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Palaeoworld 21 (2012) 69–73

Short communication

Did alder (Alnus) fires trigger rice cultivation in the lower reaches of theYangtze River, East China?

Jun-Wu Shu a,b,∗, Wei-Ming Wang a, Le-Ping Jiang c

a Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR Chinab Kyoto Prefectural University, Kyoto 606-8522, Japan

c Zhejiang Provincial Institute of Archaeology and Cultural Relics, Hangzhou 310014, PR China

Received 20 July 2011; received in revised form 28 October 2011; accepted 8 February 2012Available online 16 February 2012

bstract

It remains debatable as to how the prehistoric human communities managed the environment to enable the initial cultivation of rice during thearly Neolithic in the coastal lower reaches of the Yangtze River, East China. Previous studies proposed an environmental context for the firstice cultivation at Kuahuqiao, Hangzhou, based on an archaeological sedimentary microfossil record that had been well-dated using radiocarbonethods. Those studies suggested that early humans began burning the predominantly alder scrub in a local swampy wetland, starting about

750 cal. yr BP, which permitted the start of dedicated rice (Oryza) cultivation. Here we present a new, finer-detailed pollen-phytolith-microscopic

harcoal record from the same locality. Our result reveals that local woods dominated by oak (Quercus) and pine (Pinus) were targeted for burningy early cultivators before the start of rice agriculture.

2012 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.

eywords: Fires; Rice cultivation; Kuahuqiao culture; Lower Yangtze River

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. Introduction

The Yangtze River basin is considered as a key area for explor-ng the early Neolithic rice cultures in which the earliest culti-ation and domestication of rice may have occurred (Normile,997; Jiang and Liu, 2006; Fuller and Qin, 2007; Fuller et al.,009; Zheng et al., 2009a,b; Wang et al., 2010a). Currently, theres a growing interest in understanding the role of the environmentn the early rice cultures in East China. However, there is littleonsensus so far on how early humans managed the environmento begin rice farming (Li et al., 2006a,b; Itzstein-Davey et al.,007a,b; Shu, 2007; Atahan et al., 2008; Wang et al., 2010b).

Neolithic rice-related cultures originated and prospered

n the coastal lower Yangtze area (Fig. 1A). So far excava-ions have revealed six successive cultures: Shangshan Culture11 860–9000 cal. yr BP), Kuahuqiao Culture (8000–7000 cal. yr

∗ Corresponding author at: Nanjing Institute of Geology and Palaeontology,hinese Academy of Sciences, Nanjing 210008, PR China.el.: +81 75 703 5683; fax: +81 75 703 5683.

E-mail address: junwushu@126.com (J.-W. Shu).

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871-174X/$ – see front matter © 2012 Elsevier B.V. and Nanjing Institute of Geolooi:10.1016/j.palwor.2012.02.003

P), Majiabang Culture/Hemudu Culture (7500/7000–5900 cal.r BP), Songze Culture (5900–5200 cal. yr BP), and Liangzhuulture (5200–4200 cal. yr BP) (Stanley and Chen, 1996;

iang, 2004; Zong et al., 2007) (Fig. 1B). Previous researchesave shown that domesticated forms of rice grains begano be commonly represented in archaeological contexts lesshan approximately 7000 years ago (Liu et al., 2007; Fullert al., 2009; Zheng et al., 2009a,b; Wang et al., 2010b). Theedimentary environment was also found to be very localized,ith geographic differences resulting from a highly dynamic

nvironmental setting that was constrained primarily by chang-ng sea levels during the Holocene (Stanley and Chen, 1996,000; Stanley et al., 1999; Stanley, 2001; Li et al., 2006a,b;ao et al., 2006; Zhu and Zhang, 2006; Itzstein-Davey et al.,007a,b; Shu, 2007; Atahan et al., 2008).

Modern climate in the study area is characterized by theast Asian Monsoon. The annual temperature is 16.1 ◦C and

he annual precipitation is 1402.5 mm, most of which falls in theummer. The climatically zonal vegetation is dominated by ever-

reen broadleaved forests composed mainly of Cyclobalanopsis,astanopsis, and Cinnamomum, located around the northern-ost limit of the middle subtropical area (Editorial Committee

gy and Palaeontology, CAS. All rights reserved.

70 J.-W. Shu et al. / Palaeoworld 21 (2012) 69–73

Fig. 1. Map showing the location of the Kuahuqiao site in the lower reaches of Yangtze River in East China (A) and some other Neolithic culture sites in the innerp

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art of the coastal Hangzhou Bay, Zhejiang Province (B and C).

f Vegetation of China, 1980). This forest vegetation has beenxtensively transformed by humans into the present pine (Pinusassoniana)-dominant secondary forests in the highlands andaddy fields in the lowlands, as a result primarily of timberlearance and particularly of the intensive rice (Oryza sativa)griculture.

Geographically, middle to late Neolithic sites that are datedounger than 7000 years ago mostly lie within the wide coastalangtze Delta. In contrast, Kuahuqiao is located in the tran-itional zone between the mountains to the south and westnd the flat fluvial plains to the east and north (Fig. 1B). Thexcavated portion of Kuahuqiao is situated in a small basinccluded between two lines of low parallel hills (Fig. 1C).he organic-rich sediment at this site is expected to pro-ide good sediment archives for ascertaining the environmentalontext of the incipient rice cultivation due to its secure chrono-ogical control, abundant archaeological finds, and sheltered

ocality (Innes et al., 2009; Shu et al., 2010). Archaeologicalvidence shows that Kuahuqiao was inhabited by sedentary for-gers who initiated rice cultivation in the lower Yangtze during

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he early Neolithic (Jiang, 2004; Innes et al., 2009). Cultur-lly, it links the pre-rice cultivating Shangshan Culture to theouth, with the rice domesticating Hemudu Culture/Majiabangulture to the east and north (Fig. 1B), and therefore is crit-

cal to understanding the process of transition from sedentaryathering to full domestication in the history of early ricegriculture.

Previous investigations proposed that fire removal of the alderen carrs by humans opened the way for the immediate start ofice cultivation (Zong et al., 2007; Innes et al., 2009). Their inter-retation was based on the coincidence of the sharp drop of thelnus peak in their pollen records with a significant rise in micro-harcoal abundance during the period approximately from 7820o 7750 years ago (Zong et al., 2007; Innes et al., 2009). Theemoval of Alnus was thought to have facilitated the initiationf rice agriculture, as indicated by what was assumed to beereal rice pollen (poaceous pollen grains ≥40 �m in diameter)

n the swampy environment after 7750 cal. yr BP. However, thisrgument is not supported by our new finer-detailed microfossilork.

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. Material and methods

A newly exposed 260 cm-long archaeological sedimentaryrofile (30◦08′42′′N, 120◦13′02′′E) was sampled for acceler-tor mass spectrometry radiocarbon dating (AMS 14C) andicrofossil analyses. The sampled profile is located in the east-

rn wall of the trench T0412 excavated during 2001–2002 atuahuqiao, Zhejiang Province, approximately 10 m west of the

rench T0512 studied by Zong et al. (2007) and Innes et al.2009). In total, 60 samples were selected for pollen and micro-copic charcoal analyses and 20 samples for phytolith followinghe standard preparation methods developed by Moore et al.1991) and Wang and Lu (1993), respectively. The combinedollen-phytolith-microscopic charcoal diagram was made usinghe TILIA program (Grimm, 1991–1993) (Fig. 2). Detailed ageetermination and pollen-based vegetation reconstruction haseen reported by Shu et al. (2010), but no emphasis was placedn the issue on what kind of vegetation was disturbed by humanso initiate rice cultivation.

. Results

Three distinct landscape phases were observed in the sed-ment and microfossil evidence covering an 800-year period

tarting about 8200 cal. yr BP: the lake phase (260.0–195.0 cm,a. 8250–7950 cal. yr BP), the culture phase (195.0–46.0 cm, ca.950–7400 cal. yr BP), and the marine phase (46.0–0 cm, post-400 cal. yr BP) (Fig. 2). In general, our chronological control

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ig. 2. Simplified composite diagram for the pollen-phytolith-microsopic charcoaluahuqiao. Pollen percentages were calculated for each taxon based on the sum of te

hanges in Subzones 2a and 2b; the circles with partial fillings in the column of “Hum

rld 21 (2012) 69–73 71

nd pollen and micro-charcoal results (Table 1, Fig. 2) are similaro those of Zong et al. (2007) and Innes et al. (2009), confirminghe solidity of the reconstruction in paleovegetation and paleoen-ironment archived in the well-preserved organic-rich sedimentst Kuahuqiao. Three local microfossil zones including three sub-ones in Zone 2 are shown in Fig. 2, in which the depth of theampled profile and calibrated radiocarbon ages are included.

. Discussion and conclusions

Our results show that a natural, mixed evergreen and decid-ous broadleaved forest developed locally between ca. 8250nd 7950 cal. yr BP (Zone 1), which was progressively openedy burning primarily due to human rice-linked agriculture until400 cal. yr BP (Zone 2). This forest has since recovered becausef the absence of continued human impact due to marine inun-ation (Zone 3) (Fig. 2).

The percentage of Alnus pollen is rather low throughout theollen sequence in our data, thus casting doubt on the proposalhat Alnus-dominated communities were the main vegetationurned by local humans to prepare the ground for the earliestice cultivation at Kuahuqiao (Zong et al., 2007; Innes et al.,009).

We checked the same key horizon layers for the alder pollen

t 1-cm intervals in Subzones 2a and 2b starting from 7950 yearsgo. Alnus pollen is present at trace levels throughout the sam-led profile (Fig. 2). The short-lived high level of Alnus pollenould be interpreted as the result of a single local concentration

record showing changes in vegetation, human impact, and landscape fromrrestrial taxa. Crosses indicate values less than 0.5%; arrows display significant

an disturbance” denote the level of human activity in Zone 2.

72 J.-W. Shu et al. / Palaeoworld 21 (2012) 69–73

Table 1Comparison of the previous pollen results with that of the present study to highlight their difference.

Palynological work Alnus pollen Timing of human activity Targeted vegetation by humans Timing ofculture collapse

Zong et al. (2007), Innes et al. (2009) A single peak ca. 7700 cal. yr BP From ca.7700 cal. yr BP Alnus dominant wetland scrubs ca. 7550 cal. yrBP

This study Very few throughout the profile From ca.7950 cal. yr BP Quercus-Pinus predominant forests 7430 cal. yr BP

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f alder carrs at the site during the period from ca. 7830 to750 cal. yr BP as reported by Zong et al. (2007) and Innes et al.2009). Our interpretation is based on the fact that Alnus pollenas been documented sporadically in numerous Holocene sedi-entary records in the lowlands of East China (Yi et al., 2003;u et al., 2006; Li et al., 2006a,b; Tao et al., 2006; Yi et al., 2006;

tzstein-Davey et al., 2007a,b; Shu, 2007; Atahan et al., 2008;in et al., 2011), and that Alnus species are wind-pollinated,hich could contribute to high pollen productivity and easy dis-ersion. Even in the modern lower Yangtze region, the Alnusopulation is very limited and scattered. It does not constitutehe representative vegetation in the swampy system and tendsot to be locally important.

In contrast, our pollen data (Fig. 2) clearly suggest thatak-pine dominated forests were the primary targets of theuahuqiao people in the local small basin, even though these

orests are assumed to be undisturbed or weakly disturbed in theearby well-drained elevated highlands and hills. Quercus-Pinusoods flourished at Kuahuqiao from 8250 years ago and made

progressive retreat mainly due to low-intensity fire clearancen subzone 2a after ca. 7950 cal. yr BP (Fig. 2). A carbonizedine dugout canoe and a burned pine stump from this era haveeen discovered (Jiang, 2004; Jiang and Liu, 2005), indicatingarly human activity in the local area and pine woodlands in situear human settlements. This initial anthropogenically disturbednterval, which has never been previously reported, implies pos-ible early fire management by humans of the local oak-pineorests in the swamp-scattered basin (Table 1). This started about00 years before the first rice cultivation, as indicated by theow-frequency occurrence of rice phytoliths in subzone 2b after760 cal. yr BP, possibly demonstrating that the Kuahuqiao peo-le did not begin cultivation immediately and instead they movedithin the area hunting and gathering for a short time before set-

ling down and starting cultivation at the site (pers. comm. withong). Quercus-Pinus forests decreased dramatically after that

ime, giving way to a grass-dominated vegetation in Subzone 2chere microscopic charcoal remained abundant and rice phy-

oliths increased significantly. This demonstrates the existencef increased human activities and extensive rice farming until theuahuqiao culture was terminated due to overwhelming marineooding about 7400 years ago.

Our viewpoint is also supported by the wood flora excavatedn cultural layers at Kuahuqiao. This flora was reported in detaily Jiang (2004). Here, we use these data to calculate percentages

or each taxon, based on a total of 1155 wood remains. Theesult shows that Quercus and Pinus are the predominant taxa,long with other woods at low percentages in Group E including

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ig. 3. Subfossil wood flora excavated in cultural layers at Kuahuqiao (datarom Jiang, 2004).

runus (1.5%), Cunninghamia (1.1%), Cupressaceae (0.5%),nd Juglans (0.5%), etc. (Fig. 3). Our pollen data also suggesthe presence of oak-pine dominant forests at the site.

cknowledgements

We thank two anonymous reviewers for their critical andonstructive comments. This research is jointly funded byhe National Science Foundation of China (no. 40901032;0930006), the Japan Society for the Promotion of Scienceno. P10102), and the CAS Strategic Priority Research Programgrant no. XDA05120101).

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