Y., Wang, L. and Djanseitov,I.: 2004, ‘Reconstruction of May–July precipitation in the north Helan mountain, inner mongoliasince A.D. 1726 from tree-ring late-wood widths’, Chin. Sci. Bull. 49, 405–409.Mallory, W.: 1926, China: Land of Famine, American Geographical Society, New York, p.199.Meko, D. M., Stockton, C. W. and Boggess, W. R.: 1995, ‘The tree-ring record of severe sustaineddrought’, Water Resour. Bull. 31, 789–801.Mijiddor, R. and Namhay, A.: 1983, ‘On drought and unfavorable winter conditions recurrence inMongolia’, Transactions of the HMRI, Ulaanbaatar 11, 118–131. (in Russian)Neumann , J. and Dettwiller, J.: 1990, ‘Great historical events that were significantly affected by theweather: Part 9, the year leading to the revolution of 1789 in France (II)’, Bull. Amer. Meteorol.Soc. 71, 33–41.Park, W. K., Kim, Y. J., Lee, J. H. and Seo, J. W.: 2001a, ‘Development of tree-ring chronologies ofPinus densiflora from Mt. Sorak and Dating the years of construction of the Kyunghoe-ru Pavilionin Seoul’, J. Korean Physical Soc. 39, 790–795.Park, W. K., Seo, J. W., Liu, Y., Kim, Y. J. and Han, S. W.: 2001b, ‘Reconstruction of April–Augustprecipitation in Mt. Sorak region from tree rings’, Korea J. Quat. Res. 15, 47–52.Pederson, N., Jacoby, G. C., D’Arrigo, R. D., Cook, E. R., Buckley, B. M., Dugarjav, C. and Mijiddorj,R.: 2001, ‘Hydrometeorological reconstructions for northeastern Mongolia derived from treerings: 1651–1995’, J. Clim. 14, 872–881.Qin, N. S., Jin, L. Y., Shi, X. H., Wang, Q. C., Li, L., Chen, F. and Li, L. M.: 2004, ‘A 518-year runoffreconstruction of Tongtian river basin using tree-ring width chronologies in the source region ofYangtze river’, Acta Geog. Sin. 59, 550–556. (in Chinese with English abstract)Qin, N. S., Shao, X. M., Jin, L. Y., Wang, Q. C., Zhu, X. D., Wang, Z. Y. and Li, J. B.: 2003, ‘Climatechange over southern Qinghai Plateau in the past 500 years recorded in Sabina tibetica tree rings’,Chin. Sci. Bull. 48, 2483–2487.Qian, W. H. and Zhu, Y. F.: 2001, ‘Climate change in China from 1880 to 1998 and Its impact on theenvironmental condition’, Clim. Change 50, 419–444.Qian, W. H., Hu, Q., Zhu, Y. F. and Lee, D. -K.: 2003, ‘Centennial-scale dry-wet variations in eastAsia’, Clim. Dynamics 21, 77–89.

THE 1920S DROUGHT IN NORTHERN CHINA 431Schweingruber, F. H.: 1996, Tree Rings and Environment: Dendroecology, Paul Haupt, Berne, p. 609.Shao, X. M. and Wu, X. D.: 1994, ‘Radial growth of Huashan Pine and its response to climate’, J.Chin. Geog. 4, 88–102.Shao, X. M. and Wu, X. D.: 1996, ‘Dendroclimatological reconstruction of 500-year precipitationin late spring and early summer in the Huashan Mountain’, in Fu, C. B. and Yan, Z. W. (eds.),Global Change and the Future Life-supporting Environment of China, China Meterological Press,Beijing, pp. 17–26. (in Chinese with English abstract)Shao, X. M., Fang, X. Q., Liu, H. B. and Huang, L.: 2003, ‘Dating the 1000-year old qilian Juniperalong the eastern margin of the Qaidam Basin’, Acta Geog. Sin. 58, 90–100. (in Chinese withEnglish abstract)Shao, X. M., Huang, L., Liu, H. B., Liang, E. Y., Fang, X. Q. and Wang, L. L.: 2005, ‘Reconstructionof precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai’, Sci. China(D) 48, 939–949.Shi, F. C., Wang, G. A., Gao, Z. D., Mu, P. and Ma, G. A.: 1991, ‘Recurrence probability of 11-yearcontinuous low water period (1922 – 1932 A.D.) in the yellow river’, Adv. Water Sci. 2, 258–263.(in Chinese with English abstract)Shi, Y. F.: 2003, An Assessment on the Issues of Climate from Warm-Dry to Warm-Wet in NorthwestChina, China Meteorological Press, Beijing, pp. 1–124. (in Chinese)Snow, E.: 1937, Red Star over China, Victor Gollancz Ltd, London, p. 464.Snow, L. W.: 1981, Edgar Snow’s China: A Personal Account of the Chinese Revolution, RandomHouse, New York, p. 284.Stahle, D. W., Cleaveland, M. K., Blanton, D. B., Therrell, M. D. and Gay, D. A.: 1998, ‘The lostcolony and jamestown droughts’, Science 280, 564–567.Stahle, D. W., Cook, E. R., Cleaveland, M. K., Therrell, M. D., Meko, D. M., Grissino-Mayer, H. D.,Watson, E., and Luckman, B. H.: 2000, ‘Tree-ring data document 16th century megadrought overnorth America’, Eco 81, 121–125.Su, R. Y.: 1988, Population in China, Gansu volume, China Economy Press, Beijing, p. 345.(in Chinese)Tang, K. W., Wang, H. and Liu, C.: 2003, ‘Preliminary study of Hongjiannao lake’s variationand ecological water demand’, J. Nat. Resour. 18, 304–309. (in Chinese with Englishabstract)The Editing Committee for “The Flood/Drought Hazards in Gansu Province”: 1996, TheFlood/Drought Hazards in Gansu Province, Yellow River Conservancy Press, Zhengzhou, pp.1–657. (in Chinese)Villalba, R. and Veblen, T. T.: 1997, ‘Spatial and temporal variation in Austrocedrus growth alongthe forest-steppe Ecotone in northern Patagonia’, Can. J. For. Res. 27, 580–597.Wang, S. M., Yu, Y. S., Wu, R. J. and Feng, M.: 1990, The Daihai Lake-Environment Evolutionand Climate Change, University of Science & Technology of China Press, Hefei, pp. 105–191.(in Chinese)Wang, S. W., Zhu, J. H. and Cai, J. N.: 2004 a, ‘Interdecadal variability of temperature and precipitationin China since 1880’, Adv. Atmos. Sci. 21, 307–313.Wang, Y. J., Chen, F. H. and Gou, X. H.: 2004 b, ‘March to June runoff of Heihe river since 1770reconstructed from tree-ring data’, J. Glaciol. Geocryol. 26, 202–206. (in Chinese with Englishabstract)Weiss, H. and Bradley, R. S.: 2001, ‘Archaeology-what drives societal collapse?’, Science 291, 609–610.Wilhite, D. A.: 2000, Drought: A Global Assessment, Natural Hazards and Disasters Series, Routledge,London, p. 700.Woodhouse, C. A. and Overpeck, J. T.: 1998, ‘2000 years of drought variability in the central unitedstates’, Bull. Amer. Meteorol. Soc. 79, 2693–2714.

432 ERYUAN LIANG ET AL.Worster, D.: 1982, Dust Bowl: The Southern Plains in the 1930’s’, Oxford University Press, NewYork.Xu, G. C.: 1997, Climate Change in Arid and Semiarid Regions of China, China MeteorologicalPress, Beijing, p. 101. (in Chinese)Xu, J. H.: 1998, ‘Sun, climate, famine and national movement’, Sci. China (D) 28, 366–384. (inChinese)Yuan, Y. J., Li, J. F. and Zhang, J. B.: 2001, ‘348-year precipitation reconstruction from tree rings forthe north slope of the middle Tianshan mountains’, Acta Meteorol. Sin. 15, 95–104.Yuan, Y. J., Ye, W. and Dong, G. R.: 2000, ‘Reconstruction and discussion of 314a precipitation inYili prefecture, western Tianshan mountains’, J. Glaciol. Geocryol. 22, 121–127. (in Chinese withEnglish abstract)Zhang, J.: 1994, The Dendroclimate’s Reconstruction and Dendroclimate’s Regional DifferentiationResearch in Eastern and Western Agriculture-Animal Husbandry Zone in Inner Mongolia,M.Sc. thesis, Beijing Normal University, Beijing, p. 36. (in Chinese with Englishabstract)Zhang, J. C. and Lin, Z. G.: 1992, Climate of China, Wiley, New York, p. 376.Zhang, Q. B., Chen, G. D., Yao, T. D., Kang, X. C. and Huang, J. G.: 2003, ‘A 2,326-year tree-ringrecord of climate variability on the northeastern Qinghai-Tibetan Plateau’, Geophys. Res. Let. 30,1739–1742.Zhang, Y. B., Zheng, H. M., Long, R. Z. and Yang, B. C.: 1982, ‘Seasonal cambial activity andformation of Phloem and Xylem in eight forest tree species grown in north China’, Sci. Silv. Sin.18, 366–379. (in Chinese with English abstract)Zhang, Z. H. and Wu, X. D.: 1997, ‘Climatic reconstruction in the Qilian mountains during the past700 years using tree-ring data’, Chin. Sci. Bull. 42, 849–851. (in Chinese)Zhang, Z. H., Wu, X. D. and Li, J.: 1996, ‘Utilizing tree ring chronologies to reconstruct 300-yeardrought days in eastern Tianshan mountains’, Quat. J. Appl. Meteorol. 7, 53–60. (in Chinese withEnglish abstract)Zheng, J. Y., Hao, Z. X. and Ge, Q. S.: 2005, ‘Variation of precipitation for the last 300 years overthe middle and lower reaches of the Yellow river’, Sci. China (D) 35, 765–774. (in Chinese)(Received 9 July 2004; in revised form 15 December 2005)