Repeated high-grade metamorphic overprinting usually results in incomplete reequilibrium. This blurs the pressure-temperature-time (P-T-t) information preserved in ancient terranes, complicating the reconstruction of orogenic evolution and tectonics. This study investigated metabasites from the Daqingshan area of the North China Craton, comparing samples distal and proximal to the deformation zone. An undeformed granulite and a plastically deformed amphibolite both record an earlier ultrahightemperature (UHT) metamorphism peaking at 950-1000 degrees C and 8-9 kbar with post-peak cooling ending at fluid-absent solidi, followed by a later granulite-facies overprinting to peak conditions of 8-9 kbar and 870-890 degrees C, likely driven by prograde hydrational P-T rises. These P-T conditions were reliably constrained by three key factors: tetrahedral Al in clinopyroxene, anorthite in plagioclase, and Ti in amphibole. The overprinting assemblages vary in extent between samples (e.g., local embryos versus widespread neoblasts), suggesting that more complete petrologic records of metamorphic overprinting benefit from deformation and fluid availability. Moreover, zircon and monazite dating show that the earlier UHT metamorphism cooled at 1.94-1.92 Ga, whereas the later overprinting occurred at 1.87-1.83 Ga. The UHT metamorphism is attributed to postorogenic or backarc extension, preceded by an orogenic event that produced high-pressure granulite-facies metamorphism at ca. 1.96-1.94 Ga. The granulite-facies overprinting is attributed to a separate orogenic event involving typical crustal thickening after the UHT metamorphism, based on its P-T path and nearby geologic data.

In this study, using the data from laser disdrometer, S-band dual-polarization radars and conventional observations, the microphysical parameters and characteristics of precipitation particles during an elevated thunderstorm event in Henan Province, China occurred on February 24, 2021 were analyzed. The results indicate that: (1) The synoptic pattern during this precipitation process followed a typical cold-season elevated thunderstorm structure, extending from upper layers to the surface. Strong echo height exceeding the-20 degrees C layer was the main reason for the formation of ice-phase particles and lightning. (2) Precipitation particles displayed different size-distribution models and disparate phases during the diverse precipitation stages. During the initial stage, the particle size distribution displayed a single-peak pattern, primarily composed of drizzle and ice pellets. In the development stage, the size distribution showed both single-peak and multi-peak patterns, with particles including freezing rain, graupel, and small ice crystals. During the subsequent stable snowfall stage, the precipitation was mainly consisted of various morphological ice crystals, graupel, and wet snow particles dominated by small solid particles with a diameter less than 1 mm, the peak number concentration was 0.69 mm in diameter, and their terminal velocities were stable at 1 m s-1. (3) During the snowfall, enhanced Zdr and Kdp characteristics are observed in the upper cloud layers, with the height of Kdp maximum located below that of Zdr peak, indicating a distinct seeder-feeder mechanism in the precipitation. In the atmospheric layer of tempereature from-20 degrees C to-10 degrees C, the Bergeron process facilitated rapid ice crystal growth through vapor deposition, leading to the formation of ice-crystal aggregates and promoting sleet formation. (4) The primary mechanism of snowflake formation was the deposition and aggregation processes, and the riming and coalescence processes played a significant role in the descent of the particles. The formation of large snowflakes was attributed to the collision and aggregation of smaller snowflakes, as well as riming growth. The microphysical characteristics revealed in this study hold significant implications for understanding atmospheric physical process, improving the accuracy of cold-season weather forecasting, and optimizing weather modification operations.

Located in the northwestern edge of the modern Asian summer monsoon (ASM), the northeastern Tibetan Plateau (NETP) is sensitive to changes of the ASM climate. However, variations of climate and vegetation during the Holocene remain unclear in this marginal region of the monsoon climate. Here we present a Holocene highresolution pollen record from Lake Gahai in the NETP since 11.4 (+/- 0.3) ka BP to reconstruct regional vegetation history. A quantitative reconstruction of precipitation is also tried using fossil pollen assemblages. Results suggested that before 10.2 (+/- 0.4) ka BP in the early Holocene, the vegetation cover was low and the climate was arid. A relatively wet climate indicated by high A/C ratio values occurred between 10.2 (+/- 0.4) and 7.4 (+/- 0.2) ka BP. After 7.4 (+/- 0.2) ka BP, the A/C ratio decreased, indicating that the climate was getting drier. The overall environment of the basin has become similar to modern conditions since 5.4 (+/- 0.1) ka BP. The reconstructed precipitation is not comparable with the tree-ring-based reconstruction from the Delingha region, although the reconstruction processes passed significance tests statistically. In addition to abundant surface pollen data and gradually improved quantitative reconstruction techniques, other factors such as the environmental settings and vegetation dynamics also affect the reliability of the pollen-based quantitative reconstruction of regional precipitation. Therefore, the applicability of pollen data for quantitative precipitation reconstruction in arid regions should be assessed and the results should be treated cautiously.

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.

Asia's mountainous arid and semiarid regions feature forests in wet high-mountain areas and grasslands/deserts in dry basins. Assessing changes in millennial-scale effective moisture in mountain-basin systems can provide a valuable reference for understanding how climate change and human activities affect terrestrial water resources and drylands. Here, a continuous pollen record from Genggahai Lake on the northeastern Qinghai-Tibetan Plateau exhibited detailed changes in regional vegetation and effective moisture since similar to 15.3 ka. The pollen sequence suggests that steppe vegetation developed in the basin and that sparse forest vegetation developed in the surrounding mountain areas during 15.3-11.7 ka and 6.3-0 ka, and that desert steppe vegetation developed in the basin and denser forest vegetation developed in the surrounding mountain areas during 11.7-6.3 ka. Based on comparison of regional palaeoclimatic records, the pollen assemblage results suggest antiphase moisture changes between mountains and the basin and imply that the low Artemisia/Chenopodiaceae (A/C) ratio during 11.7-6.3 ka in the basin likely indicates that the low effective moisture conditions likely resulted from the high permeability of loose and porous sediments and the high evaporation in the basin induced by high summer solar insolation. In contrast, the high A/C ratio during 15.3-11.7 ka and 6.3-0 ka indicates a high level of effective moisture during these periods, possibly in response to less evapotranspiration loss in the basin caused by the strong water-binding capacity of palaeosols, ameliorated vegetation conditions, and low summer solar insolation. Our results also suggest that both climatic conditions and anthropogenic activities may have altered the natural vegetation in the late Holocene and that change in the percentage of tree pollen from Genggahai Lake were synchronous with changes in the intensity of the Indian summer monsoon.

通过对宜昌大老岭自然保护区不同海拔的16个表土样品孢粉分析,结合植被调查研究该地现代表土孢粉组合与植被的关系.结果表明,大老岭常绿与落叶阔叶混交林、针阔叶混交林孢粉组合中,针叶乔木的松属呈超代表性,铁杉呈适中的代表性;落叶阔叶乔木以栎属为优势成分,具高代表性,蔷薇科、桦木属、鹅耳枥属、胡桃属、水青冈属具有适中的代表性;青冈属代表性适中,杜鹃花科、忍冬科呈现低代表性,草本禾本科、菊科蒿属在山区的代表性差异明显;蕨类普遍具有超代表性,孢粉组合基本反映了现生亚热带北缘山区针阔叶混交林的主要植被特征.受花粉自身特点、小生境与人类活动的影响,花粉组合与植被类型存在一定的偏差.主成分分析(PCA)结果表明,影响大老岭抱粉科属变化的主要环境因子是温度.表土花粉E/D值(常绿阔叶乔木/落叶阔叶乔木)随着海拔的升高而降低,反映了山地植被中常绿阔叶乔木减少、落叶阔叶乔木增多的变化趋势.

The past 2000 years represent an important period of climate change. The Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) have attracted much attention, but the start and end times and humidity characteristics of these climate stages are still controversial. Here, we present a lacustrine sediment record from the Erxianyan wetland in central China covering a timespan of 1900 years. The pollen, grain size, total organic carbon (TOC) content, total nitrogen (TN) and carbon-to-nitrogen ratio (C/N) analyses of the sediments derived from the Erxianyan wetland revealed the vegetation and climate changes that have occurred in central China over the past 1900 years. From 70 to 740 CE, the water level was high, the organic matter content of the lake reached a high level, and many plants surrounded the lake. The climate was warm and humid. From 740 to 1150 CE, the forest coverage increased, the fern coverage decreased, and the lake water volume decreased. The climate gradually changed from humid to dry. From 1150 to 1990 CE, the vegetation coverage around the lake decreased, the tree proportion declined, and the proportions of terrestrial herbs and ferns increased. The climate was cold and dry. The climate change characteristics reflected in the EXY profile roughly correspond to the Qin-Han Warm Period and Sui-Tang Warm Period. The MCA was warm and dry, while the LIA was cold and arid. Based on comparisons with other climate records and modern precipitation records, we found that the Erxianyan climate changes over the past 1900 years may have been affected by the combined effects of solar radiation, the El Nin & SIM;o-Southern Oscillation (ENSO) and the East Asian Summer Monsoon (EASM). These results also confirm the complexity of the climate in the middle and upper reaches of the Yangtze River during the MCA and the LIA.

Vegetation phenology, a regular and periodic phenomenon in nature, is an important indicator for natural environment, especially climate change. The study of spatiotemporal variations of vegetation phenology is of great significance for monitoring the changes of terrestrial vegetation. In this study, the Savitzky-Golay (S-G) filtering method was used to reconstruct time-series MODIS enhanced vegetation index (EVI) data in the Qinling Mountains from 2001 to 2018. The dynamic threshold method was used to extract the spring phenological parameter (start of growth season, SOS). The correlation between multi-year mean SOS and interannual variation with altitude and slope was analyzed. The results showed that SOS was delayed by 1.82 d with every 100 m increase in altitude in the Qinling Mountains. The interannual change trends of SOS mainly concentrated in 0-5 d·(10 a)-1. The pixels with delaying trend were mainly distributed in low-altitude regions, with the delaying degree being gradually decreased with the elevation. The interannual change trend of SOS in high-altitude regions was more complex than that in lower-altitude regions. The multi-year average SOS in the northern slope was approximately 2.9 d earlier than that of the southern slope, whereas the southern slope had a more significant advancing trend. The interannual change trends of SOS in both north and south slopes showed a delaying trend in low-altitude, with little difference between north and south slopes. The advancing trend in middle and high altitude was significantly different.

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.

During the latter stages of the Holocene, and prior to anthropogenic global warming, the Earth underwent a period of cooling called the neoglacial. The neoglacial is associated with declining summer insolation and changes to Earth's surface albedo. Although impacts varied globally, in China the neoglacial was generally associated with a cooler climate and an attenuated Asian summer monsoon. Few studies in central China, however, have explored the impact of neoglacial cooling on freshwater diversity, especially in alpine regions. Here we take a palaeolimnological approach to characterise multi-decadal variability in diatom community composition, ecological guilds, and compositional turnover over the past 3500 years from the alpine Yuhuang Chi lake on Mount Taibai in the Qinling mountains. Diatoms in the high-profile guild dominate much of the record from 3500 to 615 cal BP, which suggests that few nutrients in the lake were limiting overall, and disturbance and herbivory were likely low. After 615 cal BP, low-profile and planktic guild diatoms increase, suggesting greater turbulence in the lake, alongside a decline in available nutrients. Diatom turnover highlights periods in the lake history when deterministic processes structured diatom communities. For example, an abrupt decline in turnover is coincident with the shift from high- to low-profile diatoms at 615 cal BP, and this is likely due to the onset of the Little Ice Age in the region. We suggest that Yuhuang Chi lake became more shallow during peak regional aridity, which led to the short-lived community restructuring observed in the record.

Ongoing global warming will have a significant impact on terrestrial water resources, especially in arid and semi-arid regions. Assessing changes in the hydrology and water resources in inland basins under a warm climate in the recent geological past can provide a valuable context for assessing their current and possible future status. Here we present a record from a rapidly-accumulating sediment core from Lake Dalianhai in the Gonghe Basin in the northeastern Tibetan Plateau. The chronology of the uppermost 51.63 m of the core is based on AMS C-14 dates from 11 samples of terrestrial plant microfossils and 14 bulk samples. Hydroclimatic variations within the basin during the last 23,000 yr were reconstructed from sedimentological and geochemical parameters and paleoshoreline records. The results indicate that the Gonghe Basin experienced relatively arid conditions during 23,000-14,700 cal yr BP. Lake Dalianhai was refilled at 14,700 cal yr BP and a high lake level was sustained until the beginning of the Holocene, as indicated by changes in the concentration of OH-GDGTs. However, the lake level was low during the early to middle Holocene (11,700-4700 cal yr BP) and increased during the late Holocene. Based on a comparison with lake level records and aeolian sand deposits from the region, we conclude that the climate was extremely dry in basins in the northeastern Tibetan Plateau during the early to middle Holocene. We propose that strong evaporation combined with high summer temperatures during the early to middle Holocene were responsible for the dry climate at that time, rather than changes in mid-latitude precipitation. Given the situation occurred during the early to middle Holocene, ongoing global warming may seriously threaten water resources in inland China, even if precipitation increases substantially. (C) 2020 Elsevier Ltd. All rights reserved.

通过柴达木盆地东北部地区不同植被类型的32个表土样品花粉分析与植被调查,对本区现代表土花粉组合及其与植被类型之间的关系进行了研究.结果表明,柴达木盆地东北部地区不同的植被类型具有相对独特的花粉组合特征.高寒荒漠花粉组合为禾本科+菊科+藜科型,高山草甸花粉组合为莎草科+禾本科+紫菀+菊科型,草原花粉组合为菊科+蒿属+禾本科+藜科型,荒漠草原花粉组合为蒿属+藜科+禾本科+菊科型,荒漠花粉组合为藜科+白刺+蒿属型,隐域草甸花粉组合为禾本科+藜科+莎草科+蒿属型;柴达木盆地东北部地区花粉与植物之间的关系复杂,同一花粉在不同植被类型中的代表性存在差异.蒿、藜花粉基本呈超代表性,但是在藜科植物占优势的荒漠中,藜科花粉呈等代表性.禾本科花粉在高寒荒漠呈超代表性,在高山草甸、草原、荒漠草原、荒漠及隐域草甸均呈低代表性.菊科花粉在高寒荒漠呈超代表性,在高山草甸呈等代表性,在草原、荒漠草原及荒漠呈低代表性.莎草科花粉在高山草甸呈等代表性,在高寒荒漠、草原及隐域草甸呈低代表性.白刺花粉呈等代表性.蔷薇科、豆科花粉呈低代表性;主成分分析结果显示,湿度条件的变化可能是影响柴达木盆地东北部地区各个植被类型花粉组合特征的主要因素.高山草甸、草原、荒漠的样品在前两个主因子组成的坐标系中差异明显,能较好地区分开.但高寒荒漠、荒漠草原和草原的样品因花粉组合较相似而难以区分;蒿/藜可以作为反映干湿状况的良好指标,但蒿藜花粉之和应≥20％.本研究中,蒿藜花粉之和在高山草甸中平均含量＜20％,蒿/藜偏低,不能反映高山草甸的湿润状况.高寒荒漠、草原、荒漠草原、荒漠中蒿藜花粉之和平均含量＞20％,蒿/藜从草原-荒漠草原-荒漠逐渐降低,反映出环境逐渐干燥的趋势.蒿/莎草可以将高山草甸及其他植被类型区分开.

亚洲夏季风是全球季风系统的重要组成部分,亚洲夏季风的变化对其控制区域自然生态系统的多样性和生态平衡,以及社会经济发展有重要的影响.本文选择位于现代亚洲夏季风边缘区对季风变化响应敏感的湖泊达连海为研究对象,基于陆生植物残体和全有机质的AMS14C定年建立了钻孔顶部24.6m沉积物的年代框架,利用粒度指标重建了全新世研究区水文变化过程以及亚洲夏季风衰退事件序列.结果 显示,沉积物中存在数层砂层,代表了湖泊低水位时期,进而指示了亚洲夏季风衰退事件.这些事件处在11.6～ 11.3 cal.ka B.P.、10.4～9.5 cal.ka B.P.、6.4～6.0 cal.ka B.P.、4.6～4.4 cal.ka B.P.、3.7～ 3.4 cal.ka B.P.、3.1～2.9 cal.ka B.P.以及2.0～0.9 cal.ka B.P.,可以发现中晚全新世以来亚洲夏季风衰退事件发生的频率显著增加.进一步与北半球高纬地区与低纬地区的气候突变事件记录对比显示,全新世百年-千年时间尺度上亚洲夏季风强度的变化与低纬ENSO活动存在密切的联系.

Sensitive changes in precipitation influence the stability of semiarid ecosystem, rain-fed agriculture, and densely populated society in northern monsoonal China (NC). However, shortage of regional-scale quantitative syntheses imposes restrictions on investigating long-term relationships among precipitation dynamics, possible climatic forces, and prehistoric demographic fluctuations. Herein, we contribute a regionally compiled anomaly record for Holocene annual mean precipitation (PANN) relative to its modern-day values in NC. The Holocene PANN variations in NC may be essentially determined by changing thermal gradients of continental land-ocean and west-east equatorial Pacific, profoundly affecting strength and location of West Pacific Subtropical High that may principally modulate intensity of East Asian summer monsoon and resultant rainfall in NC. Importantly, variation partitioning analysis quantitatively demonstrates that the overall changes of precipitation (43.3%) may play a more important role than temperature (3.2%) and their shared effects (0.8%) in independently accounting for long-term variation of regional-scale Holocene population fluctuations in NC. Plain Language Summary Quantitative inferences of regional-scale precipitation fluctuations on time spans longer than instrumental climatic records are requested to better predict long-term changes of East Asian summer monsoon that influences the lives of nearly one fourth of the total population in our world. Evaluating the possible role of large-scale climatic changes on affecting human population sizes of the distant past is a pressing concern and remains contentious. In this study, for the first time, we provide a regionally synthesized record of Holocene precipitation anomalies relative to present-day values for the monsoon-influenced northern China. This composite record has been demonstrated to be reliable as a representative for reflecting broad-scale precipitation variations across northern China. In addition, we first quantify the relative contribution from both precipitation and temperature on influencing the Holocene demographic changes in northern China. Our results suggest that precipitation may be more important compared with temperature when independently explaining the total variation in long-term prehistoric population patterns.

Our understanding on the spatial-temporal patterns of climatic variability over the last few millennia in the East Asian monsoon-dominated northern China (NC), and its role at a macro-scale in affecting the prosperity and depression of Chinese dynasties is limited. Quantitative high-resolution, regionally-synthesized palaeoclimatic reconstructions as well as simulations, and numerical analyses of their relationships with various fine-scale, numerical agro-ecological, social-economic, and geo-political historical records during the period of China's history, are presented here for NC. We utilize pollen data together with climate modeling to reconstruct and simulate decadal- to centennial-scale variations in precipitation or temperature for NC during the last 2200 years (-200–2000 AD). We find an overall cyclic-pattern (wet/warm or dry/cold) in the precipitation and temperature anomalies on centennial- to millennial-scale that can be likely considered as a representative for the entire NC by comparison with other related climatic records. We suggest that solar activity may play a key role in driving the climatic fluctuations in NC during the last 22 centuries, with its quasi ∼100, 50, 23, or 22-year periodicity clearly identified in our climatic reconstructions. We employ variation partitioning and redundancy analysis to quantify the independent effects of climatic factors on accounting for the total variation of 17 fine-grained numerical Chinese historical records. We quantitatively illustrate that precipitation (67.4%) may have been more important than temperature (32.5%) in causing the overall agro-ecological and macro-geopolitical shifts in imperial China with NC as the central ruling region and an agricultural heartland over the last 2200 years.

The spatial and temporal variations of microcystins (MCs) in fishes with different trophic levels were studied monthly in Lake Chaohu in 2014. MCs content in muscle was highest in phytoplanktivorous Hypophthalmichthys molitrix (H. molitrix), followed by omnivorous Carassius auratus (C. auratus), and was lowest in herbivorous Parabramis pekinensis (P. pekinensis) and carnivorous Coilia ectenes (C. ectenes). MCs concentration in liver was highest in C. auratus, followed by H. molitrix, and was lowest in P. pekinensis and C. ectene. The main uptake routes of MCs for C. auratus and H. molitrix were via the diet. The mechanism to counteract MCs had not been well developed in C. ectenes. H. molitrix and C. auratus from the western region as they had higher mean concentrations of MCs than fishes from the eastern region. The estimated daily intakes of MCs in 45.4% of muscle samples were higher than the provisional tolerable daily intake set by WHO.

Quantitative information regarding the long-term variability of precipitation and vegetation during the period covering both the Late Glacial and the Holocene on the Qinghai-Tibetan Plateau (QTP) is scarce. Herein, we provide new and numerical reconstructions for annual mean precipitation (PANN) and vegetation history over the last 18,000 years using high-resolution pollen data from Lakes Dalianhai and Qinghai on the northeastern QTP. Hitherto, five calibration techniques including weighted averaging, weighted average-partial least squares regression, modern analogue technique, locally weighted weighted averaging regression, and maximum likelihood were first employed to construct robust inference models and to produce reliable PANN estimates on the QTP. The biomization method was applied for reconstructing the vegetation dynamics. The study area was dominated by steppe and characterized with a highly variable, relatively dry climate at similar to 18,000-11,000 cal years B.P. PANN increased since the early Holocene, obtained a maximum at similar to 8000-3000 cal years B.P. with coniferous-temperate mixed forest as the dominant biome, and thereafter declined to present. The PANN reconstructions are broadly consistent with other proxy-based paleoclimatic records from the northeastern QTP and the northern region of monsoonal China. The possible mechanisms behind the precipitation changes may be tentatively attributed to the internal feedback processes of higher latitude (e.g., North Atlantic) and lower latitude (e.g., subtropical monsoon) competing climatic regimes, which are primarily modulated by solar energy output as the external driving force. These findings may provide important insights into understanding the future Asian precipitation dynamics under the projected global warming.

The seasonal variations of taste and odor (T&O) compounds in western Lake Chaohu were evaluated from July to December 2013. High values were detected in particulate fractions, with peak values 28.25 ng/L for geosmin (GEO), 45.18 ng/L for dimethyltrisulfide (DMTS), 714.77 ng/L for β-cyclocitral, 11.23 ng/L for β-ionone in surface water, and 14.21 ng/L for GEO, 103.68 ng/L for DMTS, 11.97 ng/L for β-ionone in overlying water, all exceeding their odor thresholds. The maximum off-flavor concentrations in sediment ranged from 2010.76 ng/kg for GEO to 1.7 ng/kg for β-ionone. Positive correlations could be found not only between Anabaena and particulate GEO (r = 0.813, p < 0.01), but also between Microcystis and total β-cyclocitral (r = 0.652, p < 0.01) or β-ionone (r = 0.560, p < 0.01) in surface water. TP, TN, PO 4 -P, Chl-a and organic matter contributed significantly to the variations of T&O compounds in water or sediment. The cause of the variations of T&O compounds was the accumulation and degradation of cyanobacteria in water rather than nutrient-rich sediment.

在青藏高原北缘共和盆地达连海钻取了40.92 m沉积柱,其“C年代有10个控制点,底部年龄最大值为14.5 cal ka BP,沉积柱为末次冰消期以来的湖泊沉积物.在沉积柱中按20 cm/70 a分辨率选出200个样品进行了黏土矿物、粒度、碳酸盐、沉积速率等非生物指标与生物指标的孢粉等多项指标的综合分析.结果表明:末次冰消期以来,达连海沉积柱中非生物指标与生物指标反映的气候和环境变化阶段的显著性不同,反映的气候环境的变化阶段也不尽一致,出现气候环境的相位差.冰消期黏土矿物非生物指标与孢粉生物指标有约1.0～1.2 ka的相位差;早、中全新世黏土矿物反映的气候变化时段较孢粉指标指示的时段滞后约1.0 ka;在晚全新世黏土矿物反映的气候变化较孢粉滞后约0.1 ka.造成黏土矿物和孢粉反映气候环境相位差的原因是孢粉和黏土矿物对气候响应的差异性、黏土矿物和孢粉搬运方式的不同、气候条件及其转换、地貌等多因素的综合影响.