Barchans of Minqin:quantifying migration rate of a barchan

The migration speed of a typical barchan on the border of Minqin oasis,Gansu Province,northwestern China,was estimated by means of two methods.One is on the basis of a simple physical model and short-term field measurements.The other comes from the combination of the barchan internal structure detected by ground-penetrating radar and optical/radiocarbon dating techniques.The upper limit of migration speed given by conventional C-14 dating is 3.42 m/yr.The optically stimulated luminescence dating indicates that the time-average migration speed of the studied barchan was 1.78 m/yr in 28 years prior to 2007.The physical estimation further suggests that the annual migration speed has increased in recent years.

The northern boundary of the Asian summer monsoon and division of westerlies and monsoon regimes over the Tibetan Plateau in present-day

Precipitation patterns and their variations over the Tibetan Plateau(TP) are mainly dominated by the Asian summer monsoon, westerlies, and their interactions. The exact extent of the Asian summer monsoon’s influence, however, remains undetermined. Referencing the climatological northern boundary index of the East Asian summer monsoon, we demonstrate that the 300 mm precipitation isoline from May to September can be utilized as an indicator of the northern boundary of the Asian summer monsoon over the TP, allowing for an analysis of the spatial distribution characteristics of the climatological and interannual northern boundary. Our results indicate that the climatological northern boundary of the Asian summer monsoon over the TP lies along the eastern Qilian Mountains-Tanggula Mountains-Qiangtang Plateau-Gangdise Mountains-Western Himalayas during 2001–2020. This position corresponds well with the position of the convergence of westerly(westerlies) and southerly wind(monsoon) in the lower troposphere, representing the interface between dry and wet regions in the rainy season over the TP. There is a significant positive correlation between changes in the zonal/meridional water vapor budget and variations in precipitation to the north/south of the climatological northern boundary, respectively. Additionally, a close relationship exists between the interannual fluctuation range of the northern boundary and the distribution of vegetation across the TP. Compared to the northern boundary of the summer monsoon defined by meteorological criteria, which is established based on 5-day(pentad)mean precipitation(exceeding 4 mm day^(-1)), our climatological northern boundary offers a more objective portrayal of the region that experiences persistent influence from the summer monsoon. These indicate that climatological northern boundary has a clear significance for natural geographical distribution such as the westerlies-monsoon circulation, ecology, and climate. Based on the interannual fluctuation range of the northern boundary, we divided the TP into domains of westerlies, monsoon, and westerliesmonsoon transition. This study could serve as a foundation for further investigation into the interactions between westerlies and monsoon, variations in precipitation patterns and hydrological-ecological systems over the TP.

Discussion of the“warming and wetting”trend and its future variation in the drylands of Northwest China under global warming

Since Shi et al.proposed that the climate in the drylands of Northwest China experienced a significant transition from a“warming and drying”trend to a“warming and wetting”trend in the 1980s,researchers have conducted numerous studies on the variations in precipitation and humidity in the region and even in arid Central Asia.In particular,the process of the“warming and wetting”trend by using obtained measurement data received much attention.However,there remain uncertainties about whether the“warming and wetting”trend has paused and what its future variations may be.In this study,we examined the spatiotemporal variations in temperature,precipitation,the aridity index(AI),vegetation,and runoff during 1950-2019.The results showed that the climate in the drylands of Northwest China and the northern Tibetan Plateau is persistently warming and wetting since the 1980s,with an acceleration since the 1990s.The precipitation/humidity variations in North China,which are mainly influenced by summer monsoon,are generally opposite to those in the drylands of Northwest China.This reverse change is mainly controlled by an anomalous anticyclone over Mongolia,which leads to an anomalous easterly wind,reduced water vapor output,and increased precipitation in the drylands of Northwest China.While it also causes an anomalous descending motion,increased water vapor divergence,and decreased precipitation in North China.Precipitation is the primary controlling factor of humidity,which ultimately forms the spatiotemporal pattern of the“westerlies-dominated climatic regime”of antiphase precipitation/humidity variations between the drylands of Northwest China and monsoonal region of North China.The primary reasons behind the debate of the“warming and wetting”trend in Northwest China were due to the use of different time series lengths,regional ranges,and humidity indices in previous analyses.Since the EC-Earth3 has a good performance for simulating precipitation and humidity in Northwest and North China.By using its simulated results,we found a wetting trend in the drylands of Northwest China under low emission scenarios,but the climate will gradually transition to a“warming and drying”trend as emissions increase.This study suggests that moderate warming can be beneficial for improving the ecological environment in the drylands of Northwest China,while precipitation and humidity in monsoon-dominated North China will persistently increase under scenarios of increased emissions.

The current and future of terrestrial carbon balance over the Tibetan Plateau

The contemporary carbon balance over the Tibetan Plateau is highly uncertain with a ten-fold difference between various estimates.In a warming world,the potential exists for a large carbon release from its permafrost which could compromise China’s 2060 carbon-neutral goal.Here,we used a satellite-and inventory-based approach,ecosystem models,and atmospheric inversions to estimate that the carbon sink was 33.12–37.84 TgC yr^(–1)during 2000–2015.The carbon sink induced by climate change and increasing CO_(2) levels largely overcompensated for a livestock grazing-induced carbon source of 0.38TgC yr^(-1).By 2060,the carbon sink is projected to increase by 38.3–74.5% under moderate to high emissions scenarios,with the enhanced vegetation carbon uptake outweighing the warming-induced permafrost carbon release.The restoration of degraded grassland could sequestrate an additional 9.06 TgC yr^(-1),leading to a total carbon sink of 57.78–70.52 TgC yr^(-1).We conclude that the Tibetan Plateau’s ecosystems absorbed two-and-a-half times the amount of its cumulative fossil CO_(2) emissions during 2000–2015 and that their carbon sinks will almost double in strength in the future,helping to achieve China’s pledge to become carbon neutral by 2060.

Holocene thermal maximum mode versus the continuous warming mode:Problems of data-model comparisons and future research prospects

The Holocene,the most recent interglacial,provides an important time window for evaluating current global warming and predicting future temperature changes.With the development of new temperature proxies and improvements in climate models,significant progress has been made in understanding Holocene temperature changes.However,a major debate persists about whether global temperatures during the Holocene followed a pattern of gradual warming from the end of the Last Glacial Maximum,which culminated in a temperature maximum in the early to middle Holocene,followed by gradual cooling in the late Holocene(the thermal maximum mode);or whether there was a continuous warming trend that continued to the present day(the continuous warming mode).Significant discrepancies exist between different proxy records as well as between proxy records and models,which have resulted in the “Holocene temperature conundrum” that has challenged paleoclimatologists for the past decade.Here,we summarize the progress made to date in the study of Holocene temperature change via proxy reconstructions,climate model simulations,and paleoclimate data assimilation.We emphasize that the current research has limitations in terms of the multiplicity and seasonality of proxy records,the spatial heterogeneity of temperature records,and the incorporation of feedback processes(e.g.,vegetation,cloudradiation feedback) in climate models.These limitations have hindered a comprehensive understanding of the processes and mechanisms of Holocene temperature changes.To solve the “Holocene temperature conundrum”,it is necessary to strengthen theoretical research on climate proxies from the perspective of the underlying processes and mechanisms,elucidate the seasonal response of various temperature proxies,emphasize regional differences in temperature changes,and expand quantitative temperature reconstructions to areas with limited records.However,it is also necessary to improve the simulation performance of complex feedback processes in climate models,reduce simulation errors,and advance the research on data assimilation of Holocene continental temperature records,which may ultimately lead to the optimal integration of paleoclimate records and simulations.

Food resources of the Khog Gzung site on the Tibetan Plateau revealed by sedimentary ancient DNA

Traditional zooarchaeological and archaeobotanical methods based on morphological identification of the excavated faunal and floral remains have been broadly used in reconstructing ancient subsistence economies. However, the accuracy and reliability of these methods rely heavily on the preservation state of the remains. By sequencing the ancient DNA of plants,animals, and microorganisms preserved in sediment, sedimentary ancient DNA(sedaDNA) now offers a novel approach for reconstructing the taxa composition dated back to hundreds of thousands of years. Yet, its application in open-air archaeological sites is rarely reported. In this study, we attempted to apply sedaDNA shotgun metagenomics on the archaeological deposits of the Khog Gzung site(an open-air site dated to 3160–2954 cal yr BP) on the Tibetan Plateau, and then compared the reconstructed taxonomic composition to the unearthed remains. Results showed that most of the crops and domestic animals identified by the two approaches, such as barley(Hordeum vulgare) and sheep(Ovis aries), are in general consistent. Some species, such as foxtail millet(Setaria italica), however, were only detected by sedaDNA. In addition, a variety of microorganisms were also detected by the sedaDNA. The two approaches combined revealed diversified food resources at the Khog Gzung site, which included crops such as millet, barley and wheat, domestic animals such as sheep and cattle, and likely also wild animals from fishing and hunting. Our data proves that sedaDNA has a great potential in reconstructing the faunal and floral compositions from archaeological deposits, therefore laying the foundation for its border applications.

晚更新世以来轨道尺度东亚夏季风环流和降水演化的解耦

晚更新世以来东亚夏季风轨道尺度演化特征和物理机制存在很大争议,洞穴石笋氧同位素等记录揭示过去64万年以来东亚夏季风的演化,以约2万年周期为主,响应于低纬夏季太阳辐射引起的海陆热力差异变化;而黄土磁化率和10Be等记录揭示过去80万年以来东亚夏季风变化以10万年周期为主,受高纬冰盖波动和大气CO_(2)浓度的影响.基于地球系统模式CLIMBER-2在地球轨道参数驱动下进行的过去300万年地球系统模拟试验显示,过去80万年以来东亚夏季风环流与受夏季风影响的降水存在明显的解耦现象:即2万年周期变化的东亚夏季风环流和10万年周期交化的东亚夏季风降水,分别响应于岁差和CO_(2)浓度变化.本研究揭示了地球气候系统内部过程,尤其是碳循环对东亚夏季风响应地球轨道变化具有重要调节作用.

Wetland science,ecosystem services and protection actions in China

Wetlands are widely recognized as among Earth’s most vital ecosystems.They occupy a mere 5%−8%of our global landmass,but provide unparalleled ecosystem services per unit area compared to any other habitats.Wetlands provide not only sustenance and shelter for livelihoods but also essential ecosystem functions,including biodiversity preservation,climate regulation,hydrological flow regulation,and water purification.For example,wetlands serve as biogeochemical hotspots,actively participating in greenhouse gas exchanges between the Earth’s surface and the atmosphere[1],and peatlands-peataccumulating wetlands-contain the highest soil carbon density and the largest biosphere carbon pool among all ecosystems[2].Often referred to as the“kidney of the world”,wetlands excel at removing pollutants and purifying water。

Estimation of China’s terrestrial ecosystem carbon sink:Methods,progress and prospects

China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060,during the General Assembly of the United Nations in September 2020.In this context,the potential of the carbon sink in China’s terrestrial ecosystems to mitigate anthropogenic carbon emissions has attracted unprecedented attention from scientific communities,policy makers and the public.Here,we reviewed the assessments on China’s terrestrial ecosystem carbon sink,with focus on the principles,frameworks and methods of terrestrial ecosystem carbon sink estimates,as well as the recent progress and existing problems.Looking forward,we identified critical issues for improving the accuracy and precision of China’s terrestrial ecosystem carbon sink,in order to serve the more realistic policy making in pathways to achieve carbon neutrality for China.

Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects

The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.

Early human occupation of the Tibetan Plateau

The Tibetan Plateau,the world's "Third Pole",has an average elevation above 4,000 masl (meters above sea level)and an area of over 500×10^4km^2,It is the highest and largest plateau on earth and is very sensitive to global climate change [1,2].The cold,dry and hypoxic high-altitude environment of the plateau presents a major challenge to human survival.Therefore,the history and mechanisms of prehistoric human history on the Tibetan Plateau-from brief hunting expeditions to seasonal hunting-gathering and finally to permanent settlements-has attracted both general interest and substantial scientific debates [3-6].Archaeological studies indicate that humans probably first explored the plateau at the end of the late Pleistocene.They practiced intensive seasonal hunting-gathering from 15 ka BP [6],and permanently settled regions above 3,000 masl after 3.6 ka BP,which was facilitated by the development of an agropastoral economy [3].However, the early part of the human history of the Tibetan Plateau is still poorly documented,due to the lack of well-preserved archaeological sites and reliable dating results (Fig.la).

A review on the spread of prehistoric agriculture from southern China to mainland Southeast Asia

The origins and spread of agriculture was one of the milestones in human history.When and how prehistoric agriculture spread to mainland Southeast Asia is highly concerned,which contributed to the formation of modern Austroasiatic in this region.Previous studies mainly focused on the time and route of rice agriculture’s introduction into Southeast Asia while millet agriculture was not paid proper attention.Here we analyze 31214C dating data yielded from charred seeds of rice(Oryza sativa),foxtail millet(Setaria italica)and broomcorn millet(Panicum miliaceum)from 128 archaeological sites in China and mainland Southeast Asia.The result shows that millet farming was introduced to mainland Southeast Asia in the late third millennium BC and rice farming was in the late second millennium BC.The agriculture of mainland Southeast Asia might originate from three areas,Southwest China,Guangxi-West Guangdong and coastal Fujian.The spread route of ancient agriculture in Southwest China is close to the“Southwest Silk Road”recorded in literature,which implies there was possibly a channel of cultural exchanges on the eastern margin of Tibetan Plateau already in the late Neolithic period,laying the foundation for the Southwest Silk Road later.

亚洲环境变化引擎:青藏高原地球系统研究迈入新时代

The Tibetan Plateau(TP),as the world’s highest plateau,has almost all the key elements of the entire Earth system,including interconnected lithosphere,atmosphere,cryosphere,biosphere and anthroposphere[1-3].This completeness makes the TP an ideal natural laboratory for studying multispheric interactions within the Earth system,and for cultivating key breakthroughs in geoscience of the 21st century[2,3].

Emergence of ancient cities in relation to geopolitical circumstances and climate change during late Holocene in northeastern Tibetan Plateau, China

The study of the history of human activities in ancient cities has provided valuable evidences for under- standing the evolution of human-land relations during the late Holocene. Numerous ancient cities were discovered through archaeological surveys of the east Qinghai Province, located on the northeastern border of the Tibetan Plateau, China; however, the mystery of when or why these cities were built remains unsolved. As recorded in this paper, we sampled reliable dating materials from 47 ancient cities in the area, determined their ages by radiocarbon dating, and compared the dating results with historical documents and high resolution paleoclimate records to explore the influencing factors for the develop- ment of these ancient cities. The 54 radiocarbon dates indicated that most of these cities were built or repaired during the Han Dynasty （202 BC-AD 220）, Tang Dynasty （AD 618-AD 907）, the Five Dynasties and Ten Kingdoms period （AD 907-AD 960）, the Song dynasty （AD 960-AD 1279）, and the Ming Dynasty （AD 1368-AD 1644）. The radiocarbon dates correspond well with historical records of the area. Our work suggests the ancient cities in east Qinghai Province were likely built primarily for military defense, and may have also have been affected by climate change.

Information geography: The information revolution reshapes geography

The information revolution has been one of the driving forces to the innovation in geography. However, environmental remote sensing, geographic information science and technology, and geocomputing, which once resided within the family of geography, are gradually moving close to information science but are alienated from geography. Therefore, it is necessary to reexamine the interactive convergence of geography and information science, and advance the disciplinary system of geographic science to accommodate the researches with information as subjects and methods. In this paper, we propose to reformulate the relationship between geographic science and information science with a new discipline, i.e., information geography, which not only refers to the geography of information but also a methodological system for studying geography using information science.This paper summarizes the background of information geography’s emergence, its definition, and the difference and similarities with other disciplinary concepts. The impact of information geography on geographic paradigm shift is also investigated from the ontological, epistemological, and methodological perspectives.

Weakened East Asian summer monsoon triggers increased precipitation in Northwest China

Increased precipitation/humidity in Northwest China is an important scientific issue in the context of global climatic warming(Chen et al.,2019).The climate of Northwest China is dominated by the westerly circulation and its water vapor is supplied mainly by the mid-latitude westerlies,with the rainy season occurring in summer(Chen et al.,2019;Zhang et al.,2019a).

Difference in Tree Growth Responses to Climate at the Upper Treeline: Qilian Juniper in the Anyemaqen Mountains

Three ring-width chronologies were developed from Qilian Juniper （Sabina przewalskii Kom.） at the upper treeline along a west-east gradient in the Anyemaqen Mountains. Most chronological statistics, except for mean sensitivity （MS）, decreased from west to east. The first principal component （PC1） Ioadings indicated that stands in a similar climate condition were most important to the variability of radial growth. PC2 Ioadings decreased from west to east, suggesting the difference of tree-growth between eastern and western Anyemaqen Mountains. Correlations between standard chronologies and climatic factors revealed different climatic influences on radial growth along a west-east gradient in the study area. Temperature of warm season （July-August） was important to the radial growth at the upper treeline in the whole study area. Precipitation of current May was an important limiting factor of tree growth only in the western （drier） upper treeline, whereas precipitation of current September limited tree growth in the eastern （wetter） upper treeline. Response function analysis results showed that there were regional differences between tree growth and climatic factors in various sampling sites of the whole study area. Temperature and precipitation were the important factors influencing tree growth in western （drier） upper treeline. However, tree growth was greatly limited by temperature at the upper treeline in the middle area, and was more limited by precipitation than temperature in the eastern （wetter） upper treeline.

2060年中国实现碳中和所面临的挑战:现状与展望

China’s high ambitions to reach peak CO_(2) emissions by 2030 and carbon neutrality by 2060 make carbon mitigation an urgent issue with widespread societal consequences.To develop an achievable roadmap and an effective portfolio of climate policies,it is essential that a clear picture of the magnitude and uncertainty of China’s current carbon balance is available,at both national and regional levels.

Spatiotemporal changes of epidemics and their relationship with human living environments in China over the past 2200 years

Epidemics are biological disasters resulting from the widespread occurrence of acute and severe infectious diseases that are normally caused by viruses, bacteria and parasites.They are amongst the most destructive of all natural disasters suffered by humans (Gong, 2019). The pathogens that cause epidemics have always existed in nature, understanding the spatiotemporal distribution of past epidemics is important for preventing and controlling future epidemics.

Differences in the evolutionary pattern of dust storms over the past 2000 years between eastern and western China and the driving mechanisms

The arid and semi-arid region of East Asia,principally including the deserts in eastern and western China,is the main dust source of the Northern Hemisphere.Dust storm activity in the region has attracted much research attention because of its impacts on air quality.