Modern Surface Pollen Research Articles

Modern pollen and non-pollen palynomorphs from sub-tropical central India: discerning anthropogenic signal in surface pollen assemblages

Interpretation of past vegetation using pollen analysis depends on our understanding about the relationship between the modern vegetation and surface pollen assemblages. In the present study, we sampled the modern pollen-rain in a mixed environment of cultivated land and dry and wet tropical forests in central India. We established to which extent modern vegetation types are reflected in the pollen-rain and explained biases in the modern pollen spectra. Our study revealed that the modern pollen assemblages do not fully represent the extant regional vegetation, as many of the forest components, especially trees and shrubs, are either under-represented or remained palynologically silent in the pollen records. Low pollen productivity of most of the tropical deciduous taxa, owing to entomophily, as well as low preservation potential of some tree pollen are primarily responsible for this irregularity in their representation in the pollen spectra. Moreover, Shorea robusta and Tectona grandis pollen, despite being high pollen producers, are not encountered in any sample, which could be further attributed to their poor preservation in surface soil samples, as well as to their low (pollen) dispersal efficiency. Cerealia, Amaranthaceae, Caryophyllaceae, Brassicaceae, Cannabis sativa, Artemisia spp. and Alternanthera spp. indicate agricultural practices and other human activities around the respective study areas. Moreover, the consistent presence of Asteroideae pollen indicates pastoral activities, whereas Sporormiella spp., Sordaria spp., Podosora spp., Delitschia spp., and Cercophora spp. indicate local grazing and herbivory.

Quantitative relationship between modern surface pollen and plant community at quadrat scale.

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.

Dinámica de la vegetación andina del lago Argentino (50° S, 72° O) desde el retiro de los glaciares (ca. 12.000 años cal AP)

Paleoecological studies in Patagonia provide information about vegetation and climate changes occurred during the Holocene. The climatic evolution of this region offers a unique opportunity to study the environmental variability as well as the ecosystem variations. The dynamic of the forest ecosystems is modulated by the occurrence of disturbances. Fires are one of the most important disturbances in temperate forest ecosystems, and its study allows contrasting independently about the changes experienced by ecosystems. In addition, in Patagonia, environmental and postglacial vegetation changes have been determined by variations in the temperature and westerlies winds. In order to reconstruct changes experienced by the forest ecosystem and patterns of plant diversity during the Holocene, in relation to Postglacial dynamics, natural and anthropic disturbances in the Lake Argentino, pollen and charcoal were studied in a sedimentary sequence at Península Avellaneda. Pollen assemblages suggest non-cyclic changes in plant diversity during the Holocene. The highly diverse cold grass-shrub communities dominated the area up to the Early Holocene, when they were displaced upland by less diverse forest and steppes. Also, The Early and Midd-Holocene was characterized by opposite variations of hydric balance between Andean and extra-andean plant communities present between 48° and 50° S, whereas fire activity occurs synchronously between forest (Andean) and steppe communities (Extra-andean). Late Holocene is characterized by different proxy signals depending on the geographical location of the paleoecological records. To conclude, this work provides a better understanding of the fossil pollen record by its comparison with modern surface pollen samples along an altitudinal vegetation gradient.

Spruce representation in zonal woodlands may be overestimated when using pollen spectra from peatlands

The proportion of taxa in a pollen spectrum may not correspond to their proportion in vegetation. Quantitative reconstruction models therefore consider pollen productivities or fall speeds. We argue that azonal presence of spruce, an otherwise zonal tree species, in wetlands may confound the pollen-inferred reconstructions of vegetation cover as well. Based on a large database of vegetation plots from the Western Carpathians, we demonstrate that spruce is the tree species which most frequently colonizes peatlands, more so than alder, whose effect on local pollen spectra has been frequently admitted. Using 73 sequences we further demonstrated significantly greater pollen percentages of spruce of about 20–25% when the sediments contain spruce macrofossils. Finally, we compared the proportions of spruce and beech in modern surface pollen spectra with their real proportions in the surrounding landscape where beech acts as zonal tree. We found that even a small patch of spruce alters the proportion of spruce to beech. By contrast in an open fen we observed pollen spectrum corresponding well with the real proportions of spruce and beech. All these results suggest, contrary to the premises of current models of pollen-based quantitative reconstructions in Central Europe, that fossil pollen counts from wetlands did not underestimate the representation of spruce. Instead, its representation may even be overestimated where it occurred within or in close vicinity of a wetland. We appeal to palynologists to consider macrofossils or stomata in interpretations, and to adjust quantitative reconstruction models for sites that have experienced a woodland history.

Regional-scale distributions of pollen and spore assemblages in alluvium around the Bohai Sea: An essential step toward understanding marine palynological sources in China

To better understand the provenance and transport paths of modern pollen and spores in the Bohai Sea, we analyzed 104 surface alluvial samples from its sixteen inflowing rivers and 56 modern surface pollen samples from around Bohai Sea in the East Asia Surface Pollen Database. Our results revealed that the pollen assemblages of the inflowing rivers were dominated by non-arboreal pollen types, which accounted for an average of 60% of the pollen and were represented primarily by Chenopodiaceae; the percentages of arboreal pollen reached an average of 23%; fern spores accounted for the lowest percentage of the spores and pollen. The characteristics of the pollen assemblages in the alluvium of the inflowing rivers, especially large rivers, reflected the vegetation of upstream sampling points rather than the characteristics of the vegetation around the sampling points. The vegetation types represented by the pollen and spores in the short-source rivers or seasonal rivers were beyond the range of the drainage basin, especially the trees and ferns, and differences of the watershed vegetation of the inflowing rivers led to different pollen assemblages in the alluvium in the study area. The Yellow River is the main source of modern surface pollen in the Bohai Sea. Unlike the pollen of the inflowing rivers, the pollen assemblages in the Bohai Sea were dominated by arboreal pollen, especially Pinus. The fern spores were dominated by Selaginella, but non-arboreal pollen accounted for relatively low percentages of the pollen.

A prognostic pollen emissions model for climate models (PECM1.0)

Abstract. We develop a prognostic model called Pollen Emissions for Climate Models (PECM) for use within regional and global climate models to simulate pollen counts over the seasonal cycle based on geography, vegetation type, and meteorological parameters. Using modern surface pollen count data, empirical relationships between prior-year annual average temperature and pollen season start dates and end dates are developed for deciduous broadleaf trees (Acer, Alnus, Betula, Fraxinus, Morus, Platanus, Populus, Quercus, Ulmus), evergreen needleleaf trees (Cupressaceae, Pinaceae), grasses (Poaceae; C3, C4), and ragweed (Ambrosia). This regression model explains as much as 57 % of the variance in pollen phenological dates, and it is used to create a climate-flexible phenology that can be used to study the response of wind-driven pollen emissions to climate change. The emissions model is evaluated in the Regional Climate Model version 4 (RegCM4) over the continental United States by prescribing an emission potential from PECM and transporting pollen as aerosol tracers. We evaluate two different pollen emissions scenarios in the model using (1) a taxa-specific land cover database, phenology, and emission potential, and (2) a plant functional type (PFT) land cover, phenology, and emission potential. The simulated surface pollen concentrations for both simulations are evaluated against observed surface pollen counts in five climatic subregions. Given prescribed pollen emissions, the RegCM4 simulates observed concentrations within an order of magnitude, although the performance of the simulations in any subregion is strongly related to the land cover representation and the number of observation sites used to create the empirical phenological relationship. The taxa-based model provides a better representation of the phenology of tree-based pollen counts than the PFT-based model; however, we note that the PFT-based version provides a useful and climate-flexible emissions model for the general representation of the pollen phenology over the United States.

Migration of legacy data to new media formats for long-time storage and maximum visibility: Modern pollen data from the Canadian Arctic (1972/1973)

This Data Management Plan (DMP) was created using the DMPTool. It describes modern pollen data collected along a 2500 mile (~4000 km) transect in the Canadian Arctic in 1972/73 as part of an NSF funded research project (GB-33497). The project was undertaken at the Institute of Arctic and Alpine Research at the University of Colorado Boulder. This legacy dataset originally stored as a paper copy and on 35-mm film will be migrated to digital formats that allow upload of the dataset to an international open-access library for permanent storage and visibility. This DMP was submitted to the 2015 Best Digital Data Management Plan and Practices - Competition (https://data.colorado.edu/cudmpguidance). The study provides a baseline pollen dataset for the interpretation of Holocene pollen diagrams from this region and for comparison with modern surface pollen samples, allowing the assessment of the effects of modern climate change on Arctic and subarctic ecosystems.

Modern surface pollen assemblages from the Middle and High Atlas, Morocco: insights into pollen representation and transport

Thirty-three modern surface samples were collected in the environmentally and climatologically contrasting regions of the Middle and High Atlas Mountains, Morocco. Samples representing forest and steppe montane environments (1935–2760 m above sea level) are clustered around study sites at Lake Tislit (High Atlas, semi-arid oro-Mediterranean bioclime) and Lake Sidi Ali and Michliffen (Middle Atlas, sub-humid montane Mediterranean bioclime). Good discrimination between regional pollen spectra is evident, with Middle Atlas samples reflecting higher arboreal cover (Cedrus and evergreen Quercus) and High Atlas samples with high abundances of non-arboreal taxa, including Artemisia and Fabaceae. These four taxa (Cedrus, evergreen Quercus, Artemisia and Fabaceae) are furthermore shown to be reliable indicators of local source vegetation within a 100 m2 quadrat, taking into account threshold abundances of 7%, 20%, 4% and 10%, respectively. Deciduous Quercus, Olea and Phillyrea show long-distance pollen dispersal across both regions, contributing to non-trivial arboreal pollen (AP) values of up to 35% (typically 20–30%) in the High Atlas spectra. In the Middle Atlas, AP values of 40 to 50% occur in open sampling locations and > 60% under forest canopy cover. These insights should be taken into account when interpreting ancient pollen spectra from regional lakes and bogs for palaeoenvironmental reconstruction.

Pollen-based temperature reconstructions from Jeju island, South Korea and its implication for coastal climate of East Asia during the late Pleistocene and early Holocene

We derived statistically robust, Weighted Averaging Partial Least Squares (WAPLS) transfer functions using modern surface pollen samples from Mt. Halla in Jeju Island, Korea. Pollen-based temperature reconstructions were performed by applying the best transfer function to lake sediments from Hanon maar paleolake in the southern part of Jeju Island. These quantitatively reconstructed temperatures were thereafter adjusted for the lack of warm analogue with the aid of Japanese and Russian transfer functions. Our temperature reconstructions demonstrated that annual mean temperatures during the Last Glacial Maximum (LGM) were ~8.5°C, i.e., about 8°C lower than the present, and that the Younger Dryas (YD) cooling amplitude was ~1.5°C between Bølling–Allerød (BA) (~11.3°C) and YD (~9.8°C). Spectral and wavelet analyses on detrended paleotemperatures identified significant periodicities at 1340years, primarily after 13,000calyr BP. The influence of Antarctic deglacial climate on the western North Pacific probably decreased with increasing northern latitude, as expected. Our results and Borneo oxygen isotope data showed very high correlation, indicating that Jeju Island was substantially influenced by the deglacial variabilities of the western Pacific warm pool via the Kuroshio Current. The climate of the study area seemed to have been mainly controlled by variation in the Atlantic Meridional Overturning Circulation (AMOC) before the beginning of the last deglaciation and subsequently by variation in the Western Tropical Pacific (WTP) Sea Surface Temperature (SST). We present significant information on the correlation of the late Pleistocene climate change with the Greenland oxygen isotope data and western North Pacific SST records. This correlation bridges the gap between terrestrial records, which mostly show AMOC variability, and oceanic records, which show WTP variability. These study results will increase our understanding of regional-scale climate change during the late Pleistocene and Early Holocene.

Palynological differentiation of savanna types in Carajás, Brazil (southeastern Amazonia)

Pollen rain studies in Amazonia are scarce but of utmost importance to support interpretations of pollen records. We have investigated modern surface pollen spectra and vegetation in an Amazon location, Carajás, Brazil, where open and woody types of vegetation, swamps and lakes develop under rock outcrops. Both plant inventories of different savanna types along with bryophytic surface samples were analysed with ecological ordination. The results point to taxa that can be used in the differentiation of dry and flooded systems within the savannas studied. Dry savannas, either open or wooded, are indicated by the herbs Cuphea, Asteraceae, Borreria, Caryophyllaceae and Polygonaceae, and by woody taxa such as Myrtaceae, Byrsonima, Sapotaceae, Neea and Rubiaceae. Flooded savannas (swamps) and lakes are indicated by herbs like Sagittaria, Montrichardia, Nymphaea, Cyperaceae and Mimosa and palms. Poaceae was found to have a bipolar signature, and using it as an indicator should be done with caution.

新疆石河子南山地区表土花粉研究

天山作为亚洲大陆最大的山系之一,横贯于新疆的中部,成为分隔南、北疆自然地理区系的山系,它对花粉的传播、保存、搬运与沉积具有重大作用。根据对西北干旱区域新疆石河子南山地区一条沿着海拔高度从2400 m到300 m的样带所采集的23个表土花粉样品的孢粉组合图式和现代植被样方调查资料,探讨了北坡垂直带的植被与表土花粉之间的关系。该区表土孢粉谱可分为4个孢粉组合带,分别对应森林植被带、森林草原植被带、蒿属荒漠带和典型荒漠带。比较特殊的是典型荒漠带被划分为两个亚带,一个亚带是以蒿属、藜科占主要成分的典型荒漠带,另一亚带蒿属、藜科含量较高并含有大量沼泽蕨和芦苇植硅体,兼具典型荒漠和湿地特征。在海拔400 m以上,孢粉组合与现代植被的对应关系较好,带Ⅰ中较高含量的云杉花粉验证了以云杉为主的森林植被带。带Ⅱ中以云杉为主的乔木植物和含量较高的藜科、蒿属和蓼属等草本植物为主的孢粉组合特征与森林-草原植被带的植被特征较为类似。云杉属花粉在海拔低于1350 m的地方即林带下方所占的比例很小,一方面由于距林地的距离较远,另一方面,可能是山风气流对云杉花粉往下搬运的能力较弱所致。带Ⅲ的蒿属花粉含量较高,与该带植被中绢蒿较多有一定的关系,带Ⅳ以藜科为主的花粉组合特征代表了这个植被带的荒漠植被类型。但是在海拔400 m之下,带Ⅳ的亚带Ⅳ₂的高含量的沼泽蕨和芦苇植硅体的孢粉组合在一定程度上还代表了古湿地环境。通过该部分表土花粉组合特征与草滩湖剖面孢粉谱的对比,验证了当地农业种植选址的生态可行性,同时就开垦程度对环境的影响进行了初步探讨。另外,亚带Ⅳ₂的蒿属/藜科(<em>Artemisia</em>/Chenopodiaceae(A/C))比值比亚带Ⅳ₁高,可能与该样点受人为扰动较大有关。;Tianshan Mountains, one of the largest Mountain Ridges in the Asian continent, divide Xinjiang province into two different natural geographical parts: south and north Xinjiang. They display a distinct vertical gradient distribution of vegetation and soil types and play an important role in the dispersal, preservation and deposition of pollen. In order to investigate the relationship between modern vegetation and surface pollen on the northern slopes of the Tianshan Mountains, northern Xinjiang, China, we collected 23 modern pollen samples from Nanshan hill of Shihezi city along an altitudinal gradient from 300 m to 2400 m. In this study, the altitudinal pollen spectra could be subdivided into 4 pollen assemblage zones (forest vegetation, forest-steppe, <em>Artemisia</em> desert and typical desert), and 2 subzones (<em>Artemisia</em>-Chenopodiaceae typical desert and <em>Thelypteris</em>-<em>Phragmites</em>-<em>Artemisia</em>-Chenopodiaceae typical desert), based on modern vegetation data and characteristics of the surface pollen spectra. The results show that surface pollen assemblages at elevations above 400 m provide a good indication of modern vegetation. The most remarkable characteristic of Zone Ⅰ is that it has the highest percentage of spruce and a very high mean vegetation cover of <em>Picea schrenkiana</em>. The pollen samples in Zone Ⅱ are dominated by <em>Picea</em>, Chenopodiaceae,<em> Artemisia</em> and <em>Polygonum</em> and thus represent forest-steppe vegetation. Below 1350 m, pollen percentages of spruce are very low, partly because they are far away from the spruce forest and partly because the wind-driven downhill transport of arboreal pollen to lower elevation is not strong. Higher pollen percentages of <em>Artemisia</em> in Zones Ⅲ are from relatively high vegetation cover of <em>Seriphidiam</em> sp.. The percentages of <em>Artemisia</em> and Chenopodiaceae pollen in the zone are both more than 30%, and thus reflect <em>Artemisia</em> desert vegetation. Mean vegetation covers of desert vegetation are high in Zone Ⅳ, and pollen percentages of Chenopodiaceae are also high. However, surface pollen spectra can not accurately reflect modern vegetation at elevations lower than 400 m. Regional pollen spectra reflect desert vegetation in the Zone Ⅳ₂. But a large proportion of <em>Thelypteris </em>spore and <em>Phragmites</em> fan-shaped phytolith are recorded in the zone, suggesting the local wetland environment. In order to study the surface pollen source areas, we collected surface pollen at different altitude and identified the pollen categories. As was expected, few <em>Thelypteris </em>spore and <em>Phragmites</em> phytolith are indentified at elevations above 400 m, inferring that they were not transported by flowing water and air. When compared with the pollen spectrum of Caotanhu fossil profile, it is able to verify the ecological feasibility of the selection of agricultural sites, and also investigate the influence of cultivation on environment. The <em>Artemisia</em>/Chenopodiaceae (A/C) value is a good indicator of climate change and an index for distinguishing steppe and desert vegetation in semi-arid and arid areas to a certain extent. The value in Zone Ⅳ₂ is higher than in Zone Ⅳ₁. We think that it is not linked to climatic drying but probably reflect human disturbance at Caotanhu. So in some local environments, the value should be used carefully when human disturbance is involved in reconstructing palaeoclimate and palaeoenvironment.

A modern pollen–temperature calibration data set from Korea and quantitative temperature reconstructions for the Holocene

Modern surface pollen samples from the mountains along the east coast of Korea were used to derive pollen–temperature transfer functions. Detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA) were performed to test the robustness of the relationship between the modern pollen assemblages and temperatures. The relationship exhibited a high correlation (DCA, r = −0.887; DCCA, r = −0.908). The performance of the best weighted averaging partial least squares (WA-PLS) transfer function was statistically good ([Formula: see text] = 0.74; RMSEP = 1.79°C). In order to quantitatively reconstruct the Holocene temperature changes, the best model was applied to five fossil pollen records produced from four coastal lagoons of the east coast and one high-altitude peat bog. Anomalies calculated from reconstructed paleotemperature data were combined to generate a synthesis temperature reconstruction for the east coast of Korea, in which the ‘Medieval Warm Period’, ‘Little Ice Age’, and ‘Migration Period’ were clearly shown. This study demonstrated the validity of the quantitative reconstruction of paleotemperature using the pollen–climate transfer function, even in heavily human-impacted areas such as the Korean Peninsula.

Pollen-inferred vegetation and environmental changes since 16.7 ka BP at Balikun Lake, Xinjiang

A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assemblages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effective moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was accompanied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3−3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.

Quantitative biome reconstruction using modern and late Quaternary pollen data from the southern part of the Russian Far East

In this study we present a recent compilation of 286 modern surface pollen spectra from the southern part of the Russian Far East (42–54°N, 131–141°E) and use it to test the biome reconstruction method. Seventy terrestrial pollen taxa were assigned to plant functional types and then classified to eight regional biomes. When applied to 286 surface pollen spectra, the method assigns about 70% (201 sites) of the samples to the cool mixed forest biome, 17% – to the taiga, 2% – to the cool conifer forest, 3% – to the temperate deciduous forest, and 7% – to the steppe. The steppe reconstruction is characteristic of the pollen spectra from the agricultural areas around Lake Khanka. A visual comparison shows good agreement between pollen-derived biomes and actual vegetation distribution in the region. However, pollen and botanical data, compared with the potential vegetation distribution simulated from the modern climate dataset using the BIOME1 model, demonstrate that spatial distribution of cool mixed forest is underrepresented in the model simulation. The model sets the mean temperature of the coldest month of −15 °C as the factor limiting distribution of the temperate deciduous broadleaf taxa, while vegetation and pollen data from the region demonstrate that this limit should be lowered to −26 °C. Application of the method to the Gur 3–99 pollen record (50°00 ′N, 137°03 ′E) demonstrates that tundra vegetation predominated around the site prior to 14 ka BP (1 ka = 1000 cal. years). However, the local presence of boreal trees and mixed forest-tundra vegetation is suggested by relatively high taiga scores. Soon after 14 ka BP the scores of taiga become slightly higher than tundra scores. During 11.4–10.5 ka BP a cool conifer forest is reconstructed. Establishment of the full interglacial conditions is marked by the onset of cool mixed forest by 10.5 ka BP. Between 10.3 and 2.5 ka BP the scores of temperate deciduous forest are close to those of cool mixed forest and become distinctly lower during the late Holocene.

Late Holocene palaeoenvironment change in central Tianshan of Xinjiang, northwest China

The northern slopes of central Tianshan Mountains in Xinjiang, northwestern China can provide an ideal database to research palaeoclimate as disturbance by human impact is relatively low and the vegetation zones reflect climatic gradients. In order to establish the correlation between modern climatic factors and surface pollen assemblages and to reconstruct palaeoclimate on the northern slope of central Tianshan Mountains, three Holocene sections in Daxigou, Huashuwozi and Sichanghu located at different elevations and vegetation zones were chosen for study. A total of 80 surface pollen samples in 86 vegetation quadrats were collected for pollen‐vegetation relationship analysis. The Warmth Index (WI) and Moisture Index (MI) were calculated based on averaged modern climate data during 1951 – 2000 at eight weather stations in the study area. Pollen percentages of Picea, Artemisia, Chenopodiaceae, Ephedra, and Tamarix, as well as A/C (Artemisia/Chenopodiaceae) and AP/NAP (arboreal/nonarboreal pollen) ratio were selected as pollen variables and WI and MI were chosen as climatic variables. The relationship between pollen percentages (Picea, Artemisia, Chenopodiaceae and Tamarix), A/C, AP/NAP ratio, WI and MI values were estimated (95% confidence interval) using stepwise multiple linear regression analysis. WI and MI values for the three sections were calculated using these regression equations, and palaeoclimate for the study area could be reconstructed. The results showed periods of both cool‐humid and warm‐dry conditions on the northern slopes of Tianshan Mountain during the late Holocene.

Holocene vegetation and climate history at Hurleg Lake in the Qaidam Basin, northwest China

We present fossil pollen data and discuss their climatic interpretations from a 688-cm-long sediment core from Hurleg Lake, a freshwater lake located in the Qaidam Basin on the NE Tibetan Plateau, just beyond the northern limit of the East Asian summer monsoon influence. The reconstruction of the Holocene vegetation and climate history was aided by modern surface pollen analysis. The 14000-yr chronology of the sediment core was controlled by seven AMS 14C dates on plant macrofossils. The results of the surface pollen analysis showed that modern pollen spectra faithfully reflect the regional vegetation along a transect from alpine meadow to desert steppe and desert, so fossil pollen record can be used to reconstruct Holocene vegetation change. The pollen data showed that vegetation changed from desert before the Holocene to desert steppe dominated by Artemisia from 11.9 to 9.5 ka, desert dominated by Chenopodiaceae from 9.5 to 5.5 ka, and steppe desert dominated by Artemisia and Poaceae after 5.5 ka. This vegetation sequence indicates that climate was relatively wet before 9.5 ka, dry and variable from 9.5 to 5.5 ka, and relatively wet and stable after 5.5 ka. The climate pattern reconstructed from pollen data appears to be opposite to the paleoclimate pattern inferred at Qinghai Lake, 300 km east of our study site. That site shows a moist early Holocene during the insolation and monsoon maximum followed by a drying trend during the mid- and late Holocene. The contrast between the two sites suggests the importance of the position of the subtropical monsoon, the mid-latitude westerlies and interactions between local topography and regional climate. Our finding has important implications for understanding complex regional vegetation and climate responses to large-scale forcings in arid central Asia.

MIS11–19 pollen stratigraphy from the 250‐m Choshi core, northeast Boso Peninsula, central Japan: Implications for the early/mid‐Brunhes (400–780 ka) climate signals

Abstract The 250‐m Choshi core (CHOSHI‐1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ18O) profile, with high δ18O intervals dominated by boreal conifers Picea, Abies, Pinus (subgen. Haploxylon) and Tsuga (diversifolia), whereas low δ18O intervals are dominated by temperate conifers Cryptomeria, Taxaceae‐Cephalotaxaceae‐Cupressaceae and Sciadopitys. In order to confirm pollen‐climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria/Picea and temperate/boreal conifers serve as proxies for the 100‐kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ18O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid‐latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11.

Environmental implications of pollen spectra in bat droppings from southeastern Spain and potential for palaeoenvironmental reconstructions

Pollen was analysed from bat guano from nine caves in southeastern Spain and surface soils in their immediate surroundings. We compare the pollen spectra of 34 modern dung samples from the nine caves with one modern surface pollen sample from each cave. The contents suggest reasonable pollen diversity and richness, including anemophilous and zoophilous pollen types. Since the latter is usually under-represented in atmospheric pollen, the guano spectra therefore appear to reflect the vegetation more effectively than normal surface soil samples. Despite health hazards such as histoplasmosis, the difficulties of obtaining bat guano in deep caves and possible interpretational concerns relating to behaviour and feeding habits of different bat species, this material can be very useful in palaeoecological research provided that the dung was fossilized under favourable environmental conditions that allowed the preservation of pollen.

Natural and anthropogenic rapid changes in the Kara-Bogaz Gol over the last two centuries reconstructed from palynological analyses and a comparison to instrumental records

Palynological analyses (pollen and dinocysts) of a sediment core taken in the Kara-Bogaz Gol have been used to reconstruct rapid and catastrophic environmental changes over the last two centuries (chronology based on 210Pb). A natural cyclicity (65 years) of water level changes in the Caspian Sea (CS) and in the Kara-Bogaz Gol (KBG) and anthropogenic factors (building of a dam separating the CS and the KBG waters) combine to induce rapid changes in water levels of the KBG, in the salinity of its waters and in vegetation cover of its surroundings. The impact of low water levels on the dinocysts is marked by a lower diversity and the survival of two species that are typical of the KBG, the Caspian Sea species present in the KBG having disappeared. During periods of higher water levels (AD 1871–1878), the lake is surrounded by a steppe-like vegetation dominated by Artemisia; whereas during periods of low water levels (AD 1878–1913 and AD 1955–1998), the emerged shore are colonised by Chenopodiaceae. The period of AD 1913–1955 corresponding to decreasing water levels has an extremely low pollen concentration and a maximum of reworking of arboreal taxa. During the last low-level period, humans responded by abandoning the shores of the bay. What happened to the KBG can be used as an example of what may happen in the future for the Aral Sea. A problem of reworking of Tertiary dinocysts into modern deposits has been detected owing to the knowledge of the modern dinoflagellate assemblages recently made available through a water survey. A comparison to modern surface pollen samples from Central Asia (Anzali, Caspian Sea south and central basins, Aral Sea, Lake Balkhash, Lake Issyk-Kul and the Chinese Tien-Shan range) allows us to establish the potential reworking of at least five arboreal pollen taxa possibly by run-off and dust storms.

Modern pollen samples from alpine vegetation on the Tibetan Plateau

Abstract A set of 316 modern surface pollen samples, sampling all the alpine vegetation types that occur on the Tibetan Plateau, has been compiled and analysed. Between 82 and 92% of the pollen present in these samples is derived from only 28 major taxa. These 28 taxa include examples of both tree (AP) and herb (NAP) pollen types. Most of the modern surface pollen samples accurately reflect the composition of the modern vegetation in the sampling region. However, airborne dust‐trap pollen samples do not provide a reliable assessment of the modern vegetation. Dust‐trap samples contain much higher percentages of tree pollen than non‐dust‐trap samples, and many of the taxa present are exotic. In the extremely windy environments of the Tibetan Plateau, contamination of dust‐trap samples by long‐distance transport of exotic pollen is a serious problem. The most characteristic vegetation types present on the Tibetan Plateau are alpine meadows, steppe and desert. Non‐arboreal pollen (NAP) therefore dominates the pollen samples in most regions. Percentages of arboreal pollen (AP) are high in samples from the southern and eastern Tibetan Plateau, where alpine forests are an important component of the vegetation. The relative importance of forest and non‐forest vegetation across the Plateau clearly follows climatic gradients: forests occur on the southern and eastern margins of the Plateau, supported by the penetration of moisture‐bearing airmasses associated with the Indian and Pacific summer monsoons; open, treeless vegetation is dominant in the interior and northern margins of the Plateau, far from these moisture sources. The different types of non‐forest vegetation are characterized by different modern pollen assemblages. Thus, alpine deserts are characterized by high percentages of Chenopodiaceae and Artemisia, with Ephedra and Nitraria. Alpine meadows are characterized by high percentages of Cyperaceae and Artemisia, with Ranunculaceae and Polygonaceae. Alpine steppe is characterized by high abundances of Artemisia, with Compositae, Cruciferae and Chenopodiaceae. Although Artemisia is a common component of all non‐forest vegetation types on the Tibetan Plateau, the presence of other taxa makes it possible to discriminate between the different vegetation types. The good agreement between modern vegetation and modern surface pollen samples across the Tibetan Plateau provides a measure of the reliability of using pollen data to reconstruct past vegetation patterns in non‐forested areas.