Examining bias in pollen-based quantitative climate reconstructions induced by human impact on vegetation in China

Abstract. Human impact is a well-known confounder in pollen-based quantitative climate reconstructions as most terrestrial ecosystems have been artificially affected to varying degrees. In this paper, we use a "human-induced" pollen dataset (H-set) and a corresponding "natural" pollen dataset (N-set) to establish pollen–climate calibration sets for temperate eastern China (TEC). The two calibration sets, taking a weighted averaging partial least squares (WA-PLS) approach, are used to reconstruct past climate variables from a fossil record, which is located at the margin of the East Asian summer monsoon in north-central China and covers the late glacial Holocene from 14.7 ka BP (thousands of years before AD 1950). Ordination results suggest that mean annual precipitation (Pann) is the main explanatory variable of both pollen composition and percentage distributions in both datasets. The Pann reconstructions, based on the two calibration sets, demonstrate consistently similar patterns and general trends, suggesting a relatively strong climate impact on the regional vegetation and pollen spectra. However, our results also indicate that the human impact may obscure climate signals derived from fossil pollen assemblages. In a test with modern climate and pollen data, the Pann influence on pollen distribution decreases in the H-set, while the human influence index (HII) rises. Moreover, the relatively strong human impact reduces woody pollen taxa abundances, particularly in the subhumid forested areas. Consequently, this shifts their model-inferred Pann optima to the arid end of the gradient compared to Pann tolerances in the natural dataset and further produces distinct deviations when the total tree pollen percentages are high (i.e. about 40 % for the Gonghai area) in the fossil sequence. In summary, the calibration set with human impact used in our experiment can produce a reliable general pattern of past climate, but the human impact on vegetation affects the pollen–climate relationship and biases the pollen-based climate reconstruction. The extent of human-induced bias may be rather small for the entire late glacial and early Holocene interval when we use a reference set called natural. Nevertheless, this potential bias should be kept in mind when conducting quantitative reconstructions, especially for the recent 2 or 3 millennia

Postglacial Development of Kazakhstan Pine Forests

Fossil pollen records from two peatlands and two lakes in Kazakhstan provide radiocarbon-dated evidence of vegetation change since 13 000 BP. During the Lateglacial open spruce (Picea obovata) forests started spreading along river valleys and over the Kazakhstan Foothills. By 9500 BP, the southern limit of spruce approached its present-day position. Between 9500 and 8000 BP steppe and open birch forests formed the vegetation in the south of the West Siberian Lowland. Dry steppe and semi-desert were the main types of vegetation in north Kazakhstan. From 7000 to 5500 BP Scots pine (Pinus sylvestris L.) expanded in Kazakhstan and reached its present day southern limit. Since 5500 BP pine has formed monospecific forests in the lrtysh-Semipalatinsk area and in the northern part of the Kazakhstan Foothills. By 5000 BP lime (Tilia cordata) penetrated into the northern part of the Kazakhstan Foothills. The ranges of oak (Quercus robur), elm (Ulmus glabra) and black alder (AInus glutinosa) also expanded. The period 4500-3600 BP was characterised by a drier and more continental climate. During that time, the forested area decreased. The ranges of broadleaved trees and alder were reduced. A phase of less continental climate occurred 3300-2800/ 2700 BP. By 1500 BP the present southern limit of Scots pine was established.Les données palynologiques de quatre stations au Kazakhstan ont permis de reconstituer l'histoire de la végétation depuis 13 000 BP. Au Tardiglaciaire, des pessières claires à Picea obovata ont commencé à occuper les vallées des fleuves et les collines de Kazakhs. Vers 9500 BP la limite méridionale moderne de Picea obovata fut atteinte. Entre 9500-8000 BP les steppes et forêts claires de bouleaux (Betula alba) étaient répandues au sud de la Sibérie occidentale. Des steppes sèches et des semi-déserts constituaient alors la végétation du nord du Kazakhstan. Entre 7000 et 5500 BP, le pin sylvestre (Pinus sylvestris) s'est répandu au Kazakhstan jusqu'à sa limite méridionale actuelle. Depuis 5500 BP, Ie pin a constitué des forêts monospécifiques dans la région de Semipalatinsk-lrtysh et dans la partie septentrionale des collines de Kazakhs. Vers 5000 BP. Ie tilleul (Tilia cordata) fut présent dans la partie septentrionale des collines de Kazakhs. Les aires du chêne (Quercus robur), de l'orme (Ulmus glabra) et de l'aulne (AInus glutinosa) se sont étendues. Entre 4500 et 3600 BP, le climat est devenu plus sec et plus continental. L'aire de peuplement des forêts a diminué. La répartition des arbres aux larges feuilles et de l'aulne ont diminué. Un climat moins continental s'est instauré entre 3300 et 2800/2700 BP. Vers 1500 BP, la limite méridionale actuelle du pin s'est établie.Fossile Pollen-Belege von zwei Torfmooren und zwei Seen in Kasachstan liefern mittels Kohlenstoffdatierung den Nachweis einer Vegetationverànderung seit 13 000 v.u.Z. Im Spâtglazial begannen offene Fichtenwâlder (Picea obovata) sich entlang der Flusstâler und ùber die Gebirgsauslâufer Kasachstans auszubreiten. Um 9500 v.u.Z. bildeten Steppen und offene Birkenwàlder die Vegetation im Sùden des westsibirischen Tieflands. Trockene Steppen und Halbwùsten waren die hauptsàchlichen Vegetationstypen in Nord-Kasachstan. Von 7000 bis 5500 v.u.Z. breitete sich die Fôhre (Pinus silvestris L) in Kasachstan aus und erreichte ihre heutige sùdliche Grenze. Seit 5500 v.u.Z. hat die Kiefer monospezifische Wàlder im Irtysh-Semipalatinsk-Gebiet und im nôrdlichen Teil der Gebirgsauslâufer Kasachstans gebildet. Um 5000 v.u.Z. drang die Linde (Tilia cordata) in den nôrdlichen Teil der Gebirgsauslâufer Kasachstans ein. Die Ausdehnung von Eiche (Quercus robur), Ulme (Ulmus glabra) und Schwarzerle (AInus glutinosa) nahm auch zu. Die Zeit von 4500 - 3600 v.u.Z. zeichnete sich durch ein trockeneres und mehr kontinentales Klima aus. Wâhrend dieser Zeit nahm die bewaldete Zone ab. Das Vorkommen von grossblâttrigen Bàumen und Erlen nahm ab. Eine Phase weniger kontinentalen Klimas trat zwischen 3300 - 2800/2700 v.u.Z. ein. Um 1500 v.u.Z. war die gegenwârtige sùdliche Grenze der Fôhre etabliert

Introduction to the Special Issue: "Introduction and intensification of agriculture in Central Eurasia and adjacent regions"

For well over a century, scholars from across the social and biological sciences have been trying to understand the origins and spread of agriculture. This debate is often intertwined with discussions of climate change and human environmental impact. Over the past decade, this debate has spread into Central Eurasia, from western China to Ukraine and southern Russia to Turkmenistan, a part of the world often thought to have been largely dominated by pastoralists. A growing interest in the prehistory of Central Eurasia has spurred a new chapter in the origins of agriculture debate; archaeobotanical research is showing how important farming practices in this region were in regard to the spread of crops across the Old World. While early people living in Central Eurasia played an influential role in shaping human history, there is still limited understanding of the trajectories of social evolution among these populations. In March 2015, 30 leading scholars from around the globe came together in Berlin, Germany, to discuss the introduction and intensification of agriculture in Central Eurasia and adjacent regions. At the German Archaeological Institute in Berlin (Deutsches Archäologisches Institut, DAI), these scholars presented novel data on topics covering East, South, and Central Asia, spanning a wide realm of methodological approaches. The present special edition volume deals with a selection of the papers given at this conference, and it marks a significant step toward recognizing the contribution of Central Eurasian populations in the spread and development of agricultural systems over the course of the Holocene

Identification and quantification of cannabinol as a biomarker for local hemp retting in an ancient sedimentary record by HPTLC-ESI-MS

Cannabis products have been used in various fields of everyday life for many centuries, and applications in folk medicine and textile production have been well-known for many centuries. For traditional textile production, hemp fibers were extracted from the stems by water retting in stagnant or slow-moving waters. During this procedure, parts of the plant material‚ among them phytocannabinoids‚ are released into the water. Cannabinol (CBN) is an important degradation product of the predominant phytocannabinoids found in Cannabis species. Thus, it is an excellent indicator for present as well as ancient hemp water retting. In this study, we developed and validated a simple and fast method for the determination of CBN in sediment samples using high-performance thin-layer chromatography (HPTLC) combined with electrospray ionization mass spectrometry (ESI-MS), thereby testing different extraction and cleanup procedures‚ as well as various sorbents and solvents for planar chromatography. This method shows a satisfactory overall analytical performance with an average recovery rate of 73%. Our protocol enabled qualitative and quantitative analyses of CBN in samples of a bottom sediment core‚ having been obtained from a small lake in Northern India, where intense local retting of hemp was suggested in the past. The analyses showed a maximum CBN content in pollen zone 4 covering a depth range of 262–209 cm, dating from approximately 480 BCE to 1050 CE. These findings correlate with existing records of Cannabis-type pollen. Thus, the method we propose is a helpful tool to track ancient hemp retting activities

Pollen- and charcoal-based evidence for climatic and human impact on vegetation in the northern edge of Wuyi Mountains, China, during the last 8200 years

Pollen and charcoal records derived from the sediment core of Lantianyan (LTY) peat bog, Northern Wuyi Mountain chains, eastern subtropical China, provide valuable information of landscape evolution caused by both climatic variation and anthropogenic activities over the past 8200 years. Our results reveal fluvial and lacustrine deposition between c. 8200 and 5600 cal. yr BP. The high proportion of pollen from evergreen broadleaved forests (e.g. Quercus and Castanopsis) and Alnus trees, a taxon frequently occurring in mountain wetlands, implies a humid interval, which is consistent with the Holocene moisture maximum in eastern China. After 5600 cal. yr BP, the spread of the wooded swamp taxon, Glyptostrobus, suggests shallow water conditions and peat formation caused by gradual drying. The drying trend generally corresponds with the speleothem isotope record from this region, revealing a weakening East Asian summer monsoon (EASM) due to a decrease in Northern Hemisphere summer insolation (and in air temperature). Peaks in the abundance and concentration of Glyptostrobus pollen at c. 4600–4400 cal. yr BP and c. 3300–3000 cal. yr BP suggest two periods of swamp expansions, which coincide with the drought intervals revealed by the speleothem records. The LTY pollen and charcoal record demonstrates that human-induced land cover change was negligible before 3600 cal. yr BP. We consider the first signal of intensive human activity and landscape clearing to be the noticeable increase in charcoal particles at around 3600 cal. yr BP. This anthropogenic impact is followed by a dramatic decrease in arboreal pollen and increase in Poaceae pollen percentages, likely reflecting a transition to rice-paddy agriculture in the study area

An overview

A total of 51,074 archaeological sites from the early Neolithic to the early Iron Age (c. 8000–500 BC), with a spatial extent covering most regions of China (c. 73–131°E and c. 20–53°N), were analysed over space and time in this study. Site maps of 25 Chinese provinces, autonomous regions and municipalities, published in the series ‘Atlas of Chinese Cultural Relics’, were used to extract, digitalise and correlate its archaeological data. The data were, in turn, entered into a database using a self-developed mapping software that makes the data, in a dynamic way, analysable as a contribution to various scientific questions, such as population growth and migrations, spread of agriculture and changes in subsistence strategies. The results clearly show asynchronous patterns of changes between the northern and southern parts of China (i.e. north and south of the Yangtze River, respectively) but also within these macro-regions. In the northern part of China (i.e. along the Yellow River and its tributaries and in the Xiliao River basin), the first noticeable increase in the concentration of Neolithic sites occurred between c. 5000 and 4000 BC; however, highest site concentrations were reached between c. 2000 and 500 BC. Our analysis shows a radical north- eastern shift of high site-density clusters (over 50 sites per 100 × 100 km grid cell) from the Wei and middle/lower Yellow Rivers to the Liao River system sometime between 2350 BC and 1750 BC. This shift is hypothetically discussed in the context of the incorporation of West Asian domesticated animals and plants into the existing northern Chinese agricultural system. In the southern part of China, archaeological sites do not show a noticeable increase in the absolute number of sites until after c. 1500 BC, reaching a maximum around 1000 BC

New evidence for ball games in Eurasia from ca. 3000-year-old Yanghai tombs in the Turfan depression of Northwest China

Three leather balls discovered in tombs IM157, IM209, and IM214 of the prehistoric Yanghai cemetery (42 degrees 48'N, 89 degrees 39'E) located about 43 km southeast of the modern city of Turfan, were AMS radiocarbon dated to the time interval between 1189 and 911 BCE (95% probability), and thus predate other currently known antique balls and images of ball games in Eurasia by several centuries. Our study approves the antiquity of the Yanghai balls, but the available data is not enough to answer the question how these balls were played. Although, their use in team and goal sport is likely, a suggested game similar to hockey, golf or polo cannot be confirmed, because no appropriate sticks were found in direct association with the balls. The affiliation of curved wooden sticks in Yanghai with ball games suggested earlier remains hypothetical, as all found sticks are noticeably younger in age, and other forms of use should be verified by future studies. Two of the three balls were found in the burials of the possible horse riders. Given that ball games from ancient times were considered an excellent form of physical exercise and military training, we suggest that balls (and ball games) appeared in the region at the same time as horseback riding and mounted warfare began to spread in the eastern part of Central Asia

Record of vegetation, climate change, human impact and retting of hemp in Garhwal Himalaya (India) during the past 4600 years

This study is focused on a 3.55-m-long sediment core retrieved from Badanital (i.e. the BT core) in 2008. Badanital (30°29′50″N, 78°55′26″E, 2083 m a.s.l.) is a small lake located in the upper catchment area of the Ganges in Garhwal Himalaya, northern India. The lake and the regional broad-leaved semi- evergreen forests are under the influence of the Indian Summer Monsoon (ISM) and westerly associated cyclones. Palynological investigation of the BT core revealed past vegetation changes reflecting both climate and human impact during the last 4600 years. Maximum spread of oaks occurred during c. AD 550–1100 and c. AD 1400–1630, that is, the intervals which partly overlap with the ‘Medieval Warm Period’ and the ‘Little Ice Age’, respectively. Three intervals of decreased oak pollen percentages are attributed to (1) continuously drier and cooler climatic conditions and fire activity (c. 2600–500 BC), (2) severe reduction in oak forests followed by secondary succession of alder woods (c. AD 1150–1270) and (3) pre-modern settlement activities since the British imperial occupation (after c. AD 1700). We argue that the high percentages (i.e. up to 28%) of Humulus/Cannabis type and Cannabis type pollen point to intense local retting of hemp c. 500 BC–AD 1050. Based on our age model, Cannabis fibre production at Badanital is contemporaneous with archaeological records of ancient hemp products from different parts of Eurasia suggesting possible linkages to early trade and knowledge exchange routes connecting India and the Himalaya with Central and East Asia and possibly Europe

Holocene vegetation and climate history in Baikal Siberia reconstructed from pollen records and its implications for archaeology

Past research has greatly improved our understanding of palaeoenvironmental changes in the Lake Baikal Region, but at the same time has indicated intra-regional variations in this vast study area. Here we present a new AMS-dated late glacial-middle Holocene (ca. 13,500-4000 cal. yr BP) pollen record from Lake Ochaul (54 degrees 14'N, 106 degrees 28'E; altitude 641 m a.s.l.) situated in the less-studied area of Cis-Baikal and compare reconstructed vegetation and climate dynamics with the published environmental history of Trans-Baikal based on the pollen record from Lake Kotokel (52 degrees 47'N, 108 degrees 07'E; altitude 458 m a.s.l.). Although both records show comparable major long-term trends in vegetation, there are considerable differences. Around Ochaul the landscape was relatively open during the Younger Dryas stadial, but forest vegetation started to spread at the late glacial/Holocene transition (ca. 11,650 cal. yr BP), thus ca. 1000 years earlier than around Kotokel. While in both regions taiga forests spread during the early and middle Holocene, the marked increase in Scots pine pollen in the Kotokel record after ca. 6800 cal. yr BP is not seen in that from Ochaul, where birch and coniferous taxa, such as Siberian pine, larch, spruce and fir, dominate, indicating different environmental conditions and driving forces in both study regions. However, the pollen data from Ochaul emphasizes that the Cis-Baikal area also saw a continuous increase in forest cover and in the proportion of conifers over birch trees and shrubs during the early-middle Holocene, which may have contributed to a decrease in the number of large herbivores, the main food resource of the Early Neolithic hunter-gatherer groups. This and rather abrupt reorganization of atmospheric circulation, which affected atmospheric precipitation distribution resulting in thicker and longer-lasting snow cover, may have led to a collapse of Early Neolithic Kitoi populations ca. 6660 cal. yr BP followed by a cultural "hiatus" in the archaeological records during the Middle Neolithic phase (ca. 6660-6060 cal. yr BP). The results stress the importance of sub-regional palaeoenvironmental studies and the need for a representative network of well-dated, high-resolution sediment archives for a better understanding of environmental changes and their potential impacts on the hunter-gatherer populations in the archaeologically-defined micro-regions

Ancient DNA identification of domestic animals used for leather objects in Central Asia during the Bronze Age

The arid climate of many regions within Central Asia often leads to excellent archaeological preservation, especially in sealed funerary contexts, allowing for ancient DNA analyses. While geneticists have looked at human remains, clothes, tools, and other burial objects are often neglected. In this paper, we present the results of an ancient DNA study on Bronze Age leather objects excavated from tombs of the Wupu cemetery in the Hami Oasis and Yanghai cemetery in the Turpan Oasis, both in Xinjiang Uyghur Autonomous Region of northwestern China. In addition to species identification of goat (Capra aegagrus/hircus), sheep (Ovis orientalis/aries), and cattle (Bos primigenius/taurus), mitochondrial haplogroups were determined for several samples. Our results show that Bronze Age domesticated goats and sheep from the Hami and Turpan oases possessed identical or closely related haplotypes to modern domestic animals of this area. The absence of leather produced from wild animals emphasizes the importance of animal husbandry in the cultures of Wupu and Yanghai