Reconstructing the paleofire history along the Silk Road enhances our understanding of the complex interplay between natural processes and human activities, and provides a critical perspective on the long-term ecological and environmental evolution of the region. This study conducts a multi-proxy analysis of a sedimentary profile from the Zoroastrian wetland (STCN) on the Pamir Plateau, China, integrating fossil pollen, magnetic susceptibility, and microscopic charcoal records to examine paleofire patterns and anthropogenic influence over the past two millennia. Results indicate that paleofire activity was relatively low from approximately 1900 to 1300 years ago. Beginning around 1300 cal a BP, however, a rise in synanthropic plant pollen occurred alongside increased concentrations of macro-charcoal particles (>125 mu m) and higher magnetic susceptibility. These shifts correlated with the development of the Western Regions during the Tang Dynasty and the spread of Zoroastrian fire-worship practices. Between 670 and 540 cal aBP (corresponding to the Yuan-Ming period), secondary peaks in macro-charcoal concentration and magnetic susceptibility, alongside a rise in synanthropic plant pollen and low large Poaceae (>45 mu m) content, coincided with agricultural and military activities under the Chagatai Khanate. Since 140 cal a BP, the concentrations of macro-charcoal and the abundance of large Poaceae and synanthropic plant pollen have reached their highest recorded levels, likely driven by population growth, intensified agricultural development, and recurrent warfare. Significant correlations among large Poaceae, Taraxacum pollen, and macro-charcoal particles suggest fire regimes linked to the burning of agricultural crops or anthropogenic weeds, further underscoring the role of human activity. Multi-proxy evidences indicate that human activities along the Silk Road, such as agricultural practices, ritual fire use, and military conflicts, were important factors driving paleofire activity in the region. Particularly during the Yuan-Ming period and the Qing Dynasty, the intensity of human activities showed a synchronous increase with fire frequency, macro-charcoal particle concentrations, pollen content of anthropogenic plants, and magnetic susceptibility values. This research reveals the complex interactions within the human-fire-vegetation system along the Silk Road, providing important insights into the long-term responses of arid ecosystems to human activities.

Fossil pollen and spore records provide highly creditable proxy data to investigate the past environmental changes such as palaeovegetation and palaeoclimate.Pollen database promotes past environmental studies from local to regional and global scales and from qualitative to quantitative reconstructions.This is of great significance on exploring the interactions among past vegetation,climates and anthropogenic disturbances at large spatial scale and long temporal scale,to better understand the evolution of the earth system.In this paper,a fossil pollen dataset of China is compiled,by synthesizing 372 original or digitized fossil pollen records including 790 pollen taxa in China's land and ocean during the late-Quaternary(since 50 ka BP).The dataset includes site names,latitude,longitude and altitude,pollen data source,sample type,sediment length or span,sample number of each site,dating method and dating number,age span and reference,as well as the fossil pollen percentage of each sampling site.The pollen data,mostly published from late 1980s to present,are concentrated in vegetation regions of temperate and subtropical forests,temperate grasslands,temperate deserts and alpine vegetation on the Qingzang Plateau.Sample sites are distributed at different altitudes from deep sea to high Qingzang Plateau,but the majority of the sites are located between 0-2 000 m.The dataset comprises of 178 raw pollen records(47.8％)and 194 digitized pollen records(52.2％).Pollen samples are mainly from lake sediment(151 sites),alluvial/fluvial sediment(99 sites),and peat(67 sites),accounting for 85.2％of the total sampling sites.Radiocarbon is the main dating method that accounts for 93.8％of total samples,and most of the sites have 2-10 radiocarbon dating data.Each site has an average number of pollen taxa of 19,with the most sites having 4-30 pollen taxa.The temporal and spatial distribution of representative pollen taxa(Pinus,Quercus,Artemisia and Poaceae)reveals increasing trends both in their distributional range and pollen concentration from the last glacial maximum to Holocene,but such trends have various regional patterns in different parts of China.This fossil pollen dataset is a fruitful work of collection of pollen records in most territory of China that conducted by palynologists from China and overseas during the last half century.It consolidates the valuable and fundamental data that can be potentially utilized to explore the evolution of past environments and their driving mechanism of climate change and human disturbance.

Baishanzu area in Qingyuan, Zhejiang Province, which is famous for the discovery of Abies beshanzuensis, has the most typical mid-subtropical evergreen broad-leaved forest and complete vertical zones of mountain ecosystems in China, and this provides good natural conditions for paleoclimatic reconstruction using surface soil and airborne pollen data. Based on the pollen spectra of nine surface soil pollen samples collected at 300-1,700 m altitude, the relationship between vegetation and surface soil pollen in this area was preliminarily studied. The results show that surface soil pollen in this area can be divided into three assemblage zones from top to bottom according to altitude and ratios of coniferous pollen/broad-leaved pollen and arboreal pollen/non-arboreal pollen, which correspond to the evergreen deciduous broad-leaved mixed forest and temperate coniferous forest, evergreen broad-leaved forest and warm coniferous forest, secondary forest, and farmland (caused by human interference) zones. The surface pollen assemblages were dominated by the evergreen coniferous tree species Pinus, with an average pollen content of 67.5%. The pollen of Castanopsis (6.2%), Quercus (3.4%), Betula (1.4%), and Corylus (1.4%) is common. In contrast, Cyclobalanopsis, Liquidambar, Symplocos, Tsuga, Oleaceae, and Ericaceae had lower contents. Herbaceous plants are dominated by Poaceae (11.2%), including Artemisia, Chenopodiaceae, Apiaceae, Asteraceae, etc. The spore content of fern vegetation was high, mainly Hicriopteris (38.2%) and Polypodiaceae (7.4%). Pinus pollen appeared in all samples, with the highest average content. With increasing altitude, the mean percentage gradually increased from 54.8% to 77.3%, and it is an overly represented pollen with a low sedimentation rate that is easily preserved and transported to the area. Abies pollen is only observed in the samples under the A. beshanzuensis tree at an altitude of 1,700 m. Its percentage is lower than 1%, which may be related to low pollen yield and the relatively narrow distribution range of A. beshanzuensis in this area. In addition, the pollen diversity analysis results based on Simpson's index show that human interference factors prevent the surface soil pollen at lower altitudes in this area from reflecting the regional zonal vegetation. With decreasing altitude, the deciduous component of arboreal pollen in the pollen assemblage increased from 13.2% in Zone I to 40.9% in Zone III. Zone III shows a coniferous and broad-leaved mixed forest zone caused by human factors. The content of the evergreen component in zone I is high, which is related to the high humidity at higher altitudes. This study selects Baishanzu National Park to study the surface soil pollen and preliminarily discusses the characteristics of the surface soil pollen assemblage and its relationship with vegetation, which provide research materials and the basis for Quaternary paleovegetation and paleoclimate reconstructions in the Baishanzu area, Qingyuan County, China. However, due to a lack of surface soil samples and modern vegetation investigation data, the reliability of the research results is affected. In future research, sampling and density quadrat surveys of surface sampling sites will be increased to cover as many vegetation zones as possible.

Human activities and climate change pose major challenges for the sustainable development of terrestrial biological forests. The modern vegetation in the Baishanzu area is typical mixed subtropical evergreen broad-leaved, coniferous, and deciduous broad-leaved forest, with a vegetation combination sensitive to climate change. Higher resolution pollen records from the Shangyang Lake Wetland, located in the subtropical monsoon climate of the Baishanzu area in Zhejiang, China, were combined with environmental proxy data, such as data on loss on ignition and charcoal, to reconstruct the vegetation and climate changes since the Holocene. The results show that the climate was cool and dry during the early Holocene (11660-6580 cal. aBP), when the zonal vegetation changed from evergreen deciduous broad-leaved mixed forests dominated by evergreen Quercus (Quercus(E)), Castanopsis, deciduous Quercus (Quercus(D)), and Castanea to coniferous and broad-leaved mixed forests with rich Cryptomeria. Abies pollen spread to lower altitudes during the period 9620-8020 cal. aBP with Abies beshanzuensis covering large areas of land. The increased in the East Asian summer monsoon from 6580 to 2040 cal. aBP led to the Holocene Climate Optimum, when the climate was particularly warm and humid. The zonal vegetation was middle subtropical evergreen broad-leaved forest dominated by Quercus(E), Castanopsis, and Cyclobalanopsis with particularly high forest coverage and few fire events. For the last 2000 years, coniferous and broad-leaved mixed forests, mainly Pinus taiwanensis, have dominated the vegetation in the area. Sharp increase in such flora was observed after the year 980. Decreased temperature, cold climate, and increased anthropogenic disturbances have resulted in a substantial reduction in the arboreal pollen content, including Quercus, Castanopsis, Castanea, and Ilex, and an increase in Pinus and Poaceae. The results of this study will play a positive role in fully understanding the historical background and internal mechanisms of subtropical forest changes.

在新疆艾比湖小叶桦湿地取得深度190 cm的地层剖面,结合具有较高时间分辨率的孢粉数据和AMS 14C测年揭示出该研究区3900年以来植被和环境演变的动态.在3420-3940 cal.aBP期间,该区为以藜科和蒿属植物为主的荒漠景观;2830-3420 cal.aBP时段,局域的优势种变为沼泽蕨,周围仍是以藜科和蒿属为主的荒漠植物;2640-2830 cal.aBP时期,香蒲属花粉增加并占主要地位,该局域演替成以香蒲属植物为主的典型荒漠隐域性湿地;1200-2640 cal.aBP期间,芦苇植物开始旺盛生长并成为优势种;660-1200 cal.aBP时段,桦木属种群迅速扩张,芦苇植物仍生长繁盛;340-660 cal.aBP期间,小叶桦种群成为优势种,芦苇数量减少但该地仍存在一定范围的芦苇湿地;340年以来,随着艾比湖湿地退化,地表水位逐渐降低,小叶桦仍能在水分条件相对较好的沼泽草甸土上生长.而近200年来,孢粉组合中藜科花粉百分含量骤增,小叶桦林萎缩,这与该地受人类活动的增强和全球气候变化等的影响有关.随着艾比湖湿地不断退缩,小叶桦等植物在新疆地区濒危,因此需增强对该湿地自然环境及濒危物种的保护保育工作.

Pollen record is an essential data for reconstructing paleovegetation and paleoclimate. It is important for the studies of paleoenvironmental evolution, characteristics of paleoclimate change and simulation of paleobio-geochemical cycles from site to regional and global scales. In this paper, we collected and sorted out the pollen data records from published and unpublished Chinese literature between 1960 to 2020. The records included sample numbers, sampling locations (latitude, longitude and altitude of sampling sites), sample types, data sources, data types, surrounding vegetation, references, and pollen taxa, their compositions as well. They were filtered and standardized to integrate a pollen dataset of China. This dataset consists of 4 497 modern pollen sampling sites, including 660 published data from the Chinese Quaternary Pollen Database, 1 763 from early published data and 2 074 from recently collected data, belonging to 772 pollen taxa. The samples were mainly from surface soils (3 332 sites), and the rest were from moss plosters, surface sediments from lakes and the ocean. The sampling sites are widely scattered around China representing different geographical regions and vegetation types: 24.91%. in the temperate desert region, 24.02% in the subtropical evergreen broad-leaved forest region, followed by the temperate grassland region (16.14%) and alpine vegetation region of Qingzang Plateau (15.83%). The data can be divided into the raw data (58%) and numerical data (42%) according to their sources, and grain count (59%) and calculated pollen percentage (41%) by data type as well. The database con-structed from the samples over China during the past half-century+ period is, though by far from complete, good representation of most of the areas in China, which can be effective in the reconstruction of past vegetation and climates as modern verification.

Establishing a precise relationship between modern vegetation and surface pollen is the basis and key to quantitatively reconstruct paleovegetation and paleoclimate based on pollen records. The record of plant community plots has been less considered in the statistical analysis of modern vegetation and surface pollen, which limits the quantitative estimation of its precise relationship. In this study, the quantitative relationships of compositions and quantities between modern surface pollen and plant community were analyzed, based on the Bray-Curtis dissimilarity, through the analysis of 33 surface soil samples and corresponding vegetation plots from forest, meadow steppe, typical steppe and desert steppe on the Northeast China Transect. Results showed that, in a single plot, the relationships between vegetation and pollen in compositions and quantities were different across all families and genera, dominant and common families and genera, and less common and rare families and genera, respectively, due to the differences in pollen dispersal and pollen productivity. There were significant differences among different vegetation types. The compositions of meadow steppe differed greatly, while all families and genera, dominant and common families and genera differed greatly in the quantitative relationship in forest. Less common and rare families and genera differed greatly in the compositions in meadow steppe. The vegetation-pollen relationship of different families and genera was basically the same in terms of composition and quantities. According to the Bray-Curtis dissimilarity, pollen taxa could be divided into three types: over-representative, under-representative and representative types. This dissimilarity index represented both the species composition and quantity relationship between vegetation and pollen both at quadrat scale and at specie level, which could be used as an indicator to quantitatively describe the modern vegetation-pollen relationship.

空气花粉能够用于指示植被和气候状况.本研究利用Pearson相关分析和拉格朗日混合单粒子轨道(HYS-PLIT)模型对中国西北地区的艾比湖小叶桦湿地2012年9月到2015年8月的空气花粉散布特征及其对气象因子的响应进行研究分析.结果 表明,2012年9月到2013年8月,花期时较高的温度和适宜的降水有助于桦木花粉的产量增加,再加上被外来气流从天山地区带来的云杉属花粉,导致这一年的乔木植物花粉浓度达三年来最高值;2013年9月到2014年8月的总花粉浓度为三年中的最高值,可能是由于高温低降水有利于草本植物花粉的散播,并且该年夏秋季有大量来自艾比湖西南部和中亚地区的外来花粉;2014年9月到2015年8月,夏秋季当时的气象条件不利于藜科、蒿属等旱生植物花粉散布,且源自哈萨克丘陵的外来气流携带的花粉量较少,导致该年的总花粉浓度最低.气象因子和外来气流都会对空气花粉的浓度造成显著影响,该研究结果可为桦木属花粉的散布特征研究、该区域的古环境重建以及湿地保护工作提供重要的参考资料.

Proxy-based reconstructions and modeling of Holocene spatiotemporal precipitation patterns for China and Mongolia have hitherto yielded contradictory results indicating that the basic mechanisms behind the East Asian Summer Monsoon and its interaction with the westerly jet stream remain poorly understood. We present quantitative reconstructions of Holocene precipitation derived from 101 fossil pollen records and analyse them with the help of a minimal empirical model. We show that the westerly jet-stream axis shifted gradually southward and became less tilted since the middle Holocene. This was tracked by the summer monsoon rain band resulting in an early-Holocene precipitation maximum over most of western China, a mid-Holocene maximum in north-central and northeastern China, and a late-Holocene maximum in southeastern China. Our results suggest that a correct simulation of the orientation and position of the westerly jet stream is crucial to the reliable prediction of precipitation patterns in China and Mongolia.

论文主要研究长江中游地区第四纪的构造运动对该地区的河流地貌以及人类活动的影响.长江中游地区在全新世的构造活动较为简单,主要有挤压作用产生的隆起、褶皱以及掀斜作用,还有下沉作用等.一系列的构造运动形成了该地区的地貌形态:平原,盆地、丘陵等.其中洞庭平原、江汉平原,距离水源较近,土壤肥沃,地貌在全新世较为稳定,适宜人类居住,存在许多古人类遗址的遗存,随着构造运动的发展以及河流地貌的变迁,古人类遗址也发生着迁移,构造运动在一定程度上影响着先民生存地点的选择.

The goal of this study was to provide information on the representation of pollen taxa and the human impact on vegetation by exploring the relationship between modern pollen and vegetation in the central and western regions of Yunnan Province of China. A total of 120 modern pollen samples were collected throughout the study area. The surface pollen assemblage was divided into eight pollen zones (Zones I-VIII) based on vegetation types. We analyzed the palynology and determined the hemeroby levels of each zone in the area. Our results showed that human activity is one of the most important factors that can result in the damage of natural vegetation and increase anthropochory and secondary plants. The hemeroby levels of the surface pollen samples were mainly euhemerobic except for Zones I, II, and VI, which indicates a strong and continuous anthropogenic influence in the central and western regions of Yunnan Province in recent decades. The lowest hemeroby values were observed in Zone I samples, which were collected from Mengla and Jinghong. These areas are in the Xishuangbanna region, which is the most biodiverse region in China and has been well preserved since 1959. Therefore, the extent of human influence of a region can be estimated from the degree of hemeroby established from pollen data, which can be used in the future for nature conservation.

大气花粉的运移和沉降与各地的气象因子间存在着密切的联系.通过在新疆中天山地区处于不同植被带的3个研究点(新疆天池气象站、阜康荒漠生态系统定位站及北沙窝草炭试验站)安装花粉收集器,进行了长达5年(2001年7月～2006年7月)的大气中桦木属花粉的监测,目的是为了探讨桦木属花粉的数量变化和时空分布动态特征,以及与各个气象因子之间的响应关系,研究结果表明:(1)桦木属花粉组合与植物的花期相对应,具有季节性变化,在2003年,3个研究点的桦木属花粉浓度都最低,可能与2003年年平均温度降低有关,低温致使花粉减产.(2)由桦木属花粉含量与主要气象因子的相关分析得出,天池研究点和阜康研究点的年平均温度高低直接影响着桦木属花粉浓度大小,年平均降水和日照时数则在不同地区表现出相反的影响,风速和风向对桦木属花粉的散布有一定影响.(3)新疆天池地区大气中桦木属花粉的产量能反映其植物分布情况;而中天山地区一些表土和全新世地层中的桦木属花粉含量偏高,应能直接表明其古植被中的植物区系成分的组成,且与全新世气候变化及人类活动的影响密切相关.该项研究有助于新疆地区古气候重建、大气环境监测和生态文明建设.

依据新疆石河子蘑菇湖湿地120cm的地层剖面取得的具有序列14C测年予以支持的较高时间分辨率的孢粉分析资料,揭示出在4800～1300cal,aBP期间,该区局地生长着沼泽蕨,为淡水湿地景观.气候总体上经历了相对干旱-偏湿→偏干的变化模式.在4770～3700cal.aBP期间,气候较为干旱,随之进入了长达1000多年的湿润阶段,大约从2340cal.aBP开始,气候再次转为干旱.总体上看,石河子地区自5000年以来分布着隐域性植被,一直处于由水生植物芦苇、黑三棱和沼泽蕨等相伴生组成的湿地景观,然而通过2010-2016年对当地植被连续调查的结果表明,在新疆荒漠地带分布的特有湿地类型——小叶桦(Betula microphylla)当今正在遭受着全球气候变化及人类活动的干扰,湿地在退化,小叶桦正濒临灭绝,沼泽蕨的分布正趋减少,因此亟待加强对湿地的保护和濒危物种的保育,大力推进新疆地区的生态建设和文化建设.

Palynology is a branch of botany with an increasingly important role in the development of modern nature science.It was originally established in Europe during the early twentieth century and has flourished in China since the 1950s.This paper discusses the development of palynology in China from the historical,contemporaneous,and future perspectives.Specifically,we focus on the development of Quaternary palynology since 1979.Quaternary palynology involves six research fields:plants and environment,Loess Plateau,ocean,the uplift of the Tibetan Plateau,global climate change,and environmental archaeology in this paper.Palynologists who study environmental changes mainly focus on the relationships among pollen,vegetation,and environment.The high-resolution analyses of pollen records in the surface soil and sediment profiles of Loess Plateaus have promoted the development of information about paleovegetation and paleoenvironment and enabled the comparison of past climate changes and effects of human activities with global changes.By analyzing pollen data from surface water samples and marine drilling cores,palynologists have made significant progress in elucidating the high-resolution evolutionary history of paleovegetation,paleoclimate,and paleomonsoon in South China Sea and its surrounding regions on the time scales of several million years.Such progress has benefitted research on global sea level changes.The uplift of the Tibetan Plateau has been a hot area of research for several years.Palynologists have explored the vegetational,climatic,and environmental features of different periods,such as the Late Glacial,the Last Glacial Maximum,the Younger Dryas,and the Holocene Megathermal,to reveal the mechanism and process of the uplift of the Tibetan Plateau.The application of Quaternary palynology to environmental archeology not only facilitates understanding of the needs of the economic life and food structure of ancestral humans,the evolution of paleoenvironment and the rise and fall of culture,but also promotes current research on the origin of human,agricultural and civilization.Although Quaternary palynology has made remarkable achievements in many research fields,three problems require urgent solutions.First,the low magnification and resolution of optical microscopy complicate palynological identification on the species level and introduce a degree of uncertainty to the reconstruction of paleovegetation,paleoenvironment and paleoclimate.Second,pollen does not show a simple linear relationship with vegetation.Thus,a reliable pollen-vegetation relationship model remains to be established.Third,research on modern pollen processes,which includes pollen production,transportation,source,deposition,and preservation,has a crucial role in the correct explanation of pollen data and quantitative reconstruction of the paleovegetation and paieoenvironment.Global changes and the impact of environmental evolution have provided excellent opportunities and new challenges for the development of Quaternary palynology in the new century.These opportunities and challenges are as follows:First,the accuracy of pollen identification must be improved to establish a reliable pollen-vegetation relationship model.Second,systemic theoretical studies on modern pollen processes,such as pollen production,transportation,source,deposition,and preservation,should be conducted using surfaces,atmosphere,water,and rock as media.Third,the reconstruction of paleovegetation and paleoclimate from the qualitative and quantitative analyses of high-resolution pollen assemblages should receive additional efforts.Pollen records should be analyzed using various mathematical methods.Finally,to distinguish the role of climate change and human activities in vegetation and climate dynamics,human land use data,surface and fossil pollen data,and meteorological data can be combined to quantify paleovegetation and land use patterns using appropriate mathematical models.Therefore,only by relying on the integration of multidisciplinary data and academic cooperation with colleagues at home and abroad can we further improve the Quaternary palynological research in China and better serve the needs of our society and national strategies.

基于对新疆天山东段南坡吐鲁番地区选取的一条沿着海拔高度从2000– –154 m的不同植被带的植物群落样方进行的调查及相应排序分析,结合所采集的36个现代表土花粉样品的孢粉组合图式,初步研究了吐鲁番地区的植被与表土花粉之间的对应关系,并将其与天山北坡的表土花粉谱进行了比较.结果表明吐鲁番地区表土花粉谱按照海拔高度自上至下可划分为4个孢粉组合带,分别对应于山地荒漠草原和荒漠带、戈壁砾石带、典型荒漠带以及盐沼植被带.与天山北坡的表土花粉垂直带谱相比,吐鲁番地区的花粉垂直带谱并不完整,缺少典型的森林和蒿属(Artemisia)荒漠孢粉带.即使在相似的孢粉带,吐鲁番地区的分布高度也高出北坡300 m左右.典型的乔木植物云杉属(Picea)、松属(Pinus)花粉在风力和水流的作用下,表现出明显的超代表性;用来指示干旱区半干旱区气候湿度变化的蒿属与藜科花粉的比值能大致反映出荒漠带的典型特征.此外,研究区内表土花粉组合与环境因子之间的排序分析结果表明,降水量是影响该区表土花粉组合的主要环境因子.与蒿属、藜科花粉相比,白刺属(Nitraria)花粉受降水量的影响较大.

The warming period from Marine Isotope Stage 2 (MIS 2) to the mid-Holocene provides a useful analog for assessing the impact of global warming on plant diversity. Previously published pollen records from ten loess sections across the Chinese Loess Plateau (CLP) have shown that herbs were dominant during both MIS 2 and the mid-Holocene. During MIS 2, the vegetation in the eastern part was characterized mainly by Artemisia, together with Taraxacum-type, Echinops-type and Chenopodiaceae; and by Echinops-type, Chenopodiaceae, Nitraria, Ephedra and Picea in the western part. During the mid-Holocene, Artemisia remained dominant, while Echinops-type, Chenopodiaceae, Nitraria, Ephedra and Picea decreased, and Poaceae became more prevalent. From west to east during the mid-Holocene, Corylus, Quercus and Pinus increased, while Artemisia and Taraxacum-type decreased. In the present study, two indices of plant diversity (richness and evenness) were analyzed using these published pollen data. The results demonstrate that from MIS 2 to the mid-Holocene, plant richness increased at most of the studied sites, while plant evenness decreased. The increase in plant richness during the warming interval is in accordance with numerous geological records, but differs from modern observations of the response of biodiversity to ongoing global warming. The decrease in plant evenness is attributed to the increase in precipitation, associated with the intensification of the East Asian summer monsoon, which resulted in an increase in the dominance of Artemisia, and the corresponding inhibition in the growth of other species. Therefore, our results imply that plant richness in northern China would be expected to increase in a climate warming scenario, while changes in plant evenness would largely depend on interspecific competition within a plant community.

We explore the relationship between modern pollen spectra and vegetation patterns in the Eastern Tibet, China in order to provide information on the representation of pollen taxa and improve the general knowledge of vertical pollen transport. Forty-two modern pollen samples collected in surface soil along two altitudinal transects allowed conclusions on vertical pollen dispersal from the alpine region of Dingqing County, Changdu district in Tibet. Discriminant analyses and detrended correspondence analysis (DCA) of 24 pollen taxa were used to further discuss the difference of modern pollen spectra in these alpine vegetation zones. The surface pollen assemblage is divided into three pollen zones, such as subalpine shrub meadow, montane coniferous forest and shrub steppe with sparse trees. Altitude and precipitation are two primary factors contributing to changes in surface pollen assemblage from alpine vegetation in the eastern Tibet. Large amounts of spruce pollen at higher elevations above the timberline might be introduced from lower elevations by upslope winds. Therefore, the interpretation of spruce pollen in the fossil record must take into account long distance upward wind transport. Moreover, the destruction of coniferous forest in the study area is well illustrated in the modern pollen rain.

To provide information on vegetation patterns and altitudinal distributions of pollen assemblage in surface soil layers, their complicated relationships in a dryland mountain-basin system in northwestern China and a realistic basis for paleovegetational reconstruction, we investigated 86 vegetation quadrats and analyzed 80 soil samples from the surface soil layers along an altitudinal transect on the north slope of the Middle Tianshan Mountains from alpine cushion vegetation at 3,510 m near glacier to desert vegetation at 460 m in the Gurbantunggut Desert. According to surface pollen assemblages and the results of the detrended correspondence analysis, the transect can be divided into six major altitudinal pollen zones as alpine cushion vegetation, alpine and subalpine meadows, montane Picea forest, forest-steppe ecotone, Artemisia desert and typical desert, which basically reflect the characteristics of the mountainous vegetation patterns on the north slope of the Middle Tianshan Mountains. However, Picea pollen also exists outside the spruce forest, Chenopodiaceae and Artemisia pollen appeared above the elevation of 1,300 m, indicating that most of them might be introduced from lower elevations by upslope winds. Airborne pollen researches from three regions at different elevations further suggest that a high-frequency northwest anabatic wind has a remarkable influence on the transportation and dispersion of surface pollen in the area.

如果说“将今论古”、“温故知新”作为古生物学和考古学的基本思路的话,那么“过去是了解现在及未来的钥匙”则成为古生物学研究者们的努力方向.孢粉学工作者则依据这样的思路,探讨北京地区植被的过去、现在及其未来.