Variation in annual pollen accumulation rates of Fagus along a N–S transect in Europe based on pollen traps

Annual pollen-accumulation rates (PAR) of Fagus (beech) obtained within the framework of the Pollen Monitoring Programme (PMP) were analyzed in pollen traps along a N–S transect from the Baltic Sea to the Black Sea in different European vegetation units. The study regions are situated in the lowlands of northern Poland, the uplands of SE Poland, the Czech Krkono?e Mts, the Czech ?umava Mts, the Swiss Jura Mts, the Swiss Alps, the Bulgarian Rila Mts and the Bulgarian Strandzha Mts. Most time series are 10 or 11 years long, some are 5–16 years long. Inter-annual fluctuations in Fagus PAR were analyzed and compared with seed mast years. Years with high Fagus PAR and others with low Fagus PAR occurred most frequently in parallel within each region and often in two neighbouring regions. 2006 was exceptional as it had a very high Fagus sylvatica pollen deposition in all study regions and it was also a mast year. In Bulgaria, the trend in the 5 years of Fagus orientalis PAR in the Strandzha Mts differed from that of F. sylvatica PAR in the Rila Mts. Aiming at establishing the relationship between average Fagus PAR and tree cover, differences in Fagus PAR (averaged per pollen trap) were related in each region to the proportion of beech trees in the vegetation within 2 km of the pollen traps, the distance to the nearest pollinating Fagus tree, regional or local presence of beech forests, the degree of landscape openness, and the size of forest opening in which a trap is situated. Average Fagus PAR was found to track the regional abundance of beech trees in the vegetation, not the distance of the nearest Fagus tree. Regional occurrence of beech-dominated forests was reflected by a Fagus PAR of ca. 1,400 grains cm^?2 year^?1, local abundance very close to pollen traps by ca. 2,400 grains, small patches of forest with admixture of Fagus by ca. 170–220 grains, and scarcity or absence of Fagus by ca. 40 grains or less.     

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.     

Pollen productivity estimates of key European plant taxa for quantitative reconstruction of past vegetation: a review

Information on the spatial distribution of past vegetation on local, regional and global scales is increasingly used within climate modelling, nature conservancy and archaeology. It is possible to obtain such information from fossil pollen records in lakes and bogs using the landscape reconstruction algorithm (LRA) and its two models, REVEALS and LOVE. These models assume that reliable pollen productivity estimates (PPEs) are available for the plant taxa involved in the quantitative reconstructions of past vegetation, and that PPEs are constant through time. This paper presents and discusses the PPEs for 15 tree and 18 herb taxa obtained in nine study areas of Europe. Observed differences in PPEs between regions may be explained by methodological issues and environmental variables, of which climate and related factors such as reproduction strategies and growth forms appear to be the most important. An evaluation of the PPEs at hand so far suggests that they can be used in modelling applications and quantitative reconstructions of past vegetation, provided that consideration of past environmental variability within the region is used to inform selection of PPEs, and bearing in mind that PPEs might have changed through time as a response to climate change. Application of a range of possible PPEs will allow a better evaluation of the results.     

Paternity analysis-based inference of pollen dispersal patterns, male fecundity variation, and influence of flowering tree density and general flowering magnitude in two dipterocarp species

Background and Aims

Knowledge of pollen dispersal patterns and variation of fecundity is essential to understanding plant evolutionary processes and to formulating strategies to conserve forest genetic resources. Nevertheless, the pollen dispersal pattern of dipterocarp, main canopy tree species in palaeo-tropical forest remains unclear, and flowering intensity variation in the field suggests heterogeneity of fecundity.

Methods

Pollen dispersal patterns and male fecundity variation of Shorea leprosula and Shorea parvifolia ssp. parvifolia on Peninsular Malaysian were investigated during two general flowering seasons (2001 and 2002), using a neighbourhood model modified by including terms accounting for variation in male fecundity among individual trees to express heterogeneity in flowering.

Key Results

The pollen dispersal patterns of the two dipterocarp species were affected by differences in conspecific tree flowering density, and reductions in conspecific tree flowering density led to an increased selfing rate. Active pollen dispersal and a larger number of effective paternal parents were observed for both species in the season of greater magnitude of general flowering (2002).

Conclusions

The magnitude of general flowering, male fecundity variation, and distance between pollen donors and mother trees should be taken into account when attempting to predict the effects of management practices on the self-fertilization and genetic structure of key tree species in tropical forest, and also the sustainability of possible management strategies, especially selective logging regimes.     

The relationships between the surface arboreal pollen and the plants of the vegetation in China

This paper attempts to test the relationships between the surface arboreal pollen and the plants across the entire vegetation of China. Twelve genera from major arboreal plants are selected from 680 pollen taxa in a total of 803 surface pollen assemblages for this excise. The pollen data are quantitatively compared with the gridded vegetation map on spatial similarity, direction and distance of pollen dispersal, and pollen accuracy for indicating the plant distribution density.The results show that the distributions of the pollen taxa can reflect the major patterns of the plants. Abies, Larix, Picea, Pinus, Quercus and Betula exhibit high spatial similarities between pollen and source plants. The accuracy for Tsuga, Platycarya, Fagus and Cyclobalanopsis is relatively low, probably due to the low pollen productivities and the absence of samples from southern China. In the disagreement part of the pollen-plant accuracy percentage, the pollen taxa Larix, Platycarya, Fagus and Cyclobalanopsis have high proportions in underestimating plants, likely a “convergent-type” in the pollen deposition; while pollen Tsuga, Quercus, Pinus, Betula and Ulmus have high proportions in overestimating plants, likely a “divergent-type” in the pollen dispersal.Pollen dispersal estimates suggest that southward transportation of the 12 pollen taxa is dominant, and the transport distance can be up to ca. 1000 km. This is mainly caused by several months of persistent north winds from the winter monsoon, particularly in spring seasons in eastern China. The second highest pollen dispersal direction is eastward, which occurs mainly in the boreal or sub-boreal plants of Larix, Abies, Picea, Betula and Acer and is likely influenced by the Westerlies in the mid-latitudes of China. Summer-green and evergreen Platycarya, Fagus and Cyclobalanopsis are mainly dispersed to the north, reflecting the influence of the Asian summer monsoon in eastern and southern China. Results of spatial differentiation analysis using accuracy weighting suggest that the low percentage portion (1-10%) in pollen of Abies, Picea, Betula and Quercus and high percentage portion (>40%) in pollen Pinus are acceptable for the plant representatives.These results, based upon the analyses of surface pollen and modern vegetation types of China, can provide important information for testing the various methods for reconstructing and modelling the environmental or climatic parameters during the recent geological past from palaeovegetation data.     

Reassessment of Holocene vegetation change on the upper Tibetan Plateau using the pollen-based REVEALS model

Previous studies based on fossil pollen data have reported significant changes in vegetation on the alpine Tibetan Plateau during the Holocene. However, since the relative proportions of fossil pollen taxa are largely influenced by individual pollen productivities and the dispersal characteristics, such inferences on vegetation have the potential to be considerably biased. We therefore examined the modern pollen–vegetation relationships for four common pollen species on the Tibetan Plateau, using Extended R-value (ERV) models. Assuming an average radius of 100 m for the sampled lakes, we estimated the relevant source area of pollen (RSAP) to be 2200 m (which represents the distance from the lake). Using Poaceae as the reference taxa (Pollen Productivity Estimate, PPE = 1), ERV Submodel 2 derived relative high PPEs for the steppe and desert taxa: 2.079 ± 0.432 for Artemisia and 5.379 ± 1.077 for Chenopodiaceae. Low PPEs were estimated for the Cyperaceae (1.036 ± 0.012), whose plants are characteristic of the alpine Kobresia meadows. Applying these PPEs to four fossil pollen sequences since the Late Glacial, the plant abundances on the central and north-eastern Tibetan Plateau were quantified using the “Regional Estimates of Vegetation Abundance from Large Sites” (REVEALS) model. The proportions of Artemisia and Chenopodiaceae were greatly reduced compared to their original pollen percentages in the reconstructed vegetation, owing to their high productivities and their dispersal characteristics, while Cyperaceae showed a relative increase in the vegetation reconstruction. The reconstructed vegetation assemblages of the four pollen sequence sites always yielded smaller compositional species turnovers than suggested by the pollen spectra, as revealed by Detrended Canonical Correspondence Analyses (DCCA) of the Holocene sections. The strength of the previously reported vegetation changes may therefore have been overestimated, which indicates the importance of taking into account pollen–vegetation relationships when discussing the potential drivers (such as climate, land use, atmospheric CO₂ concentrations) and implications (such as for land surface–climate feedbacks, carbon storage, and biodiversity) of vegetation change.     

The vegetational history of the northern Apennines, Italy: information from three new sequences and a review of Regional vegetational change

Abstract. The results of pollen analysis and radiocarbon dating are presented from three northern Apennine sequences; Lago Padule in northern Tuscany and Lago Pratignano and Ospitale in the Emilia-Romagnan Apennines. This is the first detailed pollen stratigraphic information from sites in Emilia-Romagna and north Tuscany and extends eastwards the area from which information on vegetational history is available. The sequence from Lago Padule is one of the most complete Holocene records known from the northern Apennine region. Lago Pratignano has the deepest sequence of organic sediments (1544 cm) and the fastest rates of sediment accumulation (up to 28 cm per 100 years) providing the highest resolution record for the mid to late Holocene periods in the region. High rates of sedimentation have also occurred at Ospitale where organic sediments are 780 cm deep and began to form at approximately 5500 bp. The record from Lago Padule is compared with Holocene records from two nearby sites and a series of Regional Pollen Assemblage Zones is defined for the eastern area of the northern Apennines. The main features of vegetational change identified are: (i) a‘pioneer’phase of rapid forest development during the early Holocene followed by the establishment of an upper forest belt dominated by Abies, and a belt of mixed deciduous forest at lower altitudes; (ii) the appearance and rapid expansion of Fagus between approximately 5200 bp and 2900 bp forming a mixed Abies-Fagus association in the upper forest belt; and (iii) the overall reduction of forest cover, and dominance of Fagus in the arboreal vegetation from around 2900 bp. The scheme of Regional PAZs for the eastern area is used as a framework for the review of pollen stratigraphic information and radiocarbon dates from other sites in the northern Apennine region. Characteristics of pollen records which can be identified in sequences from across the region are identified and the chronology of similar changes in pollen stratigraphy is examined. The scheme of four regional PAZs for the Holocene period is shown to be valid for the entire northern Apennine region. The examination of a series of pollen records shows that Fagus appeared earlier in the western than the eastern part of the region during the mid Holocene and became dominant in the northern Apennine forests post 3000 bp. The impact of anthropogenic activity and climatic change on the spread and development of Fagus are discussed. The palynological evidence which is now available from the northern Apennines is compared with information for the region shown in the‘European pollen maps’of Huntley & Birks (1983). This study provides an updated review of the representation of different tree taxa in Holocene pollen records from the northern Apennines and illustrates the role of the northern Apennines as a refugium for trees during the Wurmian Lateglacial.     

Holocene forest development in the central Scandes Mountains, Sweden

Pollen analyses of sediment cores from two small lakes within the boreal forest in the central Scandes Mountains help to elucidate the Holocene forest dynamics of the region. Analyses of pore/pollen grain diameter ratios of Alnus grains indicate the early Holocene presence of Alnus glutinosa in the study area. The results are discussed in conjunction with available pollen records to evaluate the importance of thermophilous trees during the early Holocene and to deduce the regional spread of Picea abies. Corylus avellana, Alnus glutinosa and Ulmus glabra were probably common constituents of the early Holocene forest. Tilia cordata may have occurred there as a rare tree. Pollen stratigraphies from the region do not indicate the occurrence of Quercus robur. The regional spread of Picea abies can be separated into two phases: a mid-Holocene establishment or first expansion of small outpost populations and a late-Holocene population expansion. The mid-Holocene shift in vegetation composition may have been caused by changes in the westerly airflow.     

15. Brve (Czech Republic): Vegetation development over the last about 2.5 millennia in the Bohemian Lowland close to Prague

Two Burkard seven-day recording traps have been in operation in the cities of Johannesburg and Pretoria since 1987. Pollen calendars average data for 1987 and 1988. Grass pollen is the most significant contributor in absolute and relative terms. This taxon comprises 52% of total regional pollen for the study period. Pollen of alien northern hemisphere trees is abundant, relative to that of native trees. This is attributed partly to the paucity of trees in the natural vegetation, and partly to their entomophilous nature. The flowering season for exotics is very short, possibly due to the short spring season. The greatest proportion of pollen, 58,8%, is nonseasonal. Species in this category flower throughout the year. 28.4% of taxa are spring-flowering. Annual variability is marked for most taxa.     

Forest composition changes in the Moravskoslezské Beskydy Mountains during the last millennium—A palaeoecological study

Pollen analysis of sediments carried off slope-spring mires (Jan?ík I and II) in the Moravskoslezské Beskydy Mountains made it possible to reconstruct the vegetation in the area over the last millennium. The reconstruction included changes in forest cover and composition, management methods, and changes in landscape from the Middle Ages to the present. Nearly all inferred vegetation changes were most probably anthropogenic. Most of the sediments probably resulted from water-logging following deforestation. Two distinct phases in the vegetation development were inferred. The older phase reflects the natural composition of forests and the original character of the landscape before human impact. Forest communities with dominantAbies, Fagus, andPicea still covered this part of the Moravskoslezské Beskydy Mountains at the beginning of the Wallachian colonization (end of the 15th century). Other tree species were interspersed, depending on local conditions. The vegetation changed sharply a major way at the transition to the second phase. Deforestation was considerable, many soils became water-logged, and agricultural activity expanded from the lowlands into the mountains. This is shown in the pollen diagrams by the very strong decline ofAbies andFagus, high values ofPoaceae andCyperaceae, and marked increase of cultivated species, weeds of arable fields, grassland species, and, above all, indicators of eutrophicated biotopes.     

A matter of dispersal: REVEALSinR introduces state-of-the-art dispersal models to quantitative vegetation reconstruction

The REVEALS model is applied in quantitative vegetation reconstruction to translate pollen percentage data from large lakes and peatlands into regional vegetation composition. The model was first presented in 2007 and has gained increasing attention. It is a core element of the Landcover 6k initiative within the PAGES project. The REVEALS model has two critical components: the pollen dispersal model and pollen productivity estimates (PPEs). To study the consequences of model settings, we implemented REVEALS in R. We use a state-of-the-art Lagrangian stochastic dispersal model (LSM) and compare model outcomes with calculations based on a conventional Gaussian plume dispersal model (GPM). In the LSM turbulence causes pollen fall speed to have little effect on the dispersal pattern whereas fall speed is a major factor in the GPM. Dispersal models are also used to derive PPEs. The unrealistic GPM produces PPEs that do not describe actual pollen productivity, but rather serve as a basin specific correction factor. A test with pollen and vegetation data from NE Germany shows that REVEALS performs best when applied with the LSM. REVEALS applications with the GPM can produce realistic results, but only if unrealistic PPEs are used. We discuss the derivation of PPEs and further REVEALS applications. Our REVEALS implementation is freely available as the ‘REVEALSinR’ function within the R package DISQOVER. REVEALSinR offers an environment for experimentation and analysing model sensitivities. We encourage further experiments and welcome comments on our tool.     

Pollen–vegetation relationships along steep climatic gradients in western Amazonia

Question: How accurately do Amazonian montane forest pollen spectra reflect the vegetation? Can compositional changes observed in the vegetation along environmental gradients be identified in the pollen spectra? How well do herbarium collection data and bioclimatic envelopes represent abundance changes along elevation gradients? Location: Amazonian montane forests, Peru. Methods: Moss polsters collected along five altitudinal transects spanning over 3000 m a.s.l. were used to characterize pollen spectra. Vegetation plot data from a network of 15 1‐ha permanent plots were used to correlate pollen spectra with present‐day vegetation. Probability density functions (PDFs) fitted to pollen and plot data allowed comparisons using Spearman correlation coefficients. Ordination analyses were used to summarize changes in pollen spectra. Correlations between pollen‐based PDFs and previously‐published herbarium collection PDFs were also evaluated. Results: Pollen spectra closely reflected changes in species composition along elevation gradients. A mid‐elevation shift in pollen spectra was identified using ordination analyses. Pollen spectra from the driest forest in our data set were statistically different from those of wet forests. Pollen abundance PDFs along the altitudinal gradient were significantly correlated (P<0.01) with PDFs fitted to plot abundance, basal area and herbarium collection data for ten out of 11 taxa analysed. Conclusions: Pollen spectra closely reflected the vegetation composition of Amazonian montane forests. The differentiation of pollen spectra from dry localities showed the potential of genus‐level pollen data to reflect precipitation gradients. Pollen spectra also reflected mid‐elevation compositional changes well along the lower elevation limit of ground cloud formation. Despite collection biases, herbarium‐based bioclimatic envelope PDFs also represented well forest compositional changes along elevation gradients.     

Understory vegetation response to thinning disturbance of varying complexity in coniferous stands

Question: Can augmented forest stand complexity increase understory vegetation richness and cover and accelerate the development of late‐successional features? Does within‐stand understory vegetation variability increase after imposing treatments that increase stand structural complexity of the overstory? What is the relative contribution of individual stand structural components (i.e. forest matrix, gaps, and leave island reserves) to changes in understory vegetation richness? Location: Seven study sites in the Coastal Range and Cascades regions of Oregon, USA. Methods: We examined the effects of thinning six years after harvest on understory plant vascular richness and cover in 40‐ to 60‐year‐old forest stands dominated by Douglas‐fir (Pseudotsuga menziesii). At each site, one unthinned control was preserved and three thinning treatments were implemented: low complexity (LC, 300 trees ha^?1), moderate complexity (MC, 200 trees ha^?1), and high complexity (HC, variable densities from 100 to 300 trees ha^?1). Gaps openings and leave island reserves were established in MC and HC. Results: Richness of all herbs, forest herbs, early seral herbs and shrubs, and introduced species increased in all thinning treatments, although early seral herbs and introduced species remained a small component. Only cover of early seral herbs and shrubs increased in all thinning treatments whereas forest shrub cover increased in MC and HC. In the understory, we found 284 vascular plant species. After accounting for site‐level differences, the richness of understory communities in thinned stands differed from those in control stands. Within‐treatment variability of herb and shrub richness was reduced by thinning. Matrix areas and gap openings in thinned treatments appeared to contribute to the recruitment of early seral herbs and shrubs. Conclusions: Understory vegetation richness increased 6 years after imposing treatments, with increasing stand complexity mainly because of the recruitment of early seral and forest herbs, and both low and tall shrubs. Changes in stand density did not likely lead to competitive species exclusion. The abundance of potentially invasive introduced species was much lower compared to other plant groups. Post‐thinning reductions in within‐treatment variability was caused by greater abundance of early seral herbs and shrubs in thinned stands compared with the control. Gaps and low‐density forest matrix areas created as part of spatially variably thinning had greater overall species richness. Increased overstory variability encouraged development of multiple layers of understory vegetation.     

A change from grass pollen induced allergy to tree pollen induced allergy: 30 years of pollen observation in Switzerland

Pollen monitoring with a Hirst like pollen trap for 30 years in Basel, Switzerland allows understanding of the behaviour of the different plants producing allergenic pollens. It becomes evident that in this time period the different tree pollen like Hazel and Birch increased, whereas in the control, the observed amount of a herb pollen like Artemisa did not change. Moreover, it was observed that in the different trees flowering took place earlier namely at the beginning of the year. This was especially impressive for Hazel, where flowering was shifted ofmore than one month. These aerobiological observations were supported and confirmed by some epidemiological studies, showing that tree pollen allergy has become more important in the last years compared to grass pollen allergy and herb pollen allergy. The reason for the increase of tree pollen counts and the shift in the flowering time depends on the observed increase of the annual temperature, an increased input of nutrients like CO₂or NO_x but probably also a real increase of certain trees, like birch for example, in parks and avenues. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pollen movement to flowering canopies of pistillate individuals of three rain forest tree species in tropical Australia

This study measured the quantities of effective pollen vectors and their pollen loads arriving at the canopies of dioecious tropical rain forest trees in north-east Queensland. Population flowering synchrony, effective pollinator populations and pollen loads transferred between staminate and pistillate trees were compared among three insect-pollinated tree species. All three were visited by a wide range of insects, 75% of which (mostly 3–6 mm long) carried conspecific pollen. Fewer than 8% of individual insects were found to be carrying single-species pollen exclusively and none could be described as specialist pollen foragers. The introduced honeybee carried greater quantities of pollen than any native species but was not necessarily a reliable pollinator. The brief flowering periods in Neolitsea dealbata (3–4 weeks) and Litsea leefeana (4–5 weeks) populations were synchronized among individuals. Flowering in the Diospyros pentamera population extended over 15 weeks and most individuals were in flower for most of this period. Staminate trees began flowering earlier, produced more flowers and attracted relatively more insects than did pistillate trees, suggesting a density-dependent response of pollinators to flowering performance. Pollen was trapped in greater quantities on insects at staminate trees than at pistillate trees. Insect numbers increased at peak flowering periods and Diptera were the most abundant flower visitors. Anthophilous Coleoptera were more numerous at staminate than at pistillate trees in all three tree species populations. Larger quantities of pollen were mobilized during peak flowering times although the greatest quantities were transferred to pistillate canopies towards the end of the population flowering periods. Diptera carried pollen more often to pistillate N. dealbata and L. leefeana trees than did other groups whereas Coleoptera carried pollen more often to pistillate D. pentamera trees. The two contrasting flowering performances in the three tree species are discussed with reference to mechanisms that facilitate pollen transfer between staminate and pistillate trees.     

Numerical analysis of surface and fossil pollen spectra from northern Fennoscandia

Aim Determination of the main directions of variance in an extensive data base of annual pollen deposition, and the relationship between pollen data from modified Tauber traps and palaeoecological data. Location Northern Finland and Norway. Methods Pollen analysis of annual samples from pollen traps and contiguous high‐resolution samples from a peat sequence. Numerical analysis (principal components analysis) of the resulting data. Results The main direction of variation in the trap data is due to the vegetation region in which each trap is located. A secondary direction of variation is due to the annual variability of pollen production of some of the tree taxa, especially Betula and Pinus. This annual variability is more conspicuous in ‘absolute’ data than it is in percentage data which, at this annual resolution, becomes more random. There are systematic differences, with respect to peat‐forming taxa, between pollen data from traps and pollen data from a peat profile collected over the same period of time. Main conclusions Annual variability in pollen production is rarely visible in fossil pollen samples because these cannot be sampled at precisely a 12‐month resolution. At near‐annual resolution sampling, it results in erratic percentage values which do not reflect changes in vegetation. Profiles sampled at near annual resolution are better analysed in terms of pollen accumulation rates with the realization that even these do not record changes in plant abundance but changes in pollen abundance. However, at the coarser temporal resolution common in most fossil samples it does not mask the origin of the pollen in terms of its vegetation region. Climate change may not be recognizable from pollen assemblages until the change has persisted in the same direction sufficiently long enough to alter the flowering (pollen production) pattern of the dominant trees.     

From deciduous forest to open landscape: application of new approaches to help understand cultural landscape development in western Norway

Development of the cultural landscape in a village situated by the inner fjords of western Norway is investigated by pollen analysis and quantitative reconstruction methods. Pollen samples from lake sediments and a soil profile were analysed and represent different spatial scales. The Landscape Reconstruction Algorithm (LRA) is applied to a large and a small lake to convert pollen percentages from the small lake into estimated local vegetation cover in selected time periods starting from 2800 cal bc (Middle Neolithic A). This reconstruction shows that estimated forest cover has fluctuated through time, and changes in openness related to human impact are distinct from the Early Bronze Age (1800–1200 cal bc). Pollen analyses from the soil profile indicate forest clearances from the Late Neolithic (2300–1800 cal bc). Gradual intensification of farming is recognized in both pollen diagrams throughout the Bronze and Iron Ages with increasing openness and spatial differentiation in land-use practices. Presence of pollen of cereals and flax record the cultivation of these plants from the Iron Age, and intensification of land-use may have caused erosion and re-sedimentation in the lake in medieval times. To identify a possible landscape in the past, HUMPOL software has been used with the Late Neolithic as a case study. The LRA-based estimates of forest cover are supported by the HUMPOL simulations, but several solutions to the Late Neolithic landscape pattern exist. The results clearly demonstrate how implementation of LRA and HUMPOL improve the understanding of cultural landscape development.     

Quantitative landscape dynamics in Denmark through the last three millennia based on the Landscape Reconstruction Algorithm approach

This paper explores the spatial and temporal land-cover variability within the main cultural landscape units in Denmark during the last 3,000 years. Quantitative estimates of the cover of trees, grasses, Cerealia and Calluna around nine Danish lakes were obtained using the recently developed Landscape Reconstruction Algorithm (LRA) (Sugita 2007a, b). The performance of the approach was evaluated by comparing reconstructed vegetation based on a.d. 1800 pollen spectra to land cover from historical maps of the same period. Although the model tended to overestimate grassland cover by 10–20%, the reconstructed vegetation was much more similar to the observed than the uncorrected pollen proportions. The LRA was then applied to 3,000 year long pollen records to reconstruct the vegetation development around each of the nine sites. The results support earlier conclusions regarding the relative stability of woodland, agrarian and heathland dominated landscapes in Denmark (Odgaard and Rasmussen 2000), with the distribution of the main landscape types determined by topography and soil characteristics. The present study indicates that the transition zones between agricultural and forest dominated landscapes were the most dynamic, acting as buffer zones where most of the expansions and contractions of agricultural activities took place. The quantitative vegetation reconstructions underline the importance of farming and especially pastoral activities in shaping the Danish landscapes throughout the study period.     

Entwicklung des Moores Mokré Louky bei Třeboň im Postglazial (Paläoökologische Studie)

The origin, age and development of a mire deposit in the locality of the Mokré Louky meadows near T?eboň were ascertained by means of palaeoecological methods. The first minerogenic sediments originated in a depression at the turn of the Late-Glacial and the Holocene Periods. In the course of minerogenic sedimentation, the vegetational cover was formed by stands ofFilipendula. In the middle of the Pre-Boreal Period, the first organic sediments formed by reed plant communities were deposited in the area. In the course of the following periods, plant communities of mire and marshy meadows belonging to the associations of the classScheuchzerio-Caricetea fuscae predominated on the site. Stands of willow and alder trees were formed in some parts of the deposit most probably towards the end of the Atlantic Period, with their maximum development in the Sub-Boreal to Upper Sub-Atlantic Periods. Pollen analysis produced a more precise foundation for reconstructing the forest vegetation in the centre of the T?eboňská pánev Basin. A higher presence ofQuercus and a lower one ofFagus, as compared with the results of previous pollen analyses from the borders of the Basin, were ascertained. The palaeoecological analyses are supported by radiocarbon datings.