Modern pollen/vegetation/land-use relationships in mountain environments: an example from the Champsaur valley (French Alps)

This study aims at elucidating modern pollen spectra/environmental data relationships from both natural and human-induced vegetation types as an aid for palaeo-ecological reconstructions. A set of 51 surface moss polsters was sampled from different vegetation and land-use types in the Champsaur area (French Alps) and analysed to obtain modern pollen analogues of ancient cultural landscapes in mountain ecosystems. Samples were selected from grazed areas, mown meadows, cultivated fields, fallow land and deciduous and coniferous forests. Vegetation composition around the sampling points and seventeen types of environmental variables (e.g., management type, soil and topography) were collected all for these 51 sites. Patterns of modern local pollen variation in relation to the environmental variables were explored by means of canonical correspondence analysis (CCA) and associated statistical tests. This correlative model allows us to determine the major explanatory variables and to identify taxa indicative of particular anthropogenic activities, and thus may help to calibrate fossil pollen assemblages.The indicator pollen types are evaluated in the light of comparable material from lowland and mid-elevation areas of western Europe. The results of the French data-set confirm some of the conclusions drawn from the North European data-sets, but also show some site specific features. Pollen markers with a broader global significance common to other regions include Rhinanthus type, Apiaceae and Dipsacaceae for mown meadows, Urtica type, Plantago media/major, Trifolium type and Potentilla type for grazed areas, and Cerealia type, Centaurea cyanus, and Polygonum aviculare for cultivated fields. New pollen anthropogenic indicators typical of our study area are Sanguisorba officinalis, Vicia type (mowing), Lotus type, Onobrychis type, Centaurea nigra type, Serratula type (grazing), Sinapis type and Papaver rhoeas (cultivation). This study provides potentially valuable analogues for human-induced vegetation types, and it may then become possible to interpret more objectively local pollen diagrams from Alpine mountain environments in terms of past cultural landscape development.     

Vegetation and climate reconstructions on different time scales in China: a review of Chinese palynological research

This paper reviews vegetation and climate reconstructions for different time scales based on palynological studies in China. It discusses examples of significant developments in palynological research topics within China: (1) Modern pollen—a modern pollen database (East Asia Surface Pollen Database) has been established through the collaboration of Chinese palynologists. Based on these data, modern pollen distributions and their quantitative relationship with vegetation and climate have been thoroughly studied. (2) Pre-Quaternary vegetation and climate dynamics—scientists have mapped pollen and palaeobotanical data from the Palaeogene. The vegetation distributions confirm a north–south zonal pattern during the Palaeogene that changed to an east–west monsoonal pattern during the Miocene and Pliocene. These results provide key evidence for understanding monsoon evolution. (3) Late-Quaternary vegetation—biome reconstructions based on fossil pollen data show spatial and temporal changes in vegetation since the Last Glacial Maximum, permitting a better understanding of climate change across China. (4) Quantitative climate reconstructions—some reconstructions have successfully detected Holocene climate variability thereby providing insights into monsoon history. At present, there are no comprehensive spatial reconstructions. Major possible future developments should focus on: (1) long-term vegetation reconstructions from lakes to study Asian monsoon dynamics at orbital scales; (2) quantitative reconstructions of vegetation and climate change to help stronger integration with palaeoclimate models and dynamic vegetation models; (3) land-cover and land-use change across China over the last 6,000 years to understand human impacts and provide empirical data for climate modellers; and (4) integration of pollen data with vegetation and climate modelling to understand the CO₂-vegetation relationship and climate dynamics.     

南京低山丘陵区表土及捕捉器花粉谱的差异探究

选取南京丘陵地区29处样点,分别搜集表土及捕捉器样品,开展两种采样方式下孢粉组合与植被关系研究。结果表明,南京低山丘陵地区花粉类型以松属、栎属、枫杨属、榆属、蔷薇科、菊科、禾本科为主,表土花粉组合较好地反映了现代植被特征。主成分分析可以大致区分人工草坪区、农田区以及森林区的样品。农田区表土花粉浓度最低,每克仅为4 964粒,农田的翻耕以及微生物环境是造成其花粉浓度低的重要原因;森林区花粉浓度(每克29 176粒)及花粉通量(49 358粒/平方厘米/年)均很高。人类活动的增强可能会造成孢粉浓度的下降。在探究本地区历史时期人类活动时,可运用孢粉浓度以及与农作物相关的孢粉类型的变化来分析。所有捕捉器样品的乔木花粉百分比均低于其对应的表土样品,其中以松属尤为明显。     

Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? An empirical test in southern Sweden

In this paper we test the performance of the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using pollen records from multiple small sites. We use Holocene pollen records from large and small sites in southern Sweden to identify what is/are the most significant variable(s) affecting the REVEALS-based reconstructions, i.e. type of site (lakes and/or bogs), number of sites, site size, site location in relation to vegetation zones, and/or distance between small sites and large sites. To achieve this objective we grouped the small sites according to (i) the two major modern vegetation zones of the study region, and (ii) the distance between the small sites and large lakes, i.e. small sites within 50, 100, 150, or 200 km of the large lakes. The REVEALS-based reconstructions were performed using 24 pollen taxa. Redundancy analysis was performed on the results from all REVEALS-model runs using the groups within (i) and (ii) separately, and on the results from all runs using the groups within (ii) together. The explanatory power and significance of the variables were identified using forward selection and Monte Carlo permutation tests. The results show that (a) although the REVEALS model was designed for pollen data from large lakes, it also performs well with pollen data from multiple small sites in reconstructing the percentage cover of groups of plant taxa (e.g. open land taxa, summer-green trees, evergreen trees) or individual plant taxa; however, in the case of this study area, the reconstruction of the percentage cover of Calluna vulgaris, Cyperaceae, and Betula may be problematic when using small bogs; (b) standard errors of multiple small-site REVEALS estimates will generally be larger than those obtained using pollen records from large lakes, and they will decrease with increasing size of pollen counts and increasing number of small sites; (c) small lakes are better to use than small bogs if the total number of small sites is low; and (d) the size of small sites and the distance between them do not play a major role, but the distance between the small sites and landscape/vegetation boundaries is a determinant factor for the accuracy of the vegetation reconstructions.     

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.     

Numerical analysis of modern and fossil pollen spectra as a tool for elucidating the nature of fine-scale human activities in boreal areas

Modern pollen assemblages from the major vegetation units (both natural and anthropogenic) on the island of Hailuoto, Finland are studied from 29 surface moss samples. A total of 59 pollen and spore taxa are recorded. The pollen data-set is related by redundancy analysis (RDA) to six external synthetic variables that characterize in general terms the different major ecological situations relevant to the land-use on the island (sand, humus, forest, field, deforested, treeless). Weighted average (WA) optima are calculated to identify which pollen taxa are most indicative of four of these external variables. Two fossil pollen diagrams from Hailuoto are re-interpreted by positioning their samples on the RDA plot of the modern data-set and by classifying the modern and fossil spectra together in a minimum-variance cluster analysis. The RDA plot shows that the strongest features in the modern pollen assemblages are the contrast between spectra from dry sandy soils and those from damper soils with more organic content, and between assemblages from forested and unforested areas. For anthropogenic situations the numerical analyses detect a distinction in the pollen assemblages characterizing fields from those representing farms and trackways but is less successful in separating the latter two. The WA optima indicate that most pollen taxa considered as indicator types primarily represent a mixed field/farm category of land-use. The RDA and minimum-variance cluster analysis confirm that the two fossil sites have had different vegetational histories. In neither is there any phase equivalent to the modern farm situation on Hailuoto. The initial phase in each diagram represents shore meadows and fields but because Poaceae pollen is identifiable only to family level it is not possible to separate these two habitat types.     

Pollen assemblages of tauber traps and surface soil samples in steppe areas of China and their relationships with vegetation and climate

We use 86 pollen trap and surface soil pollen samples in steppe areas of China to explore the relationships between modern pollen, vegetation, and climate. The modern pollen spectra from both sources have comparable compositions with regard to the major pollen taxa. However, the number of taxa in the traps was higher than in the surface soil samples. Both pollen accumulation rates and pollen concentrations are higher in the typical steppe areas than in the desert steppe areas. Discriminant analysis indicates that pollen spectra from trap and surface soil samples roughly reflect the vegetation zones of desert steppe and typical steppe, especially in the case of the trap samples. Detrended canonical correspondence analysis suggests that pollen assemblages have a significant relationship with the temperature of the coldest month and the mean annual precipitation.     

The use of modelling and simulation approach in reconstructing past landscapes from fossil pollen data: a review and results from the POLLANDCAL network

Information on past land cover in terms of absolute areas of different landscape units (forest, open land, pasture land, cultivated land, etc.) at local to regional scales is needed to test hypotheses and answer questions related to climate change (e.g. feedbacks effects of land-cover change), archaeological research, and nature conservancy (e.g. management strategy). The palaeoecological technique best suited to achieve quantitative reconstruction of past vegetation is pollen analysis. A simulation approach developed by Sugita (the computer model POLLSCAPE) which uses models based on the theory of pollen analysis is presented together with examples of application. POLLSCAPE has been adopted as the central tool for POLLANDCAL (POLlen/LANdscape CALibration), an international research network focusing on this topic. The theory behind models of the pollen–vegetation relationship and POLLSCAPE is reviewed. The two model outputs which receive greatest attention in this paper are the relevant source area of pollen (RSAP) and pollen loading in mires and lakes. Six examples of application of POLLSCAPE are presented, each of which explores a possible use of the POLLANDCAL tools and a means of validating or evaluating the models with empirical data. The landscape and vegetation factors influencing the size of the RSAP, the importance of pollen productivity estimates (PPEs) for the model outputs, the detection of small and rare patches of plant taxa in pollen records, and quantitative reconstructions of past vegetation and landscapes are discussed on the basis of these examples. The simulation approach is seen to be useful both for exploring different vegetation/landscape scenarios and for refuting hypotheses.     

Modern pollen-based biome reconstructions in East Africa expanded to southern Tanzania

New detailed biome reconstructions are proposed in East Africa from modern pollen data derived from 150 sites located in northern Kenya (40 sites), north-western Uganda (51 sites) and southern Tanzania (59 new sites presented as pollen diagram), which are representative of the major vegetation associations occurring in seven phytogeographical regions, mosaics or centres of endemism. We use the standard biomisation method previously published for the African continent, but we reconsider the taxa assignment to plant functional types. We include in this approach all identified taxa (408) except aquatics, ferns and exotic taxa. The method is validated by comparison with local vegetation data and we show that 124 (82.6%) sites are assigned to the correct biome and that for all the biomes under investigation, the number of correct assignments always exceeds the number of incorrect ones. When an incorrect biome reconstruction occurs, mainly toward drier biomes, this is generally linked to the local open/degraded structure of the original vegetation or to the occurrence of a mosaic of open/closed vegetation. In turn, most of the reconstructions of more humid/closed biomes than the corresponding local vegetation (8.6%) remain unexplained. A comparison of our reconstructed biomes with the main East African vegetation types of White's map indicates that 121 (80.6%) sites are assigned to the correct biomes. However, the majority of sites are incorrectly reconstructed compared to Olson and IGBP maps from satellite data, mainly due to incorrect allocation of the land cover classes compared to the potential vegetation. The application of this method to our pollen data set demonstrates that modern pollen assemblages can successfully reconstruct the main modern East African vegetation types.     

Effects of the sampling design and selection of parameter values on pollen-based quantitative reconstructions of regional vegetation: a case study in southern Sweden using the REVEALS model

The need for quantification of land cover from pollen data has led to the development of a Landscape Reconstruction Algorithm (LRA). The LRA includes several models of which the REVEALS model estimates regional vegetation abundance using pollen assemblages from large sites (lakes or bogs). In this paper we explore the effects of selection and number of pollen samples, and choice of pollen productivity estimates on the REVEALS results. The effect of the size of vegetation surveys is also tested. The results suggest that the differences between two sizes of vegetation surveys have little effect on the model validation. The “characteristic radius” of regional vegetation in southern Sweden was estimated as 200 km. However, the vegetation composition in a 100 × 100 km² square matches well with that estimated by REVEALS. Whether 25, 20 (outliers excluded) or 4 pollen samples are used does not change the REVEALS reconstructions much although the error estimates are larger when outliers are included, and very large when only four samples are used. Therefore validation of the REVEALS model and REVEALS reconstructions of past vegetation can be performed using a limited number of pollen samples, although with caution. The use of many pollen samples from multiple sites is always better whenever possible. REVEALS reconstructions are closer to the actual vegetation when the Danish Pollen Productivity Estimates (PPEs) are used instead of the Swedish PPEs for Cereals, Rumex acetosa/acetosella, Plantago lanceolata and Calluna, indicating that the Danish PPEs are more reliable than the Swedish ones for those taxa. It is recommended to test more than one set of PPEs in validation and applications of the REVEALS model for a better evaluation of the results.     

The influence of past land-use on understory plant distributions in a near-natural deciduous forest in Denmark

In regions with a long cultural history, past land-use may strongly determine floristic composition in seemingly natural vegetation. Here we examine if past land-use affects understory plant distribution in near-natural forest in a historically and environmentally heterogeneous setting, namely the 17 ha freshwater island of Borgnr (Denmark). In 107 randomly located 100 m² plots we recorded species composition and various environmental variables. The plots were classified into three groups according to past land-use: (1) Disturbed sites close to 12^th and 20^th century ruins and associated open areas; (2) formerly grazed meadow areas; and (3) forested sites without indications of strong anthropogenic influence. Past land-use, environmental variables and species traits were used to interpret floristic gradients. Unconstrained and constrained ordinations clearly separated plots with different past land-use, and showed that the main floristic gradients on Borgø correlated with hydrological-edaphic conditions and past land-use. Partial constrained ordination using the environmental parameters as covariables showed that past land-use had a unique influence on floristic composition.     

云南丽江-大理地区现代表土花粉垂直分布特征

文章主要研究云南丽江-大理地区不同海拔高度表土花粉。虽然松属花粉在各个植被带都占有优势,但是建群种花粉含量相对较高。降趋对应分析法（detrended correspondenc eanalysis,简称DCA）分析显示,表土花粉的分布和海拔之间具有非常密切的关系,DCA第一轴的值和海拔高度之间的线性相关系数达0．82（r^2=0．82）。此次研究表明,在云南山地,可以通过含量相对较高的花粉来重建古植被。     

The interpretation of fen carr pollen diagrams: pollen–vegetation relationships within the fen carr

Sediments deposited in fen carr environments are frequently used in pollen-based reconstructions of vegetation history, although few studies of modern pollen–vegetation relationships in fen carr have been undertaken to aid the interpretation of fossil assemblages. It is often assumed that the wetland pollen signal will reflect the overall composition of the fen carr system although, given the closed canopy context, it may actually be dominated by local vegetation elements. This paper seeks to determine whether the vegetation heterogeneity within a modern fen carr is reflected in the pollen signal of the wetland taxa. Vegetation composition was recorded around a series of moss polster sample points at Calthorpe and Wheatfen, two areas of fen carr in the Norfolk Broadland, UK. The spatial interrelationship between the wetland components of the vegetation and their palynological equivalents in the moss polster pollen assemblages is explored through trend surfaces and a correlation based statistical test (the Mantel Test). The representation of the major vegetation components in the pollen record is highly variable. Values for Alnus glutinosa, a dominant canopy species, range from 5.3% to 73% of total land pollen (TLP) at Calthorpe and 2.5–61% TLP at Wheatfen. In part, this variation reflects the enhanced input of pollen from dry land sources close to the wetland edge although the variation recorded at points equidistant from the dry land margin suggests that other processes are also influential. The strongest positive associations in the Mantel Test are for under-storey and ground flora elements that are poorly represented in the pollen record. Taxa for which there is no association include those with few vegetation occurrences and those for which a large proportion of the pollen appears to have been derived from outside the study areas. We conclude that modern pollen samples collected from fen carr broadly reflect the vegetation composition of the study areas. However, the input of pollen from fen carr species is spatially inconsistent. Differences between the sample points can be attributed to the distribution and pollination biology of the under-storey and ground flora elements and the structure of the vegetation around sites. The results caution against assuming that changes in the pollen representation of wetland taxa, in fossil sequences constructed from fen carr deposits, necessarily reflect changes in the overall composition of the community.     

Historical land‐use and landscape change in southern Sweden and implications for present and future biodiversity

The two major aims of this study are (1) To test the performance of the Landscape Reconstruction Algorithm (LRA) to quantify past landscape changes using historical maps and related written sources, and (2) to use the LRA and map reconstructions for a better understanding of the origin of landscape diversity and the recent loss of species diversity. Southern Sweden, hemiboreal vegetation zone. The LRA was applied on pollen records from three small bogs for four time windows between AD 1700 and 2010. The LRA estimates of % cover for woodland/forest, grassland, wetland, and cultivated land were compared with those extracted from historical maps within 3‐km radius around each bog. Map‐extracted land‐use categories and pollen‐based LRA estimates (in % cover) of the same land‐use categories show a reasonable agreement in several cases; when they do not agree, the assumptions used in the data (maps)‐model (LRA) comparison are a better explanation of the discrepancies between the two than possible biases of the LRA modeling approach. Both the LRA reconstructions and the historical maps reveal between‐site differences in landscape characteristics through time, but they demonstrate comparable, profound transformations of the regional and local landscapes over time and space due to the agrarian reforms in southern Sweden during the 18th and 19th centuries. The LRA was found to be the most reasonable approach so far to reconstruct quantitatively past landscape changes from fossil pollen data. The existing landscape diversity in the region at the beginning of the 18th century had its origin in the long‐term regional and local vegetation and land‐use history over millennia. Agrarian reforms since the 18th century resulted in a dramatic loss of landscape diversity and evenness in both time and space over the last two centuries leading to a similarly dramatic loss of species (e.g., beetles).     

Using quantitative pollen-based land-cover estimations and a spatial CA_Markov model to reconstruct the development of cultural landscape at Rõuge,South Estonia

Quantitative pollen-based land-cover reconstruction covering the last 4,000 years was performed using transformation coefficients derived from a modern pollen land-cover database and a palynological record from an annually laminated sequence in Lake Rõuge Tõugjärv. Proportions of four land-cover classes characteristic of cultural landscape were reconstructed: habitation area, arable land, grassland and woodland. A land-use change model using CA_Markov analysis was applied for spatial reconstructions for seven periods: 600 b.c., a.d. 300, 800, 1200, 1700, 1870 and 1940. Historical maps from a.d. 1684, 1870–1899 and 1935 were used for calibration of quantitative estimates and to validate spatial reconstructions. The accuracy of the estimates depends on the availability of modern analogues and differs among land-cover classes, being highest for classes with directly connectable pollen indicator types (arable land, forest) and lowest for settlement areas. Spatial reconstructions produced by the CA_Markov land-cover change model show moderate accordance with historical data. However, the large uncertainties in land-cover input data must be considered in the evaluation of the KIA results of the spatial model. Permanent low intensity, rural land-use in the Rõuge area started at the beginning of the Bronze Age (c. 1800 b.c.). The major increase in the extent of rural land-use took place at the beginning of the 13th century and culminated during the 19th century when c. 90% of the RSAP of Rõuge Tõugjärv was open. During the last century, rural land-use decreased constantly.     

Subrecent spore–pollen spectra and modern vegetation from the Lena River Delta,Russian Arctic

This paper presents the results of a pollen analysis of 40 surface samples collected from various geomorphological levels such as low and high floodplains, surfaces and slopes of terraces, tops of island remnants, etc., in different parts of the Lena River Delta. The obtained spore–pollen spectra (SPS) were compared with the modern vegetation composition. The role of long-distance transported pollen and the pollen of local plant biocenoses in the subrecent SPS formation is shown. Modern vegetation is most adequately reflected in the spectra of samples from a height range from 11 to 52 m above river level. SPS of other samples contain up to 40% of long-distance transported pollen, mostly Pinus s/g Haploxylon. This results in a significant decrease in the percentage of local pollen. The data offer the possibility of improving the reliability of palaeoclimatic reconstructions based on palaeopalynological data for Arctic regions.     

The relationship between pollen and extant vegetation across an arid urban ecosystem and surrounding desert in Southwest USA

Aim In this paper, we explore the relationship between pollen concentration in surface soil and extant perennial vegetation across a rapidly urbanizing arid ecosystem along with its surrounding agricultural and native Sonoran Desert land. We also investigate whether taxa behave as expected from known pollination characteristics (e.g. anemophilous vs. zoophilous) and whether the pollen–plant relationship differs between the undeveloped desert and agro‐urban regions. Location We used a probability‐based sampling scheme at 200, 900‐m² sites across the Central Arizona–Phoenix region, a 6400‐km² area of the south‐western USA. Methods Pollen–plant abundances were mapped across the study area using interpolation techniques, summary bar charts and scatterplots, then two statistical approaches were applied to examine the data quantitatively. Firstly, we used regression analysis of paired pollen concentration and plant cover data; secondly, pc‐ord was used on a cross‐matrix (contingency table) containing the presence/absence scores of both pollen and plants for each taxon at each site. Results Mapping and quantitative analysis revealed that pollen–plant relationships do vary both between anemophilous and zoophilous groupings and by individual taxon. They also revealed that distribution patterns of both pollen and plant abundance vary consistently across the three main landscape types (desert, urban, agricultural) and that pollen taxa groupings are consistent with pollination method and source plant distribution regardless of landscape type. Main conclusions These findings provide a broad range of comparative data to facilitate palynological reconstruction of past vegetation and aid in assessing types of prehistoric impacts on this vegetation. They also document that significant variation can occur in pollen rain across a city, even for taxa with widely distributed pollen, leading to the conclusion that forecasting pollen distribution patterns for allergy‐related pollen types using only one or a few pollen traps is likely to entail substantial error.     

Land-use history in Gamla Uppsala,southeast Sweden,established on subfossil Coleoptera remains and pollen in fluvial deposits

Insect and pollen remains in fluvial sediments from the stream bank of river Fyris and one tributary brook, Samnan, in south-eastern Sweden, were studied. The deposits cover the last 400 years, according to 1 4C dates. The insects, dominated by subfossil beetles, originate foremost from stream environments, indicating aquatic development. Scarce finds from a wider area are recorded, particularly in samples from the banks of Fyris river there is a strong influence from surrounding land. Pollen originates from the surrounding cultivated field and grazing areas as well as wet meadows. The dominance of the stream environment changes along the examined core. The land-use history as it is reflected by deposited subfossils are compared with old maps from the area. It is demonstrated that the source areas for subfossil beetle and pollen have changed over time. Consequently, it is difficult to estimate the area for which the land-use history is accurate. For test purposes, the Mutual Climatic Range (MCR) method has been used for reconstructing mean temperatures based on the beetle record.     

Human impact, soil erosion, and vegetation response lags to climate change: challenges for the mid-Scandinavian pollen-based transfer-function temperature reconstructions

Precise and accurate reconstructions of past environmental parameters from high-quality palaeoenvironmental studies are critical for realistic testing of climate models. To ascertain the reliability of the reconstructions of the past, cross-validation from a variety of proxies and methods is essential. Mid-Scandinavia, showing a variety of palaeoecological studies, is a suitable region for comparing and validating environmental reconstructions. Here, pollen-based transfer-function reconstructions show inconsistent late-glacial temperature patterns. They also show that the Holocene Thermal Maximum (HTM) occurs at ca. 7.5–4.5 cal. ka b.p. However, thermal indicators (pollen, megafossils, plant macrofossils) place the HTM at no later than ca. 10–7.5 cal. ka b.p. It is argued that after the onset of the early Holocene warming equilibrium between vegetation and climate was established over a prolonged period; i.e. ca. 1,500 and 4,000 years in the mountains and lowlands, respectively. In the mountains, soil drought, wind and winter stress were important factors causing the lag, whereas inter-specific competition and soil development delayed the succession within the species-diverse lowland forests. These lags when vegetation was not filling its thermal potential result in a distortion of the temperature signal as derived by transfer functions which assume that vegetation is essentially in equilibrium with climate. Due to widespread human impact and erosion today, many modern training set samples are unsuitable as reference material for past environmental conditions. Various recommendations are suggested towards making improvements in the pollen-transfer function approach to climate reconstructions. To overcome the difficulties resulting from vegetation lags in the early Holocene, proxies that have a faster response time to climate, such as chironomids and aquatic plants including algae, may replace terrestrial pollen.     

Pollen-based reconstructions of biome distributions for Australia, Southeast Asia and the Pacific (SEAPAC region) at 0, 6000 and 18,000 14C yr BP

Aim This paper documents reconstructions of the vegetation patterns in Australia, Southeast Asia and the Pacific (SEAPAC region) in the mid‐Holocene and at the last glacial maximum (LGM). Methods Vegetation patterns were reconstructed from pollen data using an objective biomization scheme based on plant functional types. The biomization scheme was first tested using 535 modern pollen samples from 377 sites, and then applied unchanged to fossil pollen samples dating to 6000 ± 500 or 18,000 ± 1000 ¹⁴C yr bp . Results 1. Tests using surface pollen sample sites showed that the biomization scheme is capable of reproducing the modern broad‐scale patterns of vegetation distribution. The north–south gradient in temperature, reflected in transitions from cool evergreen needleleaf forest in the extreme south through temperate rain forest or wet sclerophyll forest (WSFW) and into tropical forests, is well reconstructed. The transitions from xerophytic through sclerophyll woodlands and open forests to closed‐canopy forests, which reflect the gradient in plant available moisture from the continental interior towards the coast, are reconstructed with less geographical precision but nevertheless the broad‐scale pattern emerges. 2. Differences between the modern and mid‐Holocene vegetation patterns in mainland Australia are comparatively small and reflect changes in moisture availability rather than temperature. In south‐eastern Australia some sites show a shift towards more moisture‐stressed vegetation in the mid‐Holocene with xerophytic woods/scrub and temperate sclerophyll woodland and shrubland at sites characterized today by WSFW or warm‐temperate rain forest (WTRF). However, sites in the Snowy Mountains, on the Southern Tablelands and east of the Great Dividing Range have more moisture‐demanding vegetation in the mid‐Holocene than today. South‐western Australia was slightly drier than today. The single site in north‐western Australia also shows conditions drier than today in the mid‐Holocene. Changes in the tropics are also comparatively small, but the presence of WTRF and tropical deciduous broadleaf forest and woodland in the mid‐Holocene, in sites occupied today by cool‐temperate rain forest, indicate warmer conditions. 3. Expansion of xerophytic vegetation in the south and tropical deciduous broadleaf forest and woodland in the north indicate drier conditions across mainland Australia at the LGM. None of these changes are informative about the degree of cooling. However the evidence from the tropics, showing lowering of the treeline and forest belts, indicates that conditions were between 1 and 9 °C (depending on elevation) colder. The encroachment of tropical deciduous broadleaf forest and woodland into lowland evergreen broadleaf forest implies greater aridity. Main conclusions This study provides the first continental‐scale reconstruction of mid‐Holocene and LGM vegetation patterns from Australia, Southeast Asia and the Pacific (SEAPAC region) using an objective biomization scheme. These data will provide a benchmark for evaluation of palaeoclimate simulations within the framework of the Palaeoclimate Modelling Intercomparison Project.