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Ancient Loulan, an important city on the Silk Road, disappeared about 1500 years ago. The environmental conditions associated with the vicissitude of ancient Loulan have been debated since the city was rediscovered in ad 1900. However, little paleobotanical evidence concerning vegetation and environment in this area has so far been available. In this study, phytoliths and diatoms extracted from 16 samples including two fossil camel coprolites from sites of Loulan and Milan indicate that the landscape of ancient Loulan was a typical oasis, where reeds, grasses of Paniceae and Pooideae probably grew along with some shrubs. Also, some typical brackish diatoms might live in some water bodies in the catchment of an ancient lake, Lop Nor. Our results also suggest that common millet as staple crop, and foxtail millet and possibly naked barley as non-staple crops were the main food source for ancient Loulan and Milan residents between ad 50 and 770.

Carbon preference index (CPI) of long-chain n-alkanes preserved in surface soil increases gradually from southeastern China to the north margin of Loess Plateau. Along this latitudinal transect, the CPI value correlates to relative humidity, precipitation, and temperature with a negative linear relationship, respectively, whereas the correlation of CPI to temperature is relatively weak. In the Wuyi, Shennongjia, and Tianshan Mountains, CPI values do not change systemically with altitude increasing (or temperature decreasing). However, mean value of CPI for the individual mountain increases in turn from the humid mountain to the arid. These results jointly suggest that aridity (or humidity) is a dominate climate factor in altering soil CPI value. High CPI values of geological records therefore indicate the arid paleoclimate. Though long-chain n-alkanes in soil are derived mainly from leaf wax of terrestrial vascular plants, the regular latitudinal variations of soil CPI might not be caused by the change of vegetation. We speculate that increased long-chain n-alkanes from microbes and/or enhanced biodegradation in the humid climate lead to the decrease of soil CPI.

Past environmental changes based on diatom relative abundances have been inferred from the maar Lake Erlongwan in northeast China. The limnology of Lake Erlongwan is affected by the strongly seasonal regional climate. The composition of diatom assemblages, in turn, responds to changes in the seasonal duration of ice cover in winter, water-column turnover in spring and autumn, and thermal stratification in summer. Statistical analysis of the sedimentary diatom assemblages reveals three significant stratigraphic zones over the past 1000 yr. The highest abundance of the planktonic speciesDiscostellaspecies occurs between AD 1050 and 1400 and suggests an annual ice-free period of long duration and well-developed summer stratification of the water column. This planktonic diatom peak between ca. AD 1150 and 1200 suggests that this period was the warmest over the past 1000 yr. The interval between AD 1400 and 1800 is marked by a decline in planktonic diatoms and suggests shorter duration of the ice-free season, weaker water stratification and possibly generally cold conditions. After AD 1800 relative abundances of planktonic diatoms, includingPuncticulata praetermissaandAsterionella formosa, increase again, which indicates lengthening of the duration of the annual ice-free period and a stronger overturn of the water column. All these data imply that the pattern of the seasons is different between the MWP and the 20th century.

It is generally understood that foxtail millet and broomcorn millet were initially domesticated in Northern China where they eventually became the dominant plant food crops. The rarity of older archaeological sites and archaeobotanical work in the region, however, renders both the origins of these plants and their processes of domestication poorly understood. Here we present ancient starch grain assemblages recovered from cultural deposits, including carbonized residues adhering to an early pottery sherd as well as grinding stone tools excavated from the sites of Nanzhuangtou (11.5–11.0 cal kyBP) and Donghulin (11.0–9.5 cal kyBP) in the North China Plain. Our data extend the record of millet use in China by nearly 1,000 y, and the record of foxtail millet in the region by at least two millennia. The patterning of starch residues within the samples allow for the formulation of the hypothesis that foxtail millets were cultivated for an extended period of two millennia, during which this crop plant appears to have been undergoing domestication. Future research in the region will help clarify the processes in place.

Starch grains from 31 modern samples of millets derived from the seeds of 7 species within the genus Setaria and 2 species within the genus Panicum were analyzed to determine diagnostic morphological characteristics. Ancient starch grains recovered from a sample of broomcorn millet (Panicum miliaceum) excavated from the Cishan site (10.0-7.6 cal yr BP) in the North China Plain were then subjected to the same analyses to determine the differences in morphologies, if any, between modern and ancient samples. The data indicate that morphological features, and particularly surface and fissure features, will allow for solid identifications of ancient millet starches, while size classes will be helpful, but will not be dependable taxonomic indicators. (C) 2011 Elsevier Ltd. All rights reserved.

The evolution of vegetation and climate changes in tropical regions during the Last Glacial Maximum remains controversial. A continuous high-resolution terrestrial palynological data from 40 to 13 cal. ka BP is recorded in sediments of Huguangyan Maar Lake in southern China. The biomization technique and pollen data are used to reconstruct the history of vegetation and climate changes during the Last Glacial Maximum (LGM). The results suggest that the Huguangyan area in the Last Glacial Maximum was dominated by subtropical evergreen forest with some deciduous trees, implying that the climate was drier and colder in southern China than at present; grassland vegetation did not appear in this area. A significant drop in temperature occurred at 18.5 cal. ka BP and terminated at 15.5 cal. ka BP, and the annual mean temperature during the LGM was 2–3°C lower or even more than present. This is in agreement with previous results from tropical low-latitude regions.

The East Asian winter monsoon (EAWM) not only plays an important role within the Asian climate system, but also carries cold air from the high northern latitudes across the Equator to the Southern Hemisphere, acting as a link between the polar and tropical climate systems. However, past changes of the EAWM have not been clearly established so far due to the lack of suitable proxy records. Here, we at first establish an index of the EAWM by comparing the results of a sediment trap experiment and 100year sedimentary record from Huguang Maar Lake (HML) with modern records of the EAWM, Siberian High (SH) and Arctic Oscillation (AO). Secondly, we present a continuous record of the strength of the EAWM for the past 14,500 years based on sedimentary diatom assemblages in HML. The record is derived from fluctuations in the relative abundance of two planktonic diatom species. The link with the EAWM intensity is through high wind speeds inducing turbulent mixing, which stimulates the productivity of the meroplanktonic species Aulacoseira granulata. The diatom record of the past 14,500 years shows that the EAWM shifted from strong to weak from the early to late Holocene. This linked to both changes in winter temperature at high-latitudes and in El Nino conditions in the tropics. Our record shows that the EAWM and East Asian summer monsoon (EASM) as recorded in stalagmites, were in-phase instead of anti-correlated on orbital time scales during the Holocene. On a millennial time scales, the EAWM was anti-phase with the EASM during the Last GlacialeHolocene transition. However, during the early emiddle Holocene the relationship between the EAWM and EASM shows spatial variations. In northern China, the records show significant anti-phase, but in southern China the anti-phase was not observed. During the late Holocene, we did not find any clear relationship between the EAWM and EASM. We also explored the link between the EAWM and the Australian summer monsoon (ASM). Anti-phase of the ASM with summer insolation in the Southern Hemisphere is an enigmatic exception that cannot be explained by the classic theory of insolation. During early Holocene the EAWM was in-phase with the Australian summer monsoon (ASM), which provides the first direct evidence to support the hypothesis that the intensity of the EAWM affected, at least in part, the strength of the ASM.

Phytoliths are noncrystalline minerals that form inside cells and cell walls of different parts of plants. Organic carbon in living cells can be occluded in phytoliths during plant growth. It has been documented that the occluded carbon within phytoliths is an important long-term terrestrial carbon reservoir that has a major role in the global carbon cycle. Common millet and foxtail millet have become typical dry-farming crops in China since the Neolithic Age. The study of carbon conservation within phytoliths in these crops could provide insights into anthropogenic influences on the carbon cycle. In this study, we analyzed the carbon content in phytoliths of common millet and foxtail millet. The results indicated that (1) common millet and foxtail millet contained 0.136% ± 0.070% and 0.129%± 0.085% phytolith-occluded carbon (PhytOC) on a dry mass basis, respectively; (2) based on the mean annual production of common millet and foxtail millet in the last 10 years, the phytolith occluded carbon accumulation rate of common millet and foxtail millet was approximately 0.023 ± 0.015 and 0.020± 0.010 t CO2 ha−1 a−1, respectively; (3) assuming a similar phytolith occluded carbon accumulation rate as for common millet (the highest accumulation rate was 0.038 t CO2 ha−1 a−1), this could result in the sequestration of 2.37 × 106 t CO2 per year for the 62.4 × 106 ha dry-farming crops in China. Although there was a decline in the annual production rate and planting area of foxtail millet during 1949 to 2008, the total phytolith carbon sequestration rate was 7×106 t CO2 within the 60-year period. However, phytolith occluded carbon has not yet been fully considered as a global carbon sink. Also, this carbon fraction is probably one of the best candidates for the missing carbon sink.

The ancient kingdom of Loulan on China’s Silk Road has disappeared for about 1500 years. Historical records have documented widespread cultivation in Loulan which supported the kingdom’s prosperity for hundreds of years. However, no farmland ruins have been found although the ancient Loulan city was discovered more than 100 years ago. In this study, remotely sensed, geomorphic and geological observations of possible farmlands in Loulan were analyzed. A wide distribution of partly preserved plots with recognizable regular and straight boundaries, the existence of crossed canals, the occurrence of a gypseous incrustation layer (GIL) overlying on the surface of farmland-like blocks, and extracted large-sized pollen grains of cultivated grass from GIL samples provide new evidence for the ancient farmlands. Field observations revealed that the upper cultivated soil layer overlaid on GIL, i.e. soil horizon A, had been wind-eroded and GIL is the ruined soil horizon B. These new findings point to a well-developed agriculture of the ancient Loulan kingdom. The size and distribution of the farmlands and the thickness of the GIL suggests that irrigation for cultivation in this currently exceedingly arid area had lasted for a long time. Fluvial and lacustrine sediments in Loulan area deposited during the about 4 to ~ 8 ka BP period, revealing that the wet Holocene optimum and two arid events of about 4 and 8 ka BP occurred in the westerlies-dominated northwest China. The Loulan kingdom period was another wet stage when the ecological environment was the typical cultivated grass of oasis near wetland. The insufficiency of water during the late period of the Loulan kingdom led the decline of irrigation agriculture and finally the renunciation of the kingdom.

Fossil pollen from Nam Co and modern pollen from altitudinal vegetation belts around the lake are investigated to reveal alpine vegetation succession in response to climate changes during the Holocene in the central Tibetan Plateau. The discriminant analysis on 37 topsoil samples shows that pollen samples from alpine steppe at lower elevations (60%). Our result indicates that the pollen ratio of Artemisia to Cyperaceae (A/Cy) can be used as an indicator of the vertical shift of vegetation belts and temperature changes in the central Tibetan Plateau as suggested by previous studies. A history of the vertical shift of vegetation belts on the northern slope of Nyainqentanglha Mountains and climate changes since 8.4 kyr BP are thus recovered by 198 fossil pollen assemblages from a 332 cm core of Nam Co. Paleovegetation reconstructed from fossil pollen assemblages through discriminant analysis shows a general downward shift of altitudinal vegetation belts, suggesting a decline in the temperature trend since 8.4 kyr BP. This result is consistent with the reduction of A/Cy ratios. The fossil pollen record also reveals warm and wet climate during the early to mid Holocene, and cold and dry conditions during the late Holocene in the Nam Co area. A comparison of Holocene climatic reconstructions across the Plateau indicates that termination of maximum moisture at around 6–5.5 kyr BP in our record is associated with the southeastward retreat of the Southwest Monsoon.

This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1202 sites along an altitudinal gradient of 10 -5500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1840 mm and mean annual temperature (MAT) from -7 to 21.5 degrees C. A total of 153 pollen taxa were found with relative abundances greater than 1% in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters. Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R(2)-boot = 0.89, RMSEP = 109 mm), MAT (R(2)-boot = 0.78, RMSEP = 2.3 degrees C), ALT (R(2)-boot = 0.73, RMSEP = 597 m), HHH (R(2)-boot = 0.82, RMSEP = 4.5%), and July mean precipitation (MP7) (R(2)-boot = 0.87, RMSEP = 23 mm). Overall, our results confirm that pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environmental reconstruction based on pollen data in the regions. (C) 2011 Elsevier Ltd. All rights reserved.

The MODIS-based estimates of woody, herbaceous and bare cover percentages within a 21 × 21, 11 × 11 and 0.5 × 0.5 km window around pollen sampling sites were attributed to the respective modern pollen spectra. Reconstructions of modern woody cover using the pollen–MODIS reference data set and the modern analogue approach matched well to the original MODIS-based estimates for three selected land-cover fractions. The best of all correspondence between the reconstructed and observed values was obtained for the 21 × 21 km window, including woody ( r = 0.83), herbaceous ( r = 0.80) and bare ( r = 0.90) cover. Discrepancies in the pollen–MODIS cross-validation may be caused by long-distance pollen transport, patchy vegetation, particularly in the densely populated eastern areas and along the steep mountain slopes, under-representation of curtain woody taxa (e.g. Larix and Populus in pollen records), and possible uncertainties in the MODIS data. A series of tests performed with the reference data set including 1452 surface-pollen spectra and representing all vegetation and climatic units of China show the pollen-based reconstructions correspond well to the MODIS-based estimations of land-cover percentages within a 21 × 21 km window, supporting previously obtained results from northern Asia and North America. Results obtained for the smaller window sizes are less accurate, particularly when reconstructing woody cover. The pollen–MODIS-based modern analogue approach can reproduce present-day characteristics of land cover in China with a reasonably high degree of accuracy despite the complexity of the topography and regionally intensive land use. The generally strong correlations encourage the application of the approach to Chinese fossil pollen records.

To improve the interpretation of fossil pollen records, we analyzed the relationships between modern pollen taxa and climate data and established a pollen-climate calibration using the northern and western Chinese modem pollen dataset to demonstrate its potential for the reconstruction of past climate dynamics in the semi-arid and arid regions of China. Analysis of pollen and climate data involved Pearson's correlation ceofficient and other transfer functions, as well as the "best modem analogues" method. We also applied a technique for error estimation to calibrate reconstructed values into a probability distribution and a confidence interval for the observed values. The percentage representations of 24 pollen taxa in 546 surface pollen samples collected in northern and western China were correlated with modern climate characteristics. The relationships between individual pollen types and climate were appraised over a large spatial scale in the study area. Of investigated taxa, 41.7% had linear, 45.8% had unimodal (orthogonal polynomial), and 12.5% had monotonic (Log) distribution in response to annual precipitation. Both taxa and plant functional types (PFTs) provided similar results using the best modern analogues method for modern pollen and climate data at the 546 sites in northern and western China. Precipitation reconstructions were more accurate than climate reconstructions of any thermal parameters, suggesting that available moisture was the most important factor controlling plant distribution in the primarily semi-arid to arid study region. Climate reconstruction performed using the modern analogues technique for 112 taxa was not significantly better than reconstruction with only 37 selected taxa. Climate reconstruction based on PFTs was more accurate when using only the main pollen taxa than when using most of the taxa. Our test of the best modern analogues method with the northern and western Chinese surface pollen dataset demonstrated its reliability for reconstructing modern climate variables. (C) 2010 Elsevier B.V. All rights reserved.

In the past century, it has long been debated in the archeological, historical, geographical, and many other related communities where the capital of the Luolan and Shanshan states was in the Lop Nor region. This paper presents three AMS radiocarbon ages from a newly-discovered ancient city at about 6.3 km to the northwest of the Xiaohe Graveyard, and fifteen new radiocarbon ages from the Loulan (LA), LE, Qieerqiduke, Milan, and Tuyin sites in Lop Nor. The new investigation shows that the age of newly-discovered ancient city is at ca. 440–500 AD, belonging to the Northern Wei Dynasty (386–534 AD). This is about 100–300 years younger than Loulan (ca. 100–230 AD), LE (ca. 230–300 AD), Qieerqiduke (ca. 200 AD), and Tuyin (ca. 100 AD). A wooden beam from Milan fortress is dated to ca. 370 AD, while the age on north wall at west gate of the fortress is younger, around 770 AD, suggesting that its construction time might be at the Tang Dynasty. According to 14C ages, cultural relic style, and the geographical location, the newly-discovered ancient city is probably attributed to “Zhubin City”, as documented in the historical literature. Temporally, we name the city “ancient Zhubin River City”. However, the characteristics and functions of this ancient city are largely unknown and need more detailed archaeological excavation and investigation in the future. Given its location near the ancient postal relay of Alagan on the crossroad, there is no doubt that the newly-discovered city was at an important geographical position on the Silk Road, no matter whether it was called “Zhubin City”, or “Lielo City”, or the capital of Loulan state—“Yuni City”. Our findings provide new evidence for the temporal and spatial distribution of ancient relic sites and the development of civilization in western China, thus contributing to our understanding of the relationship between human activities and environmental change in the Lop Nor region.

Diatom data of 192 surface sediment samples from the marginal seas in the western Pacific together with modern summer and winter sea surface temperature and salinity data were analyzed. The results of canonical correspondence analysis show that summer sea-surface salinity (SSS) is highly positively correlated with winter SSS and so is summer sea-surface temperature (SST) with winter SST. The correlations between SSSs and SSTs are less positively correlated, which may be due to interactions of regional current pattern and monsoon climate. The correlations between diatom species, sample sites and environmental variables concur with known diatom ecology and regional oceanographic characters. The results of forward selection of the environmental variables and associated Monte Carlo permutation tests of the statistical significance of each variable suggest that summer SSS and winter SST are the main environmental factors affecting the diatom distribution in the area and therefore preserved diatom data from down core could be used for reconstructions of summer SSS and winter SST in the region.

Prehistoric groundstone tools including slabs (metate, mo-pan) and mullers (mano, mo-bang) are often considered to be tools that were used to process cereals in ancient China. Most archaeologists believe that groundstone tools are indicators of an agrarian economy. This study employed starch grain analysis to examine a slab and a muller excavated from the Shangzhai Site (7500-7000 cal a BP), Beijing. Identifiable starch grains recovered from the stone tools were classified into 9 genera and 12 species, most of which were from acorns and foxtail millets. Remains from the oak species Q. mongolicus, Q. acuttssima, and Q. dentate were identified as well as a few starch grains from broomcorn (Panicum miliaseum) and bean (Vigna sp.). Other starch grains were from unidentifiable roots and grasses. A variety of starch grains indicates that the grinding stone tools were used to process not only cereals, but also other seeds or roots that had to be ground or husked, thus bringing into question the aforementioned cereal hypothesis. Because the numbers of starch grains from nuts and millets were so large, both gathering and cultivation might have been important economic patterns before 7000 years ago in Beijing area. Moreover, the starch remains are derived from plants that indicate that the paleoclimate of Beijing was wetter and warmer than today’s.

A large amount of carbonized plant remains were discovered in one of the outer burial pits of the Han Yangling Mausoleum, which was built more than 2000 years ago for the Jing Emperor, Liu, Qi (188—141 cal a BC), the fourth emperor of the Western Han Dynasty. The remains are identified by phytolith analysis and macrofossil morphological features. Seeds from foxtail millet (Setaria italica), broomcorn millet (Panicum miliaceum), rice (Oryza sativa) and chenopod (possible Chenopodium giganteum) are identified, suggesting that these four crops might have been the staple plant foods in the capital area (Guanzhong area), Shaanxi Province during the Early Western Han Dynasty. Chenopods were often considered as weeds since they have only been rarely found as carbonized seeds in prehistoric sites. This is the first time such a large amount of seeds has been found at a site, which provides strong material evidence for chenopod cultivation with a long history in China. Wheat was thought to be promoted and popularized in the Guanzhong area since the Wu Emporor, Liu, Che (156—87 cal a BC), the fifth emperor of the Western Han Dynasty. No wheat was found at this site, which supports the historical document record that wheat was still secondary in the diet and agrarian economy before the Wu Emperor’s reign.

Climatic and environmental changes since the last glacial period are important to our understanding of global environmental change. There are few records from Southern Tibet, one of the most climatically sensitive areas on earth. Here we present a study of the lake sediments (TC1 core) from Lake Chen Co, Southern Tibet. Two sediment cores were drilled using a hydraulic borer in Terrace 1 of Lake Chen Co. AMS 14C dating of the sediments showed that the sequence spanned >30,000 years. Analyses of present lake hydrology indicated that glacier melt water is very important to maintaining the lake level. Sediment variables such as grain size, TOC, TN, C/N, Fe/Mn, CaCO3, and pollen were analyzed. Warm and moderately humid conditions dominated during the interval 30,000–26,500 cal year BP. From 26,500 to 20,000 cal year BP, chemical variables and pollen assemblages indicate a cold/dry environment, and pollen amounts and assemblages suggest a decline in vegetation. From 20,000 to 18,000 cal year BP, the environment shifted from cold/dry to warm/humid and vegetation rebounded. The environment transitioned to cold/humid during 16,500–10,500 cal year BP, with a cold/dry event around 14,500 cal year BP. After 10,500 cal year BP, the environment in this region tended to be warm/dry, but exhibited three stages. From 10,500 to 9,000 cal year BP, there was a short warm/humid period, but a shift to cold/dry conditions occurred around 9,000 cal year BP. Thereafter, from 9,000 to 6,000 cal year BP, there was a change from cold/dry to warm/humid conditions, with the warmest period around 6,000 cal year BP. After 6,000 cal year BP, the environment cooled rapidly, but then displayed a warming trend. Chemical variables indicate that a relatively warm/dry event occurred around 5,500–5,000 cal year BP, which is supported by time-lagged pollen assemblages around 4,800 cal year BP. Our lake sediment sequence exhibits environmental changes since 30,000 cal year BP, and most features agree with records from the Greenland GISP2 ice core and with other sequences from the Tibetan Plateau. This indicates that environmental changes inferred from Lake Chen Co, Southern Tibet were globally significant.

The geographical distribution of dominant plant species in China was georeferenced and climatic variables were interpolated into all grids. Accordingly, the percentage distributions of principal pollen taxa based on 1860 surface pollen sites in China were selected and the related climate values were interpolated with the same method. The geographical and climatic comparison between the two datasets indicated that the climate threshold of most pollen taxa from surface pollen is coherent with plant distributions. The climatic envelopes of dominant plant are mostly accordant with those of pollen taxa at certain levels. However, some distinct offsets of the climate ranges exist between the two datasets for most pollen taxa identified at family level, such as Ericaceae, Asteraceae, Poaceae and Chenopodiaceae. The present study provides for the first time rich information on temperature and precipitation in relation to pollen and plant distribution based on the datasets on a continental scale useful for global ecological modeling and Quaternary palaeoclimate reconstruction.

Fossil rice phytoliths have been identified from a lateglacial to Holocene sequence of epicontinental sediments in the East China Sea that were probably transported by the Yangtze River from its middle and/or lower reaches. The rice phytoliths occurred first in the sequence at about 13 900 cal. yr BP and disappeared during the period of 13 000–10000 cal. yr BP, implying the earliest domesticated cereal crops of the world ever reported. Based on the records of phytoliths, pollen, diatoms and foraminifera from the sequence, the climate between 13 000 and 10 000 cal. yr BP was notably colder (Younger Dryas). The coincidence of disappearance of domesticated rice phytoliths with cold climate conditions may suggest a great climatic influence on human activities during that time. Warmer and wetter conditions during the period 13900 to 13000 cal. yr BP and after 10000 cal. yr BP have probably favoured rice domestication in the area.

We present here the first high-resolution pollen record of vegetation response to interactions of hurricane and fire disturbances over the past 1200 yr from a small lake in Alabama on the Gulf of Mexico coast. The paleo tempestological record inferred from the over wash sand layers suggests that the Alabama coast was directly struck by Saffir–Simpson category 4 or 5 hurricanes twice during the last 1200 yr, around 1170 and 860 cal yr BP, suggesting an annual landfall probability of 0.17% for these intense hurricanes. The charcoal data suggest that intense fires occurred after each of these hurricanes. The pollen data suggest that populations of halophytic plants (Chenopodiaceae) and heliophytic shrubs (Myrica) expanded after the hurricane strikes, probably due to saltwater intrusion into the marshes and soil salinization caused by over wash processes. Populations of pines (Pinussp.) decreased significantly after each intense hurricane and the ensuing intense fire, suggesting that repeated hurricane–fire interactions resulted in high tree mortality and probably impeded recruitment and recovery. Our data support the hypothesis that the likelihood and intensity of fire increased significantly after a major hurricane, producing responses by vegetation that are more complex and unpredictable than if the disturbance agents were acting singly and independently.

Quantitative reconstruction of the climatic history of the Chinese Loess Plateau is important for understanding present and past environment and climate changes in the Northern Hemisphere. Here, we reconstructed mean annual temperature (MAT) and mean annual precipitation (MAP) trends during the last 136 ka based on the analysis of phytoliths from the Weinan loess section (34°24′N, 109°30′E) near the southern part of the Loess Plateau in northern China. The reconstructions have been carried out using a Chinese phytolith–climate calibration model based on weighted averaging partial least-squares regression. A series of cold and dry events, as indicated by the reconstructed MAT and MAP, are documented in the loess during the last glacial periods, which can be temporally correlated with the North Atlantic Heinrich events. Our MAT and MAP estimations show that the coldest and/or driest period occurred at the upper part of L2 unit (Late MIS 6), where MAT dropped to ca 4.4 °C and MAP to ca 100 mm. Two other prominent cold-dry periods occurred at lower Ll-5 (ca 77–62 ka) and L1-1 (ca 23–10.5 ka) where the MAT and MAP decreased to about 6.1–6.5 °C and 150–370 mm, respectively, ca 6.6–6.2 °C and 400–200 mm lower than today. However, the highest MAT (average 14.6 °C, max. 18.1 °C) and MAP (average 757 mm, max. 1000 mm) occurred at Sl interval (MIS 5). During the interstadial of L1-4–L1-2 (MIS 3) and during the Holocene warm-wet period, the MAT was about 1–2 °C and MAP 100–150 mm higher than today in the Weinan region. The well-dated MAT and MAP reconstructions from the Chinese Loess Plateau presented in this paper are the first quantitatively reconstructed proxy record of climatic changes at the glacial–interglacial timescale that is based on phytolith data. This study also reveals a causal link between climatic instability in the Atlantic Ocean and climate variability in the Chinese Loess Plateau.

Rice (Oryza sativa) is regarded as the only grass that was selected for cultivation and eventual domestication in the Yangtze basin of China. Although both macro-fossils and micro-fossils of rice have been recovered from the Early Neolithic site of Shangshan, dating to more than 10,000 years before present (BP), we report evidence of phytolith and starch microfossils taken from stone tools, both for grinding and cutting and cultural layers, that indicating barnyard grass (Echinochloa spp.) was a major subsistence resource, alongside smaller quantities of acorn starches (Lithocarpus/Quercus sensu lato) and water chestnuts (Trapa). This evidence suggests that early managed wetland environments were initially harvested for multiple grain species including barnyard grasses as well as rice and indicate that the emergence of rice as the favoured cultivated grass and ultimately the key domesticate of the Yangtze basin was a protracted process.

Detailed studies of the long-term development of plant use strategies indicate that plant subsistence patterns have noticeably changed since the Upper Paleolithic, when humans underwent a transitional process from foraging to agriculture. This transition was best recorded in west Asia; however, information about how plant subsistence changed during this transition remains limited in China. This lack of information is mainly due to a limited availability of sufficiently large, quantified archaeobotanical datasets and a paucity of related synthetic analyses. Here, we present a compilation of extensive archaeobotanical data derived from interdisciplinary approaches, and use quantitative analysis methods to reconstruct past plant use from the Upper Paleolithic to Middle Neolithic in China. Our results show that intentional exploitation for certain targeted plants, particularly grass seeds, may be traced back to about 30,000 years ago during the Upper Paleolithic. Subsequently, the gathering of wild plants dominated the subsistence system; however, this practice gradually diminished in dominance until about 6~5 ka cal BP during the Middle Neolithic. At this point, farming based on the domestication of cereals became the major subsistence practice. Interestingly, differences in plant use strategies were detected between north and south China, with respect to (1) the proportion of certain plant taxa in assemblages, (2) the domestication rate of cereals, and (3) the type of plant subsistence practiced after the establishment of full farming. In conclusion, the transition from foraging to rice and millet agriculture in China was a slow and long-term process spanning 10s of 1000s of years, which may be analogous to the developmental paths of wheat and barley farming in west Asia.

Bulliform phytoliths play an important role in researching rice origins as they can be used to distinguish between wild and domesticated rice. Rice bulliform phytoliths are characterized by numerous small shallow fish-scale decorations on the lateral side. Previous studies have shown that domesticated rice has a larger number of these decorations than wild rice and that the number of decorations ≥9 is a useful feature for identifying domesticated rice. However, this standard was established based on limited samples of modern rice plants. In this study, we analyzed soil samples from both wild and domesticated rice paddies. Results showed that, in wild rice soil samples, the proportion of bulliform phytoliths with ≥9 decorations was 17.46% ± 8.29%, while in domesticated rice soil samples, the corresponding proportion was 63.70% ± 9.22%. This suggests that the proportion of phytoliths with ≥9 decorations can be adopted as a criterion for discriminating between wild and domesticated rice in prehistoric soil. This indicator will be of significance in improving the application of fish-scale decorations to research into rice origins and the rice domestication process.

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the “present” is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7–7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8–5.3 ka and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5–8.5 ka and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

Phytoliths represent one of the few available altitudinal vegetation proxies for mountain ecosystems. This study analyzed 41 topsoil phytolith samples collected from five altitudinal zones in the southern Himalaya as far as and beyond, the timberline, from tropical forest (up to 1,000 m a.s.l.) to subtropical forest (1,000–2,000 m a.s.l.), to temperate forest (2,000–3,000 m a.s.l.), to subalpine forest (3,000–4,100 m a.s.l.) and finally to alpine scrub (4,100–5,200 m a.s.l.). The statistical results show a good correlation between phytolith assemblages and these five altitudinal vegetation zones: the five phytolith assemblages identified effectively differentiated these five altitudinal vegetation zones. In particular, coniferous phytoliths accurately indicated the timberline. Additionally, we tested the phytolith index Ic (a proxy for estimating the percentage of Pooideae vis-à-vis the total grass content) as a quantifier of phytolith variety versus altitude. Ic increased along altitude, as expected. An investigation of phytoliths provided an initial basis for the analysis of the composition of gramineous vegetation. Furthermore, redundancy analysis and discriminant analysis also suggested a significant correlation between phytolith assemblages and altitude. Our research therefore provides an up-to-date analogue for the reconstruction of changes to palaeovegetation and palaeoaltitude in mountainous areas.

InnorthernChina, the Late Miocene–Pliocene redclay in the easternLoess Plateau fills a gapofclimate records between the wellknown loess-soil sequences of the last 2.6 Ma and the Miocene loess-soil sequences from the western Loess Plateau. Previous studies indicate that the red clay is also of wind-blown origin, covering the period from ∼7– 8t o∼2.6 Ma. The red clay therefore provides a good archive to reconstruct paleoecological succession and paleoclimate change. In this study, a palynological investigation was conducted on the late Miocene–Pliocene red clay sequence at Xifeng, central Loess Plateau, which provides new insights into the nature of the evolution of vegetation and climate change from ∼6.2 to ∼2.4 Ma. Our results show that during this period the central Loess Plateau region was covered mainly by a steppe vegetation, indicating long lasting dry climatic condition. Three vegetational zones were recognized during this period. Zone A (∼6.2 to ∼5.8 Ma) is characterized by a steppe ecosystem; Zone B (∼5.8 to ∼4.2 Ma) is characterized by a significant increase of temperate forest plants, indicating a relatively humid regional climate; Zone C (∼4.2 to ∼2.4 Ma) indicates a typical steppe ecosystem. The vegetation shift at about 4.5–3.7 Ma, when the temperate forest plants decrease, the vegetation gradually changed to typical grassland and even to desert steppe. This is interpreted to represent a drying event. The uplift of the Tibetan Plateau at about 4.5 Ma that resulted in the intensification of the monsoon reversal is thought to have playedanimportantroleinthissignificantecological change.High-latitude coolingmayhavepartiallycontributedtotheclimateshift during ∼4.5 to ∼3.7 Ma in the Loess Plateau region, and most likely was the driving force for the ecological shift at about 3.7 Ma.

This study investigated the distribution of phytolith assemblages in China from surface soil samples at 243 sites along significant ecological and climatic gradients to develop transfer functions for quantitative reconstruction of palaeoenvironment. Canonical correspondence analysis (CCA) and detrended correspondence analysis (DCA) were used to determine the main environmental variables influencing phytolith distributions. The results reveal that mean annual precipitation (MAP) is the dominant variable controlling the spatial distribution of phytoliths, which accounts for 39% of the total variance. Mean annual temperature (MAT), relative humidity (Humi), and annual evaporation (VAP) are another three significant variables, accounting for 6%, 10%, and 5%, respectively, of the total variance in phytolith distributions. Transfer functions, based on weighted averaging plus partial least squares (WA-PLS), were developed for MAP ( R - boot 2 = 0.90 , root-mean-square-error of prediction (RMSEP)=148 mm), MAT ( R - boot 2 = 0.84 , RMSEP=2.52 °C), Humi ( R - boot 2 = 0.75 , RMSEP=6.36%) and VAP ( R - boot 2 = 0.59 , RMSEP=327 mm). Overall, our results confirm that phytoliths can provide reliable and robust estimates of MAP, MAT, Humi and VAP. Thus, WA-PLS is a robust calibration method for quantitative palaeoenvironmental reconstruction based on phytolith data.

A new molluscan fossil record from the late Miocene–Pliocene Xifeng Red Clay sequence in the central Loess Plateau, northern China, reveals the process of ecological environmental changes during ∼ 6.2–2.4 Ma. Three marked ecological shifts in mollusk assemblages occurred at about 5.4, 4.5, and 3.4 Ma, which reflect changes in the East Asian monsoon circulation. A predominantly cold-aridiphilous group reveals an extremely cold dry climate due to strengthened East Asian winter monsoon during ∼ 6.2–5.4 Ma. A predominantly thermo-humidiphilous group from ∼ 5.4–4.5 Ma indicates a strengthening of the East Asia summer monsoon circulation. The marked occurrence of meso-xerophilous taxa during ∼ 4.5–3.4 Ma implies mild climatic conditions. From 3.4 Ma, the cold-aridiphilious species again became dominant in the fossil assemblages, indicating that the winter monsoon was gradually intensifying towards the Quaternary glaciations. Climate changes in this region were characterized by stepwise cooling from 5.4 to 2.4 Ma with a 1 Ma rhythmicity. The cooling trend is in good agreement with the general global cooling trend during this period, as documented by marine δ18O records. The formation and development of the Northern Hemisphere ice sheets during the late Pliocene accelerated the climate deterioration towards the Quaternary glaciations. The history of environmental changes revealed by the Red Clay molluscan fossils is coupled in phase with the process of Tibetan Plateau uplift, which may be the major cause and forcing mechanism of late Miocene–Pliocene environmental changes in the Loess Plateau.

Based on a multi-proxy investigation into the deep core of the Cuoe Lake in the middle of Tibetan Plateau, a 2.8 Ma paleoclimatic and paleoenvironmental evolution is reconstructed. The result of magnetic stratum indicates that the lake basin was formed at about 2.8 MaBP, while the multi-proxy analyses of lithology, grain size, magnetic susceptibility and geochemical elements reveal that there have been three major environmental evolution stages and at least two intensive uplifts of the Tibetan Plateau in the lake basin area, i.e. during 2.8-2.5 MaBP, the lake basin came into being as a result of the disaggregation of the planation surface and rapid rising of the Tibetan Plateau. During 2.5-0.8 MaBP, with gradual uplift of the Tibetan Plateau, the environment of this area was more effectively controlled by the climatic cycle of the alternative glacial-interglacial stages. After 0.8 MaBP, the middle part of the Plateau accelerated its uplift and entered cryoshere.

This paper presents a large data set on carbon isotope composition (δ13C) of modern soils which were collected under the main vegetation communities along an altitude of 1250–5500 m above sea level in the Qinghai-Tibetan Plateau. The δ13C values of 198 samples range from −28.6 to −15.1‰ versus PDB and exhibit a clean relation to different vegetation communities from forest (−25.9 ± 1.2‰) to shrub (−24.7 ± 1.4‰), steppe (−23.1 ± 1.3‰), alpine meadow (−23.6 ± 0.7‰), alpine desert steppe (−21.3 ± 1.6‰), and alpine desert (−18.9 ± 2.5‰). We attributed the observed variability in δ13C values to that the mean annual precipitation (MAP) and the mean annual temperature (MAT) are the main factors controlling the distribution of vegetation types in the Tibetan Plateau, which causes the change in carbon isotope composition of modern soils at any given altitude. The result of both linear and nonlinear regression analyses also confirms that MAP and MAT are the major factors affecting the δ13C values of surface soils. In the absence of favorable moisture and temperature conditions, low pCO2 alone is not sufficient to cause the distinct changes in carbon isotope composition of modern soils in the Tibetan Plateau. This study provides some fundamental information on the carbon isotope composition of terrestrial carbon pools and bears some practical significance for the use of carbon isotope data to document vegetation changes and environmental conditions of the high plateau in the past.

Plant specimens are collected from the areas between latitude 27 ° 42′N and 40 ° 57′N, and longitude 88 ° 93′E and 103 ° 24′E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m, and Pennisetum centrasiaticum, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant’s tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau.

A series of seven piston cores from the Huguang maar lake situated near the South China Sea coastline provides insight into regional palaeoenvironmental and palaeoclimatic changes in southern China over the last 78,000 years. The data set comprises a high-resolution record of magnetic susceptibility, dry density and water content, total organic carbon and inorganic carbon, total nitrogen, biogenic silica (BSiO2), and palynological results. The time scale was developed by AMS 14C dating of 17 terrestrial plant macro-fossils. During the Last Glacial the Huguang record is characterised by an alternation of more temperate and humid periods (from 78 to 58 and 48 to 40.5 ka BP) and periods with predominance of grassland vegetation and possibly lowered lake level (from 58 to 48 and ca 40.5 to 15 ka BP). The Huguang data have been compared to regional marine and terrestrial records in order to discuss variability of the South-East Asian monsoon system. For most of the Last Glacial period the Huguang proxies do not exhibit marked millennial-scale variability as known from some long SE Asian and many North Atlantic records. This picture changes at about 15 cal ka BP when the Huguang and Greenland records appear to correlate well. A short climatic reversal which is assumed to reflect a Younger Dryas-type event is well recorded in the Huguang record. During the Holocene the Huguang multi-proxy data show a much higher variability than during the Last Glacial stage probably reflecting, at least for the early mid-Holocene, fluctuations in monsoon activity. However, the last 4000 years of the sediment record are clearly influenced by enhanced human activity and thus difficult to interpret in terms of palaeoclimate change.

Thirty-four grass species were collected for phytolith analysis from a variety of coastal environments in the southeastern USA (Georgia, Florida, and Louisiana), including salt marshes, freshwater/brackish marshes, pine/oak forests, maritime hardwood forests, and sand dunes. Phytoliths produced by these modern grasses include a large diversity of shapes and types. We propose a preliminary relationship between modern coastal plant communities and their predominant phytolith contents. The dominant grasses of coastal sand dunes, such as Uniola paniculata, produce primarily flat tower and two-horned tower phytoliths. Rondel/ saddle ellipsoid phytoliths are mainly produced by Spartina alterniflora, the most common plant in coastal salt marshes. Rondel and spool/horned tower phytoliths are common in brackish marsh grasses. Plants from interdune meadow produce primarily dumbbell phytoliths, as well as small cross and Cyperaceae-type phytoliths. These results provide a basis for the interpretation of fossil phytolith assemblages and the reconstruction of coastal environmental changes. 2003 Elsevier Ltd. All rights reserved.

The study of natural vegetation of geological and historical periods in the Loess Plateau is an important scientific and practical issue for the development of northwestern China. However, interpretation of the natural vegetation before human reclamation is still controversial. The paper aims to analyze the potential factors that cause the difference in knowledge of Holocene natural vegetation developing in different topographies of the Loess Plateau. The distribution of paleovegetation in this region shows significant difference among rocky mountains, valleys, and Yuan lands (the plain area), i.e. it does not follow the natural vegetation zonation, as that in eastern China does. The Yuan lands with thick loess accumulation were never covered by a vast of dense forests during the Holocene. Forests (or open forests) developed preferably in valleys in the southern part of the Plateau and rocky mountains on the Plateau during the warm period of the Holocene. Some of local vegetation outside of the Loess Plateau are more subjected to the control of geomorphology and ground water.

Phytolith analysis of grasses is a useful tool in palaeoenvironmental and archaeobotani- cal research. Lobate phytolith is one of the most important morphotypes of grass phytoliths. This study describes morphological variations of diag- nostic lobate phytoliths and produces a tentative classification scheme based on 250 modern grass species from China and the south-eastern U.S.A. Eighty-five grass species were found to contain lobate phytoliths. They are derived mainly from Panicoideae, but also include the Chloridoideae, Oryzoideae and Arundinoideae subfamilies. Twenty-five lobate morphological types were observed from different subfamilies, genera or tribes of grasses, based on two important param- eters: (1) the length of the lobate shank and (2) the shape of the outer margin of the two lobes. The identification of grass tribe or even genus is possible based on the differences in lobate shape parameters or the composition of assemblages. However, not all of the lobate assemblages have a definite relationship with the genera that produce them, because grasses can only produce a limited range of lobate shapes that often over- lap from one genus to another. Several C3 grasses and Chloridoideae subfamily grasses also produce characteristic lobate phytoliths. The variations of lobate morphologies can be related to environmen- tal factors, especially moisture. Typical hygrophytic grasses tend to yield lobate phytoliths with very short shank, whereas typical xerophytic grasses tend to produce lobate phytoliths with a very long shank. The potential link between phytolith morphology, grass taxonomy and environmental conditions opens the possibility that phytolith morphology may be used as a proxy in palaeocli- matic reconstruction.

The geochemistry of dated sediment cores from Lake Huguangyan (21°9′N, 110°17′E), tropical South China, reveals distinct stratigraphical patterns in total organic and inorganic carbon (TOC, TIC), biogenic silica (BS) and total nitrogen (TN) over the past 1400 years. In this hydrologically closed lake, TIC variations may re‘ ect changes in the precipitation/evaporation ratio, which controls the evaporative enrichment of carbonate. TOC, BS and TN in the sediment are proxy indicators of lake productivity and nutrient input, which we believe are linked to local precipitation. High TIC content correlates with low concentrations of TOC, BS and TN, and indicates two drought episodes dated to ad 670–760 and ad 880–1260 in the sediments of Lake Huguangyan. Local historical chronicles support these data, suggesting that the climate of tropical South China was dry during the ‘Mediaeval Warm Period’ (MWP) and wet during the ‘Little Ice Age’ (LIA). The detected MWP drought is temporally correlated with evidence for lower precipitation on the Guliya (China) and Quelccaya (Peru) ice caps, and with increased salinity in Moon Lake (US Great Plains).

The history of tea is poorly known, mainly due to the questionable identification of decayed tea plants in archaeological samples. This paper attempts to test the utility of calciphytoliths (calcium oxalate crystals) for the identification of tea in archaeological samples. It provides the first survey of the macropatterns of calciphytoliths in several species of Theaceae and common non-Theaceae plants. Crystals were extracted from 45 samples of tea, Theaceae and common non-Theaceae plants and detected microscopically between crossed polarizers. In tea plants, druse and trichome base are the most distinctive crystals. Druses have the smallest diameter (11.65 ± 3.64 μm) and trichome bases have four distinctive straight and regular cracks, similar to a regular extinction cross. The results provide morphological criteria for distinguishing tea from other plants, specifically the presence of identifiable druses together with calcified trichome bases. The implications are significant for understanding the history of tea and plant exploitation, especially for plants for which the preservation of macrofossils is poor.

To understand the origin of the ultrafine pedogenic components responsible for the magnetic susceptibility (MS) enhancement remains a major challenging problem in linking magnetic signal with paleoclimate. Here we examine the effect of the natural fires on the MS signal of both plants and modern soils and in particular the MS difference between C3 and C4 plant ashes and their influence on magnetic susceptibility. We also proved the influence of the different floral root systems on the MS signal of modern soils. We find that the C3 and C4 plants are different in their ability to enhance MS signal of modern soils. Increased MS signal of modern soils by C4 plants was much greater than that by C3 plants.

The analysis of carbon isotope in phytoliths from modern plants and surface soils in China shows that the values of carbon isotope are consistent with those from C3 and C4 plants, and the processes of photosynthesis of the original plants can be clearly identified by carbon isotope in phytoliths. The value of carbon isotope varied from −23.8‰ to −28‰, with the maximum distributed in the latitude zone from 34°N to 40°N in North China and East China areas, and the minimum in the Northeast China and South China regions. The values of carbon of phytoliths tend to increase from low to high and then reduce to low value again as the latitude increases. In the same latitude zone, the carbon isotope in phytoliths from grassland soil under the trees is obviously lower than that from grassland soil without any trees with the difference of 1%–2‰

An investigation of magnetic properties using magnetic susceptibility (χ) and frequency-dependent susceptibility (χfd) was conducted on representative modern pollutants, which include smelted slag dust, automobile exhaust dust and coal ash. Their magnetic susceptibility values are more than 500ξ108 m3/kg, and frequency-dependent susceptibility values less than 3%, indicating that ample ferrimagnetic and scanty superparamagnetic grains occurred in the studied pollutants. Similar to the artificially synthetic polluted soils, the industrially-polluted soils display a negative relationship between magnetic susceptibility and frequency-dependent susceptibility. However, the unpolluted soils, e.g. the Quaternary loess in the Chinese Loess Plateau, show a positive relationship between them. In this note, we propose a convenient and effective approach for identifying the polluted soils.

There exist five primary periods of 2 930, 1 140, 490, 250 and 220 a in the Holocene climatic variations in the Huguangyan Maar Lake, according to the energy-spectrum and filter analyses of high-resolution time sequences (10–15 a) of the sediment dry density. The peak values of the three temperature-decreasing periods with the 2 930 a cycle occur at about 7 300, 4 250 and 1 200 Cal. aBP. There are 7–8 temperature-decreasing periods with the 1 140 a cycle, and the climate fluctuation range is largest in the early Holocene, and reduces gradually in the middle and late Holocene. The millennial-scale climatic change in the Holocene may adjust the global water cycle and the thermohaline circulation intensity through the harmonic tones of the earth’s precession cycle, which in turn influences the global climate change.

The concentrations of biogenic silica, total organic carbon, total nitrogen and total hydrogen inferred from the sediments of tropical Maar Lake Huguangyan, southern China, provide a climate record of the last deglaciation with century resolution. The records fully demonstrate the existence of the two-step shape of the last deglaciation in tropic East Asia, and they point out noticeable differences between the low and high latitudes in the Northern Hemisphere. Thus, the Boiling first warming at the last deglaciation in the low latitude may have preceded that of the high latitude, whereas the cooling of the Younger Dryas occurred synchronously in the two regions. These results likely suggest that the links between the low and high latitude climates in the Northern Hemisphere during this period are complexity.

To understand the origin of the ultrafine pedogenic components responsible for the magnetic susceptibility (MS) enhancement remains a major challenging problem, in linking the magnetic signal with paleoclimatic conditions. Here we examine the influence of natural fires on the MS signal of both plants and modern soils and in particular the MS difference between C3 and C4 plant ashes and their influence possibly on soil magnetic susceptibility. We demonstrate that burning of C3 and C4 plants can enhance MS signal of modern soils. We show that C4 plants have greater potential to enhance the MS signal. The average MS value of C4 plant ashes is (532±61)×10−8m³ kg−1, much higher than the average MS value of (120±65)×10−8m³ kg−1 of C3 plant ashes. The Fe2O3 concentration in C4 plant is two to four times higher than that in C3 plant. One burning of the grassland, mainly consisting of C4 plants, can enhance MS value of the surface soil up to about 30–40%.

Grey microstructure of microbanding in thin sections of stalagmite T9501 from Shihua Cave, Beijing was studied. The types of grey and the morphologic features of organic material were classified. The signification of microbanding and annual layer was discussed. The standard distinguishing the false annual layer and the multi-year layer is set up, which provides the theoretic fundaments for paleoclimatic study.

Here we presented a high-resolution 5350-year pollen record from a maar annually laminated lake in East Asia (EA). Pollen record reflected the dynamics of vertical vegetation zones and temperature change. Spectral analysis on pollen percentages/concentrations of Pinus and Quercus and a temperature proxy, revealed ~500-year quasi-periodic cold-warm fluctuations during the past 5350 years. This ~500-year cyclic climate change occurred in EA during the mid-late Holocene and even the last 150 years dominated by anthropogenic forcing. It was almost in phase with a ~500-year periodic change in solar activity and Greenland temperature change, suggesting that ~500-year small variations in solar output played a prominent role in the mid-late Holocene climate dynamics in EA, linked to high latitude climate system. Its last warm phase might terminate in the next several decades to enter another ~250-year cool phase and thus this future centennial cyclic temperature minimum could partially slow down man-made global warming.

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20–19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that ( i ) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20–19 kaBP similar to that in the WPWP, and ( ii ) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18–15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3–4 ka.

Mollusk remains are abundant in archaeological sites in the Guanzhong Basin of Northwestern China, providing good opportunities for investigations into the use of mollusks by prehistoric humans. Here we report on freshwater gastropod and bivalve mollusks covering the time interval from about 5600 to 4500 cal. yrs BP from sites of Mid-Late Neolithic age. They are identified as Cipangopaludina chinensis and Unio douglasiae, both of which are currently food for humans. The shells are well preserved and have no signs of abrasion. They are all freshwater gastropods and bivalves found in pits without water-reworked deposits and have modern representatives which can be observed in rivers, reservoirs, and paddy fields in the studied region. Mollusk shells were frequently recovered in association with mammal bones, lithic artifacts, and pottery. These lines of evidence indicate that the mollusks are the remains of prehistoric meals. The mollusk shells were likely discarded into the pits by prehistoric humans after the flesh was eaten. However, these mollusk remains may not have been staple food since they are not found in large quantities. Mollusk shell tools and ornaments are also observed. Shell tools include shell knives, shell reaphooks and arrowheads, whereas shell ornaments are composed of pendants and loops. All the shell tools and ornaments are made of bivalve mollusks and do not occur in large numbers. The finding of these freshwater mollusk remains supports the view that the middle Holocene climate in the Guanzhong Basin may have been warm and moist, which was probably favorable to freshwater mollusks growing and developing in the region.

Carbon isotope ratio (δ13Corg) values of organic matter in lake sediments are commonly used to reconstruct environmental change, but the factors which influence change are varied and complex. Here we report δ13C values for sediments from Erlongwan maar lake in northeast China. In this record, changes in δ13C cannot be explained by simple changes in aquatic productivity. Instead, values were likely influenced by differences in the ratio between planktonic and benthic algae, as indicated by the remains of diatoms. This is because the variation of δ13Corg in algae from different habitats is controlled by the thickness of the diffusive boundary layer, which is dependent on the turbulence of the water. Compared with benthic algae, which grow in relatively still water, pelagic algae are exposed to greater water movement. This is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe δ13C depletion. In Erlongwan maar lake, low values were linked to the dominance of planktonic diatoms during the period commonly known as the Medieval Warm Period. Values gradually increased with the onset of the Little Ice Age, which we interpret as being driven by an increase in the proportion of benthic taxa, due to effect of the colder climate. The increase in planktonic diatoms at the end of the Little Ice Age, linked to higher temperature and a reduction in ice cover, resulted in a further decline in δ13Corg.