Pollen Representation Research Articles

Modern Pollen Signatures and Vegetation Dynamics in Northwestern Himalaya, India

ABSTRACT Palynological studies have been conducted for the first time in the Renukaji Wildlife Sanctuary (RWS), a Sal-dominated region within the foothills of Northwestern (NW) Himalaya in Himachal Pradesh, India. This research enhances our understanding of the relationship between modern pollen rain and vegetation, as well as pollen representation in sediments. Furthermore, it contributes to palaeovegetation reconstruction based on paleoclimatic trends by improving our interpretation of pollen deposition patterns. The study area was delineated into three distinct zones based on biological niche characteristics: Zone 1 (Recreation Zone), Zone 2 (Buffer Zone), and Zone 3 (Core Zone). Pollen analysis conducted on 30 surface soil samples and moss cushions, collected from all three zones, reveals the dominance of dry deciduous taxa, followed by extra-terrestrial taxa and wet deciduous taxa. Land Use Land Cover (LULC) analysis performed using satellite data reveals that Shorea robusta (Sal) mixed forest covers 32% of land, followed by Pinus spp. (8%) and their associates (25%). Shorea robusta, a mixed wet deciduous taxon and high pollen producer, exhibits low pollen counts, possibly due to chemical and microbial decomposition or low pollen dispersal efficiency. This study utilises a comparative database correlating pollen data with contemporary vegetation patterns to establish a robust framework for assessing sedimentary pollen sequences. Through this approach, we aim to elucidate past vegetation dynamics and infer climate fluctuations within the NW Himalaya.

Modern pollen distribution along a Himalayan elevation gradient in Central Nepal

Modern pollen distribution and its relationship to environmental variables in tropical to alpine vegetation zones are investigated to provide a reference for palaeoenvironmental reconstructions and to improve the understanding of pollen dispersal patterns in Central Nepal. A total of 100 samples (from soil and moss) were collected from along an elevational gradient ranging from 173 to 4615 m above sea level. Results show that the alpine zone is dominated by arboreal pollen (AP) and the sub-alpine zone also shows good representation of coniferous taxa pollen such as Pinus, Abies, Tsuga, and Picea along with Ericaceae. The temperate zone has a good representation of Quercus (Evergreen) and Pinus pollen, whereas the sub-tropical zone is characterized by Alnus pollen and agricultural taxa such as Cerealia (planted Poaceae) and Brassicaceae. In the tropical zone, non-arboreal pollen (NAP), mainly Cerealia dominate, reflecting intensive agricultural practices. Shorea is completely silent in pollen representation. A redundancy analysis indicates that elevation is the primary factor influencing pollen distribution in this region. Overall, the pollen data reflect the vegetation distribution but Pinus is over-represented and Shorea is unrepresented, which should be taken into consideration when interpreting fossil pollen in Central Nepal.

The relationships between modern pollen rain assemblages and vegetation from Sougna Mountain (Rif Mountains-Northern Morocco)

This study discovers the distribution of vegetation in the Sougna Mountain and its modern pollen representation and investigates the relationships with environment and land use variables. A total of 31 moss polsters were collected between 138 and 1364 m above sea-level from wooded to open areas (e.g. cork oak forest, pine reforestation, and shrubland). At each sampling site land use and environment variables were collected. The vegetation in the Sougna Mountain is scattered in a mosaic along three vegetation belts which are displayed in distinct pollen assemblages dominated by the pollen equivalents of the vegetation types (Quercus suber forest, matorrals of Erica spp. and Cistus spp. and Pinus pinaster reforestation). The variation between the variables and pollen data was performed using CCA analysis. The anthropogenic variables such as grazing, and cultivation, contribute to discrimination of the degraded and grazed areas. High precipitation and altitude have a rather good correlation to wooded communities and consequently a good relation to the tree cover. Our results show that the pollen types of Poaceae, Cannabis, Plantago, Nicotiana, Asteraceae, and Urtica are related mostly to human practice and distinguish the disrupted communities. The presence of those taxa in the pollen diagram must be interpreted carefully. A high taxonomic resolution is recommended to prevent the overestimation of the abundance of some taxa. Our results contribute to the advancement of palynological reconstructions of past vegetation and land use in Sougna Mountain and generally in the Rif landscape.

Revealing the palaeoecology of silent taxa: selecting proxy species from associations in modern vegetation data

AbstractAimSpecies severely under‐represented in fossil pollen records leave gaps in interpretations and reconstructions of past vegetation. These ‘silent taxa’ leave little or no trace due to low pollen production, dispersal, preservation and taxonomic resolution. An approach for including them is through associating them with other species with reliable pollen representation. Here, we demonstrate a method for selecting such a proxy species for the Holocene using modern vegetation data.LocationNew Zealand.TaxonBeilschmiedia tawa (A.Cunn.) Benth. & Hook. F. ex Kirk (Lauraceae).MethodsWe used vegetation plot data to perform a pairwise co‐occurrence analysis of the New Zealand indigenous forest metacommunity to identify species with a strong positive association with Beilschmiedia tawa (tawa), a common tree severely under‐recorded in the pollen record. For those species, we then modelled their realised climatic niches to identify species with high niche overlap. We discuss how well those species could be interpreted from the Holocene fossil pollen record based on the representation of their pollen taxa.ResultsKnightia excelsa (rewarewa; Proteaceae) is a potential proxy for B. tawa in Holocene fossil pollen records, and other, range‐limited species may provide community‐specific proxies. We show combining resampling with sub‐sampling is a robust method for reducing the high false positive rate associated with large co‐occurrence analyses (1000+ sites) by limiting the sample size to 100 sites.Main ConclusionsWe show that the palaeoecology of silent taxa can be studied via proxy species, allowing their past distributions to be better understood. We highlight the importance of modelling many aspects of the realised niche to understand the usefulness and limitations of the silent–proxy association. Future research should focus on testing the underlying assumptions of the silent–proxy relationship so that models built on modern data can confidently be applied to palaeoecological data.

A reference database of the pollen representation of the current vegetation in the Dry Puna of Argentina: Contributions to the interpretation of pollen fossil sequences and archeological evidence during the Holocene

The present research is framed within an interdisciplinary archeological project that aims to reconstruct the environmental conditions in which human occupations developed in the locality of Barrancas, Dry Puna Argentina, during the Holocene. The aims of this work were to: (1) study the regional vegetation and the modern pollen dispersal-sedimentation process; and (2) generate a reference database for interpretation of the fossil pollen records of the Holocene in the Dry Puna (3) provide information for the study of the relationship between human populations and vegetation in the area during the Late-Holocene. The results show that the main pollen types that characterize the regional vegetation were represented in the surface samples (herbaceous steppe, shrub steppe, mixed steppe, and vegas). Also the environments with evidence of anthropic impact were identified by specific plant species and the corresponding pollen grain. The representation of the vegetation was quantified according to the different pollen types. The study used indices of association to establish relationships between modern pollen and vegetation, and showed a weak association for Solanaceae and Verbenaceae; an over-representation of Ephedrae, Alnus acuminata, Malvaceae, Chenopodiaceae-Amaranthaceae; an association of Asteraceae; the absence of association of Cactaceae and Portulacaceae; and a strong association of Poaceae. These results allow us to specify the interpretation of fossil records and past environments in relation to anthropic modifications on the landscape.

Modern pollen dispersal in relation to present vegetation distribution and land use in the Baspa valley, Kinnaur, western Himalayas.

Interpretation of a fossil pollen data for the vegetation and climate reconstruction of any region needs a modern pollen-vegetation analogue for its calibration. We analyzed the surface sediments and moss polsters for the pollen and microcharcoal records to understand the modern pollen-vegetation relationship and human activities in the Baspa Valley, Kinnaur, Himachal Pradesh. Presently, valley is occupied by the arboreal and non-arboreal vegetation of temperate to subalpine habitats and land use activities. The recovered pollen assemblages showed variability in the dispersal behavior of pollen of taxa growing along the valley transect and also captured the signals of human activities over land use. The overall dominance of arboreal pollen in the recovered pollen assemblage corresponds with the dominant growth of conifers and broadleaf tree taxa and represents the valley vegetation at a regional scale. However, the profuse pollen production of a few arboreal taxa and long distance pollen transport from one vegetation zone to other by the strong upthermic valley winds could bias the pollen representation of in-situ vegetation. The high pollen frequency of non-arboreal taxa in the open meadows represents the near vicinity to their plant source. Human activities like fire burning and cultivation by the local population are evident by the recovery of microcharcoal particles and pollen of plants belonging to Cerealia Poaceae, Asteraceae, Amaranthaceae, Polygonaceae, Rosaceae, Juglandaceae, etc. The dataset taken as modern pollen-vegetation analogue is useful to assess past changes in the vegetation and land cover in relation to climate and human factors for future sustenance.

Climate and sea-level fluctuations on the western coast of Bohai Bay during the 4.2 ka event: Multi-proxy evidence from the Nandagang area of Cangzhou, China

The 4.2 ka event was an important climatic event during the mid–late Holocene, with significant effects on the ecological environment and climatic evolution of different regions. Coastal wetlands, as a transitional ecosystem between land and sea, are sensitive to changes in climate and sea level; hence, research on coastal wetlands is important for reconstructing past climate and sea-level changes and for predicting future changes. However, little research has been conducted on the characteristics of the 4.2 ka event on the western coast of Bohai Bay in China. We analyzed the pollen assemblages (214 samples), grain size, and geochemical element contents of a mid–late Holocene sedimentary sequence from the Nandagang (NDG) wetland on Bohai Bay, with the chronology based on 13 AMS 14C dates. The results revealed the history of climate and sea-level changes on the western coast of Bohai Bay during the interval of 5000–3600 cal yr BP. High sedimentary arboreal pollen concentrations indicated that the NDG area had a relatively dense cover and humid climate during 5000–4450 cal yr BP. During the 380-year interval of 4450–4070 cal yr BP, corresponding to the 4.2 ka event, the decreased representation of arboreal pollen indicated a decrease in the regional forest cover and an arid climate. The internal structure of the 4.2 ka event recorded in core NDG showed a dry-wet-dry temporal structure during the intervals of 4450–4290 cal yr BP, 4290–4170 cal yr BP, and 4170–4070 cal yr BP, respectively, together with a relatively low sea level. Comparison of the relative sea level (RSL) record of the NDG wetland with similar records from other coastal regions in East Asia during the 4.2 ka event revealed contrasting trends. During 4070–3600 cal yr BP, the tree pollen concentration increased again, indicating that the forest vegetation coverage increased and the climate became wetter. Overall, our results suggest that the 4.2 ka event, as recorded in Bohai Bay, was related to the reduced influence of the western Pacific Ocean Warm Pool and the more frequent occurrence of the El Niño–Southern Oscillation.

Pollen and non-pollen palynomorph depositional patterns in Kaziranga National Park, India: Implications for palaeoecology and palaeoherbivory analysis

The main aim of this study is to produce a modern analog for pollen and non-pollen palynomorphs (NPPs) preserved in soil in relation to the different vegetation types and herbivore impact in the Kaziranga National Park (KNP). The pollen data obtained reflects both the extant vegetation types in each habitat as well as landuse, but some site-by-site variation was observed with respect to the coprophilous fungal spores present in the palynoassemblage. Canonical correspondence analysis (CCA) analysis of pollen data reveals the presence of five significantly different vegetation types, while the non-pollen palynomorphs are relatively similar in relation to the different vegetation types. The long-term association of the wildlife and their impact on different vegetation types is one of the main reasons for the variation seen in the depositional pattern in the assemblage. The openland area is one of the most important areas for wildlife in the KNP as indicated by the presence of marker pollen and coprophilous fungal spores in the palynoassemblages. Coprophilous fungal spores were most abundant in this vegetation type reflecting the higher density of herbivores. The representation of pollen and coprophilous fungal spores from the swamp samples reflected the overall composition of all vegetation types existing in the KNP. This data can be utilized as a baseline for the interpretation of paleoecological and paleoherbivory studies in other parts of the Indian subcontinent as well as its potential application at a global level.

Distribution and sources of surface soil pollen in different coastal wetlands and their relationship with land cover: A case study of northwest Bohai Bay, north China

Understanding the relationship between modern pollen and vegetation in coastal wetlands is essential for reconstructing long-term land cover changes, and for determining the response of coastal wetland ecosystems to global changes. We selected 68 sampling sites in different types of coastal wetland in northwest Bohai Bay, North China, for palynological analysis, and hence to determine the relationships between pollen and environmental factors, such as soil grain size, salinity, and pH. A back-trajectory model and remote sensing LUCC data were used to reveal the pollen source area and the pollen representation for different land cover types. The results show that the pollen assemblages of these coastal wetlands are dominated by Chenopodiaceae and Poaceae. The pollen assemblages are significantly different between silty and sandy coastal wetlands, and they also reflect different vegetation landscapes. Chenopodiaceae pollen is a potential indicator of saline-alkali soil environments in coastal areas. In addition to the vegetation coverage and sedimentary environment, pollen concentrations are negatively correlated with the grain size of the surface soil. The pollen diversity is higher in areas with strong human influences (e.g., cultivated land, villages, roads), but lower in natural wetlands with a high vegetation coverage. The arboreal pollen is generally sourced from the northern and northwestern mountains, while the major dispersal area of halophyte and hygrophyte pollen is on a local scale, constrained by the local vegetation canopy and its settlement characteristics. Fern spores are mainly waterborne, carried by rivers and surface runoff from mountain areas. The arboreal and upland herbaceous pollen is over-represented for forest and grassland landscapes. Halophyte and hygrophyte pollen show a good correlation with the area of coastal wetland, and they can be used as an indicator of the extent of coastal wetland influenced by climate change and human activities.

Relationship between pollination syndromes, pollen morphology and plant ecology in Quaternary deposits of the Cerrado

This study presents morphological descriptions and ecological information for 58 terrestrial pollen taxa and seven water-related pollen taxa from the Brazilian Cerrado, obtained from two sediment cores, Lake Feia (LFB1) and Getulio Swamp (VGE-17), encompassing the last 5000 and 15,000 cal yr BP, respectively. The relationships between the ecological and morphological traits (pollination syndrome, vegetation stratum and grain size) within each of the two depositional environments were investigated. In the LFB1 core, the pollen assemblages were dominated by arboreal pollen from closed physiognomies and lower storey trees (<10 m in height), while a combination of closed and open physiognomies was observed in the pollen assemblages from the VGE-17 core. The vast majority of the pollen taxa exhibited the entomophilous pollination syndrome, and a higher influx of entomophilous pollen was observed in both cores. Anemophilous and anemophilous/entomophilous syndromes were less well represented. Small and medium pollen grain classes were the most abundant, while the large pollen grain class was rare. The influx of small pollen grains was slightly more abundant in the lake record, while in the swamp record medium pollen grains were more abundant. Our results show that swamps and lakes differ in their representation of local versus regional pollen and in their sensitivity and responses to water-level changes. Landscape physiognomy also influences pollen dispersion: a closed physiognomy increases the local pollen signal, while a more open physiognomy results in better representation of local and regional signals.

Assessment of Pollen Representation in NW Italy (Liguria and Piedmont)

This research focuses on the recent pollen image of several vegetation types in NW Italy. In 201 arboreal, shrubby, and herbaceous plant populations, pollen samples were taken from moss polsters, and the corresponding vegetation was recorded using the phytosociological method. Since studies on recent pollen rain in the Mediterranean mountains and coast are rare, this research aims to provide new data and tools to better interpret fossil pollen spectra. Pollen analysis provided data for the comparison between surface spectra and vegetation. Davis indices, fidelity, dispersion, and the relation with vegetation data were calculated for each taxon, and PCA was carried out. Most vegetation types are identifiable through the taxa dominating the pollen spectra, as frequently happens in woodlands (e.g., beech woods, chestnut woods, etc.). Characterizing shrubland and certain tree-dominated vegetation types (e.g., Larix forests) through pollen data is more complex. In this regard, Davis indices are particularly useful for identifying pollen/plant association, over- and underrepresentation of pollen, and taxa indicating vegetation types. Pollen threshold values were calculated which allow the assessment of the local presence of a plant. Overall, the achieved results partially confirm those of previous research carried out in the region, greatly expanding the comparisons between several different plant communities and the database in view of future sharing through the EMPD.

‘Pine Decline or pine declines?’ Analysis and Interpretation of Bog-Pines from Wem Moss, Shropshire, UK

A dendrochronological investigation was undertaken on subfossil Scots pine (Pinus sylvestris L.) stumps following their discovery during conservation management at Wem Moss, a small (28 ha) former raised mire in Shropshire, UK. Two ring-width chronologies were constructed from 14 of the 17 trees sampled spanning 198 and 208 years, respectively. Whilst dendrochronological dating was not possible, radiocarbon assays provided an estimated age for this mire-rooting woodland of between 3015 and 2505 years cal. BCE, coinciding with the age traditionally associated with the widespread mortality of pine trees throughout much of the UK and Ireland, often referred to as the Pine Decline (ca. 4000 radiocarbon years BP). Placed in a wider geographical context, the Wem Moss pines are located within the lowland Meres and Mosses region, where previous studies on subfossil pine have demonstrated protracted declines in mire-rooting trees. These have included tree mortality significantly post-dating the Pine Decline, especially at larger peatland sites that exceed 5 km2. Such macrofossil evidence for the presence of Scots pine into the late Holocene is supported by continuous Pinus pollen representation at peatland sites in the Welsh Marches (English–Welsh border), suggesting the possible survival of native Scots pine trees in this area up to the present day. The investigation of Wem Moss bog pines and their wider geographical context highlights the incomplete and patchy nature of palaeo-vegetational records and also the need for future genetic research on living Scots pine in possible refugial areas in Britain and Ireland.

Plant distribution and modern pollen deposition across an elevation eco-gradient: The lesson learnt from a case study in the Italian Alps

This study investigates the distribution of vegetation and its modern pollen representation along an elevation gradient in the Italian Alps and explores the relationships with terrain and climate variables. Moss polsters were collected at 25 sites between ca. 300 and 1400 m asl from open areas, deciduous, and conifer forests. At each site vegetation was surveyed at 1.8 and 10 m radius according to the Braun-Blanquet method. Climatic data, bioclimatic indices, and terrain parameters were obtained for each sampling site. Three distinct pollen associations reflect the characteristic vegetation altitudinal belts present in the study area. Uphill dispersal, the regional load and the presence of high producers influence the abundance of pollen and the representation of taxa along the gradient. CCA ordination technique reveals the predictive power of environmental variables on modern pollen and vegetation datasets. The most relevant factors controlling vegetation distribution are identified in elevation, insolation, Pspring, Tsummer, the Ellenberg quotient, and Summer Water Balance (SWB). Elevation, insolation, summer P and T, the Ellenberg quotient, and the Gams’ hygric continentality index (GAMS) explain more variance within the pollen dataset. A qualitative comparison among pollen and the corresponding parent plant occurrence qualifies Abies alba, Fagus sylvatica, Poaceae and Cyclamen pollen as suitable indicators taxa of the local vegetation in the study area. Several high producers with very effective, long-distance anemophilous dispersal ( Pinus, Ostrya, Alnus, and Juglans) or mixed pollination mechanisms (anemophilous and insect-pollination: Fraxinus ornus, and Castanea) show no or little association with their parent plants.

Modern Pollen Assemblages From Lake Sediments and Soil in East Siberia and Relative Pollen Productivity Estimates for Major Taxa

Modern pollen–vegetation–climate relationships underpin palaeovegetation and palaeoclimate reconstructions from fossil pollen records. East Siberia is an ideal area for investigating the relationships between modern pollen assemblages and near natural vegetation under cold continental climate conditions. Reliable pollen-based quantitative vegetation and climate reconstructions are still scarce due to the limited number of modern pollen datasets. Furthermore, differences in pollen representation of samples from lake sediments and soils are not well understood. Here, we present a new pollen dataset of 48 moss/soil and 24 lake surface-sediment samples collected in Chukotka and central Yakutia in East Siberia. The pollen–vegetation–climate relationships were investigated by ordination analyses. Generally, tundra and taiga vegetation types can be well distinguished in the surface pollen assemblages. Moss/soil and lake samples contain generally similar pollen assemblages as revealed by a Procrustes comparison with some exceptions. Overall, modern pollen assemblages reflect the temperature and precipitation gradients in the study areas as revealed by constrained ordination analysis. We estimate the relative pollen productivity (RPP) of major taxa and the relevant source area of pollen (RSAP) for moss/soil samples from Chukotka and central Yakutia using Extended R-Value (ERV) analysis. The RSAP of the tundra-forest transition area in Chukotka and taiga area in central Yakutia are ca. 1300 and 360 m, respectively. For Chukotka, RPPs relative to both Poaceae and Ericaceae were estimated while RPPs for central Yakutia were relative only to Ericaceae. Relative to Ericaceae (reference taxon, RPP = 1), Larix, Betula, Picea, and Pinus are overrepresented while Alnus, Cyperaceae, Poaceae, and Salix are underrepresented in the pollen spectra. Our estimates are in general agreement with previously published values and provide the basis for reliable quantitative reconstructions of East Siberian vegetation.

Modern analogs for understanding pollen-vegetation dynamics in a Mediterranean mosaic landscape (Balearic Islands, Western Mediterranean)

This paper presents the study of modern pollen analogs from the Balearic Islands. While similar studies have been largely applied to mainland areas, research focused on modern vegetation dynamics on Mediterranean islands remains very rare. In this research, we combine vegetation surveys, pollen analysis and multivariate statistics to understand landscape composition. The main objectives of are: (1) to examine pollen-vegetation relationships in relation to environmental and land-use variables; (2) to understand modern pollen representation in a mosaic landscape structure; and (3) to propose pollen indicators that characterize the primary vegetation types from the Balearic Islands to better interpret past pollen records in Mediterranean island environments. Pollen results and Redundancy Analysis (RDA) distinguish three major groups: (a) Holm oak and box formations; (b) maquis and garrigues; and (c) anthropogenic and open habitats. Landscape form, mean decadal rainfall, mean decadal temperature, fire activity, trampling, slope percentage, wet/flooded soil, saline soil, distance to agropastoral cells, gHM index, domestic herbivory presence, agropastoral use, and soil type are the major variables explaining modern pollen assemblage variation in our research. Poaceae undiff., Plantago sp., Apiaceae undiff., Cerealia-t, and Cichorieae are highly correlated to human activities but should be interpreted cautiously when occurring in low values. Quercus ilex-t, Hypericum, and Buxus are correlated to humid locations while Pistacia, Pinus, Juniperus-t, and Olea to high mean decadal temperatures. Our study indicates how pollen analysis and multivariate analysis are powerful tools for characterizing the mosaic landscape, with special focus on the main vegetation types of the Balearic Islands.

Pollen R-values in arid central Asia for quantitative palaeo-vegetation reconstruction

Establishing the relationship between surface pollen assemblages and related modern vegetation provides a bridge for reconstructing the palaeo-vegetation succession and related climate changes. Numerous contributions have demonstrated an inconsistency between the relative abundance values of surface pollen assemblages and corresponding modern vegetation for some taxa, which is attributed to differences in their pollen production, dispersal mode and preservation potential. Consequently, the concept of R-value was introduced as a correction coefficient to counterbalance this discrepancy. Unlike most of the complex forest and grassland ecosystems, desert vegetation with fewer dominant taxa provides a simpler model to demonstrate how to use the R-value to correct this deviation. Here, we propose a scheme of Rrel median values from modern desert vegetation types based on calculated R and Rrel adjustment coefficients of the dominant taxa using surface pollen and related modern vegetation data from 145 sample plots along an east-west desert transect in the eastern arid central Asia (ACA). These data revealed that 1) taking Nitraria as a reference, Chenopodiaceae, Artemisia and Ephedra are highly represented, while Tamaricaceae, Zygophyllaceae, Asteraceae (excluding Artemisia), Calligonum and Poaceae are poorly represented. 2) the pollen representation was constrained by their pollination strategies. For example, anemophilous plants (e.g., Ephedra, Artemisia and Chenopodiaceae) are mostly over-represented, while those of entomophilous taxa (e.g., Nitraria, Tamaricaceae, Zygophyllaceae and Calligonum) are under-represented. The scheme and findings mentioned above cast a new light on the future of quantitative reconstruction of palaeo-vegetation succession in the ACA.

Modern pollen – vegetation – plant diversity relationships across large environmental gradients in northern Greece

Past vegetation and biodiversity dynamics, reconstructed using palaeoecological methods, can contribute to assessing the magnitude of the current biodiversity crisis and anticipating future risks and challenges. Among the different palaeoecological techniques, pollen analysis is probably the most widely used to reconstruct vegetation and plant diversity changes through time. Such reconstructions demand robust and comprehensive calibration studies addressing the pollen representation of extant vegetation to be sound. However, calibration studies are rare in the Mediterranean biodiversity hotspot, particularly regarding plant diversity. Here, we contribute to filling this gap by investigating the modern pollen signature of Mediterranean vegetation across a large environmental gradient in northern Greece. At each sampling site ( n = 61), we quantitatively compared the composition and diversity of plant (vegetation surveys) and pollen assemblages (moss/topsoil samples) using numerical techniques. Further, we compared these terrestrial pollen assemblages with those from lake sediment surface samples of the same region. We found an overall good match between plant and pollen assemblages, with maquis and mixed deciduous forest displaying particularly distinct pollen signatures. In contrast, the high regional importance of pines and oaks and their large pollen production blurred the pollen representation of other forested vegetation types and of shrublands and grasslands. Plant and pollen richness and their evenness showed similar declining trends with increasing altitude, but plant and pollen evenness bore a better match than richness. A more detailed vegetation-specific view on the data suggests that pine pollen seriously affected pollen richness and evenness in most of the pine-dominated stands. Lastly, our results suggest a rather straightforward application of vegetation-pollen relationships from moss/topsoil samples to interpret pollen assemblages from lakes in Mediterranean settings.

Anthropogenic mountain forest degradation and soil erosion recorded in the sediments of Mayinghai Lake in northern China

The late Holocene vegetation of the Loess Plateau in China was influenced by both climate change and human activities, however, details of how humans modified the vegetation are unclear, especially in the mountain region of northern China. In this study we used pollen and charcoal analysis of a radiocarbon-dated sediment core from Mayinghai Lake, in northern China, to reconstruct the history of vegetation change and burning over the past 4500 years. Four stages of vegetation change are documented: 1) During 2500 BCE – 600 BCE, the vegetation was forest steppe, dominated by Betula, Quercus, Pinus, Artemisia, Poaceae and Amaranthaceae. 2) During 600 BCE – 1050 CE, there was a slight decrease in tree pollen representation with evidence of more intense human disturbance, especially during 600 BCE – 200 CE. 3) During 1050 CE – 1500 CE, tree pollen frequencies decreased rapidly and then increased again. 4) After 1500 CE, the tree pollen frequencies decreased to their lowest level within the sequence, and the vegetation was steppe, dominated by herbs such as Artemisia, Poaceae and Amaranthaceae. An increase in cereal-type Poaceae/Poaceae (CTP/P) ratio, charcoal and Humulus pollen from 950 CE onwards indicates increased human impacts in the area, associated with early deforestation as a result of intensified agricultural activity during the Northern Song dynasty. Additionally, much higher sediment accumulation rates resulted from deforestation within the lake catchment. However, after 1400 CE, the forest was largely cleared, partly for agriculture, and the climatic cooling of the Little Ice Age (LIA) likely also inhibited forest development. Regional warfare may also have contributed to the reduction of the regional forest vegetation during the intervals of 900 CE – 1000 CE and 1400 CE – 1650 CE.

Pollen‐chemistry variations along elevation gradients and their implications for a proxy for UV‐B radiation in the plant‐fossil record

Abstract Research indicates that phenolic compounds (e.g. para‐coumaric acid) found within pollen grains may be useful as a proxy to reconstruct the UV‐B radiation received at the Earth's surface in the geological past. However, application of this method to the plant‐fossil record currently relies on a series of untested assumptions surrounding the ecological factors driving the response of pollen grains in the contemporary environment. Here, we investigate the relationship of Pinus spp. pollen to UV‐B radiation using individuals of five populations sampled from three elevation gradients across Europe. We develop a novel radiation‐modelling approach, which allows us to estimate the UV‐B radiation dose of individual trees, weighted by different UV‐B action spectra. We then use linear mixed‐effects modelling to investigate: (a) whether the variations in UV‐B‐absorbing compounds in Pinus pollen are best described by models using coarser (subgenus) or finer (population) taxonomic levels; and (b) the duration of the period of accumulation of UV‐B‐absorbing compounds in pollen, ranging from 8 to 28 days. Our results demonstrate an overall positive relationship between para‐coumaric acid and UV‐B radiation, best described by applying a UV‐B‐accumulation period spanning 12–19 days. However, we also show clear evidence for population‐level factors influencing this relationship across the study locations. Synthesis. Our multidisciplinary approach, which combines expertise from palaeoecology, plant physiology and atmospheric physics, provides clear evidence that pollen‐grain chemistry is subject to population‐level variations. We suggest that quantitative reconstructions of long‐term changes in springtime UV‐B radiation are still achievable using fossil reconstructions, but only with careful consideration of the factors leading to pollen representation in sediments. Future improvements are dependent on mechanistic understanding of the local factors which mediate the UV‐B response across different populations, and on upscaling knowledge at the plant level to incorporate longer‐term chemical variations represented within sediment samples.

Towards quantifying changes in forest cover in the Araucaria forest-grassland mosaic in southern Brazil

Quantitative estimates of past vegetation cover are needed both regionally so human-landscape interactions can be better understood, and globally to evaluate the effects of changing vegetation cover on the climate system. Models reducing the bias in the pollen representation of vegetation cover have been developed in the temperate regions of the northern hemisphere, while experience applying them in other parts of the world is limited. The Araucaria forest-grassland mosaic of southern Brazil is an area where open and forested plant communities exist naturally and have changed their cover over time due to changing climate and human activities. Therefore, this area is of particular interest for such studies. Modern pollen and vegetation comparisons were carried out in two protected areas: Vila Velha State Park in Paraná state and Aparados da Serra National Park in Rio Grande do Sul. Vegetation mapping and analysis focused on Araucaria angustifolia as the characteristic tree of this vegetation type. In the Araucaria forest-grassland mosaic open vegetation and woodland change at a scale of hundreds of metres. These changes are difficult to capture based on pollen proportions in surface samples. While the abundance of Poaceae pollen is not a good indicator of locally open conditions, several pollen taxa can be used as indicators of the local vegetation cover. Pollen vegetation ratios (R-values) compare well between the two study regions, indicating that pollen production of individual species within the large plant families of Poaceae and Asteraceae are similar within the overall region. Araucaria angustifolia pollen is underrepresented with regards to its vegetation cover, while Poaceae are among the highest pollen producers in the region. Diverse woodland species other than A. angustifolia were grouped as one forest taxon and as the species composition of woodlands differed between the two study areas, so did the estimated pollen productivity of this group. It would be rewarding in future investigations to estimate pollen productivity for groups of trees with the same pollen dispersal syndrome. The application of pollen dispersal models designed for closed canopy in the protected areas was challenging. Further model development is required to deal with pollen released at different levels in semi-open vegetation types.