Asian dust storms have long been a major environmental concern in China, affecting the lives of about one billion people. However, it is unclear whether the mechanisms responsible for Asian dust storms during the Holocene varied on different timescales, and thus it is unclear whether there was a shift from a natural forcing to an anthropogenic forcing of dust storms. We reconstructed a high-resolution Holocene record of dust storms from the sediments of an undisturbed alpine lake on the Chinese Loess Plateau. We found that Asian dust storm activity generally increased during the Holocene, with the largest fluctuations occurring during the past 2000 years. The increase in dust storm activity was in contrast to the decrease in East Asian winter monsoon (EAWM) intensity during the Holocene, indicating that the EAWM played a limited role in modulating dust storms. By contrast, the increase in dust storms corresponded to a decrease in EASM precipitation. This demonstrates that EASM precipitation was the dominant control of dust storm activity on a millennial timescale, because decreased EASM precipitation expanded the desert area and thus increased the dust storm activity. The increasing intensity of human activity in the region since the Bronze Age resulted in an acceleration of dust storm activity against the background of decreased EASM precipitation. As human disturbance continued to intensify, beginning at least at ~2 cal ka BP, increased dust storms were closely linked to increasing human populations in the dust source regions, and there is a strong temporal coherence between increased dust storms and higher EASM precipitation. This was completely different from when natural processes are dominant. During that period, fewer dust storms occurred during periods of a strengthened EASM. Therefore, there was a shift from a natural forcing to an anthropogenic forcing of dust storms on a multi-decadal to centennial timescale, and was a mode in which "human activity overtook the EASM as the dominant control of the Earth surface system".Copyright © 2021 Science China Press. Published by Elsevier B.V. All rights reserved.

During the past few years, an increasing number of studies in both China and abroad have highlighted a long-term warming trend during the Holocene. However, this trend challenges the traditional view of a long-term Holocene cooling trend and a "mid-Holocene Megathermal". Comparison of long-term records indicating a rising global sea level, a decreasing area of terrestrial ice-sheets, and increasing radiative forcings of insolation and GHGs (greenhouse gases) leads us to conclude that a long-term Holocene warming trend is more reasonable than the cooling trend. In the original literature documenting a "mid-Holocene Megathermal" and the subsequent late Holocene cooling trend in China, the uncertainties in the supporting evidence are clearly indicated. These uncertainties have been further demonstrated by recent results that the most significant uncertainty arises from the impacts of human activities on sedimentary proxies, especially in the late Holocene when these impacts were greatly intensified. Thus, reconstructions of late Holocene temperature history based on sedimentary proxies are potentially biased by human impacts. Given that the current debate regarding temperature history of the Holocene focuses on the late Holocene, we propose that future emphasis should be placed on the temperature history of the late Holocene. We suggest that more reliable late Holocene temperature records should come from areas and/or sedimentary proxies that are weakly influenced by human activities, which is especially important to studies on the development of Chinese civilization that lasted for over several millennia. Overall, reliable late Holocene temperature records can potentially provide a reliable foundation for improving our understanding of the following themes: (1) the development of Chinese civilization under the background of long-term temperature change; (2) the evolutionary history of "human-land relationship" during the late Holocene; and (3) the climatic and environmental issues associated with global warming.

最新一些研究结果强调了全新世期间的长期增温趋势,综合全球平均海平面、大陆冰盖面积、大气温室气体和太阳辐射证据来看,这比传统观点所认为的全新世期间的长期降温趋势,更具有合理性。回顾历史,结合最新的一些研究进展,发现支持“中全新世大暖期”和“晚全新世降温趋势”的证据存在明显的不确定性,最核心的问题为晚全新世加强的人类活动对代用指标或者证据的强烈扰动,使得其不能准确地反映真实的气候变化过程。鉴于目前全新世温度历史争论的核心关键在于晚全新世,因此有必要加强晚全新世温度变化研究。在人类活动影响较小的地区,或者利用对人类活动不敏感的代用指标开展研究,有望可以获得更可靠的晚全新世温度历史重建结果,为准确认识中华数千年文明的长期温度变化背景,进而理解期间的“人地关系”演化历史,并最终客观认识现今面临的以全球变暖为主要特征的气候环境问题,提供一定的科学基础。

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.

Based on the tree-ring increment cores of Juniperus przewalskii Kom. collected from the Maoniu Mountain in inner Qaidam Basin, the new 2710-year tree-ring width chronology was developed, and the correlation coefficients were calculated between the chronology and meteorological data during the instrumental period of 1957-2017. The results showed that the highest correlation existed between the total precipitation from July of previous year to June of current year and the chronology (r = 0.753, n = 60, p < 0.01). Based on the correlation relationship, total precipitation variation from July of previous year to June of current year was reconstructed from 392 BC to 2017 AD. The reconstruction explained 64% of the variation in the total precipitation from previous July to current June for the calibration period (1957-2017 AD). The results showed that there were nine wet periods which occurred during 106-75 BC, 6-39 AD, 179-229 AD, 581-646 AD, 823-914 AD, 1026-1095 AD, 1378-1414 AD, 1567-1609 AD and 1985-2017 AD, and seven dry periods occurring during 328-297 BC, 86-151 AD, 694-747 AD, 1168-1199 AD, 1444-1525 AD, 1680-1725 AD and 1792-1860 AD in the past 2409 years. Among these wet and dry periods, 1792-1860 AD was the driest period. Power spectral analysis revealed cyclic fluctuations of the precipitation series on 2~8 years, 40 years, 80 years and 225 years (p < 0.01). In addition, the solar minimum phases were in accord with the dry period in our study area in the past 2409 years, and the results of superposed epoch analysis showed that the precipitation decreased significantly in the following year after large volcanic eruptions observed at low-mid latitudes. The results indicated that solar activity and large volcanic eruptions were factors impacting precipitation variation in our study area.

Numerous studies have focused on environmental changes and lacustrine ecological transitions in the modern industrial era. However, little is known about the processes of ecological transitions during early human disturbances. The current lake ecosystem state is the result of long-term integrated human influences on lakes. In this study, we present multi-proxy evidence of changes in the lacustrine environment, ecosystem, and human activities inferred from a sediment core collected from Beilianchi Lake in the southwestern Chinese Loess Plateau, to document the lacustrine ecological transitions with increasing human disturbances during the past 5000 years. Our data reveal the lacustrine ecosystem was quite stable with unchanging terrestrial versus aquatic sourced organic matter before major human disturbances (4400-1400 BP), although there was a decline in precipitation and a transition from tree-to herb-dominated vegetation. From 1400 to 300 BP, when early humans began to occupy and disturb the catchment, the lake experienced high-magnitude, centennial-to decadal-scale oscillations between aquatic and terrestrial sourced organic contributions. Thereafter, as human activities further increased, the lacustrine ecosystem finally stabilized at a state with terrestrial dominated organic matter. Our results suggest that the lake experienced large-magnitude ecological oscillations during the period of 1400 -300 BP, probably indicating the lake ecosystem retained the capability of recovery from the modest early human disturbances on the catchment. The recovery of the ecosystem to these external disturbances lasted hundreds of years with centennial to decadal scales oscillations. With further increased human influences since 300 BP, the lacustrine ecosystem probably finally shifted to another state largely deviating from its natural (climate-driven) background. (C) 2018 Elsevier Ltd.

Based on the results of lacustrine environmental proxies from Erhai Lake, Yunnan Province,the lake responses of human activities recorded by lacustrine sediment in the catchment have been discussed. The Erhai Core of 310 cm long was sampled in the center of Erhai Lake with the water depth of 4 6 m. The modern sedimentation rate by 137 Cs test is ≤0 25 mm/a, which is consistent with the average sedimentation rate of the upper 100 cm with radio carbon years of 4 473±40 a BP at the bottom. Because the surface soil are rich in magnetic materials. The environmental proxy of magnetic susceptibility was obviously influenced by the way of land use especially the occurrence of farming agriculture. So the sharp increase of magnetic susceptibility at 100 cm with ca 4 500 a BP means the intensification of human activities especially the occurrence of farming agriculture. The time of the ancient farming occurrence recorded by the lake sediment is older than the archaeological relics with the radio carbon years of ca 3 800 a BP in Baiyang Village near the catchment of Erhai Lake. The surface soil is rich with elements of Fe and Al in the catchment of Erhai Lake. So the changes of chemical elements contents （Fe, Al） had close relationship with surface water soil erosion which controlled by the human activities in the catchment. The huaman relics of Malong in the catchment of Erhai Lake with the age of 34003100aBP which corresponding with the sharp increase of element Fe and Al. The lower content of Fe, Al in the upper 15 cm may be affected by the aquatic vegetation which can absorb some chemical elements including Fe and Al. The variations of pigments indicated the process of lake eutrophication induced by human activities. The first and second peaks of pigments correspond with the time of Malong Relics and the first population summit of Yunnan Province. The obvious increase of pigments was occurred in 1100 AD with the large population migrated to Yunnan. The proxies of lacustrine magnetic susceptibility, chemical elements and pigments are the efficient parameters to demonstrate the human activities in the catchment, which has important significance in the research on archaeology.

根据湖泊沉积记录的环境指标变化,对云南洱海地区人类活动的湖泊沉积响应进行了系统的讨论。洱海湖泊沉积物记录显示,湖泊沉积物磁化率参数对洱海流域土地利用方式变化特别是耕作农业的出现有显着响应；沉积物元素Fe、Al含量的变化也与流域人类活动影响下的地表水土流失有密切联系； 沉积物色素的变化则指示湖泊富人为营养化的历史。湖泊沉积物磁化率、元素、色素指标的变化是指示湖泊流域人类活动的有效指标并具有重要的科学考古学意义。

According to the Second Chinese Glacier Inventory (SCGI) that were mostly compiled based on Landsat TM/ETM+images, the Qilian Mountains contained 2684 glaciers covering an area of 1597.81±70.30βkm2 and ice volume of ~84.48βkm3 from 2005 to 2010. While most glaciers are small (85.66% are smaller than 1.0βkm2), some larger ones (12.74%, with each having 1.0 and 5.0βkm2) cover 42.44% of the total glacier area. The Laohugou No.12 Glacier (20.42βkm2) located on the north slope of the Daxue Range is the only one larger than 20 km2 in the Qilian Mountains. The average median altitude of glacier was 4972.7βm a.s.l. and gradually rose from east to west. Glaciers in the Qilian Mountains are mostly distributed in Gansu and Qinghai provinces, which have 1492 glaciers (760.96βkm2) and 1192 glaciers (836.85βkm2), respectively. In 11 watersheds, the Shule River contains most of the glaciers in either area or volume. However, the Heihe River, the second longest interior river in China, has the minimum average area of glacier. Comparison of glaciers from the SCGI and the revised glacier inventory based on topographic maps and aerial photos taken from 1956 to 1983 indicated that all the glaciers in the Qilian Mountains were receding, which is consistent with other mountains and plateaus in western China. In the past half century, the area and volume of glaciers decreased by 420.81βkm2 (-20.88%) and 21.63βkm3 (-20.26%), respectively. The glaciers which are smaller than 1.0βkm2 constituted the main body of glacier number depression and area recession. Due to shrinkage, the glaciers below 4000βm a.s.l. completely disappeared.

基于修订后的祁连山区第一次冰川编目（1956-1983年）和最新发布的第二次冰川编目数据（2005-2010年）,对祁连山区冰川变化进行分析。结果表明：① 祁连山区现有冰川2684条,面积1597.81&#x000b1;70.30&#x003b2;km²,冰储量约84.48&#x003b2;km³。其中,甘肃省和青海省各有冰川1492条和1192条,面积分别为760.96&#x003b2;km²和836.85&#x003b2;km²。② 祁连山区冰川数量和面积分别以面积&#x0003C; 1.0&#x003b2;km²的冰川和面积介于1~5&#x003b2;km²的冰川为主;冰川平均中值面积海拔为4972.7&#x003b2;m,并自东向西由4483.8&#x003b2;m逐渐上升为5234.1&#x003b2;m。③ 疏勒河流域冰川面积和冰储量最大,占祁连山冰川总量的31.91%和35.11%;其次是哈尔腾河流域,巴音郭勒河流域冰川面积最小,为2.20&#x003b2;km²;黑河流域是祁连山区冰川平均面积最小的四级流域,冰川平均面积仅0.21&#x003b2;km²。④ 近50年间祁连山冰川面积和冰储量分别减少420.81&#x003b2;km²（-20.88%）和21.63&#x003b2;km³（-20.26%）。面积&#x0003C; 1.0&#x003b2;km²的冰川急剧萎缩是该区冰川面积减少的主要原因,海拔4000&#x003b2;m以下山区冰川已完全消失,海拔4350~5100&#x003b2;m区间冰川面积减少量占冰川面积总损失的84.24%。冰川数量和面积在各个朝向均呈减少态势,其中朝北冰川面积减少最多,朝东冰川面积减少最快,而西北朝向冰川变化最为缓慢。⑤ 祁连山冰川变化呈现明显的经度地带性分异,东段冰川退缩较快,中西段冰川面积减少较慢。

Arid and semi-arid ecosystems are increasingly recognized as important carbon storage sites. In these regions, extensive sequestration of dissolved inorganic carbon can occur in the terminal lakes of endorheic basins-basins that do not drain to external bodies of water. However, the global magnitude of this dissolved inorganic carbon sink is uncertain. Here we present isotopic, radiocarbon, and chemical analyses of groundwater, river water, and sediments from the terminal region of the endorheic Shiyang River drainage basin, in arid northwest China. We estimate that 0.13 Pg of dissolved inorganic carbon was stored in the basin during the mid-Holocene. Pollen-based reconstructions of basin-scale productivity suggest that the mid-Holocene dissolved inorganic carbon sink was two orders of magnitude smaller than terrestrial productivity in the basin. We use estimates of dissolved inorganic carbon storage based on sedimentary data from 11 terminal lakes of endorheic basins around the world as the basis for a global extrapolation of the sequestration of dissolved organic carbon in endorheic basins. We estimate that 0.152 Pg of dissolved inorganic carbon is buried per year today, compared to about 0.211 Pg C yr(-1) during the mid-Holocene. We conclude that endorheic basins represent an important carbon sink on the global scale, with a magnitude similar to deep ocean carbon burial.

The Holocene environmental change of Juyan Lake in northwestern China was studied through combination of analyzing magnetic parameters of lacustrine core from G36 drilling hole in Juyan Lake, investigating total organic carbon content and grain size and other environmental proxies, and precisely AMS14C dating. Results show that most magnetic carrier minerals appeared in coarse sediments and the main magnetic minerals are contained in coarse multi-domain magnetite particles. The change mechanism of magnetic susceptibility is complicated and there is no simple positive or negative relationship between magnetic susceptibility change and environmental arid-wet change. Analysis of environmental proxies showed that the Holocene environmental changes of Juyan Lake could be divided into four arid-wet alternating periods: arid period in 6 700~4 600 a BP, wet period in 4 600~3 100 a BP, arid period in 3 100~2 500 a BP, and the lake drying up period since 1 800 a BP. In this four periods, two significant wet events and two outstanding arid events are recorded by magnetic parameters.

对居延海G36钻孔进行了系统磁性特征分析,并结合总有机碳含量和粒度等环境代用指标,在精确测年的基础上,探讨了居延海地区全新世时期以来的环境变化。结果显示,居延海岩芯磁性矿物主要存在于粗颗粒的沉积物中,载磁矿物为颗粒较粗的多畴磁铁矿;磁化率变化机制比较复杂,与干湿环境变化没有简单正（反）关系。根据G36沉积物环境代用指标的变化,大致可以将其分为4个干湿交替时期:6 700~4 600 a BP干旱时期,4 600~3 100 a BP湿润时期,3 100~2 500 a BP干旱时期以及1 800 a BP以来湖泊干涸。在这4个时期中,磁学参数记录了两次显著湿润事件和两次显著干旱事件。

. Pollen records from large lakes have been used for quantitative palaeoclimate reconstruction, but the influences that lake size (as a result of species-specific variations in pollen dispersal patterns that smaller pollen grains are more easily transported to lake centre) and taphonomy have on these climatic signals have not previously been systematically investigated. We introduce the concept of pollen source area to pollen-based climate calibration using the north-eastern Tibetan Plateau as our study area. We present a pollen data set collected from large lakes in the arid to semi-arid region of central Asia. The influences that lake size and the inferred pollen source areas have on pollen compositions have been investigated through comparisons with pollen assemblages in neighbouring lakes of various sizes. Modern pollen samples collected from different parts of Lake Donggi Cona (in the north-eastern part of the Tibetan Plateau) reveal variations in pollen assemblages within this large lake, which are interpreted in terms of the species-specific dispersal and depositional patterns for different types of pollen, and in terms of fluvial input components. We have estimated the pollen source area for each lake individually and used this information to infer modern climate data with which to then develop a modern calibration data set, using both the multivariate regression tree (MRT) and weighted-averaging partial least squares (WA-PLS) approaches. Fossil pollen data from Lake Donggi Cona have been used to reconstruct the climate history of the north-eastern part of the Tibetan Plateau since the Last Glacial Maximum (LGM). The mean annual precipitation was quantitatively reconstructed using WA-PLS: extremely dry conditions are found to have dominated the LGM, with annual precipitation of around 100 mm, which is only 32% of present-day precipitation. A gradually increasing trend in moisture conditions during the Late Glacial is terminated by an abrupt reversion to a dry phase that lasts for about 1000 yr and coincides with \"Heinrich event 1\" in the North Atlantic region. Subsequent periods corresponding to the Bølling/Allerød interstadial, with annual precipitation (Pann) of about 350 mm, and the Younger Dryas event (about 270 mm Pann) are followed by moist conditions in the early Holocene, with annual precipitation of up to 400 mm. A drier trend after 9 cal. ka BP is followed by a second wet phase in the middle Holocene, lasting until 4.5 cal. ka BP. Relatively steady conditions with only slight fluctuations then dominate the late Holocene, resulting in the present climatic conditions. The climate changes since the LGM have been primarily driven by deglaciation and fluctuations in the intensity of the Asian summer monsoon that resulted from changes in the Northern Hemisphere summer solar insolation, as well as from changes in the North Atlantic climate through variations in the circulation patterns and intensity of the westerlies.

Paleoenvironmental history in the monsoonal margin in the northeast Tibetan Plateau provides important clue to the regional climate. Previous researches have been limited by either poor chronology or low resolution. Here we present a high-resolution pollen record from a 40.92-m-long sediment core (DLH) taken from Dalianhai, a terminal lake situated in the Gonghe Basin, the northeast Tibetan Plateau for reconstructing the vegetation and climate history since the last deglacial on the basis of a chronology controlled by 10 AMS 14C dates on plant remains preserved in the core sediments. The pollen assemblages in DLH core can be partitioned into 6 pollen zones and each zone is mainly characterized by the growth and decline of tree or herb pollen percentage. During the periods of 14.8-12.9 ka and 9.4-3.9 ka, the subalpine arboreal and local herbaceous pollen increased, indicating the subalpine forest developed in the surrounding mountains and a desert steppe or typical steppe developed in Gonghe Basin under a relatively moister climate. During the periods of 15.8-14.8 ka, 12.9-9.4 ka and 3.9-1.4 ka, the forest shrank or disappeared according to different degrees of aridity, and the desert steppe degraded to a more arid steppe desert in the basin, indicating a dry climate. After 1.4 ka, vegetation type around Dalianhai was mainly dominated by steppe suggested by increased Artemisia. Our results suggested the climate history in this region was dry from 15.8-14.8 ka, humid from 14.8-12.9 ka and dry from 12.9-9.4 ka, after which the climate was humid during 9.4-3.9 ka, followed by dry conditions during 3.9-1.4 ka and humid conditions in the last 1.4 ka. The change of pollen percentage and the evolution of palaeovegetation in Dalianhai since the last deglacial were similar to those recorded in Qinghai Lake. The forest expanded in the mountains around Dalianhai during the B?lling-Aller?d period, shrank during the Younger Dryas and the early Holocene, then it developed and reached its maximum in the mid-Holocene. During the late Holocene, the vegetation began to shrink till disappearance. However, the timing of forest expansion in the Holocene lagged behind that of Qinghai Lake, and this spatial heterogeneity was probably caused by the different forest species between these two places. The maximum of forest development in the mid-Holocene was inconsistent with the period of stronger summer monsoon in the early Holocene indicated by stalagmite records, the reason might be related to the complexity of vegetation response to a large-scale climatic change.

Holocene is one of the most important period in PAGES. Haxi section sites on the first terrace of Haxi river in the north piedmont of eastern Qilian Mountains, and it has a thickness of 324 cm for aeolian loess and palaeosol. Susceptibility, CaCO 3 content and Organic Carbon content are used as the good indexes of climatic changes(mainly the precipitation changes) in loess palaeosol research. Study on Haxi section indicates that in this area it entered Holocene before 9560 a B.P.. In the early Holocene,climate changed frequently and had a obvious instability. The climate suitable stage and climate optimum took place within about 6.8-3.6 ka B.P. and about 5.0-3.6 ka B.P. respectively; scores of climatic indexes kept high during these two stages. There was a cold but still a little humid stage during 6.0-5.0 ka B.P., while evidences from other region showed it was cold and dry in those area during this period. After 3.6 ka B.P., it became drier. In 1.5-0.8 ka B.P., score of susceptibility was high than that of the climatic optimum, but the leaching depth of CaCO 3 was shallow than the latter. These conclusions are different from other climate records and traditional climate characteristics. In arid and semi arid region of northern China, the increase of summer monsoon will engenders more precipitation and an increase of temperature; but, the higher temperature may increase more evaporation and reduce humidity. So the Megathermal Maximum is different from the climatic optimum in conception,the former referred to temperature and the latter to assembly of climate(mainly water and thermal).And those two maybe not occurred in the same time. Comparison with Dunde Ice-core record shows it was cold wet during 7.8-7.2 ka B.P. and 1.5-0.8 ka B.P., especially the latter has plenty of proofs. During the Megathermal Maximum(7.2-6.0 ka B.P.), the environment was not at the best (optimum) in the whole Holocene because of intense evaporation. In the climatic transition processes(from cold to warm or from warm to cold), it was usually dry. It was the most dry stage during 9.0-8.7 ka B.P. when the climate changed abruptly and drastically(from the coldest to the warmest within 200 years)and deposited silt loess. The precipitation reached its maximum during 5.0-3.6 ka B.P., and, an ancient civilization was flourishing in our research region. Many researches indicate that during 5.0-3.6 ka B.P. it was warm and wet in other regions, such as in eastern and northern China. In arid and semi arid regions, water is the most important environment factor, so, warm wet climate assembly may be the finest of climate in these areas.

磁化率、碳酸钙含量和有机碳含量可用作良好的气候指标,主要是反映了降水量的变化。祁连山东段北麓哈溪剖面研究表明,9560aB.P.时本区已进入全新世。大暖期是对温度而言,与气候适宜期是不同的概念,二者在时间上也不一定是同时的。本区的气候适宜期为6.8~3.6kaB.P.,气候最宜期为5.0~3.6kaB.P.,与其它记录有不同之处。在7.8~7.2kaB.P.和1.5~0.8kaB.P.间出现了"冷湿"的气候组合,这与传统的气候组合不同,但后一阶段的"冷湿"是有大量证据的。9.0~8.7kaB.P.间是全新世最干旱的时段,堆积了砂黄土。

A high-resolution pollen record, c. 50 yr/sample, from terminal lake sediments in the Shiyang River drainage basin on the present margin of the summer monsoon was used to reconstruct vegetation and climate history during the Holocene. Forest trees from mountainous areas of the drainage, including Sabina, Picea and Pinus, dominated pollen assemblages in the early Holocene (11.6-7.1 cal. ka). In the mid-Holocene (7.1-3.8 cal. ka) desert and steppe shrubs and herbs around the lake, including Nitraria, Poaceae, Compositae and Artemisia, were dominant. The late Holocene (3.8-0 cal. ka) was again dominated by alternation of Pinus-Sabina tree pollen and desert-steppe pollen. The early Holocene forest expansion in the mountains and subsequent increase in the river transport of tree pollen corresponds with maximum precipitation during the East Asian summer monsoon maximum. The timing of these changes in our record from arid China is different from that of East China, where the Holocene monsoon maximum appeared in the middle Holocene. This difference indicates that the extent and development of summer monsoon circulation in the Holocene was complex. Changes in the pollen record appear to show pervasive and persistent centennial-to millennial-scale oscillations throughout both wet and dry periods of the Holocene. Our results imply the continental interior was sensitive to changing moisture conditions and responsive to Holocene climatic events.

Several factors influence the long-term 13C record of the organic component in lake sediments. Two of the more predominant ones are changes in hardness of the water and changes in organic productivity. In general, during colder climatic episodes, 13C values are lower. Of 12 lakes studied, 4 have 13C records with large changes in 13C content that are to a certain degree correlative with climatic changes.

Studies on the amount and spatial distribution of soil organic carbon/nitrogen in Inner Mongolia and their relationship to main climate factors showed that the content of soil organic carbon and nitrogen was 3.24～43.24 kg·m^-3 and 269.56～3085.60 g·m^-3,respectively, and the C/N ratio was about 4.46～17.13. The correlation between soil organic carbon/nitrogen and temperature was negative, and R was 0.557 and 0.460,respectively.Soil organic carbon/nitrogen had a weak positive correlation to precipitation, and Rwas 0.285 and 0.203. Soil organic carbon and nitrogen appeared a reducing trend with increasing temperature and decreasing precipitation from northeast to southwest.

Based on salt mineral composition and chronology, we reconstructed the lake evolution of Huahai Lake since the Late Glacial in the marginal area of the Asian monsoon in the Hexi Corridor of China. Results show that mirabilite deposition in the Late Glacial and Younger Dryas periods indicated high water salinity. Alluvial and aeolian deposition before 10.47 cal ka BP indicated an arid environment. During 10.47-8.87 cal ka BP, carbonate mineral deposition indicated water salinity decreasing and high lake levels. Between 8.87cal ka BP and 5.50 cal ka BP, salt minerals fluctuated intensively. In 8.8 cal ka BP, the layers were formed mainly on sulphate depositions, suggesting a salination process. After that, carbonate mineral became the main mineral in the layers and the lake salinity was low. After 5.50 cal ka BP, hiatus indicated the lake shrank. Holocene millennial-scale lake evolution and climate changes in Huahai Lake was controlled by the Asian monsoon and westerly winds.

通过分析河西走廊花海古湖泊沉积物中的盐类矿物组成，结合年代序列，重建了花海晚冰期以来湖泊演化过程及其对气候变化的响应。结果表明：晚冰期及新仙女木时期，花海湖泊以芒硝沉积为主，属硫酸盐型湖泊，湖水的盐度较高且周期性波动频繁；全新世早期（10.47 cal ka BP以前），湖泊以洪泛堆积和风成沉积为主，揭示了湖泊萎缩、甚至干涸；全新世早期至全新世中期（10.47～8.87 cal ka BP）盐类矿物以碳酸盐沉积为主，为碳酸盐型湖泊，湖水淡化，湖泊水位开始逐渐回升；全新世中期（8.87～5.50 cal ka BP）盐类矿物呈现一定的波动变化，其中，8.8 cal ka BP 时期盐类矿物以硫酸盐沉积为主，湖泊由碳酸盐型转化为硫酸盐型，湖水咸化，盐度升高；随后盐类矿物以碳酸盐沉积为主，湖泊由硫酸盐型转化为碳酸盐型，湖水盐度降低、湖泊扩张；全新世中晚期（5.50 cal ka BP以来）出现沉积间断，表明中晚全新世时期湖泊逐渐萎缩。在全新世期间，花海湖泊千年尺度演化过程揭示了该区域气候干湿状况受亚洲季风和西风共同控制的影响。

Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.

The precipitation change over the Qinghai-Tibet Plateau in Holocene is of great importance to the study of global change in the past. There is a lack of practical and effective methods to reconstruct precipitation in a large-scale region in the previous studies on global change, and in order to solve this problem, this study takes the Qinghai-Tibet Plateau as the research area and combines the method of partitioned space simulation of ancient precipitation and multi-area weighted method for the purpose of reconstructing the precipitation series of Qinghai-Tibet Plateau in Holocene. As the vegetation variation of Qinghai-Tibet Plateau can well reflect the precipitation change, this study mainly takes pollen as the circumstantial evidence, selects ten pollen reconstructed precipitation series of sampling points on the plateau, acquires 716 signaled quantitative precipitation records and reconstructs the precipitation series of the plateau in Holocene. With the help of GIS analysis, based on the geographical simulation of spatial distribution of modern plateau precipitation, and integrated with the ancient precipitation records, this paper quantitatively reconstructed the 200-resolution precipitation series of the plateau during the Holocene. The results indicated that during the Holocene the precipitation went up rapidly, reaching a peak of 500 mm at 9 ka BP, 170 mm more than that in modern times. The period 9-5.6 ka BP was a moist period with the total precipitation 80 mm more than that at present. However it showed a downward trend. Since 5.6 ka BP the precipitation went down compared with the present time with small fluctuation. Synthetic series are comparable to the other records in a high or low resolution, which means synthetic series are representative and accurate.

A 5-year-resolution absolute-dated oxygen isotope record from Dongge Cave, southern China, provides a continuous history of the Asian monsoon over the past 9000 years. Although the record broadly follows summer insolation, it is punctuated by eight weak monsoon events lasting approximately 1 to 5 centuries. One correlates with the "8200-year" event, another with the collapse of the Chinese Neolithic culture, and most with North Atlantic ice-rafting events. Cross-correlation of the decadal- to centennial-scale monsoon record with the atmospheric carbon-14 record shows that some, but not all, of the monsoon variability at these frequencies results from changes in solar output.

Stratigraphically precise AMS-radiocarbon-dated plant remains, pollen, charcoal, and microtephra analyses from the Faroe Islands were used to establish the timing and effects of the first human settlement. The first occurrence of cultivated crops from three locations dated from as early as the sixth century A.D. and was older than implied from previous archaeological and historical studies, but consistent with earlier palaeoecological investigations. The effects of settlement on the vegetation were rapid and widespread. The transformation of the flora of this fragile ecosystem was best expressed by the large assemblage of ruderal, postsettlement plants recorded as macrofossils. The earliest known introduction of domestic animals (sheep/goat) was ca. A.D. 700. Their arrival on these relatively small islands probably contributed to the widespread change in vegetation and the loss of restricted native woody cover. Settlement was the critical disturbance that transformed an ecosystem that was already stressed by climatic change, as sensed by regional marine sediments. The settlement dates conform to a pattern of older dates developing from throughout the north Atlantic region.

Modern human societies live in strongly altered ecosystems. However, anthropogenic environmental disturbances occurred long before the industrial revolution. About 2,600 y ago, a forest–savannah mosaic replaced dense rainforests in Western Central Africa. This rainforest crisis was previously attributed either to the impact of climate change or, to a lesser extent, to the expansion of Bantu peoples through Central Africa. A 10,500-y sedimentary record from Lake Barombi, Southwest Cameroon, demonstrates that the rainforest crisis was not associated with any significant hydrological change. Based on a detailed investigation of a regional archaeological database, we present evidence that humans altered the rainforest ecosystem and left detectable traces in the sediments deposited in Lake Barombi.

We find evidence that black soot aerosols deposited on Tibetan glaciers have been a significant contributing factor to observed rapid glacier retreat. Reduced black soot emissions, in addition to reduced greenhouse gases, may be required to avoid demise of Himalayan glaciers and retain the benefits of glaciers for seasonal fresh water supplies.

Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees.

We present a 2000-year high-resolution diatom record from Bosten Lake (Yanqi Basin, Xinjiang), which is the largest inland freshwater lake in China. Our aims were to investigate the influence of climate change and human activity on its aquatic ecology during the late Holocene. During AD 280–480, a low water level and high salinity occurred, based on the dominance of epipelic and brackish diatoms. In addition, the diatom stratigraphy, combined with records of mean grain size and carbonate content, suggests that the lake experienced a high level of eolian input from the surrounding dunes. We hypothesize that during this interval, Loulan Kingdom, an important city of the Han Dynasty, located downstream of Bosten Lake, was abandoned due to the increasing scarcity of water resources and related harsh environmental conditions, including stronger eolian activity, which were the consequences of climate change. The dominance of meso-eutrophic small fragilarioid diatoms coincides with warm and arid intervals which also correspond to intensified human activity. These intervals correspond to the development of the Tang Dynasty (from ~AD 600), the ‘Medieval Warm Period’ (AD 1000–1200), and the last ~200 years. A shift from meso-eutrophic/benthic diatoms to oligotrophic/planktonic diatoms occurred during an interval of enhanced precipitation throughout the humid ‘Little Ice Age’ (AD 1600–1800). A return to markedly eutrophic conditions and a decreasing lake level occurred after the ‘Little Ice Age’, reflecting the more arid regional environment of the last 200 years. The high variability of the proxies suggests that both climate change and human activity were the major drivers of the ecological status of Bosten Lake during the late Holocene. We suggest that both the continuous increase of human activity and ongoing global warming will cause the major eutrophication or salinization of the freshwater lakes in the arid zone of northwest China.

The trajectory, pattern, and mechanism of the human-land co-evolution process is a critical issue in the field of human geography. The pattern of human-environment interaction has varied significantly during different phases of human evolution, suggesting a series of changes in the driving force of human-land co-evolution. Although a variety of underlying mechanisms specific to the key periods of human history (e.g., Paleolithic, Neolithic, Bronze, and historical ages) have been intensively investigated, there are still significant gaps in the widely accepted model of the fundamental law that governs human-land co-evolution across human history. In this paper we propose the Fulcrum Cognitive Model (FCM), with the objective of disentangling the mechanism of human-land co-evolution. The FCM focuses on the equilibrium between the natural ecosystem and human social system, which can be disturbed by both climatic/environmental change and human activities, and restored by an adjustment of the human social system. Moreover, we propose a "quantitative-change equilibrium pattern" and "qualitative-change equilibrium pattern" on the basis of FCM, to further describe the mechanism of past human-land co-evolution in different contexts. In the former pattern, a new equilibrium between the natural ecosystem and human social system is rebuilt by the corresponding changes in population size, without a shift in the fulcrum position. In contrast, in the latter pattern, societies improve their social resilience to the deterioration of the living environment through social and/or technological changes. In this case, the fulcrum position of the original equilibrium shifts and the pattern of human-environment interaction is transformed. Social resilience is gradually strengthened during the evolutionary process and the dominant influencing factor moves from natural causes towards anthropogenic factors. To test its feasibility, we applied the model to the changing patterns of the human-land relationship in Shanxi, Shaanxi, and Henan provinces in central north China between the Yangshao period (~5000-3000 BCE) and Zhou Dynasty (1046-256 BCE), based on a comprehensive analysis of updated archaeological and paleoclimatic data. The results suggested that the mechanism controlling the human-land relationship during ~4000-2600 BCE and 2600-256 BCE could be explained by the "quantitative-change equilibrium pattern" and "qualitative-change equilibrium pattern", respectively. The mechanism of human-land co-evolution in the past is very complicated and the interaction of these two patterns may vary in terms of its spatiotemporal scale, which will require further study in the future.

人地关系演变的历史、规律和机制是地理学研究的重要科学问题。在人类社会演化的不同阶段,人与环境相互作用的模式存在显著差异,揭示人地关系在时间维度上的演变轨迹和机制可为有效衔接古今人地关系研究提供重要依据。基于对过去人地关系研究案例的分析和总结,我们提出“支点”概念模型尝试解释人地关系演变的规律和机制。当特定区域人口数量增长到一定程度时,自然生态系统和人类社会系统达到平衡状态,随后的气候环境变化和人类活动变化都有可能打破其平衡状态。人类社会系统在面对生存环境变化压力时可能出现两种不同方式的响应：① 通过人口数量的调节适应生存环境变化而达到新的平衡,其特点是人与环境相互作用的模式（人类社会与自然生态系统平衡“支点”位置）不变;② 通过人类社会组织结构或技术革新方式使社会适应生存环境变化的“韧性”增强,体现为人与环境相互作用模式发生改变。随着时间的推移,社会韧性呈增强趋势,人地关系演变的主导因素也整体呈现由自然因素向人为因素的偏移。最后,以河南、山西和陕西三省仰韶文化时期（约公元前5000—公元前3000年）至周代（公元前1046—公元前256年）的人地关系研究为例,运用“支点”概念模型分析了其演变机制。

Landscapes have been shaped by human activities for millennia and there is a pressing need to characterize pre-industrial impacts in order to mitigate present-day effects. We present the analysis of two sediment cores from Dian Lake in Yunnan, China, which span 4000 years. We compare cores from the northern and southern ends of the lake to investigate spatial variability in natural and anthropogenic environmental changes in this large (300 km2) lake. To document the initiation of human impacts on the landscape and characterize the attendant changes in the lake water and sediment quality, we rely on organic and inorganic geochemical measurements as well as sedimentology and stratigraphy. The character and magnitude of proxy changes are coherent between the two core sites with slight differences in the timing of events. At both core sites, we find definitive evidence for substantial anthropogenic change beginning AD 100 (1850 yr BP), coincident with the introduction of terraced agriculture. Sedimentological shifts are distinctive and characterized by an increase in magnetic susceptibility values and a visible change to red, fine-grained clay. The geochemistry of this sediment suggests that it was sourced from the eastern catchment of the lake and delivered into the basin following intensive agriculture and soil erosion. Anthropogenic impacts intensify after AD 900 through hydrologic modification and cultural eutrophication resulting from increased nutrient loading. This study presents evidence that human-affected landscapes have been present in this region of China for longer than previously believed and that ‘small-scale’ land use change can have measureable impacts on lakes.

Soil sustainability is reflected in a long-term balance between soil production and erosion for a given climate and geology. Here we evaluate soil sustainability in the Andean Altiplano where accelerated erosion has been linked to wetter climate from 4.5 ka and the rise of Neolithic agropastoralism in the millennium that followed. We measure in situ cosmogenic 14C directly on cultivated hilltops to quantify late Holocene soil loss, which we compare with background soil production rates determined from cosmogenic 26Al and 10Be. Our Monte Carlo-based inversion method identifies two scenarios to account for our data: an increase in erosion rate by 1–2 orders of magnitude between ~2.6 and 1.1 ka, or a discrete event stripping ~1–2 m of soil between ~1.9 and 1.1 ka. Coupled environmental and cultural factors in the Late Holocene signaled the onset of the pervasive human imprint in the Andean Altiplano seen today.