A comparison between modern pollen spectra of moss cushions and Cundill pollen traps

Pollen spectra of 23 Cundill pollen traps from 23 different sampling sites in Southwest Turkey are compared with the corresponding pollen spectra of moss cushions from the same sites. The Cundill pollen traps represent the modern pollen rain data from one year whereas the moss cushions represent the pollen rain of several years. The comparative study reveals some main differences between the two pollen entrapment media. The one-year entrapment medium (pollen trap) appears to be more sensitive for local (releve area 10x10 m) and regional (100-500 m, or a few kilometres for Olea europaea) vegetation. Pollen spectra of moss cushions are dominated by high pine pollen percentage values and hardly sense fine vegetation structures. The conclusion of this comparative modern pollen study allows to interpret fossil sediment spectra from the Near East in a more critical way. It is concluded that one should preferably sample rapidly deposited sediments for palynological analyses, as the resulting highresolution pollen diagrams will be most informative about the former vegetation patterns.     

Do moss samples,pollen traps and modern lake sediments all collect pollen in the same way? A comparison from the forest limit area of northernmost Europe

Moss polsters, pollen traps and lake surface sediment samples are commonly used as climate calibration data or as modern analogues for reconstructing vegetation from fossil profiles, but the differences in pollen content between these media have received little attention. This study aims to analyse how the three media differ in reflecting individual vegetation types and spatial differences in vegetation. 119 modern samples (64 moss polsters, 37 lake surface sediment samples and 18 pollen traps from which a collection was made annually) were taken from northern Fennoscandia and the Kola Peninsula as a broad transect crossing the northernmost forest limits of Betula pubescens ssp. czerepanovii (mountain birch), Pinus sylvestris (Scots pine) and Picea abies (Norway spruce). The pollen assemblages from these samples were compared with the surrounding vegetation visually and via PCA (principle components analysis) and cluster analysis. Both comparisons allow a correct distinction between pollen assemblages of arctic/alpine heath, mountain birch dominated areas, and boreal coniferous forests. The differences between the vegetation zones are stronger than the differences between the sampling media. Nevertheless, lake sediment samples from the mountain birch woodland zone tend to overestimate pine and underestimate birch. Pollen traps are biased towards lower tree pollen percentages and higher values of shrubs, herbs and Cyperaceae. This bias is especially strong in traps that have missing years in the data. Irrespective of the vegetation zone, pollen traps tend to have lower Pinus pollen percentages than in the adjacent moss polsters.     

样地尺度现代表土花粉与植物群落的定量关系

建立现代植被与表土花粉的精确关系,是基于孢粉记录定量重建古植被与古气候的基础与关键.截止目前,植物群落样方记录较少参与到现代植被与花粉的统计分析中,限制了其精确关系的定量表达.本文通过中国东北样带的森林、草甸草原、典型草原和荒漠草原33个表土样品分析及植被样方调查,基于Bray-Curtis相异系数,研究了东北样带现代...     

Five decades of rapid forest spread in the Pieria Mountains (N. Greece) reconstructed by means of high-resolution pollen analysis and aerial photographs

The rapid spread of pine forests on the western side of the Pieria Mountains (N. Greece) began in 1945 and was facilitated by the recession of human activity and the siliceous geological substrate of the area. The pine expansion is visible not only in the vegetation maps for the years 1945, 1960 and 1992 but is also reflected in pollen data acquired from the high resolution analysis of a peat sequence covering the period 1945–1997, according to ²¹⁰Pb and ¹³⁷Cs dating. A possible inflation of the calculated PAR values due to discrepancies in the dating model is suspected and indirectly traced from the comparison of the Pinus mean PAR values for the most recent eight years of the monolith with those of a Tauber trap placed in the same mire. The presence of a high pollen producer such as pine enables the calculation of reliable PAR values, despite any discrepancies in the age-depth model. The Pinus PAR values “quantify” better the expansion of this timberline species, while pollen percentages reflect the same event in a “qualitative” way, i.e. as part of the general vegetation changes that take place in the area.     

Modern pollen and vegetation relationships in the mountains of southern California,USA

The relationship between modern pollen assemblages and modern vegetation along two elevational transects within the Transverse and Peninsular Ranges of southern California, USA, is demonstrated using cluster analysis of the pollen data. Cluster analysis separates the Sonora Desert vegetation, Valley grassland/agricultural land and chaparral vegetation types on the San Jacinto Mountains transect. Chaparral is not easily separated on the San Bernardino Mountains transect, probably due to the presence of Quercus dumosa (scrub oak) there. The lower montane Quercus – Pinus (oak – pine) community is distinct from other forest types, and can be subdivided palynologically based upon relative importance of Quercus, Pinus and Cupressaceae [primarily Calocedrus decurrens (incense cedar)] pollen. Subdivisions include Quercus – Pinus – Cupressaceae, Quercus – Cupressaceae – Pinus and Quercus – Pinus assemblages. Higher elevation Pinus – Abies (pine – fir) and Pinus-dominated communities are also differentiated from one another, although the subalpine vegetation type only occurs on the San Bernardino Mountains transect. Though the study area presently straddles a transition between winter-wet and summer-wet climatic regimes, differences between the pollen assemblages in the two mountain ranges are minimal. Pollen assemblages from lower elevations document the effects of human activities, primarily agriculture, on the modern pollen rain of the region, with the occurrence of introduced citrus (Citrus sp.) and shade (Eucalyptus sp.) trees and weedy disturbance indicators (e.g., Brassicaceae).     

Can we detect a west Norwegian tree line from modern samples of plant remains and pollen? Results from the DOORMAT project

In the DOORMAT (Direct Observation of Recent Macrofossils Across Treeline) project, the modern representation of local vegetation by pollen and plant remains (plant macrofossils) across a west Norwegian tree line, composed of Betula pubescens and Pinus sylvestris, has been studied over 2 years. The aim was to discover if the modern tree line could be detected and therefore how precisely past tree-line movements could be reconstructed and related to Holocene climate changes by using one proxy or a combination of both. Traps were placed in the vegetation from 663 to 1,120 m a.s.l., spanning the pine altitudinal species limit, the birch tree-line ecotone, and the vegetation zones up to the mid-alpine zone. Three traps were also set in the small lake Trettetjørn close to the modern tree line at 800 m a.s.l. Traps were emptied twice a year to sample both summer and winter seasons. Macrofossils represent their local vegetation well. However, tree Betula remains were trapped above the tree line and Pinus and Picea remains were recorded 1.0–1.5 km away from their sources, demonstrating considerable dispersal capacity. This shows that rare macrofossil remains do not necessarily represent the local presence of these trees. Aerial tree pollen deposition in traps at the upper limit of pine woodland and in the subalpine birch woodland was unexpectedly low, whereas pollen accumulation rates (PAR) were orders of magnitude higher in the lake traps. We hypothesise that the lake receives regional pollen rain washed in from its catchment by snow meltwater and that high values in traps are due to continuous suspension of pollen in the lake water during summer. The interpretation of tree-line changes from existing Holocene pollen and plant macrofossil data from Trettetjørn was supported and refined by the DOORMAT macrofossil data, but the modern pollen data were anomalous.     

Tracing and interpreting fine-scale human impact in northern Fennoscandia with the aid of modern pollen analogues

A set of moss samples (n=58) was collected and analysed to obtain modern pollen analogues for both natural and human induced vegetation types in northern Fennoscandia. Vegetation types with settlement, trampling and grazing were selected from the different latitudinal forest zones (birch, pine, and mixed forest). The moss species varied between samples but the size of the sample was kept constant. Numerical analyses such as Redundancy Analysis (RDA) indicate that in northern areas human presence is mainly visible as increased values of Gramineae, Rumex acetosa/acetosella, R. obtusifolius, Solidago-type and Achillea-type pollen. Partial RDA further reveals that settlement is strongly correlated with high values of Rumex acetosa/acetosella, whereas trampled sites are significantly characterised by Gramineae and, to a smaller extent, Cyperaceae pollen. It is therefore possible to distinguish the impact of different types of human activities on vegetation on the basis of the pollen spectra. Later, these data will be used to interpret the presence, nature, and duration of human impact from fossil records from the same area. Received June 6, 2001 / Accepted December 12, 2001     

Spatial patterns and vegetation–site relationships of the presettlement forests in western New York, USA

Aim The purposes of this study were to develop a Geographic Information System and spatial analytical methodology to reconstruct and represent the presettlement vegetation in a spatially continuous manner over large areas and to investigate vegetation–site relationships before widespread changes of the vegetation had taken place. Location The study area was the Holland Land Company Purchase in western New York, a 14,400 km² area extending across the physiographic provinces of the Erie–Ontario Lowlands and the Appalachian Uplands. Methods Bearing‐tree records from the Holland Land Company township surveys of western New York in c. 1800 were collected and analysed. The geostatistical method of indicator kriging was used to map spatially continuous representations of individual tree species. Rule‐based and statistically clustered approaches were used to analyse and classify the reconstructed tree species distributions in order to obtain the vegetation association distribution. Contingency table analysis was conducted to quantify species relationships with soil conditions. Results The presettlement vegetation at both the tree species and the vegetation association levels were easier to interpret and visually more effective as a spatially continuous representation than as a discontinuous distribution of symbols. The results for tree species were probability occurrences of species distribution, showing spatial patterns that were not apparent in discrete maps of points or in summary tables of species frequencies. Analysis of the 8792 bearing trees suggested the dominance of American beech (Fagus grandifolia) and sugar maple (Acer saccharum) in the forest composition 200 years ago. Both soil drainage and texture were important site determinants of the vegetation in western New York. The rule‐based and statistically clustered approaches had the advantage of summarizing vegetation compositional patterns in a single image, thus avoiding the need to delineate manually and subjectively the location of boundaries between adjacent vegetation associations. Main conclusions The study offers more insights into the spatial pattern of presettlement forests in western New York than do prior studies. The spatially continuous representation could also enable the comparison of vegetation distribution from data sources that have different sampling schemes, for example the comparison of presettlement vegetation from the presettlement land survey records with current vegetation from modern forest inventories. The results are of value, providing a useful benchmark against which to examine vegetation change and the impacts of human land use.     

Modern pollen and vegetation relationships in northeastern Patagonia (Golfo San Matías,Río Negro)

The understanding of modern pollen is a critical component of palaeoecological research. The pollen assemblages reflect general patterns in vegetation distribution; however, pollen representation is biased by several factors such as differences in pollen production, dispersal and preservation. Therefore, this relationship cannot be applied directly in pollen records of the past. The aim is to study the relationship between modern pollen and vegetation and to apply this new information on the interpretation of Holocene pollen records. Classification of the vegetation into groups corresponding to different geomorphological units was carried out by cluster analysis. Discriminant analysis was applied on the surface samples to test if different vegetation types could be distinguished by their pollen assemblages. To evaluate the relationship between pollen assemblages and vegetation types, association (A), under-representation (U) and over-representation (O) indexes were calculated for all present taxa in both plant and pollen dataset. The main vegetation types are reflected in pollen assemblages but with greater differences in the proportions of Poaceae, Hyalis argentea, Chenopodiaceae, Asteraceae subf. Asteroideae and Larrea divaricata. Association and representation indexes provided information related to the production rate and pollen dispersal. This study helps to interpret Holocene vegetation and environmental changes from fossil pollen records of the study area.     

Pollen distribution in the bottom sediments of the western North Atlantic Ocean

An extensive survey of pollen distribution in surficial sediments from the slope and rise between 29° and 72°N, shows patterns which reflect the distribution of vegetation in eastern North America and the effects of aeolian, fluvial, and marine sedimentation. The results of the analysis of 94 core tops show that pollen concentration ranges from 23,000 to 10 grains per gram, and decreases offshore with distance from vegetation sources and northward in relation to lower vegetation density. Maximum concentration occurs in organic-rich, fine-grained lutum deposited off rivers draining the southeastern United States. Low pollen concentrations are associated with high-energy environments, such as the Western Boundary Undercurrent and the Labrador Current. Percentages of dominant pollen types generally correspond with onshore distribution of pollen and vegetation. Oak and other deciduous pollen types are the most abundant in marine sediments off the deciduous forests of eastern United States. Hemlock pollen is essentially restricted to sediments off the hemlock-oak forests of northeastern U.S. and southeastern Canada, and spruce pollen is most abundant adjacent boreal forests and forest-tundra formations. The relative increase in pine pollen seaward reflects the selective effects of marine transport. Synthesis of pollen data by Q-mode factor analysis shows that major vegetation formations of eastern North America produce distinctive, regional marine pollen assemblages.     

Modern pollen representation of source vegetation in the Qaidam Basin and surrounding mountains, north-eastern Tibetan Plateau

We use a data set of 35 surface pollen samples from lake sediments, moss polsters and top soils on the north-eastern Tibetan Plateau to explore the relationship between modern pollen assemblages and contemporary vegetation patterns. The surface pollen transect spanned four vegetation zones––alpine meadow, steppe, steppe desert and desert––under different climatic/elevational conditions. Relative representation (R _rel) values and Principal Components Analysis (PCA) were used to determine the relationships between modern pollen and vegetation and regional climate gradients. The results show that the main vegetation zones along the regional and elevational transects can be distinguished by their modern pollen spectra. Relative to Poaceae, a high representation of Artemisia, Nitraria and Chenopodiaceae was found, while Cyperaceae and Gentiana showed values in the middle range, and Ranunculaceae, Asteraceae, Ephedra and Fabaceae had low relative representation values. PCA results indicate a high correlation between the biogeoclimatic zones and annual precipitation and annual temperature and July temperature. The Artemisia/Chenopodiaceae ratio and the Artemisia/Cyperaceae ratio are useful tools for qualitative and semi-quantitative palaeoenvironmental reconstruction on the north-eastern Tibetan Plateau. Surface lake sediments are found to have different palynomorph spectra from moss cushion and soil samples, reflecting the larger pollen source area in the contemporary vegetation for lakes.     

Differentiating vegetation types from eastern South American ecosystems based on modern and subfossil pollen samples: evaluating modern analogues

In south and southeast Brazil land use caused profound changes in natural vegetation and consequently the value of the pollen composition in surface samples as modern analogues. In order to test the capability of modern pollen to represent the natural vegetation, three different time slices of pollen assemblages from 27 sites spread over southern and south-eastern Brazil and the Misiones Province in Argentina were collated. Pollen samples from the pre-colonization period, selected from the moment just before abrupt changes evidenced on pollen diagrams caused by the colonization process throughout the last 500 years, were assumed to represent the natural vegetation conditions once the climate remained stable within this period. Thus we used pre-colonization assemblages to compare with modern samples to explore to what extent surface pollen may be biased in representing the natural vegetation types. Furthermore, to compare man made vegetation change to climate driven vegetation change we also compared to these 20 out of 27 samples dated to 3,000 years bp. Guided by ordination and cluster analysis, but using abundance thresholds of indicator taxa we classified the pollen spectra of pre-colonization time into seven groups consistent with the main vegetation types in the area. Ordination analyses capture the differentiation between grassland and forested vegetation and between tropical and subtropical vegetation types. Comparing the pre-colonization with other time slices we observed that based on Poaceae abundance, 70 and 85 % respectively of sites from 3,000 bp and modern assemblages maintained their classification. Based on finer classification criteria these values decreased to 40 and 52 % respectively. Square chord dissimilarity indicates that colonization impact altered the pollen composition as strongly as 3,000 years of climate induced vegetation change. The surface samples still represent important environmental gradients; however, their use as modern analogue requires careful treatment and eventual exclusion of highly impacted sites.     

Numerical analysis of pollen samples from central Canada: A comparison of methods

The compilation of large and complex sets of modern pollen data has stimulated the use of new methods, including the use of multivariate statistical techniques, for summarizing and presenting these data. This paper compares several of these methods by applying them to Lichti-Federovich and Ritchie's (1968) 131 sediment samples of modern pollen from central Canada. Maps of the major pollen types are presented, and the data are analyzed by canonical variates analysis, principal components analysis, principal coordinates analysis, and minimum-variance cluster analysis.The maps show the geographical distribution of the principal pollen types and reveal that steep gradients in the percentages of eight of the nineteen pollen types used in this study separate the samples in the southwest from the remaining samples. Excluding the southwestern samples, the maps show the frequencies of the other pollen types to be aligned north to south with high values of sedge, birch, and heath pollen in the north, high values of pine in the south, and high values of spruce and alder in between. This same general structure is evident in the results of the four multivariate analyses. The samples are distributed in a closely similar manner along the first two axes derived from canonical varietes analysis, principal components analysis, and principal coordinates analysis. The first axis of each analysis separates the samples in the southwest from the rest of the samples, and the second axis shows these latter samples to be spread fairly evenly along a north—south gradient from the tundra samples to the mixed coniferous—deciduous forest samples. Minimum-variance cluster analysis also shows these divisions by clustering the samples into three major groups: the southwestern samples from the prairie, aspen parkland, and deciduous forest; the northern samples from the tundra and forest—tundra; and the intermediate samples from the mixed forest and closed coniferous forest regions. Further division by the clustering technique yields fourteen groups, and these show the pollen samples to cluster slightly differently from their classification based on their location within the vegetational units. For example, the samples of the forest—tundra and the open coniferous forest are grouped together, but the samples of the upland mixed forest are too heterogeneous in pollen composition to be placed in one group.These results indicate the power of these numerical methods that use prescribed mathematical steps to analyze all samples and major pollen types simultaneously and thereby reveal the basic structure in the data based on numerical criteria alone. These summaries aid an investigator in visualizing the important trends and divisions in a data set and in finding those samples needed for a particular comparison.     

A new methodology for reconstructing climate and vegetation from modern pollen assemblages: an example from British Columbia

Aim We used modern pollen assemblages to develop a method for climate reconstruction that reduces the spatial autocorrelation of residuals and accounts for the strong topographic and climatic variation that occurs in British Columbia, Canada. Location British Columbia, Canada, including sites both on the mainland and on adjacent islands (Queen Charlotte Islands and Vancouver Island). Methods New pollen assemblages from surface‐sediment samples collected in British Columbia were combined with other published and unpublished samples (n = 284). Multivariate rank‐distances between sample sites and a randomized set of sites within the province were calculated for climate parameters to determine whether gaps in the current network of present‐day pollen sample sites exist. Lacustrine surface‐sediment pollen assemblages (n = 145) were ordinated using non‐metric multidimensional scaling (NMDS), and a generalized additive model (GAM) was used to reconstruct modern mean warmest month temperature (MWMT) and mean annual precipitation (MAP) from the NMDS ordination. The results were compared with standard climate reconstruction techniques, including the modern analogue technique, partial least squares, weighted averaging, weighted averaging–partial least squares and factor analysis. Results Reconstructions of MWMT and MAP using NMDS and GAM were comparable to those of existing models. When reconstructing MWMT, the NMDS/GAM method had a lower root‐mean‐squared error of prediction (RMSEP), lower spatial autocorrelation and higher correlation with observed temperature values than the other methods tested. When reconstructing MAP, the partial least squares method performed better than the NMDS/GAM method for RMSEP and correlation with observed values; however, the NMDS/GAM method had a lower spatial autocorrelation of residuals. Main conclusions NMDS reveals strong relationships among modern pollen assemblages, vegetation and climate parameters. Climate models using NMDS and GAM are comparable to other palaeoecological reconstruction models, but provide lower spatial autocorrelation of residuals for both parameters tested. An inverse distance‐weighted surface of multivariate rank‐climate distances generated from the network of pollen sample sites indicates that greater sampling intensity in north‐western and central‐interior British Columbia is required in order to obtain an accurate representation of climatic and vegetation diversity in the province.     

Modelling pollen sedimentation in Danish lakes at c.ad 1800: an attempt to validate the POLLSCAPE model

Aims To validate the POLLSCAPE simulation model of pollen dispersal and deposition, and evaluate the effect of factors such as pollen productivity, wind speed and regional plant abundance, using a data set of ad 1800 pollen assemblages and historical land cover data. Location Denmark. Methods ad 1800 land cover from historical maps is digitized for 2000 m radii around 30 Danish lakes (3.5–33 ha). The simulation model POLLSCAPE is used to predict sedimentary pollen assemblages in the lakes from the plant abundance data inferred from these maps, with different model parameter settings for wind speed, pollen productivity, regional pollen loading, etc. The model predictions are compared with observed ad 1800 pollen assemblages from the lake sediment records. Furthermore, pollen productivity is estimated from the ad 1800 pollen and vegetation data using the Extended R‐value model. Results Generally the model reproduces the patterns in the observed pollen assemblages, and for most pollen types there are significant correlations between observed and predicted pollen proportions. The pollen proportions predicted by the POLLSCAPE model are sensitive to the pollen productivity estimates used, the regional background pollen loading and average wind speed. There is a difference in background pollen loading between eastern and western Denmark, especially of Calluna pollen. The fit between predicted and observed pollen assemblages is best at wind speeds around 2.5 m s^?1, and decreases rapidly at lower wind speeds. The pollen productivity estimates from the ad 1800 data set are comparable with estimates from moss polsters in modern analogues of traditional cultural landscapes in Sweden and Norway. Main conclusions The POLLSCAPE model reproduces the patterns in the observed pollen assemblages from the lakes well, considering the uncertainty in the historical plant abundance data. This study indicates that the simulation model can be a useful tool for investigating relationships between vegetation and pollen composition, but also that the simulated pollen proportions are sensitive to the pollen productivity estimates, the regional background and to wind speed.     

Modern vegetation–pollen–climate relationships for the Pampa grasslands of Argentina

Aim To analyse the relationships between potential natural vegetation, pollen and climate in order to improve the interpretation of fossil pollen records and provide the background for future quantitative palaeoclimatic reconstructions. Location Pampa grasslands of Argentina, between 33–41° S and 56–67° W. Methods Modern pollen data were obtained from a pollen data base developed by the Grupo de Investigación de Paleoecología y Palinología, Universidad Nacional de Mar del Plata, Argentina (143 surface samples and 17 pollen types). Analysis of pollen and climate data involved multivariate statistics (cluster analysis and principal components analysis), scatter diagrams, Pearson’s correlation and isopoll mapping. Results Vegetation patterns at regional scales (grasslands and xerophytic woodlands) and local scales (edaphic communities) were identified by cluster analysis of pollen surface samples. The main climatic variables that appear to constrain the vegetation distribution and abundance of taxa are mean annual precipitation, annual effective precipitation and summer temperature. Individual pollen types such as Chenopodiaceae, Apiaceae, Cyperaceae, Prosopis, Schinus, Condalia microphylla and other xerophytic taxa are good indicators of moisture regime. Many pollen types are significantly correlated with summer temperature. The modern vegetation–pollen–climate relationships vary in a broadly predictable manner, supporting the contention that fossil pollen assemblages can be related to particular climatic characteristics. Main conclusions An expanded suite of modern analogues facilitated new insights into vegetation–pollen–climate relationships at the regional scale in Pampa grasslands. Relationships between individual pollen types and climate are appraised at a regional scale and new modern analogues are presented. The results provide the basis for improved vegetation and climate reconstruction from fossil records of the study area.     

南京紫金山山麓湖泊表层沉积物的孢粉分析

本研究对南京紫金山山麓玄武湖和前湖共17个湖泊表层沉积物样品进行孢粉分析,旨在获得花粉组合新数据,揭示湖泊表层花粉与现生植被的关系,为开展第四纪湖泊地层孢粉学研究提供现代过程的参考.研究结果表明,花粉组合在剔除非自然分布的种植木本植物干扰花粉外,主要以木本花粉的松属(Pinus)和栎属(Quercus)占优势,其他常见...     

A survey of modern pollen and vegetation along a south–north transect in Mongolia

Aim This modern pollen‐rain study documents the spatial and quantitative relationships between modern pollen and vegetation in Mongolia, and explores the potential for using this relationship in palaeoclimatic reconstructions. Location East‐central Mongolia. Methods We collected 104 pollen surface samples along a south–north transect across five vegetation zones in Mongolia. Discriminant analysis was used to classify the modern pollen spectra into five pollen assemblages corresponding to the five vegetation zones. Hierarchical cluster analysis was used to divide the main pollen taxa into two major groups and seven subgroups representing the dry and moist vegetation types and the main vegetation communities within them. Results Each vegetation zone along the transect can be characterized by a distinctive modern pollen assemblage as follows: (1) desert zone: Chenopodiaceae–Zygophyllaceae–Nitraria–Poaceae pollen assemblage; (2) desert‐steppe zone: Poaceae–Chenopodiaceae pollen assemblage; (3) steppe zone: Artemisia–Aster‐type–Poaceae–Pinus Haploxylon‐type pollen assemblage; (4) forest‐steppe zone: Pinus Haploxylon‐type–Picea–Artemisia–Betula, montane forb/shrub and pteridophyte pollen assemblage; and (5) mountain taiga zone: Pinus Haploxylon‐type–Picea–Poaceae–Cyperaceae, montane forb/shrub and Pteridophyte pollen assemblage. Main conclusions Based on the ratio between the major pollen taxon groups and subgroups, we propose two pollen–climate indices that represent the precipitation and temperature conditions in the study region. When plotted along our south–north transect, the moisture indices (M) and temperature indices (T) mimic the regional gradients of precipitation and temperature across Mongolia very closely. These pollen–climate indices can be used for palaeoclimatic reconstruction based on fossil pollen data.     

Pollen-vegetation richness and diversity relationships in the tropics

Tracking changes in biodiversity through time requires an understanding of the relationship between modern diversity and how this diversity is preserved in the fossil record. Fossil pollen is one way in which past vegetation diversity can be reconstructed. However, there is limited understanding of modern pollen-vegetation diversity relationships from biodiverse tropical ecosystems. Here, pollen (palynological) richness and diversity (Hill N₁) are compared with vegetation richness and diversity from forest and savannah ecosystems in the New World and Old World tropics (Neotropics and Palaeotropics). Modern pollen data were obtained from artificial pollen traps deployed in 1-ha vegetation study plots from which vegetation inventories had been completed in Bolivia and Ghana. Pollen counts were obtained from 15 to 22 traps per plot, and aggregated pollen sums for each plot were >?2,500. The palynological richness/diversity values from the Neotropics were moist evergreen forest?=?86/6.8, semi-deciduous dry forest?=?111/21.9, wooded savannah?=?138/31.5, and from the Palaeotropics wet evergreen forest?=?144/28.3, semi-deciduous moist forest?=?104/4.4, forest-savannah transition?=?121/14.1; the corresponding vegetation richness/diversity was 100/36.7, 80/38.7 and 71/39.4 (Neotropics), and 101/54.8, 87/45.5 and 71/34.5 (Palaeotropics). No consistent relationship was found between palynological richness/diversity, and plot vegetation richness/diversity, due to the differential influence of other factors such as landscape diversity, pollination strategy, and pollen source area. Palynological richness exceeded vegetation richness, while pollen diversity was lower than vegetation diversity. The relatively high global diversity of tropical vegetation was found to be reflected in the pollen rain.