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Ecology and hydrology of early rice farming: geoarchaeological and palaeo-ecological evidence from the Late Holocene paddy field site at Maoshan, the Lower Yangtze

Ecology and hydrology of early rice farming: geoarchaeological and palaeo-ecological evidence... The well-preserved Maoshan paddy fields (4700–4300 BP) were built on an intermediate landscape between the foothills and alluvial plain of the Lower Yangtze River. Despite several interdisciplinary research, there has been a lack of detailed environ- mental and ecological data to contextualise the reconstructed rice farming practices within a wider paleo-environmental back- ground. Our research provides key information on the chronology, vegetation, and long-term hydrological fluctuations at and surrounding the paddy fields. Our 14C and OSL dates show that the initial occupation began at around 5740 ± 140 cal. BP, and the paddy fields were built at around 4675 ± 145 cal. BP and were in use continuously until around 4000 cal. BP. Our pollen, diatom and phytolith data shows that whilst the vegetation in the field was sensitive to changes caused by water management and rice farming, the ecological system surrounding the fields was relatively stable. We suggest that this high frequency of in-field vegetation changes was closely related to intensifying water management for rice farming. This thesis is supported by our geophysical and geochemical analyses of bulk sediments, which shows that the steady build-up of the alluvial sequence was punctuated by several short-term episodes of high-energy surface runoff, including strong flushing in of sandy sediments into the fields perhaps through irrigation activities. Our paleo-ecological and geoarchaeological investigation at Maoshan permits an overview of the development of rice farming and intensifying water management practices in a wider environmental context and offers significant insights to the ongoing debate on the wet-dry dichotomy of early rice farming. . . . . Keywords Paddy fields Liangzhu culture Lower Yangtze River Hydrology Ecology Introduction During the protracted cultivation and domestication process, prehistoric communities first managed and modified natural The Lower Yangtze River is one of the key areas where rice habitats of wild rice for the initial cultivation of rice (Zong was consumed from the beginning of the Holocene and sub- et al. 2007) and later constructed man-made paddy fields for sequently domesticated (Fuller et al. 2009; Liu et al. 2007). increasingly large-scale rice farming (Ding 2004). The con- struction of paddy fields was also accompanied by increasing ecological intervention and biological modification in the fields. * Yijie Zhuang A recent research trend is to apply palaeo-ecological ap- y.zhuang@ucl.ac.uk proaches to investigate water management strategies and the ecology of rice farming in the Lower Yangtze River. For College of Urban and Environmental Sciences, Peking University, instance, through their detailed examination of phytolith Beijing 100871, China assemblages collected from a number of ancient and modern Zhejiang Provincial Institute of Cultural Relics and Archaeology, rice farming sites, Weisskopf et al. (2015) investigate the long- Hangzhou 310014, China term fluctuations of water conditions in rice fields and the Department of Earth Sciences, The University of Hong Kong, Hong evolution of rice farming system in the Lower Yangtze Kong, China River. They suggest that the paddy fields at Caoxieshan Institute of Archaeology, University College London, 31-34 Gordon (6000–5800 BP) were dominated by dry species, Square, London WC1H 0PY, UK 1852 Archaeol Anthropol Sci (2019) 11:1851–1863 corresponding to an emphasis on drainage in the fields. A centennial, minor changes. The rise of sea levels slowly in- return to wetter conditions in the paddy fields at Maoshan creased between c.4000 and 3000 cal. BP, reaching the present was indicated by evidence for a ‘highly irrigated paddy sys- level at the end of this period (Yang and Xie 1984;Feng and tems’ (Weisskopf et al. 2015, p. 1060). This accords well with Wang 1986;Chenand Stanley 1998; Zong 2004). The the research conducted by Zhuang et al. (2014)of the Holocene sedimentation process in the Linping area (Fig. 1) geoarchaeological evidence regarding greater control of the is dominated by alluvial activities, with localised colluvial in-field water situation and intensifying farming practices. processes. Typical Holocene sedimentation sequences are This research provides a detailed information on the compli- dominated by light yellowish silty clay, with abundant iron- cated patterns of early water management and the physio- manganese nodules. At some locations, this yellowish silty biological changes of rice caused by in-field ecological inter- clay either overlies on top of, or is covered by, light greyish vention of the prehistoric Lower Yangtze River. However, silty clay whose light colour was caused by iron depletion contextualising such water management practices and corre- under reducing conditions. This indicates that these locations sponding ecological changes within long-term cultural and were on low topography and subject to long inundations. The environmental backgrounds at these early paddy sites remains Middle to Late Holocene climate in the Yangtze Delta and challenging, mainly due to the lack of high-resolution chrono- nearby regions was humid and wet as consistently shown by logical data from both in- and off-site contexts. The current several pollen and geochemical studies (Atahan et al. 2008; lack of precise chronological data hinders any effective corre- Tao et al. 2006;Yietal. 2003;Yuet al. 2000). This climate lation between different kinds of proxy data collected from condition promoted the expansion of ‘subtropical evergreen- various contexts for palaeo-environmental and palaeo- deciduous broadleaved forests’ (Yi et al. 2003) between c. ecological reconstructions. 7600 and 4800 cal. BP in the Yangtze Delta. These sub- The Late Liangzhu period (4700–4300 paddy fields at tropical arboreal species grew on the mountains and Maoshan in the Lower Yangtze River were built on the foot- hillslopes, including Cyclobalanopsis, Castanopsis/ hills of the Maoshan Hill (48.8 m in elevation) (Ding et al. Lithocarpus, Castanea, along with many other species, whilst 2011; Zheng et al. 2014). In this intermediate landscape be- in the low-relief areas or wetlands, aquatic plants such as tween the foothills and alluvial plain, the fields were next to a Trapa, Euryale, Oryza rufipogon, Typha, Cyperaceae and residential area on the slope, slightly higher up on the hill and other hydrophilic species, flourished (Qin et al. 2010;Yi at the same time connected to both natural and man-made et al. 2003). rivers and creeks on the ground below. A geoarchaeological The Liangzhu culture (5300–4300 cal. BP) is one of the survey was carried out in 2011, during which many soil sam- most developed Neolithic cultures in prehistoric China. The ples were collected. Our high-resolution palaeo-ecological da- densely-populated Liangzhu site complex, possessed a large- ta, supported by 14C and optically stimulated luminescence sized urban centre with earthen walls, palatial buildings and (OSL) dates, provides key information towards a better under- elite burials with elaborately carved jade items (Qin 2013), as standing of rice farming, water management and environmen- well as a recently discovered and excavated hydraulic enter- tal change at the Maoshan site. We will present this data and prise 20 km to the northeast of the Liangzhu centre (Liu et al. discuss its significance, particularly focusing on the following 2017;Liu andRenfrew 2018). Around 20 Liangzhu period aspects: (1) chronology of the construction, use and abandon- sites have been found in the Linping area, forming a sub- ment of the paddy fields; (2) the vegetation history of the centre in the outskirt of the Liangzhu site complex. The paddy fields and surrounding areas; and (3) long-term fluctu- Maoshan site is one of the sites in the Linping sub-centre that ations of the hydrological regimes in the fields resulting from was excavated in 2009–2011. The site was occupied during both water management practices and regional alluvial the Late Majiabang and Songze period (c. 6500–5300 cal. BP), processes. before the Liangzhu period paddy fields were constructed. The Majiabang period archaeological features include house foundations, burials, a large number of pits and wells, all con- Environmental settings and archaeological centrated on the hillslope of the Mountain Hill (Zhuang et al. backgrounds 2014;Ding et al. 2011). By the Liangzhu period, houses and burials were continuously built on the hillslope. At the same The Hangzhou Bay is in a tectonically stable area, with only time, paddy fields were built in the intermediate area between minor subsidence during the Holocene. The Holocene sea- the hillslope and the low-lying alluvial plain. Two phases of level fluctuations are the main factor influencing regional hy- paddy fields have been excavated to date. Twenty-six early- drology. After the steady increase from the beginning of the phase (c. 4900–4700 BP) paddy fields have been excavated Holocene, the sea-level reached to c. − 2.5 m of the present and were found to have been directly built on top of mid- level at around 7000–6500 cal. BP. Between 7000/6500 and Holocene alluvial sediments. These fields were small, from 2 2 4200/4000 cal. BP, sea levels remained stable, with several 1to2m to a maximum of 40 m , and irregular in shape. Archaeol Anthropol Sci (2019) 11:1851–1863 1853 Fig. 1 Holocene environment and locations of archaeological sites mentioned in the text Wells were dug in the fields, which were connected to a creek Samples were taken from the different layers for OSL dat- through small ditched outlets. In contrast, the late-phase paddy ing, 14-C dating, particle size distribution, pollen, diatom and fields were built on top of light yellowish alluvial materials, geochemical analyses. The methods are briefly summarised covering the early-phase fields. A dramatic increase in size below. In the field, five OSL dating samples were collected occurred in the late-phase fields. Separated by narrow path- by using metal tubes (c. 20 cm long) sealed with aluminium ways in a north-southerly direction, the fields were 1000 m in foil to prevent exposure to sunlight. Pre-treatment were con- size, with some reaching nearly 2000 m . The entire fields ducted at the OSL dating laboratory at the School of measured approximately 5.5 ha by this phase. A new creek Archaeology and Museology, Peking University. In the dark was dug to the north of the field, along with other water man- room, approximate 100 g of sediments was grounded and agement facilities such as ditches and wells. These pro- sieved. First, 30% HCL and 30% H O were added to 2 2 nounced changes in the scale and structure of the fields from 20 μm of this ground and sieved sediment to remove the the early to late phase were closely related to changes in farm- carbonates and organic matter and then H SiF (30%) was 2 6 ing and water management practices. added to obtain fine-grained quartz. The measurements were performed using an OSL reader following the standard single- aliquot technique described by Duller et al. (2003). Water saturation was not measured in the field; an average 15% Materials and methods saturation rate was adopted for all samples. U, Th and K con- tents were measured at the Institute of Atomic Energy of The stratigraphy under examination below was located at the China. Four samples were collected for AMS 14C dating. edge of the paddy fields close to the residential area on the The samples were processed at the pre-treatment laboratory foothill. The sedimentation process at this location was influ- at the School of Archaeology and Museology and dated by the enced by farming activities in the fields and alluvial and col- School of Physics, Peking University. OxCal v3.10 was used luvial processes which brought in sediments from the low- to calibrate the dates using the IntCal04 curve. lying areas and hillslopes. From the top to bottom, the stratig- Sixty-three pollen samples were processed at the raphy is divided into five main units: (1) topsoil (layer 1); (2) Laboratory for Earth Surface Processes, College of Urban Late-Holocene flooding deposits (layers 2–5,); (3) peat-like and Environmental Sciences at Peking University, using the sediments (layers 6–9) containing the Liangzhu period and standard hydrofluoric acid (HF) method (Berglund and succeeding Guangfulin period (c. 4100–3900 BP,cf.Zhai Ralska-Jasiewiczowa 1986.). One gram of the sediment was 2006;Ding et al. 2011) and associated cultural remains; (4) dried and mixed with one Lycopodium spore. Ten per cent greyish alluvial deposits (layer 10); and (5) dark alluvial de- HCL was slowly added to remove the carbonates. HF (40%) posits (layers 11–12), rich in organic matter and containing was added to the washed sediments in a tube that was placed sandy lens (Table 1). 1854 Archaeol Anthropol Sci (2019) 11:1851–1863 Table 1 Descriptions and Depth Period Descriptions sampling units of the examined Layer (m) sedimentary sequence at Maoshan 10–0.33 Topsoil, brownish silty clay with abundant iron-manganese nodules resulting from repeated wet-dry alternations. 20.33–0.48 Post-paddy field Light greyish silty clay, embedded with yellowish iron flooding deposits nodules and hard horizontal laminae. 30.48–0.80 Brownish silty clay with abundant iron nodules 40.80–1.11 Dark brownish silty clay, abundant iron nodules in the upper part, and reduced number of iron nodules in the middle and lower sections. 51.11–1.31 Brownish silty clay, containing the most abundant iron nodules amongst the upper 5 units of the profile. In the middle part of this unit, there are also abundant manganese nodules. There are 1–6-cm-thick dark greyish clay laminae at the bottom of this unit. 61.31–1.37 Paddy fields Organic-rich darkish clay, at the top there are thin laminae of plant ash with some Guangfulin-period pottery sherds. 71.37–1.42 Dark greyish silty clay, with abundant vertically situated ironised plant roots; some Late Liangzhu period pottery sherds are also present. 81.42–1.63 Dark greyish silty clay, with abundant vertically situated ironised plant roots; there are also dark, organic rich laminae in the middle-lower part of this unit. 91.63–1.92 Light greyish silty clay, with vertically situated, ironised plant roots; some pottery sherds present. 10 1.92–2.30 Early-to-Middle Dark greyish silty clay, a 3-cm-thick sandy layer embedded Holocene alluvial in the middle part. sequence 11 2.30–2.48 Light greyish to brownish silty clay. 12 2.48–2.66 Brownish silty clay, with vertically situated ironised plant roots in a boiling water bath until the reaction stopped. HCL (36%) LiBO in a crucible, which was heated in a fusion machine to was added at this stage to remove the silicates. The mounted 700 °C, followed by 1080 °C. The sample was then shaken for slides were examined under a microscope, with percentages of 5 min whilst gradually adding 40 mg of NH l. The major pollen species counted. Diatom samples from layers 4, 5 and element compositions of the sediments were determined on 10 were processed at the Department of Earth Sciences, an X-ray fluorescence spectrometer. Trace element composi- University of Hong Kong. Diatom processing followed the tions were measured by running a HR-ICP-MS analysis on an procedures described by Palmer and Abbott (1986). Samples Agilent 7500 mass spectrometer. (1–3 g) were dissolved in 20% H O in hot water bath for 2 2 24 h. Several drops of concentrated solutions were mounted to cover slips with 10 drops of distilled water. The dried cover Results slips were placed onto a glass slide using Zrax. The species were identified based on Vos and Wolf (1993) and others OSL and 14C dates (Round et al. 2007; Zong and Sawai 2015). Phytoliths mounted on the same slides as diatoms were also identified The four 14C dates from layers 9–6 show a consistent chro- and counted. nological order from the bottom to the top of the profile, com- One hundred and fifteen samples were analysed for particle parable with relative chronology reconstructed by the excava- size distribution using the Malvern Mastersizer 2000 laser tor based on pottery typology (Table 2;Fig. 2). The 14C dates particle sizer, following the procedures described by Steve of 4580–4340 cal. BP from MS-6 is older than the designated Boreham from the Department of Geography, University of relative age of the Guangfulin culture, which falls between Cambridge (https://www.geog.cam.ac.uk/facilities/ 4100 and 3900 BP (Ding et al. 2011). The 14C dates from laboratories/techniques/psd.html). Geochemical analysis was the other three horizons correspond well to the established conducted at the HR-ICP-MS laboratory, Peking University. absolute and relative chronologies of the Liangzhu and the Abulk sample of 0.4gwasmixedwith 4 g of Li B O and 2 4 7 Late Majiabang-Songze period (Ding et al. 2011). Archaeol Anthropol Sci (2019) 11:1851–1863 1855 Table 2 Results of the AMS 14C dating Sample and cultural period Depth (cm) Lab no. Material 14C age Calibrated date (year BP) (95.4% prob.) MS-6 (Guangfulin) 133–135 BA121233 Peat 3980 ± 35 2580–2340 BC MS-7 (Late Liangzhu) 138–140 BA121234 Charcoal 4125 ± 25 2870–2580 BC MS-8 150–152 BA121235 Charcoal 4770 ± 30 3640–3380 BC MS-9 (Majiabang-Songze) 178–180 BA121236 Charcoal 4980 ± 35 3930–3650 BC Age reversals occurs in the OSL dates between the fifth to Pollens third yellowish silty clay layer (Table 3; Fig. 2). These OSL dates, however, fall into the broad time span of 4000–3200 BP, The pollen densities of the 63 examined samples varied great- which is within the chronological framework for the wide- ly. Several samples produced less than 100 pollen grains per spread flooding event in the region. The other two OSL dates slide, but the majority of the samples contained at least 300 from the eleventh and twelfth layers are of Late Pleistocene pollen grains per slide, with several samples having more than ages, significantly older than the other dates. This suggests 500 pollen grains per slide (Fig. 3). A large number of arboreal that the building up process of the alluviums had begun by and herbaceous plants as well as ferns and algae were identi- the Late Pleistocene. fied. Based on the changing percentages of arboreal, herba- Thus, these dates, combined with the stratigraphic order ceous and fern pollen, we can divide the pollen profile into and cultural characteristics of artefacts discovered during the three main zones. In zone 1 (2.66–1.92 m, layers 12–10, cor- excavation, support our chronological division of the sedi- responding to Early-to-Middle Holocene alluvial sequence), mentary sequence described in Table 1. Layers 12–10 repre- the pollen assemblage contained about 20% tree and shrub sent the Early-Middle Holocene alluvial sequence preceding species, with low percentages of fern species. Evergreen spe- the use of the paddy fields. Layers 9–6 correspond to the use cies such as Quercus were dominant in the arboreal pollen, but of the paddy fields, which include an early and later phase pollen of Pinus and deciduous Quercus and Ulmus was also (corresponding to the Middle-to-Late Liangzhu phase and present. Percentages of herbaceous species were high, repre- Late Liangzhu phase). Layers 5–2 were deposited during the sented by Gramineae, Cyperaceae and Typha,with Artemisia, flooding periods after the field was abandoned. This recon- Chenopodiaceae and Cruciferae also present. In the second struction provides a useful framework for our discussion of zone (1.92–1.31 m, layers 9–6, corresponding to the Middle- the pollen and other records (but see our further discussion to-Late Liangzhu phase and Late Liangzhu phase), the per- below on ‘chronology’). centages of tree and shrub species again accounted for around Fig. 2 Stratigraphical sequences and sampling locations for AMS 14C and OSL dates 1856 Archaeol Anthropol Sci (2019) 11:1851–1863 Table 3 Results of the OSL Sample Dose rate (Gy/ka) De (Gy) OSL age (ka) Age (BP) Age error dating MS-3 (65 cm) 3.25 ± 0.12 10.89 3.50 ± 0.17 3500 170 MS-4 (95 cm) 3.30 ± 0.12 12.58 3.99 ± 0.40 3990 400 MS-5 (120 cm) 4.30 ± 0.15 12.99 3.17 ± 0.15 3170 150 MS-11 (240 cm) 3.65 ± 0.23 49.38 13.50 ± 0.98 13,500 980 MS-12 (255 cm) 3.71 ± 0.23 93.66 25.20 ± 1.80 25,200 1800 20% in the early stage, this slightly decreased to around 10– addition of Artemisia and Chenopodiaceae species to the as- 15% but gradually increased to 25–30% with more evergreen semblage towards the top of this unit. Gramineae species Quercus in the later stage. Fern species included Monolites decreased whilst Typha species gradually increased in the later and Trilites had low percentages in the early stage but in- stage. In zone 3 (1.31–0.33 m, layers 5–2, corresponding to creased significantly in the later stage. Gramineous, post-paddy field flooding deposits), Pinus pollen grains be- Cyperaceae and Typha species continued to be abundant with came abundant, whilst the percentage of evergreen Quercus a significant increase of these three species, along with the gradually dropped. In the later stage, an important change was Fig. 3 Diagram of pollen concentrations and species Archaeol Anthropol Sci (2019) 11:1851–1863 1857 the increase of both Alnus and Betula species in the pollen and Synedra unla. Slides from the sixth to ninth layers assemblage along with the high percentages of fern species (1.31–1.92 m, corresponding to the Middle-to-Late included Monolites and increasingly Trilites. The three com- Liangzhu phase and Late Liangzhu phase) contain some reed mon herbaceous species, Gramineae, Cyperaceae and Typha, phytoliths, but diatoms were not found. For the fifth and experienced a significant drop in their abundance, which is in fourth layers (0.8–1.31 m), only a small amount of reed contrast with the steady increase of Chenopodiaceae and phytoliths were present, and some brackish water diatom spe- Artemisia species first and later also of Cuciferae species. cies, such as Coscinodiscus blandus and Actinocyclus sp., can These changes in the pollen assemblages in the upper part of be seen. This drastic change from predominant freshwater the profile seem to correspond to a gradually cooler and drier diatom species at the bottom to mainly brackish water species regional climate regime. at the top is closely related to regional and local hydrological changes, which is discussed further below. Diatoms and phytoliths Geochemical analyses and particle size distributions The diatom results are presented in Fig. 4.It should bemen- tioned that as well as diatom species, reed phytoliths were also The detailed results of the particle size distributions and geo- counted in these slides. A large number of reed phytoliths and chemical analyses are shown in Figs. 5 and 6. These results freshwater diatom species were found in the tenth layer (1.92– provide important information regarding the sedimentary and 2.3 m). The latter include Eunotia lunaris, Gomphonema post-depositional processes. In 266-230 cm (layers 12–11), parvulum, Hantzschia amphioxys, Pinnularia microstauron fine-sized particles (silt and clay) contributed the most to the Fig. 4 Concentrations and species of diatoms and phytoliths. Note that the phytolith concentrations are calculated based on six scales: ranging from 0 (none) to extremely abundant (scale 5) 1858 Archaeol Anthropol Sci (2019) 11:1851–1863 Fig. 5 Results of particle size distribution analysis sedimentation, along with a very low percentage of coarse dramatic decrease at the same level. This might be caused particles. The average values for Al O /Na O, K O/Na O, by the decrease of coarse particles of quartz (Fig. 6)asSiO 2 3 2 2 2 2 CaO/MgO and Rb/Sr ratios were 17.2, 1.9, 0.7 and 1.5, re- is mainly composed of quartz rather than from fine-sized par- spectively (Fig. 6), whilst the rare element compositions were ticles such as clay. The sedimentary process in 131–111 cm higher than the average for the whole profile. The high abun- (layer 5) was characterised by the significant increase of fine- dance of Al O and Fe O might be due to the fact that they sized particles. The reversal of trends can be seen in the ratios 2 3 2 3 are not easily removable and thus resistant to the in situ of Al O /Na O, K O/Na O, Rb/Sr and CaO/MgO: the former 2 3 2 2 2 weathering process. Correspondingly, the relatively low per- three increased (19, 3.6 and 1.5, respectively) whilst the last centages of CaO and MgO might be due to their high mobility one decreased (0.4). The rare element compositions reached a in predominantly weathering conditions. In 230–192 cm peak at this stage. From 111 to 80 (layer 4) and 80 to 33 cm (layers 10), there was an obvious increase in coarse sand- (layers 3–2), percentages of clay particles dropped significant- sized particles in the sediments, especially from the sandy ly and percentages of silt and coarser particles increased to as layers embedded in layer 10. The Al O /Na O, K O/Na O high as 85%, indicative of fundamental shifts in sedimentary 2 3 2 2 2 and Rb/Sr values (14, 1.7, and 0.9, respectively) slightly de- regimes. Coupled with these changes were the drastic changes creased and correspondingly the CaO/MgO ratio saw a slight in Al O /Na Oand K O/Na O ratios (6.1 and 1.2, respective- 2 3 2 2 2 increase (0.8). Rare element compositions also showed a pro- ly, in 111–80 cm (layer 4); and 6.2 and 1.2, respectively, in nounced decrease. Several changes, particularly the contribu- 80–33 cm (layers 3–2)), whilst the values of CaO/MgO and tions of coarse particles, can be observed in 192–131 cm Rb/Sr ratios changed slightly (0.7 and 0.8, respectively, in (layers 9–6, corresponding to the Middle-to-Late Liangzhu 111–80 cm (layer 4); and 0.7 and 0.6, respectively, in 80– phase and Late Liangzhu phase). The Rb/Sr was stable (0.9), 33 cm (layers 3–2)). Rare element compositions dropped to but ratios of Al O /Na Oand K O/Na O, and CaO/MgO con- a very low level. Regarding other changes determined by the 2 3 2 2 2 tinued to show reversals in trends, with the latter having a geochemical analyses, K O and Na O experienced a slight 2 2 higher value. Similarly, rare element compositions also expe- increase in the upper part of the profile. This increase may rienced obvious fluctuations. The Al O and T-Fe O values be related to the contribution from saline water. 2 3 2 3 showed a pronounced increase in layer 6 (c.131 cm, corre- sponding to the Guangfulin cultural phase). Similar changes can be seen for both CaO and MgO values. This stage was Discussion dominated by continuous deposition of sediments with weak in situ weathering or post-depositional processes. This means Chronology that these values reflect those of the exogenous sediments, including the possible contribution from the marine sedi- The 14C date of the peat layer was older than expected. This ments, caused by the high CaO value as calcium is more might be due to the intrinsic difficulties of dating peat sedi- readily precipitated in seawater (Zhong and Mucci 1989). ments (Shore et al. 1995), as essentially the 14C dates are the We should also mention that the SiO value experienced a 2 mean results of organic matter (humic and fulvic acids) which Archaeol Anthropol Sci (2019) 11:1851–1863 1859 Fig. 6 Results of geochemical analyses is normally compacted after deposition. In addition, taphono- directly related to the deposition of the yellowish silty clay my might be responsible for this chronological discrepancy deposits dates to around 4000 BP, our OSL dates demonstrate between the 14C dates and relative chronology derived from that these flooding events lasted for a substantial period of pottery typology. The pottery recovered from the peat sedi- time. These new dates are significant as they help us under- ment was most likely deposited on the peat horizon through stand the magnitude and duration of these floods. The effects scattered human activities. In other words, the peat horizon of these flooding events and their implications to the mecha- was deposited first, on top of which human activities took nisms of societal responses should be reassessed in light of place. For the age reversals amongst the OSL dates of the light these new dates. yellowish silty clay sediments, the reasons are equally com- plicated. As the deposition of these sediments are related to the Vegetation dynamics and ecology of the early rice post-Liangzhu period flooding events, there might be problem farming of impartial exposure to light before deposition, a common issue encountered in OSL dating of fluvial deposits. The rea- The landscape around the site of Maoshan consist of several son for the OSL age in MS-5 (120 cm) being significantly niches that had distinctive vegetative patterns: the Maoshan younger than the overlying samples is because of its high dose Hill, the residential area and the paddy fields and the wetlands. rate (4.30 ± 0.15 Gy/ka). As to the transition from the peat The microfossil plant remains we have discovered provide horizon (layer 6, corresponding to the Guangfulin cultural first-hand data to reconstruct local vegetation dynamics that phase) to the flooding deposits (layers 5–2), determined by were under the combined effects of long-term climatic/ 14-C and OSL dates, respectively, given the chronological environmental and land use changes. The intrinsic gap, there might be depository hiatus between these two sed- taphonomical issues of pollen transportation and deposition imentary events. As well as being compacted, parts of the often undermine the reliability of using pollen records to re- peat-like sediments might be eroded away before the deposi- construct past climate changes. However, our geochemical tion of the yellowish silty clay. and particle size distribution (PSD) analyses provide supple- Despite all these issues, the combination of 14C and OSL mentary information on local sedimentary processes and the dating techniques has helped to refine the chronology of the changing sources of the sediments to refine our interpretation construction and use of the paddy fields at Maoshan, the de- of the pollen records. On a temporal scale, pollen grains from position of the peat-like sediments and the flooding events that zone 2 at Maoshan reflect local vegetation changes, whilst eventually marked the abandonment of the site. The initial those from zones 1 and 3 of the profile are most closely related occupation at the site began at around 5740 ± 140 cal. BP, to regional vegetation changes as the sediments for these lasting to until 5460 ± 130 cal. BP, corresponding to the Late levels underwent long-distance transportation. In terms of Majiabang and Songze cultural period (6000–5300 BP, the taxa, roughly speaking, the arboreal species provide infor- Nanjing Museum et al. 2016; Zhejiang Provincial Institute mation regarding the vegetative changes on the hills, of Cultural Relics and Archaeology 2005). The middle- hillslopes and alluvial plains, whilst the herbaceous, fern and phase paddy fields (layer 7, corresponding to the Early-Late algae species reflect the changing ecological and hydrological Liangzhu cultural phase) were built at around 4675 ± 145 cal. conditions in the field and the low-lying wetlands. BP and continuously used until around 4000 cal. BP.This also The majority of the tree and shrub pollen belonged to ev- means that the initial use of the paddy field (layer 9, corre- ergreen and deciduous species such as Quercus, Betula, sponding to the Middle Liangzhu cultural phase) was earlier Ulmus and Pinus. Even though the abundance of Quercus than 4600 cal. BP. Whilst it is clear that the flooding events pollen, for instance, changed over time, the fluctuations were 1860 Archaeol Anthropol Sci (2019) 11:1851–1863 not significant until the later stage of zone 2 when Quercus the ecological system surrounding the fields was relatively pollen became particularly abundant. This coincides with the stable. This might be a result of deliberate water management peak of human activities at the site, so we cannot rule out the as discussed below. possibility that there was deliberate management of the forests on the hill or nearby the Maoshan site. Hydrological regimes and water management In contrast, drastic changes in arboreal species in zone 3 are evident with increases and short-term fluctuations in Our diatom results have provided unambiguous evidence for Pinus, Almus, Betula and deciduous Quercus pollen. Even the shift from a freshwater dominant hydrological condition though all these pollen grains were very likely transported before and during the use of the paddy fields to one that was by the flood waters or surface runoff from elsewhere before strongly affected by brackish water after the abandonment of they were re-deposited at the site, they reflect the regional the fields. The latter was caused by a relative sea-level rise in vegetation changes caused by environmental and climatic the region, as many studies have demonstrated (Zong 2004; oscillations, which were becoming cooler and drier. Such Zong et al. 2011). Whilst these diatom results are a useful changes are corroborated by the increase in Artemisia pol- indication of the regional hydrological situation, the other len, and probably also Chenopodiaceae pollen as well, al- proxy data we have obtained has provided more detailed in- though many Chenopodiaceae species grow in both wet formation regarding the reconstruction of in-field water con- and dry conditions and therefore their implications to envi- ditions that were influenced by both regional hydrological ronmental changes should be treated with caution. Overall, conditions and the changing water management practices. the vegetation taxa became less diverse across the whole The rising water level was coupled with several short-term region before the onset of massive floods. This might be events of high-energy surface runoff during the use of the related to intensified agricultural activities and increasing paddy fields. From 230-cm-depth upwards, we can observe deforestation in the region during the Late Liangzhu period a continuous increase of coarse particles in the sediments, (cf. Zheng et al. 2014). This vegetative pattern accords well indicative of more frequent surface runoff in and out of the with the geochemical results which showed gradually de- fields. The embedded sandy lens, indeed, point to a strong, creasing values of Al O /Na O and Rb/Sr, which are indic- albeit short term, flushing in of sediments into the fields. 2 3 2 ative of the transition from warm and humid conditions to Given that the use of artificial and natural ditches and creeks cooler and drier conditions. Whilst this change might be located at the both ends of the fields would have effectively related to regional climate events (e.g. the so-called 4.2 ka absorbed eroded materials from the upland, we suggest that BP event), a convincing link for these ecological changes in these coarse fractions in the sediments were flushed into the the field and the regional climate event has not been fields through irrigation activities. This sedimentary change is established yet. The K O/Na O and to a certain extent, the compatible with the increase of CaO, MgO, K Oand Na O 2 2 2 2 CaO/MgO values stayed roughly unchanged. These K O/ values as discussed above from layers 9–6 (corresponding to Na O and CaO/Mgo values might reflect the geochemical the Middle-to-Late Liangzhu phase and Late Liangzhu phase) properties inherited from the source sediments in residual as the artificial control of the hydrological conditions in the forms rather than derived from post-depositional weathering. field effectively stopped the leaching of these chemical ele- The spike in changes amongst the geochemical results oc- ments (also cf. Driese and Medaris 2008; Vepraskas and curred between c.130 and 120 cm, for instance, must be relat- Faulkner 2001). In addition, the increasing coarse-sized parti- ed to the process just described. However, caution should be cles might be related to sediments being flushed in the field taken for the above interpretation as without a detailed under- during irrigation. standing of the chemical precipitation and biological uptake of The overall pollen grain density started to drop from layer 9 the values of diagnostic elements (e.g. Rb and Sr), the possi- (corresponding to the Middle Liangzhu cultural phase) up- bility that these geochemical results were related to post- wards whilst the percentages of the Gramineae pollen grains depositional changes cannot be entirely ruled out (cf. Zeng experienced a steady increase. These contrasting trends indi- et al. 2011 and references therein). cate that weeding might have been practiced by the Maoshan Gramineae taxa were abundant in the pollen zones 1–2, rice farmers. Of great significance to our understanding of with evident increases from the middle stage to the later stage water management practices is the changing curve of Typha of zone 2. Such increases coincided with rice farming at the pollen. Typha is a wet-loving species commonly growing in site. Some of the large-sized (> 40 μm) pollen grains might wetlands or similar habitats such as paddy fields subject to belong to the cultivated crops and related weeds. Reed frequent and/or prolonged water saturation (Keddy 2010;Li phytoliths remained abundant from later stage of zones 1 to et al. 2010). Typha pollen remained abundant after the initial 2. This, on the one hand, suggests that reeds are less sensitive wetlands were converted to rice farming (corresponding to to hydrological changes (e.g. from freshwater to brackish wa- zone 1 to the lower part of zone 2), with frequent fluctuations. ter) than other plants, and on the other hand, also implies that A noticeable increase started to occur at the middle stage of Archaeol Anthropol Sci (2019) 11:1851–1863 1861 zone 2, corresponding to the late phase of the paddy fields, depth understanding of the palaeo-hydrological and ecologi- before it began to decrease in the flooding deposits. This in- cal changes in the paddy fields on both local and regional dicates a clear return to a wetter condition during the late scales, permitting a robust understanding of the development phase of the use of the paddy field. The abundance of of rice farming and water management at the site, which was Cyperaceae species, another type of plants closely related to closely related to environmental changes in the region. wet habitats, shows a similar trend, but it did not witness a The Maoshan site was first occupied during the Late significant increase in the end of zone 2. Both curves suggest Majiabang and Songze period (c. 6000–5300 cal. BP). The that the water level did continue to rise, with frequent fluctu- initial rice farming began during the Middle Liangzhu period, ations during the use of the paddy field. Related to these trends followed by an expansion characterised by its impressive in- is the change in the overall pollen grain density, which expe- crease in scale of the size of the fields and intensified water rienced a drop. management practices. This intensification process of rice Our observation of hydrological changes is comparable farming coincided with a favourable climatic regime in the with the one made by Weisskopf et al. (2015), based upon region, which is well demonstrated in our micro-fossil plant their examination of the phytolith assemblage of rice and records and other published data. More importantly, the re- weeds collected from the Maoshan paddy fields. Using their gional water table, which was mainly determined by the sea established fixed and sensitive morphotypes as the respective level and alluvial hydrology, during this period of rice farming ecological indicators of dry and wet fields, they found that the expansion remained relatively low, compared with the return to a wetter condition at Maoshan was marked by a high succeeding period, and also stable. This facilitated successful percentage of sensitive morphotypes of phytoliths. Weisskopf water management by the Maoshan rice farmers who also et al.’s samples were collected from both ‘river edge’ and built irrigation facilities such as ditches and creeks. Our pollen ‘paddy fields’, whereas samples for our present research were records and geochemical-physical analyses have proved to be from a mainly complete sequence on the edge of the fields. a useful way to explore these irrigation practices, including Whilst these two sets of samples, from Weisskopf et al. and some sensitive plant species such as Typha and geophysical- this present paper, might reflect the spatial-temporal variations chemical indicators such as coarse-sized particles and values of the vegetation dynamics at the site, the general trend of of certain chemical elements. The intensifying rice farming rising water in the region, it is the return to wetter conditions and water management was accompanied with a gradual re- in the fields detected by both studies that is the most convinc- turn to a wet hydrological condition at the paddy field site and ing piece of evidence. However, our records also present ev- in the region. Whilst the climate experienced a shift from idence of vegetation changes caused by frequent wet-dry al- warm and wet conditions during the Middle to Late ternations in the fields throughout the different phases, com- Liangzhu period to a relatively drier and cooler situation dur- pared with relatively stable ecological conditions in the wet- ing the Guangfulin period, the regional water table also rose to lands surrounding the fields (e.g. reeds). We would suggest a very high level. This change had a devastating impact on the that this high frequency of in-field vegetation changes is close- rice farming and water management at Maoshan and beyond, ly related to intensifying water management for rice farming marking the eventual abandonment of the paddy fields at the in the transition from the early to late phase use of the paddy site. The Maoshan paddy field site present a good opportunity fields. The latter is also supported by the micromorphological to examine the combined effects of regional sea-level rise, study of the cultivated soils conducted by the aforementioned hydrological change in the major rivers and water bodies research by Zhuang et al. (2014) at the site. This intensifying (e.g. the Qiantang River and the Taihu Lake), and possible water management practice, however, became unsustainable increased sedimentation inputs to the rivers and lakes on the as the water level rose to a high level, marking the abandon- development of prehistoric rice farming and water manage- ment of the paddy fields at Maoshan during the Guangfulin ment in the Lower Yangtze River. period. The latter is also confirmed by the increasing pollen Our research also offers valuable methodological implica- grain density from layer 6 (corresponding to the Guangfulin tions and theoretic significance to the heated debate on the cultural phase) with abundant Gramineae, Typha and other wet-dry narratives of early rice farming across the monsoon related species, indicating that the fields were colonised by areas of Asia (Bray 1994;Kirch 1994; Weisskopf et al. 2015). hydrophilic weedy plants and related species with the rising Whilst it is generally agreed that the increasing investment in water table. the construction of hydro-infrastructures for irrigation has a profound social impact on rice farming societies (cf. Fuller and Qin 2009), the trajectory to intensification of rice farming Conclusions is certainly not a linear one and does not share same paths in different rice farming regions. Local ecological and hydrolog- In conclusion, our geoarchaeological and paleo-ecological in- ical conditions, technologies and other factors all contribute to the evolution of rice farming systems. In some regions, dry vestigation at Maoshan offers detailed information for an in- 1862 Archaeol Anthropol Sci (2019) 11:1851–1863 Liu B et al (2017) Earliest hydraulic enterprise in China, 5,100 years ago. farming systems also persist. To further unpack such a dichot- PNAS 1–6(early edition) omy, we need to focus more on the palaeo-ecology of early Liu B, Renfrew C (2018) The emergency of complex society in China: rice farming in wider paleo-environmental contexts. The case of Liangzhu. Antiquity. (in press) Nanjing Museum, Zhangjiagang Municipal Commission for Funding information This research is funded by National Social Science Conservation of Ancient Monuments, Zhangjiagang Museum Fund of China (11&ZD183), National Natural Science Foundation of (2016) Dongshancun site: the Neolithic period excavation report. China (41171006), National Key Technology Research and Cultural Relics Press, Beijing Development Program of the Ministry of Science and Technology of Palmer AJM, Abbott WH (1986) Diatoms as indicators of sea-level China (2013BAK08B02) and National Natural Science Foundation of change. In: van de Plassche O (ed) Sea-level research: a manual China (41701220). for the collection and valuation of data. Ge Books, Norwich, pp 457–488 Open Access This article is distributed under the terms of the Creative Qin L (2013) The Liangzhu culture. In: Underhill AP (ed) A companion Commons Attribution 4.0 International License (http:// to Chinese archaeology. 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Ecology and hydrology of early rice farming: geoarchaeological and palaeo-ecological evidence from the Late Holocene paddy field site at Maoshan, the Lower Yangtze

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Springer Journals
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Copyright © 2018 by The Author(s)
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Earth Sciences; Earth Sciences, general; Archaeology; Chemistry/Food Science, general; Geography, general; Life Sciences, general; Anthropology
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1866-9557
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10.1007/s12520-018-0639-1
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Abstract

The well-preserved Maoshan paddy fields (4700–4300 BP) were built on an intermediate landscape between the foothills and alluvial plain of the Lower Yangtze River. Despite several interdisciplinary research, there has been a lack of detailed environ- mental and ecological data to contextualise the reconstructed rice farming practices within a wider paleo-environmental back- ground. Our research provides key information on the chronology, vegetation, and long-term hydrological fluctuations at and surrounding the paddy fields. Our 14C and OSL dates show that the initial occupation began at around 5740 ± 140 cal. BP, and the paddy fields were built at around 4675 ± 145 cal. BP and were in use continuously until around 4000 cal. BP. Our pollen, diatom and phytolith data shows that whilst the vegetation in the field was sensitive to changes caused by water management and rice farming, the ecological system surrounding the fields was relatively stable. We suggest that this high frequency of in-field vegetation changes was closely related to intensifying water management for rice farming. This thesis is supported by our geophysical and geochemical analyses of bulk sediments, which shows that the steady build-up of the alluvial sequence was punctuated by several short-term episodes of high-energy surface runoff, including strong flushing in of sandy sediments into the fields perhaps through irrigation activities. Our paleo-ecological and geoarchaeological investigation at Maoshan permits an overview of the development of rice farming and intensifying water management practices in a wider environmental context and offers significant insights to the ongoing debate on the wet-dry dichotomy of early rice farming. . . . . Keywords Paddy fields Liangzhu culture Lower Yangtze River Hydrology Ecology Introduction During the protracted cultivation and domestication process, prehistoric communities first managed and modified natural The Lower Yangtze River is one of the key areas where rice habitats of wild rice for the initial cultivation of rice (Zong was consumed from the beginning of the Holocene and sub- et al. 2007) and later constructed man-made paddy fields for sequently domesticated (Fuller et al. 2009; Liu et al. 2007). increasingly large-scale rice farming (Ding 2004). The con- struction of paddy fields was also accompanied by increasing ecological intervention and biological modification in the fields. * Yijie Zhuang A recent research trend is to apply palaeo-ecological ap- y.zhuang@ucl.ac.uk proaches to investigate water management strategies and the ecology of rice farming in the Lower Yangtze River. For College of Urban and Environmental Sciences, Peking University, instance, through their detailed examination of phytolith Beijing 100871, China assemblages collected from a number of ancient and modern Zhejiang Provincial Institute of Cultural Relics and Archaeology, rice farming sites, Weisskopf et al. (2015) investigate the long- Hangzhou 310014, China term fluctuations of water conditions in rice fields and the Department of Earth Sciences, The University of Hong Kong, Hong evolution of rice farming system in the Lower Yangtze Kong, China River. They suggest that the paddy fields at Caoxieshan Institute of Archaeology, University College London, 31-34 Gordon (6000–5800 BP) were dominated by dry species, Square, London WC1H 0PY, UK 1852 Archaeol Anthropol Sci (2019) 11:1851–1863 corresponding to an emphasis on drainage in the fields. A centennial, minor changes. The rise of sea levels slowly in- return to wetter conditions in the paddy fields at Maoshan creased between c.4000 and 3000 cal. BP, reaching the present was indicated by evidence for a ‘highly irrigated paddy sys- level at the end of this period (Yang and Xie 1984;Feng and tems’ (Weisskopf et al. 2015, p. 1060). This accords well with Wang 1986;Chenand Stanley 1998; Zong 2004). The the research conducted by Zhuang et al. (2014)of the Holocene sedimentation process in the Linping area (Fig. 1) geoarchaeological evidence regarding greater control of the is dominated by alluvial activities, with localised colluvial in-field water situation and intensifying farming practices. processes. Typical Holocene sedimentation sequences are This research provides a detailed information on the compli- dominated by light yellowish silty clay, with abundant iron- cated patterns of early water management and the physio- manganese nodules. At some locations, this yellowish silty biological changes of rice caused by in-field ecological inter- clay either overlies on top of, or is covered by, light greyish vention of the prehistoric Lower Yangtze River. However, silty clay whose light colour was caused by iron depletion contextualising such water management practices and corre- under reducing conditions. This indicates that these locations sponding ecological changes within long-term cultural and were on low topography and subject to long inundations. The environmental backgrounds at these early paddy sites remains Middle to Late Holocene climate in the Yangtze Delta and challenging, mainly due to the lack of high-resolution chrono- nearby regions was humid and wet as consistently shown by logical data from both in- and off-site contexts. The current several pollen and geochemical studies (Atahan et al. 2008; lack of precise chronological data hinders any effective corre- Tao et al. 2006;Yietal. 2003;Yuet al. 2000). This climate lation between different kinds of proxy data collected from condition promoted the expansion of ‘subtropical evergreen- various contexts for palaeo-environmental and palaeo- deciduous broadleaved forests’ (Yi et al. 2003) between c. ecological reconstructions. 7600 and 4800 cal. BP in the Yangtze Delta. These sub- The Late Liangzhu period (4700–4300 paddy fields at tropical arboreal species grew on the mountains and Maoshan in the Lower Yangtze River were built on the foot- hillslopes, including Cyclobalanopsis, Castanopsis/ hills of the Maoshan Hill (48.8 m in elevation) (Ding et al. Lithocarpus, Castanea, along with many other species, whilst 2011; Zheng et al. 2014). In this intermediate landscape be- in the low-relief areas or wetlands, aquatic plants such as tween the foothills and alluvial plain, the fields were next to a Trapa, Euryale, Oryza rufipogon, Typha, Cyperaceae and residential area on the slope, slightly higher up on the hill and other hydrophilic species, flourished (Qin et al. 2010;Yi at the same time connected to both natural and man-made et al. 2003). rivers and creeks on the ground below. A geoarchaeological The Liangzhu culture (5300–4300 cal. BP) is one of the survey was carried out in 2011, during which many soil sam- most developed Neolithic cultures in prehistoric China. The ples were collected. Our high-resolution palaeo-ecological da- densely-populated Liangzhu site complex, possessed a large- ta, supported by 14C and optically stimulated luminescence sized urban centre with earthen walls, palatial buildings and (OSL) dates, provides key information towards a better under- elite burials with elaborately carved jade items (Qin 2013), as standing of rice farming, water management and environmen- well as a recently discovered and excavated hydraulic enter- tal change at the Maoshan site. We will present this data and prise 20 km to the northeast of the Liangzhu centre (Liu et al. discuss its significance, particularly focusing on the following 2017;Liu andRenfrew 2018). Around 20 Liangzhu period aspects: (1) chronology of the construction, use and abandon- sites have been found in the Linping area, forming a sub- ment of the paddy fields; (2) the vegetation history of the centre in the outskirt of the Liangzhu site complex. The paddy fields and surrounding areas; and (3) long-term fluctu- Maoshan site is one of the sites in the Linping sub-centre that ations of the hydrological regimes in the fields resulting from was excavated in 2009–2011. The site was occupied during both water management practices and regional alluvial the Late Majiabang and Songze period (c. 6500–5300 cal. BP), processes. before the Liangzhu period paddy fields were constructed. The Majiabang period archaeological features include house foundations, burials, a large number of pits and wells, all con- Environmental settings and archaeological centrated on the hillslope of the Mountain Hill (Zhuang et al. backgrounds 2014;Ding et al. 2011). By the Liangzhu period, houses and burials were continuously built on the hillslope. At the same The Hangzhou Bay is in a tectonically stable area, with only time, paddy fields were built in the intermediate area between minor subsidence during the Holocene. The Holocene sea- the hillslope and the low-lying alluvial plain. Two phases of level fluctuations are the main factor influencing regional hy- paddy fields have been excavated to date. Twenty-six early- drology. After the steady increase from the beginning of the phase (c. 4900–4700 BP) paddy fields have been excavated Holocene, the sea-level reached to c. − 2.5 m of the present and were found to have been directly built on top of mid- level at around 7000–6500 cal. BP. Between 7000/6500 and Holocene alluvial sediments. These fields were small, from 2 2 4200/4000 cal. BP, sea levels remained stable, with several 1to2m to a maximum of 40 m , and irregular in shape. Archaeol Anthropol Sci (2019) 11:1851–1863 1853 Fig. 1 Holocene environment and locations of archaeological sites mentioned in the text Wells were dug in the fields, which were connected to a creek Samples were taken from the different layers for OSL dat- through small ditched outlets. In contrast, the late-phase paddy ing, 14-C dating, particle size distribution, pollen, diatom and fields were built on top of light yellowish alluvial materials, geochemical analyses. The methods are briefly summarised covering the early-phase fields. A dramatic increase in size below. In the field, five OSL dating samples were collected occurred in the late-phase fields. Separated by narrow path- by using metal tubes (c. 20 cm long) sealed with aluminium ways in a north-southerly direction, the fields were 1000 m in foil to prevent exposure to sunlight. Pre-treatment were con- size, with some reaching nearly 2000 m . The entire fields ducted at the OSL dating laboratory at the School of measured approximately 5.5 ha by this phase. A new creek Archaeology and Museology, Peking University. In the dark was dug to the north of the field, along with other water man- room, approximate 100 g of sediments was grounded and agement facilities such as ditches and wells. These pro- sieved. First, 30% HCL and 30% H O were added to 2 2 nounced changes in the scale and structure of the fields from 20 μm of this ground and sieved sediment to remove the the early to late phase were closely related to changes in farm- carbonates and organic matter and then H SiF (30%) was 2 6 ing and water management practices. added to obtain fine-grained quartz. The measurements were performed using an OSL reader following the standard single- aliquot technique described by Duller et al. (2003). Water saturation was not measured in the field; an average 15% Materials and methods saturation rate was adopted for all samples. U, Th and K con- tents were measured at the Institute of Atomic Energy of The stratigraphy under examination below was located at the China. Four samples were collected for AMS 14C dating. edge of the paddy fields close to the residential area on the The samples were processed at the pre-treatment laboratory foothill. The sedimentation process at this location was influ- at the School of Archaeology and Museology and dated by the enced by farming activities in the fields and alluvial and col- School of Physics, Peking University. OxCal v3.10 was used luvial processes which brought in sediments from the low- to calibrate the dates using the IntCal04 curve. lying areas and hillslopes. From the top to bottom, the stratig- Sixty-three pollen samples were processed at the raphy is divided into five main units: (1) topsoil (layer 1); (2) Laboratory for Earth Surface Processes, College of Urban Late-Holocene flooding deposits (layers 2–5,); (3) peat-like and Environmental Sciences at Peking University, using the sediments (layers 6–9) containing the Liangzhu period and standard hydrofluoric acid (HF) method (Berglund and succeeding Guangfulin period (c. 4100–3900 BP,cf.Zhai Ralska-Jasiewiczowa 1986.). One gram of the sediment was 2006;Ding et al. 2011) and associated cultural remains; (4) dried and mixed with one Lycopodium spore. Ten per cent greyish alluvial deposits (layer 10); and (5) dark alluvial de- HCL was slowly added to remove the carbonates. HF (40%) posits (layers 11–12), rich in organic matter and containing was added to the washed sediments in a tube that was placed sandy lens (Table 1). 1854 Archaeol Anthropol Sci (2019) 11:1851–1863 Table 1 Descriptions and Depth Period Descriptions sampling units of the examined Layer (m) sedimentary sequence at Maoshan 10–0.33 Topsoil, brownish silty clay with abundant iron-manganese nodules resulting from repeated wet-dry alternations. 20.33–0.48 Post-paddy field Light greyish silty clay, embedded with yellowish iron flooding deposits nodules and hard horizontal laminae. 30.48–0.80 Brownish silty clay with abundant iron nodules 40.80–1.11 Dark brownish silty clay, abundant iron nodules in the upper part, and reduced number of iron nodules in the middle and lower sections. 51.11–1.31 Brownish silty clay, containing the most abundant iron nodules amongst the upper 5 units of the profile. In the middle part of this unit, there are also abundant manganese nodules. There are 1–6-cm-thick dark greyish clay laminae at the bottom of this unit. 61.31–1.37 Paddy fields Organic-rich darkish clay, at the top there are thin laminae of plant ash with some Guangfulin-period pottery sherds. 71.37–1.42 Dark greyish silty clay, with abundant vertically situated ironised plant roots; some Late Liangzhu period pottery sherds are also present. 81.42–1.63 Dark greyish silty clay, with abundant vertically situated ironised plant roots; there are also dark, organic rich laminae in the middle-lower part of this unit. 91.63–1.92 Light greyish silty clay, with vertically situated, ironised plant roots; some pottery sherds present. 10 1.92–2.30 Early-to-Middle Dark greyish silty clay, a 3-cm-thick sandy layer embedded Holocene alluvial in the middle part. sequence 11 2.30–2.48 Light greyish to brownish silty clay. 12 2.48–2.66 Brownish silty clay, with vertically situated ironised plant roots in a boiling water bath until the reaction stopped. HCL (36%) LiBO in a crucible, which was heated in a fusion machine to was added at this stage to remove the silicates. The mounted 700 °C, followed by 1080 °C. The sample was then shaken for slides were examined under a microscope, with percentages of 5 min whilst gradually adding 40 mg of NH l. The major pollen species counted. Diatom samples from layers 4, 5 and element compositions of the sediments were determined on 10 were processed at the Department of Earth Sciences, an X-ray fluorescence spectrometer. Trace element composi- University of Hong Kong. Diatom processing followed the tions were measured by running a HR-ICP-MS analysis on an procedures described by Palmer and Abbott (1986). Samples Agilent 7500 mass spectrometer. (1–3 g) were dissolved in 20% H O in hot water bath for 2 2 24 h. Several drops of concentrated solutions were mounted to cover slips with 10 drops of distilled water. The dried cover Results slips were placed onto a glass slide using Zrax. The species were identified based on Vos and Wolf (1993) and others OSL and 14C dates (Round et al. 2007; Zong and Sawai 2015). Phytoliths mounted on the same slides as diatoms were also identified The four 14C dates from layers 9–6 show a consistent chro- and counted. nological order from the bottom to the top of the profile, com- One hundred and fifteen samples were analysed for particle parable with relative chronology reconstructed by the excava- size distribution using the Malvern Mastersizer 2000 laser tor based on pottery typology (Table 2;Fig. 2). The 14C dates particle sizer, following the procedures described by Steve of 4580–4340 cal. BP from MS-6 is older than the designated Boreham from the Department of Geography, University of relative age of the Guangfulin culture, which falls between Cambridge (https://www.geog.cam.ac.uk/facilities/ 4100 and 3900 BP (Ding et al. 2011). The 14C dates from laboratories/techniques/psd.html). Geochemical analysis was the other three horizons correspond well to the established conducted at the HR-ICP-MS laboratory, Peking University. absolute and relative chronologies of the Liangzhu and the Abulk sample of 0.4gwasmixedwith 4 g of Li B O and 2 4 7 Late Majiabang-Songze period (Ding et al. 2011). Archaeol Anthropol Sci (2019) 11:1851–1863 1855 Table 2 Results of the AMS 14C dating Sample and cultural period Depth (cm) Lab no. Material 14C age Calibrated date (year BP) (95.4% prob.) MS-6 (Guangfulin) 133–135 BA121233 Peat 3980 ± 35 2580–2340 BC MS-7 (Late Liangzhu) 138–140 BA121234 Charcoal 4125 ± 25 2870–2580 BC MS-8 150–152 BA121235 Charcoal 4770 ± 30 3640–3380 BC MS-9 (Majiabang-Songze) 178–180 BA121236 Charcoal 4980 ± 35 3930–3650 BC Age reversals occurs in the OSL dates between the fifth to Pollens third yellowish silty clay layer (Table 3; Fig. 2). These OSL dates, however, fall into the broad time span of 4000–3200 BP, The pollen densities of the 63 examined samples varied great- which is within the chronological framework for the wide- ly. Several samples produced less than 100 pollen grains per spread flooding event in the region. The other two OSL dates slide, but the majority of the samples contained at least 300 from the eleventh and twelfth layers are of Late Pleistocene pollen grains per slide, with several samples having more than ages, significantly older than the other dates. This suggests 500 pollen grains per slide (Fig. 3). A large number of arboreal that the building up process of the alluviums had begun by and herbaceous plants as well as ferns and algae were identi- the Late Pleistocene. fied. Based on the changing percentages of arboreal, herba- Thus, these dates, combined with the stratigraphic order ceous and fern pollen, we can divide the pollen profile into and cultural characteristics of artefacts discovered during the three main zones. In zone 1 (2.66–1.92 m, layers 12–10, cor- excavation, support our chronological division of the sedi- responding to Early-to-Middle Holocene alluvial sequence), mentary sequence described in Table 1. Layers 12–10 repre- the pollen assemblage contained about 20% tree and shrub sent the Early-Middle Holocene alluvial sequence preceding species, with low percentages of fern species. Evergreen spe- the use of the paddy fields. Layers 9–6 correspond to the use cies such as Quercus were dominant in the arboreal pollen, but of the paddy fields, which include an early and later phase pollen of Pinus and deciduous Quercus and Ulmus was also (corresponding to the Middle-to-Late Liangzhu phase and present. Percentages of herbaceous species were high, repre- Late Liangzhu phase). Layers 5–2 were deposited during the sented by Gramineae, Cyperaceae and Typha,with Artemisia, flooding periods after the field was abandoned. This recon- Chenopodiaceae and Cruciferae also present. In the second struction provides a useful framework for our discussion of zone (1.92–1.31 m, layers 9–6, corresponding to the Middle- the pollen and other records (but see our further discussion to-Late Liangzhu phase and Late Liangzhu phase), the per- below on ‘chronology’). centages of tree and shrub species again accounted for around Fig. 2 Stratigraphical sequences and sampling locations for AMS 14C and OSL dates 1856 Archaeol Anthropol Sci (2019) 11:1851–1863 Table 3 Results of the OSL Sample Dose rate (Gy/ka) De (Gy) OSL age (ka) Age (BP) Age error dating MS-3 (65 cm) 3.25 ± 0.12 10.89 3.50 ± 0.17 3500 170 MS-4 (95 cm) 3.30 ± 0.12 12.58 3.99 ± 0.40 3990 400 MS-5 (120 cm) 4.30 ± 0.15 12.99 3.17 ± 0.15 3170 150 MS-11 (240 cm) 3.65 ± 0.23 49.38 13.50 ± 0.98 13,500 980 MS-12 (255 cm) 3.71 ± 0.23 93.66 25.20 ± 1.80 25,200 1800 20% in the early stage, this slightly decreased to around 10– addition of Artemisia and Chenopodiaceae species to the as- 15% but gradually increased to 25–30% with more evergreen semblage towards the top of this unit. Gramineae species Quercus in the later stage. Fern species included Monolites decreased whilst Typha species gradually increased in the later and Trilites had low percentages in the early stage but in- stage. In zone 3 (1.31–0.33 m, layers 5–2, corresponding to creased significantly in the later stage. Gramineous, post-paddy field flooding deposits), Pinus pollen grains be- Cyperaceae and Typha species continued to be abundant with came abundant, whilst the percentage of evergreen Quercus a significant increase of these three species, along with the gradually dropped. In the later stage, an important change was Fig. 3 Diagram of pollen concentrations and species Archaeol Anthropol Sci (2019) 11:1851–1863 1857 the increase of both Alnus and Betula species in the pollen and Synedra unla. Slides from the sixth to ninth layers assemblage along with the high percentages of fern species (1.31–1.92 m, corresponding to the Middle-to-Late included Monolites and increasingly Trilites. The three com- Liangzhu phase and Late Liangzhu phase) contain some reed mon herbaceous species, Gramineae, Cyperaceae and Typha, phytoliths, but diatoms were not found. For the fifth and experienced a significant drop in their abundance, which is in fourth layers (0.8–1.31 m), only a small amount of reed contrast with the steady increase of Chenopodiaceae and phytoliths were present, and some brackish water diatom spe- Artemisia species first and later also of Cuciferae species. cies, such as Coscinodiscus blandus and Actinocyclus sp., can These changes in the pollen assemblages in the upper part of be seen. This drastic change from predominant freshwater the profile seem to correspond to a gradually cooler and drier diatom species at the bottom to mainly brackish water species regional climate regime. at the top is closely related to regional and local hydrological changes, which is discussed further below. Diatoms and phytoliths Geochemical analyses and particle size distributions The diatom results are presented in Fig. 4.It should bemen- tioned that as well as diatom species, reed phytoliths were also The detailed results of the particle size distributions and geo- counted in these slides. A large number of reed phytoliths and chemical analyses are shown in Figs. 5 and 6. These results freshwater diatom species were found in the tenth layer (1.92– provide important information regarding the sedimentary and 2.3 m). The latter include Eunotia lunaris, Gomphonema post-depositional processes. In 266-230 cm (layers 12–11), parvulum, Hantzschia amphioxys, Pinnularia microstauron fine-sized particles (silt and clay) contributed the most to the Fig. 4 Concentrations and species of diatoms and phytoliths. Note that the phytolith concentrations are calculated based on six scales: ranging from 0 (none) to extremely abundant (scale 5) 1858 Archaeol Anthropol Sci (2019) 11:1851–1863 Fig. 5 Results of particle size distribution analysis sedimentation, along with a very low percentage of coarse dramatic decrease at the same level. This might be caused particles. The average values for Al O /Na O, K O/Na O, by the decrease of coarse particles of quartz (Fig. 6)asSiO 2 3 2 2 2 2 CaO/MgO and Rb/Sr ratios were 17.2, 1.9, 0.7 and 1.5, re- is mainly composed of quartz rather than from fine-sized par- spectively (Fig. 6), whilst the rare element compositions were ticles such as clay. The sedimentary process in 131–111 cm higher than the average for the whole profile. The high abun- (layer 5) was characterised by the significant increase of fine- dance of Al O and Fe O might be due to the fact that they sized particles. The reversal of trends can be seen in the ratios 2 3 2 3 are not easily removable and thus resistant to the in situ of Al O /Na O, K O/Na O, Rb/Sr and CaO/MgO: the former 2 3 2 2 2 weathering process. Correspondingly, the relatively low per- three increased (19, 3.6 and 1.5, respectively) whilst the last centages of CaO and MgO might be due to their high mobility one decreased (0.4). The rare element compositions reached a in predominantly weathering conditions. In 230–192 cm peak at this stage. From 111 to 80 (layer 4) and 80 to 33 cm (layers 10), there was an obvious increase in coarse sand- (layers 3–2), percentages of clay particles dropped significant- sized particles in the sediments, especially from the sandy ly and percentages of silt and coarser particles increased to as layers embedded in layer 10. The Al O /Na O, K O/Na O high as 85%, indicative of fundamental shifts in sedimentary 2 3 2 2 2 and Rb/Sr values (14, 1.7, and 0.9, respectively) slightly de- regimes. Coupled with these changes were the drastic changes creased and correspondingly the CaO/MgO ratio saw a slight in Al O /Na Oand K O/Na O ratios (6.1 and 1.2, respective- 2 3 2 2 2 increase (0.8). Rare element compositions also showed a pro- ly, in 111–80 cm (layer 4); and 6.2 and 1.2, respectively, in nounced decrease. Several changes, particularly the contribu- 80–33 cm (layers 3–2)), whilst the values of CaO/MgO and tions of coarse particles, can be observed in 192–131 cm Rb/Sr ratios changed slightly (0.7 and 0.8, respectively, in (layers 9–6, corresponding to the Middle-to-Late Liangzhu 111–80 cm (layer 4); and 0.7 and 0.6, respectively, in 80– phase and Late Liangzhu phase). The Rb/Sr was stable (0.9), 33 cm (layers 3–2)). Rare element compositions dropped to but ratios of Al O /Na Oand K O/Na O, and CaO/MgO con- a very low level. Regarding other changes determined by the 2 3 2 2 2 tinued to show reversals in trends, with the latter having a geochemical analyses, K O and Na O experienced a slight 2 2 higher value. Similarly, rare element compositions also expe- increase in the upper part of the profile. This increase may rienced obvious fluctuations. The Al O and T-Fe O values be related to the contribution from saline water. 2 3 2 3 showed a pronounced increase in layer 6 (c.131 cm, corre- sponding to the Guangfulin cultural phase). Similar changes can be seen for both CaO and MgO values. This stage was Discussion dominated by continuous deposition of sediments with weak in situ weathering or post-depositional processes. This means Chronology that these values reflect those of the exogenous sediments, including the possible contribution from the marine sedi- The 14C date of the peat layer was older than expected. This ments, caused by the high CaO value as calcium is more might be due to the intrinsic difficulties of dating peat sedi- readily precipitated in seawater (Zhong and Mucci 1989). ments (Shore et al. 1995), as essentially the 14C dates are the We should also mention that the SiO value experienced a 2 mean results of organic matter (humic and fulvic acids) which Archaeol Anthropol Sci (2019) 11:1851–1863 1859 Fig. 6 Results of geochemical analyses is normally compacted after deposition. In addition, taphono- directly related to the deposition of the yellowish silty clay my might be responsible for this chronological discrepancy deposits dates to around 4000 BP, our OSL dates demonstrate between the 14C dates and relative chronology derived from that these flooding events lasted for a substantial period of pottery typology. The pottery recovered from the peat sedi- time. These new dates are significant as they help us under- ment was most likely deposited on the peat horizon through stand the magnitude and duration of these floods. The effects scattered human activities. In other words, the peat horizon of these flooding events and their implications to the mecha- was deposited first, on top of which human activities took nisms of societal responses should be reassessed in light of place. For the age reversals amongst the OSL dates of the light these new dates. yellowish silty clay sediments, the reasons are equally com- plicated. As the deposition of these sediments are related to the Vegetation dynamics and ecology of the early rice post-Liangzhu period flooding events, there might be problem farming of impartial exposure to light before deposition, a common issue encountered in OSL dating of fluvial deposits. The rea- The landscape around the site of Maoshan consist of several son for the OSL age in MS-5 (120 cm) being significantly niches that had distinctive vegetative patterns: the Maoshan younger than the overlying samples is because of its high dose Hill, the residential area and the paddy fields and the wetlands. rate (4.30 ± 0.15 Gy/ka). As to the transition from the peat The microfossil plant remains we have discovered provide horizon (layer 6, corresponding to the Guangfulin cultural first-hand data to reconstruct local vegetation dynamics that phase) to the flooding deposits (layers 5–2), determined by were under the combined effects of long-term climatic/ 14-C and OSL dates, respectively, given the chronological environmental and land use changes. The intrinsic gap, there might be depository hiatus between these two sed- taphonomical issues of pollen transportation and deposition imentary events. As well as being compacted, parts of the often undermine the reliability of using pollen records to re- peat-like sediments might be eroded away before the deposi- construct past climate changes. However, our geochemical tion of the yellowish silty clay. and particle size distribution (PSD) analyses provide supple- Despite all these issues, the combination of 14C and OSL mentary information on local sedimentary processes and the dating techniques has helped to refine the chronology of the changing sources of the sediments to refine our interpretation construction and use of the paddy fields at Maoshan, the de- of the pollen records. On a temporal scale, pollen grains from position of the peat-like sediments and the flooding events that zone 2 at Maoshan reflect local vegetation changes, whilst eventually marked the abandonment of the site. The initial those from zones 1 and 3 of the profile are most closely related occupation at the site began at around 5740 ± 140 cal. BP, to regional vegetation changes as the sediments for these lasting to until 5460 ± 130 cal. BP, corresponding to the Late levels underwent long-distance transportation. In terms of Majiabang and Songze cultural period (6000–5300 BP, the taxa, roughly speaking, the arboreal species provide infor- Nanjing Museum et al. 2016; Zhejiang Provincial Institute mation regarding the vegetative changes on the hills, of Cultural Relics and Archaeology 2005). The middle- hillslopes and alluvial plains, whilst the herbaceous, fern and phase paddy fields (layer 7, corresponding to the Early-Late algae species reflect the changing ecological and hydrological Liangzhu cultural phase) were built at around 4675 ± 145 cal. conditions in the field and the low-lying wetlands. BP and continuously used until around 4000 cal. BP.This also The majority of the tree and shrub pollen belonged to ev- means that the initial use of the paddy field (layer 9, corre- ergreen and deciduous species such as Quercus, Betula, sponding to the Middle Liangzhu cultural phase) was earlier Ulmus and Pinus. Even though the abundance of Quercus than 4600 cal. BP. Whilst it is clear that the flooding events pollen, for instance, changed over time, the fluctuations were 1860 Archaeol Anthropol Sci (2019) 11:1851–1863 not significant until the later stage of zone 2 when Quercus the ecological system surrounding the fields was relatively pollen became particularly abundant. This coincides with the stable. This might be a result of deliberate water management peak of human activities at the site, so we cannot rule out the as discussed below. possibility that there was deliberate management of the forests on the hill or nearby the Maoshan site. Hydrological regimes and water management In contrast, drastic changes in arboreal species in zone 3 are evident with increases and short-term fluctuations in Our diatom results have provided unambiguous evidence for Pinus, Almus, Betula and deciduous Quercus pollen. Even the shift from a freshwater dominant hydrological condition though all these pollen grains were very likely transported before and during the use of the paddy fields to one that was by the flood waters or surface runoff from elsewhere before strongly affected by brackish water after the abandonment of they were re-deposited at the site, they reflect the regional the fields. The latter was caused by a relative sea-level rise in vegetation changes caused by environmental and climatic the region, as many studies have demonstrated (Zong 2004; oscillations, which were becoming cooler and drier. Such Zong et al. 2011). Whilst these diatom results are a useful changes are corroborated by the increase in Artemisia pol- indication of the regional hydrological situation, the other len, and probably also Chenopodiaceae pollen as well, al- proxy data we have obtained has provided more detailed in- though many Chenopodiaceae species grow in both wet formation regarding the reconstruction of in-field water con- and dry conditions and therefore their implications to envi- ditions that were influenced by both regional hydrological ronmental changes should be treated with caution. Overall, conditions and the changing water management practices. the vegetation taxa became less diverse across the whole The rising water level was coupled with several short-term region before the onset of massive floods. This might be events of high-energy surface runoff during the use of the related to intensified agricultural activities and increasing paddy fields. From 230-cm-depth upwards, we can observe deforestation in the region during the Late Liangzhu period a continuous increase of coarse particles in the sediments, (cf. Zheng et al. 2014). This vegetative pattern accords well indicative of more frequent surface runoff in and out of the with the geochemical results which showed gradually de- fields. The embedded sandy lens, indeed, point to a strong, creasing values of Al O /Na O and Rb/Sr, which are indic- albeit short term, flushing in of sediments into the fields. 2 3 2 ative of the transition from warm and humid conditions to Given that the use of artificial and natural ditches and creeks cooler and drier conditions. Whilst this change might be located at the both ends of the fields would have effectively related to regional climate events (e.g. the so-called 4.2 ka absorbed eroded materials from the upland, we suggest that BP event), a convincing link for these ecological changes in these coarse fractions in the sediments were flushed into the the field and the regional climate event has not been fields through irrigation activities. This sedimentary change is established yet. The K O/Na O and to a certain extent, the compatible with the increase of CaO, MgO, K Oand Na O 2 2 2 2 CaO/MgO values stayed roughly unchanged. These K O/ values as discussed above from layers 9–6 (corresponding to Na O and CaO/Mgo values might reflect the geochemical the Middle-to-Late Liangzhu phase and Late Liangzhu phase) properties inherited from the source sediments in residual as the artificial control of the hydrological conditions in the forms rather than derived from post-depositional weathering. field effectively stopped the leaching of these chemical ele- The spike in changes amongst the geochemical results oc- ments (also cf. Driese and Medaris 2008; Vepraskas and curred between c.130 and 120 cm, for instance, must be relat- Faulkner 2001). In addition, the increasing coarse-sized parti- ed to the process just described. However, caution should be cles might be related to sediments being flushed in the field taken for the above interpretation as without a detailed under- during irrigation. standing of the chemical precipitation and biological uptake of The overall pollen grain density started to drop from layer 9 the values of diagnostic elements (e.g. Rb and Sr), the possi- (corresponding to the Middle Liangzhu cultural phase) up- bility that these geochemical results were related to post- wards whilst the percentages of the Gramineae pollen grains depositional changes cannot be entirely ruled out (cf. Zeng experienced a steady increase. These contrasting trends indi- et al. 2011 and references therein). cate that weeding might have been practiced by the Maoshan Gramineae taxa were abundant in the pollen zones 1–2, rice farmers. Of great significance to our understanding of with evident increases from the middle stage to the later stage water management practices is the changing curve of Typha of zone 2. Such increases coincided with rice farming at the pollen. Typha is a wet-loving species commonly growing in site. Some of the large-sized (> 40 μm) pollen grains might wetlands or similar habitats such as paddy fields subject to belong to the cultivated crops and related weeds. Reed frequent and/or prolonged water saturation (Keddy 2010;Li phytoliths remained abundant from later stage of zones 1 to et al. 2010). Typha pollen remained abundant after the initial 2. This, on the one hand, suggests that reeds are less sensitive wetlands were converted to rice farming (corresponding to to hydrological changes (e.g. from freshwater to brackish wa- zone 1 to the lower part of zone 2), with frequent fluctuations. ter) than other plants, and on the other hand, also implies that A noticeable increase started to occur at the middle stage of Archaeol Anthropol Sci (2019) 11:1851–1863 1861 zone 2, corresponding to the late phase of the paddy fields, depth understanding of the palaeo-hydrological and ecologi- before it began to decrease in the flooding deposits. This in- cal changes in the paddy fields on both local and regional dicates a clear return to a wetter condition during the late scales, permitting a robust understanding of the development phase of the use of the paddy field. The abundance of of rice farming and water management at the site, which was Cyperaceae species, another type of plants closely related to closely related to environmental changes in the region. wet habitats, shows a similar trend, but it did not witness a The Maoshan site was first occupied during the Late significant increase in the end of zone 2. Both curves suggest Majiabang and Songze period (c. 6000–5300 cal. BP). The that the water level did continue to rise, with frequent fluctu- initial rice farming began during the Middle Liangzhu period, ations during the use of the paddy field. Related to these trends followed by an expansion characterised by its impressive in- is the change in the overall pollen grain density, which expe- crease in scale of the size of the fields and intensified water rienced a drop. management practices. This intensification process of rice Our observation of hydrological changes is comparable farming coincided with a favourable climatic regime in the with the one made by Weisskopf et al. (2015), based upon region, which is well demonstrated in our micro-fossil plant their examination of the phytolith assemblage of rice and records and other published data. More importantly, the re- weeds collected from the Maoshan paddy fields. Using their gional water table, which was mainly determined by the sea established fixed and sensitive morphotypes as the respective level and alluvial hydrology, during this period of rice farming ecological indicators of dry and wet fields, they found that the expansion remained relatively low, compared with the return to a wetter condition at Maoshan was marked by a high succeeding period, and also stable. This facilitated successful percentage of sensitive morphotypes of phytoliths. Weisskopf water management by the Maoshan rice farmers who also et al.’s samples were collected from both ‘river edge’ and built irrigation facilities such as ditches and creeks. Our pollen ‘paddy fields’, whereas samples for our present research were records and geochemical-physical analyses have proved to be from a mainly complete sequence on the edge of the fields. a useful way to explore these irrigation practices, including Whilst these two sets of samples, from Weisskopf et al. and some sensitive plant species such as Typha and geophysical- this present paper, might reflect the spatial-temporal variations chemical indicators such as coarse-sized particles and values of the vegetation dynamics at the site, the general trend of of certain chemical elements. The intensifying rice farming rising water in the region, it is the return to wetter conditions and water management was accompanied with a gradual re- in the fields detected by both studies that is the most convinc- turn to a wet hydrological condition at the paddy field site and ing piece of evidence. However, our records also present ev- in the region. Whilst the climate experienced a shift from idence of vegetation changes caused by frequent wet-dry al- warm and wet conditions during the Middle to Late ternations in the fields throughout the different phases, com- Liangzhu period to a relatively drier and cooler situation dur- pared with relatively stable ecological conditions in the wet- ing the Guangfulin period, the regional water table also rose to lands surrounding the fields (e.g. reeds). We would suggest a very high level. This change had a devastating impact on the that this high frequency of in-field vegetation changes is close- rice farming and water management at Maoshan and beyond, ly related to intensifying water management for rice farming marking the eventual abandonment of the paddy fields at the in the transition from the early to late phase use of the paddy site. The Maoshan paddy field site present a good opportunity fields. The latter is also supported by the micromorphological to examine the combined effects of regional sea-level rise, study of the cultivated soils conducted by the aforementioned hydrological change in the major rivers and water bodies research by Zhuang et al. (2014) at the site. This intensifying (e.g. the Qiantang River and the Taihu Lake), and possible water management practice, however, became unsustainable increased sedimentation inputs to the rivers and lakes on the as the water level rose to a high level, marking the abandon- development of prehistoric rice farming and water manage- ment of the paddy fields at Maoshan during the Guangfulin ment in the Lower Yangtze River. period. The latter is also confirmed by the increasing pollen Our research also offers valuable methodological implica- grain density from layer 6 (corresponding to the Guangfulin tions and theoretic significance to the heated debate on the cultural phase) with abundant Gramineae, Typha and other wet-dry narratives of early rice farming across the monsoon related species, indicating that the fields were colonised by areas of Asia (Bray 1994;Kirch 1994; Weisskopf et al. 2015). hydrophilic weedy plants and related species with the rising Whilst it is generally agreed that the increasing investment in water table. the construction of hydro-infrastructures for irrigation has a profound social impact on rice farming societies (cf. Fuller and Qin 2009), the trajectory to intensification of rice farming Conclusions is certainly not a linear one and does not share same paths in different rice farming regions. Local ecological and hydrolog- In conclusion, our geoarchaeological and paleo-ecological in- ical conditions, technologies and other factors all contribute to the evolution of rice farming systems. In some regions, dry vestigation at Maoshan offers detailed information for an in- 1862 Archaeol Anthropol Sci (2019) 11:1851–1863 Liu B et al (2017) Earliest hydraulic enterprise in China, 5,100 years ago. farming systems also persist. To further unpack such a dichot- PNAS 1–6(early edition) omy, we need to focus more on the palaeo-ecology of early Liu B, Renfrew C (2018) The emergency of complex society in China: rice farming in wider paleo-environmental contexts. The case of Liangzhu. Antiquity. (in press) Nanjing Museum, Zhangjiagang Municipal Commission for Funding information This research is funded by National Social Science Conservation of Ancient Monuments, Zhangjiagang Museum Fund of China (11&ZD183), National Natural Science Foundation of (2016) Dongshancun site: the Neolithic period excavation report. China (41171006), National Key Technology Research and Cultural Relics Press, Beijing Development Program of the Ministry of Science and Technology of Palmer AJM, Abbott WH (1986) Diatoms as indicators of sea-level China (2013BAK08B02) and National Natural Science Foundation of change. In: van de Plassche O (ed) Sea-level research: a manual China (41701220). for the collection and valuation of data. Ge Books, Norwich, pp 457–488 Open Access This article is distributed under the terms of the Creative Qin L (2013) The Liangzhu culture. In: Underhill AP (ed) A companion Commons Attribution 4.0 International License (http:// to Chinese archaeology. 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Archaeological and Anthropological Sciences – Springer Journals

Published: Apr 25, 2018

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