Reconstruction of Indian monsoon variability over the past 230,000 years: Planktic foraminiferal evidence from the NW Arabian Sea open-ocean upwelling area

We determined the faunal composition and total number of tests (#/g) of planktic foraminifera (> 125 μm) in core KH00-05 GOA 6 near Oman in order to decipher monsoon-induced variability of oceanographic productivity in the open-ocean upwelling area in the northwest Arabian Sea. The core contains a continuous record of sedimentation over the last 230 kyr, with the age model based on oxygen isotope and accelerator mass spectrometry ¹⁴C dates. We focused on species (Globigerina bulloides and Globigerinita glutinata) typical for SW monsoonal upwelling and species typical for NE monsoon conditions (Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerinoides ruber, and Globigerinoides sacculifer). The changes in relative abundance of these monsoonal indicators suggest that the open-ocean upwelling area was dominated by the SW monsoon during interglacial periods, but by the NE monsoon during glacial periods.Increases in total test abundance during glacial periods confirmed that the NE monsoon rather than SW monsoon contributes largely to planktic foraminiferal productivity in this area. We argue that three types of circumstances resulted in high productivity, with nine high productivity events occurring at a 23-kyr frequency. The first type caused high productivity events at 102 and 199 ka (interglacial periods), characterized by the dominance of upwelling species, indicating high productivity during strong SW monsoons, correlated with high July insolation at 45° N. An exceptional high productivity event occurred at 37 ka during interglacial marine isotope stage (MIS) 3, with contributions from both SW and NE monsoons. The second type of high productivity event occurred at 61, 147, and 175 ka, during glacial periods, characterized by dominance of NE monsoon species, and correlated with low January insolation at 45° N. In addition, a high productivity event at 85 ka (interglacial period) also was induced by enhanced NE monsoons. The last two high productivity events occurred during transitional periods from glacial to interglacial (MIS 6/5.5 and 2/1), were characterized by the replacement of NE monsoon species with upwelling species, and corresponded to abrupt climate warming, suggesting that they are related to both accelerated SW monsoon systems and reduced NE monsoon systems.     

High-resolution vegetation history of West Africa during the last 145 ka

The essential characteristics of the vegetation dynamics of tropical Africa remain only partially known. This study assesses the succession of vegetation-types over Central Africa during the last two glacial/interglacial cycles. Analysis of core KZai 02, which contains pollen from the Zaire River watershed (latitudes 9°N–13°S), allows the investigation of long-term patterns of plant ecosystem development and their climatic causes. Core KZai 02 (18.20 m long) was recovered from 6°24.20′S/9°54.10′E in the uppermost axial edifice of the Zaire deep sea fan. The chronology of this sedimentary archive was established using nannofossils and correlations of pollen and total organic carbon signals with the nearby core GeoB1008. The pollen record indicates that: (i) glacials (MIS 6, 4, 2) are marked by the development of afromontane (Podocarpus) forest at high altitudes when central basin lowlands were occupied by Cyperaceae marshes and savannah; (ii) during interglacials (MIS 1, 5) lowland forests were developed, marked by the successive expansion of pioneer, warm-temperate, rain forests, and mangrove indicating sea-level rise; (iii) glacial-interglacial transitions (MIS 6/5, 2/1) display similar vegetation dynamics. The strong evidence of afromontane forest and the opening of the vegetation during glacials suggest a reduced latitudinal distribution of rainfall by the strengthening of the trade wind system. West African monsoon systems were enhanced during interglacials, allowing the progressive development of lowland forests. The development of rain and pioneer forests during glacial Heinrich stadials suggests an enhancement of water availability in tropical Africa associated with these high-latitude events. However, no augmentation of wind activity described by previous studies is evidenced by our pollen record. Similar vegetation successions during glacial/interglacial transitions suggest the diachronous and stepped intervention of CO₂ (emphasizing the influence of temperature on plant ecosystems) and water availability.     

High frequency palaeoceanographic changes during the past 140?000 yr recorded by the organic matter in sediments of the Iberian Margin

Biogenic records of the marine palaeoproductivity (carbonates, organic carbon, and C₃₇ alkenones) and the molecular stratigraphy of past sea surface temperatures (SSTs; U₃₇^K′) were studied at high resolution in two cores of the Iberian Margin. The comparison of these records indicates that the oceanographic conditions switched abruptly during the past 160 kyr between three kinds of regimes. A first regime with high (17-22°C) SST and low productivity typifies the interglacial periods, marine isotopic stages (MIS) 5 and 1. Several periods during MIS 6, 2, and the terminations II and I are characterised by about 4-5°C colder SST and a higher organic matter accumulation, both of which define the second regime. This anticorrelation between SST and marine productivity suggests that these variations are related to the intensity of the coastal upwelling. By contrast with this upwelling behaviour, extremely low biological productivity and very cold SST (6-12°C) occurred during short phases of glacial MIS 6, 4, and 2, and as abrupt events (≈1 kyr or less) during MIS 3. The three oceanographic regimes are consistent with micropalaeontological changes in the same cores based on foraminifera and diatoms.The general trend of these hydrologic changes follows the long-term glacial/interglacial cycle, but the millennium scale variability is clearly related to Heinrich events and Dansgaard-Oeschger cycles. Strengthening of the upwelling corresponds probably to an intensification of the subtropical atmospheric circulation over the North Atlantic which was influenced by the presence of continental ice sheets. However, extreme glacial conditions due to massive discharges of icebergs interrupted the upwelling. Interestingly, both terminations II and I coincided with strong but transient intensification of the upwelling.     

A modern pollen rain study from the central Andes region of South America

Aim To provide a greater understanding of the modern pollen rain for the central Andes region of South America, thus laying the groundwork for future pollen studies and the derivation of pollen‐climate transfer functions and response surfaces. Location Peru, Bolivia and Chile. Methods Standard palynological techniques for surface soil sampling and discriminant analysis. Results Statistical analysis of the 40 surface samples revealed four palynologically distinct assemblages: (1) the Yungas on the eastern slopes of the Andes; (2) the puna grasslands of the Altiplano; (3) the Coastal Deserts to the west of the Andes; and (4) the Southern Bolivian Highlands. Main conclusions The Yungas group is characterized by high percentages of Urticaceae/Moraceae pollen and fern spores along with trace amounts of pollen from common zoophilous lowland taxa such as Piperaceae, Bignoniaceae and Malpighiaceae. The puna assemblage of the Altiplano is characterized by the dominance of grass (Poaceae) in combination with moderate frequencies of Asteraceae pollen, which tend to increase slightly towards the southern (drier) locations of the Altiplano. Lower percentages of grass pollen and the greater prevalence of Asteraceae, Solanaceae, and the Chenopodiaceae/Amaranthaceae families define the coastal deserts to the west of the Andes. Samples taken from the Southern Bolivian Highlands are characterized by the dominance of Solanaceae in the area, in combination with the pollen of other xerophytic taxa.     

The late Pleistocene climates of the Lake Zeribar region (Kurdistan,western Iran) deduced from the ecology and pollen production of nonarboreal vegetation

The concept of an arid pleniglacial in the Middle East depends primarily on the interpretation of pollen diagrams including those of Lake Zeribar in the Zagros Mountains of western Iran. It has been assumed that Lake Zeribar was surrounded by a Chenopodiaceae-Artemisia steppe and that the climate was therefore dry. Both assumptions are questioned. The environment of Pleistocene Lake Zeribar may have been similar to the tragacanthic or alpine zone of the modern Zagros Mountains. The dominance by pollen of Chenopodiaceae and Artemisia is explained by low pollen production of high-altitude vegetation, preferential incorporation of pollen of late-blooming plants into the sediments, and high production and long-distance transport of lowland pollen. In any case, high percentages of Chenopodiaceae and Artemisia pollen do not necessarily indicate low annual precipitation but a highly seasonal climate with cold winters and hot, dry summers. Such a climatic regime was in effect continuous except for a period beginning about 10600 B. P. during which summer rainfall or reduced summer drought occurred. This change in seasonality resulted in the dominance of Poaceae pollen and the initial increase in arboreal pollen. A moisture curve based on the ratio between Chenopodiaceae and Artemisia pollen indicates a pleniglacial climate with wet winters and a late-glacial and early-Holocene climate with periods of intense aridity. The climatic history presented here is compatible with non-palynological evidence of regional late Pleistocene climates and with seasonality changes suggested by climatic modelling based on orbital parameters.Abbreviations C/A Chenopodiaceae-Artemisia ratio     

Aeropalynological monitoring in Bishkek, Kyrgyzstan

The pollen spectrum of Bishkek was investigated by a gravity method, during March-October in 1984, 1988 and 1992. The recovered pollen types belong to 20 families and 26 taxa. Only 4 types reach significant levels of deposition of over 10% as annual average. These include: Artemisia, Chenopodiaceae/Amaranthaceae, Quercus and Poaceae. Pollinosis in Bishkek is mainly induced by Artemisia and Poaceae pollen. Hay fever patients showed polyvalent allergy to Artemisia and Poaceae pollen (32 to 51%), Artemisia and Atriplex pollen (34.5%).     

Vegetation and climatic history of southwest Africa: A marine palynological record of the last 300,000 years

A continuous palynological record from the marine core GeoB1016-3 from the Angola Basin reveals the regional vegetation and climate history of the last 300 ka. Pollen and spores found at the studied site have their source areas in the different vegetation zones of the adjacent part of the West African continent. Those vegetation zones comprise tropical rain forest, coastal mangrove swamp, Miombo woodland, dry forest, Afromontane forest, desert and semi-desert. The main pollen transport agent is the southeast trade wind system. Ocean currents also partly play a role in transporting pollen and spores. During the interglacial periods, ocean currents also transported palynomorphs southward. During the glacial periods, increased trade winds are indicated by high influx of pollen and spores and high pollen percentages of Poaceae and taxa from desert and semidesert vegetations. Reconstruction of the geographical position of palaeo-vegetation zones shows that the northern boundary of the Namib Desert did not move north of 12°S during the last 300 ka. This implies that northward shifts of the Angola-Benguela Front did not pass the latitude of 12°S.     

Variability in glacial and Holocene marine pollen records offshore from west southern Africa

The distribution of pollen in marine sediments is used to record vegetation changes over the past 30,000 years on the adjacent continent. A transect of marine pollen sequences from the mouth of the river Congo (∼5°S) to Walvis Bay and Lüderitz (∼25°S) shows vegetation changes in Congo, Angola and Namibia from the last glacial period into the Holocene. The comparison of pollen records from different latitudes provides information about the latitudinal shift of open forest and savannahs (Poaceae pollen), the extension of lowland forest (rain forest pollen) and Afromontane forest (Podocarpus pollen), and the position of the desert fringe (pollen of Caryophyllaceae, Chenopodiaceae and Amaranthaceae). High Cyperaceae pollen percentages in sediments from the last glacial period off the mouth of the river Congo suggest the presence of open swamps rather than savannah vegetation in the Congo Basin. Pollen from Restionaceae in combination with Stoebe-type pollen (probably from Elytropappus) indicates a possible northwards extension of winter rain vegetation during the last glacial period. The record of Rhizophora (mangrove) pollen is linked to erosion of the continental shelf and sea-level rise. Pollen influx is highest off river mouths (10–2000 grains year⁻¹ cm⁻²), close to the coast (300–6000 grains year⁻¹ cm⁻²), but is an order of magnitude lower at sites situated far from the continent (<10 grains year⁻¹ cm⁻²).     

Temporal and spatial changes of vegetation cover on the Chinese Loess Plateau through the last glacial cycle: evidence from spore-pollen records

To reconstruct the palaeovegetation cover of the Chinese Loess Plateau over different time intervals of the last glacial–interglacial cycle, the spore-pollen representation of loess-soil samples in six loess sections along a north–south transect is analyzed and previously published pollen data reviewed. Results show that the temporal changes in the vegetation cover of the Plateau are controlled essentially by the history of the East-Asian summer monsoon; there is a general pattern that the pollen components indicating relatively humid climatic conditions are better represented during interglacial and interstadial periods than during glacial and stadial periods. The herbaceous pollen concentrations show a general increase from south to north with the decrease of monsoonal precipitation over the Loess Plateau. Through the last 130 ka or so, the main body of the Loess Plateau has been covered by an Artemisia-dominated grassland vegetation, suggesting that future rehabilitation of the landscape that aims for soil–water preservation on the Loess Plateau should focus on the planting of herbs.     

Airborne pollen in Kiev (Ukraine): Gravimetric sampling

This article presents the results of aeropalynological observations in Kiev, carried out with a gravimetric method, during January–October, 1994. The six most abundant pollen types were: Betulaceae (21%), Chenopodiaceae/Amaranthaceae (10%), Ambrosia (10%), Artemisia (9%) Pinaceae (8%) and Poaceae (6%). Seasonal fluctuations of the atmospheric presence of tree/shurb and herb/grass pollen during the period March–September, 1993 and 1994, are also shown.     

Possible paleohydrologic and paleoclimatic effects on hominin migration and occupation of the Levantine Middle Paleolithic

This paper explores the impact of major glacial/interglacial paleohydrologic variations in the Middle-Paleolithic Levant on hominin migration and occupation. The climatic reconstruction is based primarily on the most straight-forward paleohydrologic records recently published. These terrestrial proxies convey direct paleoenvironmental signals of effective precipitation and aquifer recharge. The two main proxies are temporal changes of terminal lake levels in the Dead Sea basin and periods of deposition or non-deposition of speleothems. Other records, such as stable isotopes, if interpreted correctly, correspond well with these two direct proxies. All the records consistently indicate that the last two glacial periods in the central Levant were generally wet and cool, while the last two interglacials were dry and warm, so more water was available for the ecosystem and thus hominins during glacial periods than during interglacials. Some proxies indicate that the higher precipitation/evaporation ratio during glacial periods involved higher precipitation rather than only reduced evaporation. Beyond the general mean glacial/interglacial climate suggested here, variations occurred at all temporal scales throughout glacial or interglacial periods. In the Sahara-Negev arid barrier, moister conditions occurred during Marine Isotope Stage (MIS) 6a-5e, when Anatomically Modern Humans apparently migrated out of Africa. We suggest that this migration, as well as the later Neanderthal expansion from Southeast Europe or the Anatolian plateau into the Levant during early MIS 4, could be facilitated by the observed major climatic variations.     

Airborne pollen in Kiev (Ukraine): gravimetric sampling

This article presents the results of aeropalynological observations in Kiev, carried out with a gravimetric method, during January–October, 1994. The six most abundant pollen types were: Betulaceae (21%), Chenopodiaceae/Amaranthaceae (10%), Ambrosia (10%), Artemisia (9%) Pinaceae (8%) and Poaceae (6%). Seasonal fluctuations of the atmospheric presence of tree/shrub and herb/grass pollen during the period March–September, 1993 and 1994, are also shown.     

Vegetation in the mountains of northwest Iberia during the last glacial-interglacial transition

A new core taken from a site in the Sierra de Courel range of mountains in the northwest Iberian peninsula, Spain, enables a palaeoenvironmental reconstruction to be made of the biological events resulting from climatic changes and human activities during the last 17,000 years in the area. The sequence begins with a phase characterised by the dominance of Gramineae (Poaceae) and Pinus. A markedly arid period with prevalence of Artemisia pollen occurred between 17,5000 and 15,500 uncal. B.P. Subsequently, a succession of woodlands with Betula, Pinus and other mesophilous and thermophilous trees was recognised during the period 15,500-13,500 uncal. B.P. Between 13,500 and 10,300 uncal. B.P. herbaceous vegetation formations indicating moister conditions dominated the pollen record, although a maximum of Gramineae has been dated during the period 11,300-10,300 uncal. B.P. Comparison with other pollen data from neighbouring mountains allows an interpretation of the vegetation changes during the glacial/interglacial transition in the mountains of northwest Iberia. The Holocene pollen record from the site does not differ markedly from other records in the area, tree expansion occurring before 10,000 uncal. B.P. and high values of deciduous Quercus mixed with other trees and shrubs persisting until 3500 uncal. B.P., when increased human activities are shown by a fall of the tree pollen percentages. Received July 7, 1999 / Accepted May 22, 2000     

Analysis of airborne pollen in the town of Almería (South-East Spain), 1995–1996

The first results are presented of an aerobiological analysis of the atmosphere of the town of Almería, carried out between November 1995 and October 1996. A Lanzoni volumetric spore trap was used for sample collection. The composition and seasonal evolution of the pollen spectrum were determined over a 1-year period in relation to the vegetation and climatic conditions of the study area. Twenty-six pollen types were identified as accounting for >0.05% of the total pollen collected. The main sources of airborne pollen were Palmae (17.76%),Olea (16.10%), Chenopodiaceae/Amaranthaceae (13.99%), Urticaceae (10.18%) and Poaceae (8.64%). The annual pollen variation presented a period of maximum emission from March to June, with a subsequent, less intensive period from August to November. The minimum pollen values were obtained from December to February. The highest concentrations occurred in May, which was also the month which presented the highest pollen diversity, whereas the lowest values were observed in January.     

A 26,000-year integrated record of marine and terrestrial environmental change off Gabon, west equatorial Africa

Dinoflagellate cysts, pollen and charred cuticle fragments from two sediment cores (giant piston Calypso core MD03-2708 and giant gravity Casq core MD03-2708CQ) collected off the Ogooué River mouth, Gabon (01°10.33′S-08°19.01′E, 920 m water depth) have been analysed to identify the direction and timing of marine-terrestrial environmental changes over western equatorial Africa during the last 26,000 yr. Changes in the proxy records indicate that both terrestrial and oceanic domains off Gabon were impacted synchronously by significant climate changes during the last glacial-interglacial transition and Holocene. Leading into, and during, the Last Glacial Maximum (LGM), heterotrophic dinoflagellate cysts and Ca X-ray fluorescence intensity suggest nutrient enrichment off the river mouth, while pollen records indicate expansions of open forest, savannah woodland, and the Afromontane forest in the catchment area. From the deglaciation to mid-Holocene, however, a marked decrease in Brigantedinium spp. as well as in Poaceae, Cyperaceae and Podocarpus pollen reflects a reduction in nutrient supply to the coastal ocean in parallel with a reduction in grassland, herbaceous communities and Afromontane forest within the catchment. A sharp decline or even disappearance of heterotrophic species during this period is almost contemporaneous with an appearance of Operculodinium aguinawense, reflecting enhanced river influence in the study area. A marked increase of Rhizophora (mangrove) pollen during this transition also indicates eustatic sea-level rise after the LGM which forced a major expansion of the mangrove ecosystem across the gradually submerging shelf. The combination during the late Holocene of a reoccurrence of heterotrophic dinoflagellate cysts with increased Poaceae, Cyperaceae and Podocarpus pollen indicates enhanced nutrient supply to the ocean concordant with a shift to cooler/drier conditions over the Gabon basin. This appears to be linked to a deterioration of the monsoon system induced by the low sea-surface temperatures in the tropical Atlantic Ocean in association with decreased summer insolation.     

Late Quaternary stratigraphy and paleoecology of northwest Labrador Sea

Sedimentological study of 20 piston cores from the northwestern Labrador Sea shows that thin bedded distal turbidites are important constituents of the Quaternary strata on the continental slope and rise. Sedimentation on the outer shelf (ca. 500–900 m) is dominated by ice-rafting and hemipelagic deposition. Detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9. Studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern Labrador Sea during the early-middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time. Microfossil data indicate that late glacial stages were characterized by year around sea-ice cover and arctic surface water, and by the dominance of cold, dry Arctic air masses. Transitions from glacial to interglacial stages are marked by the presence of low salinity melt water. These data support models which postulate that open water in the Labrador Sea played an important role in supplying moisture to Laurentide and Greenland ice-sheets.     

The variation of upper ocean structure and paleoproductivity in the Kuroshio source region during the last 200 kyr

A core from the source region of the Kuroshio warm current (east of the Luzon Island) was analyzed using several proxies in order to study the variability of the Western Pacific Warm Pool (WPWP) during the last two glacial–interglacial cycles. Primary productivity (PP) variations were deduced from variations in the coccolith flora. Primary productivity was higher during glacial periods (the end of Marine Isotope Stage [MIS] 3, some periods in MIS 2 and 6), and decreased during interglacial periods (MIS 7, MIS 5e and probably MIS 5c–5d), with the lowest PP in MIS 5e. Variations in the δ¹³C difference in benthic and bulk carbonate, thus in the vertical gradient of δ¹³C in dissolved inorganic carbon (Δδ¹³C_{C. wuellerstorfi–N. dutertrei} and Δδ¹³C_{C. wuellerstorfi–coccolith}) coincided with the PP changes, showing that export productivity was low during interglacial periods (MIS 7, MIS 5e and Holocene) and high during glacial periods (MIS 6, probably MIS 5c–5d, late MIS 4 and late MIS 3). Comparison of foraminiferal carbonate dissolution indicators and PP changes reveals that nannofossil assemblage in core Ph05-5 is not sensitive to carbonate dissolution intensity. The depth of the thermocline (DOT) was estimated from planktonic forminiferal assemblages, and was relatively greater during interglacial periods (MIS 7, MIS 5e, probably MIS 5c and Holocene) than during glacials (middle MIS 6, probably MIS 5b and 5d, some periods in MIS 4, MIS 3 and MIS 2). Good coherence between the paleoproductivity records and the DOT suggests that the DOT changes could be the primary control factor in changes of paleoproductivity, and the glacial high productivity in the Kuroshio source region could be associated with a global increase of nutrient concentration in the intermediate waters that upwelled into the photic zone. The low CO₂ values derived for intervals of high productivity and a relatively shallow DOT suggest that the changes in biological productivity and DOT in the equatorial Pacific could have modified atmospheric CO₂ concentrations. High Sea Surface Temperatures (SSTs) during the warm MIS 5e in combination with intensified monsoonal rain fall could have resulted in a more intense stratification of the upper waters, resulting in low nutrient supply to the surface waters and a resulting decrease in productivity.     

Airborne pollen concentration in Seville (Spain), 1993–1996. First results obtained with Hirst’s method

The data presented constitute the longest historical series of results obtained in Seville with a Hirst-type sampler, and are a further contribution to earlier aerobiological studies carried out in the city with a Cour trap. This work supplies an updated pollen calendar of the city, together with pollen counts and other aerobiological parameters for the 14 most important types in the 4-year period of sampling. These werePlatanus hispanica, Olea europaea, Quercus, Cupressaceae, Poaceae, Urticaceae, Moraceae, Chenopodiaceae/ Amaranthaceae,Plantago, Pinaceae,Rumex, Myrtaceae, Compositae, andCasuarina.     

Refugia,colonization and diversification of an arid‐adapted bird: coincident patterns between genetic data and ecological niche modelling

Phylogeographical studies are common in boreal and temperate species from the Palaearctic, but scarce in arid‐adapted species. We used nuclear and mitochondrial markers to investigate phylogeography and to estimate chronology of colonization events of the trumpeter finch Bucanetes githagineus, an arid‐adapted bird. We used 271 samples from 16 populations, most of which were fresh samples but including some museum specimens. Microsatellite data showed no clear grouping according to the sampling locations. Microsatellite and mitochondrial data showed the clearest differentiation between Maghreb and Canary Islands and between Maghreb and Western Sahara. Mitochondrial data suggest differentiation between different Maghreb populations and among Maghreb and Near East populations, between Iberian Peninsula and Canary Islands, as well as between Western Sahara and Maghreb. Our coalescence analyses indicate that the trumpeter finch colonized North Africa during the humid Marine Isotope Stage 5 (MIS5) period of the Sahara region 125 000 years ago. We constructed an ecological niche model (ENM) to estimate the geographical distribution of climatically suitable habitats for the trumpeter finch. We tested whether changes in the species range in relation to glacial–interglacial cycles could be responsible for observed patterns of genetic diversity and structure. Modelling results matched with those from genetic data as the species' potential range increases in interglacial scenarios (in the present climatic scenario and during MIS5) and decreases in glacial climates (during the last glacial maximum, LGM, 21 000 years ago). Our results suggest that the trumpeter finch responded to Pleistocene climatic changes by expanding and contracting its range.     

Modern pollen assemblages from human-influenced vegetation in northwestern China and their relationship with vegetation and climate

Modern pollen spectra can improve the interpretation of fossil pollen records used to reconstruct past vegetation, climate and human impacts. It is important, therefore, to carefully examine the relationships between modern pollen spectra, vegetation, climate and human activity. Here, we present the results of an analysis of the pollen spectra of 143 surface pollen samples from farmland, wasteland, desert, steppe/meadow, forest and river valley along a transect from Lanzhou to Urumqi, in northwestern China. The modern pollen assemblages are mainly composed of Amaranthaceae, Artemisia, Poaceae, Asteraceae, Ephedra and Nitraria. The results indicate that in general the surface pollen assemblages of different vegetation types reliably represent the modern vegetation in terms of the composition of the main taxa and the dominant types. Farmland is dominated by cereal-type (≥?15%) and Amaranthaceae (≥?20%), while the pollen assemblages of wasteland (i.e. the vegetation immediately surrounding farmland) are mainly composed of Amaranthaceae (≥?25%), Artemisia (≥?20%), Poaceae (≥?10%), Asteraceae (≥?5%) and Cyperaceae (≥?5%). Amaranthaceae (≥?45%) and Ephedra (≥?10%) are the most important taxa in desert, and Cyperaceae (≥?35%) and Thalictrum (≥?2%) are the dominant pollen types in steppe/meadow. Forest and river valley samples are characterized by high frequencies of Picea (≥?10%) and Cyperaceae (≥?20%). Both constrained and partial canonical ordination techniques (RDA and partial RDA) of the main pollen types and environmental variables show that the modern pollen spectra are primarily controlled by mean annual precipitation (MAP). Cyperaceae, Thalictrum and Brassicaceae are positively correlated with MAP and negatively correlated with mean July temperature (T_July), while the representation of certain other types, such as Amaranthaceae, Ephedra and Nitraria, is negatively correlated with MAP and positively correlated with T_July. The Human Influence Index (HII) is significantly correlated with cereal-type pollen, and it can also differentiate human-influenced and natural vegetation. Our results provide a basis for improving the interpretation of fossil pollen records from arid northwestern China and similar regions.