Reconstruction Of Past Vegetation Research Articles

Early Pleistocene landscapes and the colonization of Europe

The paleoecological context of hominin occupation in South Asia during the early and middle Pleistocene is virtually unknown. Attirampakkam, India, is an archeological site of global importance, with an early Acheulian occupation (age bracket of ~ 1.07–1.77 Ma) succeeded by Middle Paleolithic levels. Here we report on the recovery of phytoliths from artifact-bearing Quaternary deposits in excavated trenches. We focus on the reconstruction of past vegetation during hominin occupation of the site. The present study provides information on hominin microenvironments and local habitats in South Asia, situating them in a more tangible ecological context than so far achieved. Results show that this region was arid during the earlier stages of the early Pleistocene, and was occupied by hominins living in a landscape locally lacking woody plants. Herbaceous vegetation was dominated by C4 Chloridoid grasses. In the later phase of the early Pleistocene, the landscape was wooded and dominated by C4 Panicoid grasses, with a significant reduction of C4 Chloridoid grasses indicating a shift from a drier to a relatively more humid climate. A diverse husk and leaf phytolith assemblage of wild Oryza spp. (rice) occurring as natural annual or perennial components of the vegetation in the area, other herbaceous plants such as Cyperaceae (sedges), and the continuous presence of blackened phytoliths, suggest the establishment a grassland landscape with enclaves of wetland habitat affected by seasonal flooding and frequent fires. The transition from the early to the middle Pleistocene was marked by a moderately humid climate, with a shift toward aridity during the late Pleistocene, during which we note an environment dominated by C4 Chloridoid grasses, by a sharp reduction of C4 Panicoid grasses, and by a rise in woody taxa. During the middle to late Pleistocene, Middle Paleolithic populations would have witnessed water bodies near the site, as reflected by the presence of plants adapted to swampier conditions such as Cyperaceae and Oryza spp. The archeological record terminates in Layer 1, when human occupation decreased drastically, possibly because of increased aridity and/or greater environmental variability. The phytolith fingerprint at ATM sheds light on the co-occurrence of, vegetation, fire and early prehistoric land occupation. An important aspect is the evidence of Oryza spp., suggesting that wild rice occurred in the environment frequented by these early hominins.

A continuous record of vegetation and climate change over the past 50,000 years in the Fujian Province of eastern subtropical China

A 425cm core has been collected from the Gantang subalpine peat bog, in Pingnan County, Fujian Province of Southern China. High-resolution pollen analysis of the core has allowed for the reconstruction of past vegetation and climate changes over the last 50,000years. Today, Fujian province is located in the eastern part of middle subtropical zone where the dominant vegetation is evergreen broadleaved forest that receives its precipitation from the East Asian Monsoon. The pollen record testifies that the vegetation in Fujian varied between subtropical evergreen and warm temperate deciduous forests during the last glacial-interglacial cycle. It appears that during Marine Oxygen Isotope Stage 3, this area was covered with broadleaved forest suggesting warm and wet subtropical condition, whereas the flora was quite different with many ancient elements. The Last Glacial Maximum is distinguished by an increase in warm temperate deciduous taxa, particularly Fagus and Alnus accompanied by abundant Ericaceae, implying a spatial shift of zonal vegetation during this coldest episode in the world. Local swamp developed soon after the Younger Dryas event coinciding with the formation of peatlands in the Northern Hemisphere possibly linked with atmospheric carbon accumulation. A rapid increase in evergreen broadleaved taxa that dominated the local forest occurred at ~ca. 8.2calka BP, indicating the inception of the regional thermal maximum during the Holocene, which was generally characterised by more humid conditions. The middle to late Holocene sees a progressive decline in arboreal elements, and an increase in grasses and Ericaceae. These changes beginning from around 4kacal BP were concordant with the general weakening of the East Asian Monsoon during the Holocene, corresponding with an orbitally induced reduction of boreal summer insolation. This is the first terrestrial high-resolution record from eastern part of middle subtropical areas that evaluates the forest changes through the last glacial-interglacial cycle.

Detecting the provenance of Galápagos non-native pollen: The role of humans and air currents as transport mechanisms

The influence of non-native pollen, both long-distance transported and from introduced taxa, on reconstruction of past vegetation is not often well quantified in palynological investigations. We examined both fossil and modern samples from the Galápagos Islands, a remote archipelago lying 1000 km from the nearest continent. These islands are particularly well-suited for such an assessment, as (1) the native flora is limited and well-known, enabling increased taxonomic resolution within the palynological record, and (2) human impact in the Galápagos started after discovery by Europeans in 1535, allowing clear distinctions to be made between native and introduced taxa. Pollen samples were collected from five profiles in the Galápagos and grouped in (a) a pre-human-impact period, (b) an early human-impact period after c. 1535, and (c) a late human-impact period after c. 1973 when the introduced Cinchona pubescens tree started to expand. Introduced taxa accounted for approximately 10% of total pollen (excluding Cyperaceae) throughout the human-impact periods and long-distance transported pollen for approximately 5%. Twenty pollen taxa of introduced plants were found. Cinchona, which grows abundantly near the study sites, accounted for most of the introduced pollen, but an appreciable part also came from introduced plants growing in low numbers and at more distant locations within the archipelago. Total long-distance transported pollen (35 taxa) increased from 3% of total pollen in the pre-human-impact period to 5% in the human-impact periods, probably due to destruction of native vegetation through fire and thus reduction of local pollen production. These phenomena might lead to erroneous interpretation of local plant occurrence when the native/non-native or local/extra-local status of plants is not known.

Atlas of pollen, spores and further non-pollen palynomorphs recorded in the glacial-interglacial late Quaternary sediments of Lake Suigetsu, central Japan

The record of well preserved palynomorphs from sediment samples of Lake Suigetsu mirrors temporal changes in the flora around the lake and spatial changes in the vegetation cover of central Japan during the late Quaternary. This study presents photographic images of 169 identifiable types of moss, lycophyte and fern spores and pollen of gymnospermous and angiospermous plants from the SG06 core sediment obtained at a standard magnification of ca. 750×. Additionally non-pollen palynomorphs (NPPs), which appeared in the pollen slides, are documented, including remains of fungi, rhizopods, arthropods, rotifers, flatworms as well as green algae and plant tissue fragments. All documented taxa are presented in taxonomical order on 66 plates, including 55 plates for pollen and spores of higher plants and 11 plates for NPPs. This study renders an overview on quality of preservation and on the range of palynomorphs found in the last glacial-interglacial sediments of Lake Suigetsu, and furthermore, may serve as a handy and thorough guide for palynological investigations, aiming at the reconstruction of past vegetation, environmental and climate dynamics.

Combining phytoliths and δ13C matter in Holocene palaeoenvironmental studies of tropical soils: An example of an Oxisol in Brazil

Many plants deposit the soluble silica absorbed from the soil as monosilicic acid (H4SiO4) in and between their cells, generating bodies of opal silica (SiO2·nH2O) called phytoliths. Although phytoliths are susceptible to dissolution under extreme pH conditions, they generally do remain in the soil for long periods of time and can help in the reconstruction of past vegetation and climates. In the present study, phytolith analysis was used to reconstruct the palaeoenvironmental conditions that contributed to the pedogenetic processes, the deposition of organic matter and its stabilization in a very thick (>1 m) umbric epipedon of a Humic Hapludox profile from Minas Gerais State (Brazil). The results from the phytolith assemblages were also compared to the fractions and isotopic data of soil carbon of the same profile. The result from studying these two palaeoenvironmental proxies together has shown that the environment under which the umbric epipedon was formed was a mixture of vegetation with predominance of C3 plants in mesothermic conditions and with little variation in humidity since Middle Holocene.

Relative pollen productivity estimates of major anemophilous taxa and relevant source area of pollen in a cultural landscape of the hemi-boreal forest zone (Estonia)

Estimates of relevant source area of pollen (RSAP) and relative pollen productivity (PPE) are critical parameters for quantitative reconstructions of past vegetation and land cover. This study provides estimates for PPE relative to Poaceae for ten taxa, characterizing the cultural landscape of south Estonia and the RSAP for 40 lakes with an average radius of approximately 100 m (22–274 m, average 101 m) in the region. We evaluate the effects on those estimates of various combinations of factors, such as the analytical methods (i.e. three Extended R value (ERV) sub-models), the distance-weighting methods used to determine plant abundance, and alternative classification schemes of vegetation and land cover data around study sites. Different combinations of ERV sub-models and distance-weighting methods lead to estimates of RSAP varying between 1500 m and 2000 m. The differences in the estimated RSAP are strongly related to the patch size of the vegetation data. According to ERV sub-model 1, which shows the highest log-likelihood among the three sub-models, most of the taxa have PPE that are higher ( Picea, Pinus, Quercus), slightly higher ( Salix, Artemisia, Filipendula) or similar ( Betula, Cerealia, Cypreraceae) to that of Poaceae. The three ERV sub-models produce only slightly different PPE. However, the selection of distance-weighting method for vegetation has considerable influence on the PPE values. The inverse distance-weighting methods, which do not consider inter-taxonomic differences in pollen dispersal, tend to underestimate PPE for taxa with heavy pollen grains and overestimate PPE for taxa with light pollen grains, compared to the results obtained using other methods that consider taxon specific pollen-dispersal. General land-cover data, based on the classification scheme similar to the CORINE (COoRdination of Information on the Environment) database, could be used for estimating the RSAP and PPE, although some potential problems remain when the classification is too simplified and consolidated.

Reconstruction of Neogene zonal vegetation in South China using the Integrated Plant Record (IPR) analysis

Reconstructions of past vegetation are crucial for our understanding of palaeoenvironments. However, we still lack good quantitative reconstructions for the Neogene vegetation of China. This geological time is key for the development of the modern vegetations in China because it corresponds to the establishment and evolution of the South-East Asian monsoon system. The present study uses Integrated Plant Record (IPR) vegetation analysis for the first time on the Chinese Neogene data including 71 palaeobotanical sites from five time intervals: early Early Miocene (Aquitanian, early Burdigalian), late Early to early Middle Miocene (late Burdigalian, early Langhian), late Middle Miocene (late Langhian, Serravalian), Late Miocene to earliest Pliocene (Tortonian, Messinian, early Zanclean), and Pliocene (late Zanclean, Piacenzian). Based on the ecophenological type of the nearest living relative to the fossils, IPR analysis reconstructs six types of vegetation: broad-leaved deciduous forests, mixed mesophytic forests, broad-leaved evergreen forests, subhumid sclerophyllous forests, xeric open woodlands, and xeric grasslands or steppe. The geographic distribution of reconstructed palaeovegetation shows a distinct latitudinal gradient which is congruent with the latitudinal temperature gradient recognised from previous studies. Throughout the Neogene the broad-leaved deciduous (BLD) component is greater in the more northern regions whereas the broad-leaved evergreen (BLE) component is greater in the more southern areas. During the Pliocene there was a further rise of the BLE component in the southern areas, indicating an increasingly warm and moist climate. An episodic longitudinal aridity gradient was also recorded during the Neogene: the more western areas were drier than the eastern ones in the Early Miocene; but this gradient vanished in the Late Miocene with all areas having a balanced supply of moisture. A second episode of aridification of the western regions occurred in the Pliocene.

Reconstruction of vegetation transects for the Messinian–Piacenzian of Italy by means of comparative analysis of pollen, leaf and carpological records

The first comprehensive and comparative analysis of the main micro (pollen) – and macro (leaves, fruits and seeds) – palaeobotanical data from northern and central Italian sites, allows four transects of ancient vegetation for the Messinian to Piacenzian interval to be constructed. Standard criteria for the reconstruction of vegetation transects are established, so that our approach could be extended to other basins or regions bearing Neogene palaeofloras, and would permit readily comparable reconstructions of past vegetation to be obtained. Messinian to Piacenzian lowland plant communities, as reconstructed by means of this integrated and standardized approach, show the dominance of warm temperate forest taxa in northern and central Italy, with the highest floristic affinity to present day forests of the eastern part of central China. Some panholartic conifers, usually interpreted as “cool temperate” taxa in Neogene assemblages, are assigned to the upland vegetation; they are scarcely represented in Messinian and Zanclean pollen records (with the exception of some intervals characterized by increases in Picea and Cedrus) and almost completely lacking in leaf and carpological ones; during the Piacenzian, notably from 2.8 Ma, the pollen percentage of such taxa, in particular Picea, progressively increased. The overall scantiness of non-aquatic herbs, not only in the macrofossil record, but also in the pollen one, indicates the absence of dry conditions and excludes long-lasting expansion of open vegetation. The type of vegetation (“subtropical humid forest”) reconstructed for the evaporitic Messinian (ca. 5.9 to 5.6 Ma) suggests that the Adriatic-Padane basin would have been under predominant moist conditions, even during the deposition of evaporites. Slightly drier phases in the post-evaporitic Messinian are suggested at first by the short period of increase of Lygeum, a steppe plant, close to 5.5 Ma, then by the ecological preferences of some unusual macrofossil taxa ( Cupressus, Medicago, Vitex). These are, however, still associated with arboreal plants which require humid conditions, definitely indicating that forested environments persisted (“subtropical sub-humid forest”). The Zanclean and Piacenzian transects are extremely similar to the evaporitic Messinian one, and the mesic lowland (zonal) vegetation can still be defined as “subtropical humid forest”.

Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord-Ålesund area, western Norway

Birks, H. H. & van Dinter, M. 2010: Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord–Alesund area, western Norway. Boreas, Vol. 39, pp. 783–798. 10.1111/j.1502-3885.2010.00161.x. ISSN 0300-9483. Modern climate in western Norway shows a strong west–east gradient in oceanicity–continentality (coast to inner fjord) and altitudinal temperature gradients that control the regional and altitudinal zonation of vegetation. To discover if similar gradients existed during the Lateglacial and early Holocene, plant-macrofossil analyses were made from five lacustrine sediment sequences in the Nordfjord–Alesund region selected to sample the present climatic gradients. The macrofossil assemblages could be interpreted as analogues of the present vegetation, thus allowing reconstruction of past vegetation and climates. When the five sites were compared, climatic gradients could be detected. During the Lateglacial interstadial, mid-alpine assemblages with Salix herbacea and S. polaris occurred at the lowland coast and upland inland sites, whereas the inland lowland site had low-alpine dwarf-shrub heath dominated by Betula nana, demonstrating a strong west–east gradient in temperature and precipitation and an altitudinal gradient inland. During the Younger Dryas stadial, assemblages at the lowland coast and upland inland sites resembled high-alpine vegetation, whereas the inland lowland site was warmer with mid-alpine vegetation, demonstrating west–east and altitudinal temperature gradients. Gradients became less pronounced in the Holocene. The early abundance of Betula nana in the inner fjord sites but its rarity at the coast is striking and reflects the oceanicity gradient. All sites became forested with Betula pubescens a few centuries into the Holocene. This forest was probably close to tree line at 370 m a.s.l. at the coast. Inland, there was no detectable altitudinal gradient, with the tree line well above 400 m a.s.l. reflecting the present pattern of tree-line elevation.

Phytoliths of East African grasses: An assessment of their environmental and taxonomic significance based on floristic data

Relations between phytolith occurrences, taxonomy, and habitat are assessed for 184 East African grass species through the re-analysis of two qualitative surveys of phytolith types in leaf epidermis. This is done in conjunction with data on grass subfamily, photosynthetic pathway, and requirement for light and moisture compiled from floras and the literature. This survey includes ca 79% of the grass genera listed in the flora of tropical East Africa. It aims to further investigate the potential for grass short cell phytoliths to characterize the environment, and therefore improve reconstructions of past vegetation and climate in Africa. In this analysis, we identified ca 60 phytolith types (within the main categories Rondel, Trapeziform Short Cell, Bilobate, Cross, Polylobate, Saddle, and Trapeziform Sinuate) reported to occur in 10 grass subfamilies (Pharoideae, Bambusoideae, Ehrhartoideae, Pooideae, Danthonioideae, Arundinoideae, Chloridoideae, Centothecoideae, Panicoideae, and Incertae Sedis Streptogyna). These subfamilies include hydrophytic, helophytic, mesophytic and xerophytic species, with C3 or C4 photosynthetic pathways, and with affinities for shade, open, or semi-shade habitats. Analysis of phytolith occurrences shows that few morphotypes are restricted to some species only. However, there are morphological variations (of size and number of lobes) within the main phytolith categories Rondel, Bilobate, and Cross, which could additionally be considered to improve environmental and taxonomical interpretation of phytolith assemblages. The Rondel phytolith with a base diameter > 15 μm was only reported in C3-Pooideae, while the Rondel with a base diameter of < 15 μm occurs in several grass subfamilies (including Pooideae). Bilobates with long shanks between the two lobes are most frequently reported in xerophytic species, while Bilobates with short shanks are most frequently reported in mesophytic grass species. Finally, three-lobed crosses are reported only in Panicoideae and Chloridoideae, all being C4, light-loving species. A correspondence analysis confirms already known relationships between 1) Saddle forms, C4 pathway, open and xeric habitats, 2) Bilobates, Crosses, Polylobates, shaded and hydric habitats, 3) Trapeziform Sinuates and Pooideae. Of major implication for palaeoenvironmental reconstructions in East Africa, we found that the Trapeziform Sinuate phytoliths mark the presence of C3-grasses in the Afromontane zone, whereas the Rondels alone do not because they also occur in many C4 species of the Chloridoideae subfamily. We also establish that collapsed saddles are not diagnostic for Bambusoideae closed-habitat grasses since they occur in xerophytic species of the Chloridoideae, characteristic of several open habitats. In conclusion, this study contributes to better characterize Afromontane vegetation and better discriminate mesic and xeric vegetation types in East Africa. It also brings caution for future phytolith studies that rely on the presence of diagnostic types instead of phytolith assemblage analysis to trace the presence of particular taxa and/or environments in East Africa.

Estimating the Relevant Source Area of Pollen in the past cultural landscapes of southern Sweden — A forward modelling approach

In this paper, we estimate the Relevant Source Area of Pollen (RSAP) in past hypothetical landscapes of the Middle and Late Holocene in southern Sweden, in order to explore the possible effects of past changes in vegetation composition, openness and structure in terms of patch size and spatial distribution. The RSAP of small basins (bogs or lakes) in the past has to be estimated if quantitative reconstruction of past vegetation at the local spatial scale is to be achieved using Sugita's Landscape Reconstruction Algorithm (LRA). In this study we apply a forward modelling approach to estimate past RSAP using the computer simulation model HUMPOL. The landscape designs are based on past landscape maps produced using a combination of palaeobotanical, archaeological and historical data, and the area's geology and soil characteristics. Four time windows characterised by different landscape/land-use were selected, i.e. Early Neolithic, Late Bronze Age, Viking Age, and Middle Ages. We found that RSAP estimates for hypothetical past landscapes in Skåne differ by ca. 600 m to 1200 m between the selected time periods, whatever the size of the basin (lake or bog, 25–250 m radius). The most probable explanation for the differences in RSAP between time slices is variable patch size and spatial distribution of patches in the landscape. The RSAPs vary between ca. 1200 and 2300 m for small basins (25 m and 70 m radius), and between ca. 2000 and 3000 m for larger basins (250 m radius). These values are within the range of earlier estimates of modern and past RSAPs for southern Scandinavia obtained using simulated or empirical data. These results suggest that, given the type of setting of that region in terms of taxa composition and traditional land-use, the RSAP for small-size lakes (25–250 m radius) will generally be in the range ca. 1200–3000 m. The forward modelling approach is found to be useful to assess the possible effects on RSAP of changes in vegetation/landscape characteristics between different periods of the past. Moreover, comparison of RSAP estimates obtained using both the forward and backward modelling approaches will be important to identify the most credible RSAP estimates for the past.

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.

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.

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 x 100 km(2) 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.

A step further towards quantitative reconstruction of past vegetation in Fennoscandian boreal forests: Pollen productivity estimates for six dominant taxa

Pollen productivity estimates (PPE) are needed for producing quantitative reconstructions of the past landscapes by means of modelling. This study aims to provide estimates of relative pollen productivity for the two main tree species ( Pinus sylvestris L. and Betula sp .), for Cyperaceae and Gramineae, and the dominant dwarf shrubs ( Empetrum, Vaccinium sp .) of northern boreal forest vegetation in Finnish Lapland. A set of 24 moss samples were collected and their pollen content analysed, and detailed vegetation analyses were carried out within a 10.5 m radius around the samples. Vegetation further away, up to 10 km from the sites, was analysed from the Finnish Land Survey data. Vegetation proportions were calculated from the remotely sensed data using the program PolFlow, and distance weighting was applied using the program ERV_v6. The distance weighted vegetation data from the field survey and the Land Survey data were combined, and analysed with the pollen data using the ERV model. The resulting PPEs were evaluated by simulating pollen loadings with the POLLSCAPE model for an independent set of eight moss samples from the same area, using the obtained PPEs. The estimated pollen loadings and the observed pollen loadings were compared using paired samples t-tests. The PPEs obtained for the two major tree species are in keeping with expectations: PPE for Pinus is 8.4 (reference taxon Gramineae = 1) and for Betula 4.6. For Cyperaceae (0.002), Empetrum (0.07), and Vaccinium (0.01) the PPEs are very low and, according to paired samples t-test of the predicted and actual pollen loading, not reliable for Cyperaceae and Gramineae. The radius of the relevant source area of pollen (RSAP) is estimated to be ca. 1000 m. The pollen productivity estimates of the species, especially Pinus and Betula, are different in the northern boreal forest than in previously studied areas, such as southern Sweden. This has great implications for quantitative interpretations of fossil pollen records from the region.

Abandonment of farmland and vegetation succession following the Eurasian plague pandemic of ad 1347–52

AbstractAim This paper reviews the available documentary, archaeological and palaeoecological evidence for the abandonment of agricultural land and consequent regeneration of the forest in Europe after the Black Death.Location Western and northern Europe.Methods This review is the result of an exhaustive search of the historical, archaeological and palaeoecological literature for evidence indicating agricultural decline and forest regeneration in Eurasia during the 14th century. The available evidence for landscape change can be divided into two categories: (1) documentary and archaeological sources, and (2) palaeoecological reconstructions of past vegetation. In the past few years, several pollen diagrams from north‐west Europe have been reported with precise chronologies (decadal and even annual scale) showing the abandonment of farmland and consequent ecological change in the late medieval period.Results and main conclusions There is strong evidence of agricultural continuity at several sites in Western Europe at the time of the Black Death. The effects of the Black Death on the European rural landscape varied geographically, with major factors probably including the impact of the plague on the local population, and soil quality. At two sites in western and northern Ireland, the late medieval decline in cereal agriculture was probably a direct result of population reduction following the Black Death. In contrast, the decline in cereal production began at sites in Britain and France before the Black Death pandemic of ad 1347–52, and was probably due to the crisis in the agricultural economy, exacerbated by political instability and climate deterioration. Much of the abandoned arable land was probably exploited for grazing during the period between the decline in cereal farming and the Black Death. In the aftermath of the Black Death, grazing pressure was greatly reduced owing to reductions in the grazing animal population and a shortage of farmers. Vegetation succession on the abandoned grazing land resulted in increased cover of woody tree species, particularly Betula and Corylus, by the late 14th century. The cover of woodland was greatest at c.ad 1400, before forest clearance and agriculture increased in intensity.

Theory of quantitative reconstruction of vegetation I: pollen from large sites REVEALS regional vegetation composition

Quantitative reconstruction of past vegetation is one of the primary goals in Quaternary palynology and palaeoecology but still remains difficult. This paper proposes a model, REVEALS, that estimates regional vegetation composition using pollen from ‘large lakes’ that have small site-to-site variations of pollen assemblages even if vegetation is highly heterogeneous. Once these data have been used to quantify regional vegetation composition within 104 -105 km2, background pollen, one of the parameters crucial for vegetation reconstruction, can be estimated for smaller-sized sites, and incorporated into the Landscape Reconstruction Algorithm (LRA), a multistep framework for quantitative reconstruction of vegetation in smaller areas (≤ 104 ha). Simulations using the POLLSCAPE modelling show that REVEALS can provide accurate estimates of regional vegetation composition in various landscapes and under different atmospheric conditions. If pollen assemblages from lakes that are much smaller than ‘large lakes’ are used, estimates of regional vegetation at individual sites could be significantly different from the expected values, and their site-to-site variation could be large. However, when pollen data from multiple lakes ≥ 100-500 ha in size are available, REVEALS can provide accurate estimates of the regional vegetation with relatively small standard errors. Quantitative reconstruction of regional landscape and vegetation change will be critical for testing some of the controversial hypotheses and concepts in global change and conservation research, such as the impacts of agricultural activities on global climate over the last 8000 years and the open-woodland hypothesis in northern Europe in the early Holocene.

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

AbstractAim 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.

Laboratory production of Vouchered reference charcoal from small wood samples and non‐woody plant tissues

Taxonomic identification of small fragments of burned plant tissue in lake sediment profiles can enhance reconstructions of past vegetation, fire regimes, and climate. Vouchered reference collections of charcoal prepared from both soft and woody plant tissues, analogous to modern pollen reference collections, will be required for making rigorous identifications and for knowing the level of certainty achieved. Published methods of laboratory production of charcoal may only poorly mimic pyrolysis as it occurs in wildfires, and tend to require large volumes of plant material. We present a method for preparing reference charcoal from dried plant specimens that is simple, provides a high degree of control, yet requires only small tissue samples. Based on results of a series of experiments, we recommend placing dried samples in 25 cm3 perforated‐base porcelain Gooch filtering crucibles, surrounded by 250–500 μm sand; saturating the sand with water and draining; and placing for eight to nine minutes in a furnace heated to 550°C. The wet sand delays heating so that temperature rise is steep. Pyrolysis is brief and occurs under hypoxic conditions due to temporary oxygen flushing by water vapor. Using our method we achieved excellent results on both woody and soft tissues from a variety of plant taxa.

LABORATORY PRODUCTION OF VOUCHERED REFERENCE CHARCOAL FROM SMALL WOOD SAMPLES AND NON-WOODY PLANT TISSUES

Abstract Taxonomic identification of small fragments of burned plant tissue in lake sediment profiles can enhance reconstructions of past vegetation, fire regimes, and climate. Vouchered reference collections of charcoal prepared from both soft and woody plant tissues, analogous to modern pollen reference collections, will be required for making rigorous identifications and for knowing the level of certainty achieved. Published methods of laboratory production of charcoal may only poorly mimic pyrolysis as it occurs in wildfires, and tend to require large volumes of plant material. We present a method for preparing reference charcoal from dried plant specimens that is simple, provides a high degree of control, yet requires only small tissue samples. Based on results of a series of experiments, we recommend placing dried samples in 25 cm3 perforated-base porcelain Gooch filtering crucibles, surrounded by 250–500 µm sand; saturating the sand with water and draining; and placing for eight to nine minutes in ...