Paleovegetation Reconstruction Research Articles

Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part 1: stable isotopes and sugar biomarkers

Abstract. Today, on the Sanetti Plateau in the Bale Mountains of Ethiopia, only fragmented patches of Erica species can be found at high altitudes (between 3900 and 4200 m a.s.l.). However, it is hypothesized that during the later part of the last glacial period and the early Holocene the plateau was extensively covered by Erica shrubs. Furthermore, it is assumed that the vegetation was later heavily destroyed by human-induced fire and/or climate change phenomena. The objective of this study is to contribute to paleovegetation reconstructions of the Sanetti Plateau by evaluating the potential of stable isotopes (δ13C and δ15N) and sugar biomarkers for distinguishing the dominant plant species, including Erica, and the soils below the plants. In a companion paper (Lemma et al., 2019a) we address the same issue by evaluating lignin-derived phenols and leaf-wax-derived n-alkane biomarkers. The stable carbon (δ13C) and nitrogen (δ15N) isotope values of the plant samples range from −27.5 ‰ to −23.9 ‰ and −4.8 ‰ to 5.1 ‰, respectively. We found no significant δ13C and δ15N differences between the dominant plant species. Mineral topsoils (Ah horizons) yielded more positive values than plant samples and organic layers (O layers), which reflects mineralization processes. Moreover, the δ15N values became generally more negative at higher altitudes. This likely indicates that the N cycle is more closed compared to lower altitudes. δ15N maxima around 4000 m a.s.l. point to fire-induced opening of the N cycle at the chosen study sites. Erica species yielded the lowest overall total sugar concentration (ranging from 58 to 118 mg g−1), dominated by galactose (G) and mannose (M). By contrast, Festuca species revealed much higher total sugar concentrations ranging from 104 to 253 mg g−1, dominated by the pentose sugars arabinose (A) and xylose (X). Although a differentiation between Erica versus Festuca, Alchemilla and Helichrysum is possible based on (G + M) ∕ (A + X) ratios, Erica cannot be unambiguously distinguished from all other plant species occurring on the Sanetti Plateau. In addition, plant-characteristic (G + M) ∕ (A + X) sugar patterns change during soil organic matter formation in the Ah horizons. This can be likely attributed to degradation effects and soil microbial build-up of galactose and mannose. In conclusion, soil degradation processes seem to render sugar biomarker proxies unusable for the reconstruction of the past extent of Erica on the Sanetti Plateau, Bale Mountains, Ethiopia. This finding is of relevance beyond our case study.

Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part II: lignin-derived phenols and leaf-wax-derived <i>n</i>-alkanes

Abstract. Erica is a dominant vegetation type in many sub-afroalpine ecosystems, such as the Bale Mountains in Ethiopia. However, the past extent of Erica is not well known and climate versus anthropogenic influence on altitudinal shifts are difficult to assign unambiguously, especially during the Holocene. The main objective of the present study is to chemotaxonomically characterize the dominant plant species occurring in the Bale Mountains using lignin phenols and n-alkane biomarkers and to examine the potential of those biomarkers for reconstructing vegetation history. Fresh plant material, organic layer and mineral topsoil samples were collected along a northeastern and a southwestern altitudinal transect (4134–3870 and 4377–2550 m a.s.l., respectively). Lignin-derived vanillyl, syringyl and cinnamyl phenols were analyzed using the cupric oxide oxidation method. Leaf-wax-derived n-alkanes were extracted and purified using Soxhlet and aminopropyl columns. Individual lignin phenols and n-alkanes were separated by gas-chromatography and detected by mass spectrometry and flame ionization detection, respectively. We found that the relative contributions of vanillyl, syringyl and cinnamyl phenols allow us to chemotaxonomically distinguish contemporary plant species of the Bale Mountains. Erica in particular is characterized by relatively high cinnamyl contributions of >40 %. However, litter degradation strongly decreases the lignin phenol concentrations and completely changes the lignin phenol patterns. Relative cinnamyl contributions in soils under Erica were <40 %, while soils that developed under Poaceae (Festuca abyssinica) exhibited relative cinnamyl contributions of >40 %. Similarly, long-chain n-alkanes extracted from the leaf waxes allowed for differentiation between Erica versus Festuca abyssinica and Alchemilla, based on lower C31 ∕ C29 ratios in Erica. However, this characteristic plant pattern was also lost due to degradation in the respective O layers and Ah horizons. In conclusion, although in modern-day plant samples a chemotaxonomic differentiation is possible, soil degradation processes seem to render the proxies unusable for the reconstruction of the past extent of Erica on the Sanetti Plateau, Bale Mountains, Ethiopia. This finding is of high relevance beyond our case study.

Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part 1: stable isotopes and sugar biomarkers

Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part 1: stable isotopes and sugar biomarkers

Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia.

Despite the fact that the vegetation pattern and history of the Bale Mountains in Ethiopia were reconstructed using pollen, little is known about the former extent of Erica species. The main objective of the present study is to identify unambiguous chemical proxies from plant-derived phenolic compounds to characterize Erica and other keystone species. Mild alkaline CuO oxidation has been used to extract sixteen phenolic compounds. After removal of undesired impurities, individual phenols were separated by gas chromatography and were detected by mass spectrometry. While conventional phenol ratios such as syringyl vs. vanillyl and cinnamyl vs. vanillyl and hierarchical cluster analysis of phenols failed for unambiguous Erica identification, the relative abundance of coumaryl phenols (>0.20) and benzoic acids (0.05—0.12) can be used as a proxy to distinguish Erica from other plant species. Moreover, a Random Forest decision tree based on syringyl phenols, benzoic acids (>0.06), coumaryl phenols (<0.21), hydroxybenzoic acids, and vanillyl phenols (>0.3) could be established for unambiguous Erica identification. In conclusion, serious caution should be given before interpreting this calibration study in paleovegetation reconstruction in respect of degradation and underground inputs of soil organic matter.

Evidence for fire in the Pliocene Arctic in response to amplified temperature

Abstract. The mid-Pliocene is a valuable time interval for investigating equilibrium climate at current atmospheric CO2 concentrations because atmospheric CO2 concentrations are thought to have been comparable to the current day and yet the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the amplified Arctic temperature response and its impact on Arctic ecosystems. Only the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the currently proposed feedbacks is limited by scarce terrestrial records of climate and environment. Here we reconstruct the summer temperature and fire regime from a subfossil fen-peat deposit on west–central Ellesmere Island, Canada, that has been chronologically constrained using cosmogenic nuclide burial dating to 3.9+1.5/-0.5 Ma. The estimate for average mean summer temperature is 15.4±0.8 ∘C using specific bacterial membrane lipids, i.e., branched glycerol dialkyl glycerol tetraethers. This is above the proposed threshold that predicts a substantial increase in wildfire in the modern high latitudes. Macro-charcoal was present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in charcoal was synchronous with a change in vegetation that included an increase in abundance of fire-promoting Pinus and Picea. Paleo-vegetation reconstructions are consistent with warm summer temperatures, relatively low summer precipitation and an incidence of fire comparable to fire-adapted boreal forests of North America and central Siberia. To our knowledge, this site provides the northernmost evidence of fire during the Pliocene. It suggests that ecosystem productivity was greater than in the present day, providing fuel for wildfires, and that the climate was conducive to the ignition of fire during this period. The results reveal that interactions between paleo-vegetation and paleoclimate were mediated by fire in the High Arctic during the Pliocene, even though CO2 concentrations were similar to modern values.

Paleovegetational reconstruction from fossil opal phytolith assemblages in the soil of tropical seasonal forests in Thailand

Paleovegetational reconstruction from fossil opal phytolith assemblages in the soil of tropical seasonal forests in Thailand

Modern alluvial pollen distribution in Ganges–Brahmaputra–Meghna (GBM) floodplain and its paleoenvironmental significance

Research into modern alluvial pollen constitutes essential information on understanding pollen–vegetation, vegetation–climate, and vegetation distribution pattern, which in turn facilitate reconstruction of paleovegetation and paleoenvironment. However, such studies are scarce in globally renowned Ganges–Brahmaputra–Meghna (GBM) floodplain region, Bangladesh. In order to determine the main characteristics of modern alluvial pollen distributions and its relationship with corresponding vegetation and climate, 47 alluvial sediment samples were collected from GBM riverbed, and a palynological analysis was carried out. The results indicated a clear dominance of herb pollens such as Poaceae, Amaranthaceae, Brassicaceae, and Asteraceae in the GBM floodplain region, because of their uninterrupted presence in the agricultural lands along the floodplain and being high pollen producer. Among tree pollens, Pinus and Tsuga were dominant which were transported by wind and/or water from the Himalayan region indicating the regional source of pollens in the alluvium. A gradual decreasing pattern of Pinus pollens toward the Bay of Bengal may be attributed to the gradual increase in distance from the source vegetation in the Himalaya. Fern and Fungi spores were relatively higher in the upstream of the Ganges, Brahmaputra, and Surma rivers than the Meghna River region and downstream indicating relatively higher humid conditions in the upstream than downstream. Variation in palynomorphs assemblages reflects both local and regional variations in vegetation along catchments on the GBM Rivers; however, tree pollen was under-represented in the pollen spectra due to their lower pollen productivity and preservation as well as sparse abundance in the study area. Based on PCA and variation in palynomorphs it is clear that human activities and hydrodynamic effects play a principal role in alluvial pollen dispersion, although wind effects cannot be neglected. Modern palynomorphs and its relation with climate corresponded well and can be applied for paleoclimatic study; however, the dominance of only Poaceae is not solely an indicator of aridity instead indicate highly agricultural activities in this region. These findings are of critical importance in the Quaternary as well as Holocene sequence interpretation of paleoenvironment and paleovegetation in the GBM floodplain, Bangladesh.

Plant functional indicators of vegetation response to climate change, past present and future: I. Trends, emerging hypotheses and plant functional modality

Plant functional traits are widely applied in models that simulate the effects of climate change on biodiversity and resource management. Here the aim is to examine the potential role of specific plant functional traits and their whole-plant syndromes (Plant Functional Types or PFTs as specific ‘modal’ trait assemblages) as indicators of vegetation response to climate change, past, present and future. Because plant functional characteristics have evolved through time, it is widely argued that models of vegetation performance under future climates should benefit from a study of plant response under previous climates. This paper presents an overview first, of developmental concepts underlying the current use of PFTs as indicators of plant response to environmental change, second, implications arising from species acclimation and third, process-based models used in reconstruction of vegetation under mainly Holocene environments but also with respect to present and future climates. In this regard the role of individual functional traits in ‘biomization’ procedures in vegetation response models is briefly discussed. It is concluded that, while PFTs possess limited indicator value at biome scale, uncertainties in the delimitation of local paleohabitats greatly restrict their use as indicators for paleovegetation reconstruction at community level. Emerging hypotheses are: 1) A whole-plant system of modal PFTs based on a novel set of functional traits can provide an improved alternative to PFTs and traits used in models of vegetation response to climate change, 2) Modal PFTs are potentially more efficient indicators of vegetation response to climate change than individual traits, 3) Improved plant functional selection criteria can lead to more efficient parameterization of Earth System and Dynamic Global Vegetation Models.

Stable carbon isotopes from paleosol carbonate and herbivore enamel document differing paleovegetation signals in the eastern African Plio-Pleistocene

Analyses of stable carbon isotopes (δ13C) from herbivore dental enamel and paleosol carbonates are important tools for Plio-Pleistocene paleovegetation reconstructions. A single herbivore tooth documents an isotopic record of vegetation on the order of 10–1–1 years and in proportion to that individual's foraging range. Paleosol carbonates, conversely, record environmental information on longer time scales (102–3 years) but smaller spatial scales (101 m2). Given that these two proxies document paleoenvironments at different spatiotemporal scales, it is worth comparing them to see if they offer redundant or complementary paleovegetation information. Here, we compare δ13C patterns from herbivore enamel and paleosol carbonates from geological (sub)members in the Awash Valley, Ethiopia, and Turkana Basin, Kenya, from ~ 4.4–1 million years ago. We find that median herbivore enamel δ13C is typically ~ 5–7 per mil (‰) higher than that from paleosol carbonates within a given (sub)member. The distributions of paleosol carbonate δ13C values usually have less spread (variation) than herbivore enamel. The bias in median and spread between these two data types likely reflects the different spatial and temporal scales at which these proxies record paleoenvironmental information. Most Plio-Pleistocene fossiliferous deposits are formed in fluvial settings in which paleosol carbonates sample the immediate habitat of floodplain woodlands and shrubs, resulting in a lower δ13C (i.e., more C3) signal. On the other hand, fossil teeth of wide-ranging herbivores could generate a higher (i.e., more C4) and more variable δ13C signal if some taxa fed in floodplain woodlands while others fed on open grasslands distal to the floodplain. We conclude that δ13C values from herbivore enamel and paleosol carbonates offer paleovegetation data at different spatiotemporal scales, both of which are informative for hominin habitat reconstructions. Careful consideration of the spatial and temporal signals inherent in these and other proxies should be applied in future studies.

Reliability of phytoliths for reconstructing vegetation dynamics in northern temperate forest regions: A case study in northeast China

Phytolith records have provided a new perspective on the reconstruction and interpretation of palaeovegetation in forested regions. However, the reliability of phytolith records for vegetation reconstruction in northern temperate forest regions has not been fully determined, and it needs to be assessed before they can be used in palaeoecological contexts. To address this issue, we analyzed surface soil phytolith assemblages at 108 sites and established a modern soil phytolith reference database for five dominant vegetation communities in Northeast China. The phytolith reference dataset was then used to analyze a stratigraphic sequence of fossil phytolith assemblages from the same region to confirm the reliability of the phytolith-based paleovegetation reconstruction. The results demonstrate that both the phytolith assemblages of surface soils and the phytolith indices (Iw, Ic, Iph and W/G) vary substantially in different temperate forest habitats, and the indices are also well correlated with the vegetation inventory data. Thus, we conclude that modern soil phytoliths are reliable analogues for reconstructing paleovegetation. The modern phytolith reference-based paleovegetation reconstruction indicates that the study area has experienced substantial vegetation change since the late-glacial. The vegetation types ranged from open Larix mixed forest to open woodland, to closed broadleaf forest, and finally to closed Pinus koraiensis mixed forest. The phytolith-based vegetation types since the late-glacial are consistent with those reconstructed by a pollen record from the same stratigraphic profile, and thus our study confirms the reliability of phytolith analysis for interpreting both the entire vegetation landscape and vegetation changes in the northern temperate forest region. Moreover, fossil phytoliths also provide additional information - including the composition of grasses in the understory, changes in the proportions of C3/C4 plants, Larix abundance and tree cover density - which complements that provided by pollen analysis. Our study provides new perspectives on the reliability of phytoliths for reconstructing vegetation dynamics in the northern temperate forest region, and it provides a robust foundation for the application of phytolith analysis in the region.

The potential of leaf wax biomarkers from fluvial soil-sediment sequences for paleovegetation reconstructions - Upper Alazani River, central southern Greater Caucasus (Georgia)

Leaf wax-derived long-chain n-alkanes are increasingly used for paleovegetation reconstructions, but have hardly been applied to fluvial sediments so far. However, such analyses could significantly enhance knowledge of the former vegetation in many regions devoid of non-fluvial sediment archives. Therefore, this exemplary study investigates potentials and challenges of n-alkane biomarker analyses in a fluvial sediment-paleosol sequence (FSPS) along the upper Alazani River in the central southern Greater Caucasus. Generally, FSPS contain two different biomarker-signals: a catchment signal in fluvial sediments, and a local in-situ signal in intercalated paleosols. This allows paleovegetation reconstructions for both catchment area and sampling site. However, several archive-related challenges exist. Concerning the catchment signal from fluvial sediments, (i) this could be biased by different vegetation zones/land use histories in subcatchments, (ii) long-term pedogenesis on the slopes or intermediate sediment storage in the catchment could have caused a time lag between biomarker formation and sedimentation, (iii) taphonomic processes could have biased the preserved n-alkane pattern, (iv) there could be petrogenically inherited or in-river produced n-alkanes, (v) the signal could be overprinted by post-sedimentary processes. Concerning the local paleosol signal, this could be biased by inherited catchment-derived biomarkers or by taphonomic processes. These factors are thoroughly discussed for the investigated FSPS.With respect to paleovegetation patterns, our investigations gave the following results: (i) Leaf waxes in fluvial sediments deposited prior to/around the Pleistocene/Holocene transition and between ca. 5 and 1.7 cal. ka BP are indicative of more deciduous trees/shrubs in the catchment compared with the other periods that were dominated by grasses/herbs. Considering a possible time lag of ca. 1–4 ka between biomarker formation and deposition, this indicates delayed Holocene reforestation in the catchment compared with western and central Europe, in agreement with regional pollen studies. The subsequent decline of deciduous trees/shrubs could be linked to human activity in the catchment during the late Holocene. (ii) Leaf waxes in floodplain paleosols indicate local grass/herb dominance throughout the Holocene, which is possibly caused by long-lasting local human activity.

Carbon concentration and isotope composition of black carbon in the topsoil of the central and southeastern Qinghai-Tibetan Plateau, and their environmental significance

The carbon concentration and carbon isotope of black carbon (BC) have been widely used to reconstruct fire history and vegetation change. In order to establish the relationship between BC, contemporary vegetation and climate at the high altitudes of the Qinghai-Tibetan Plateau (QTP), we investigated the carbon concentration and carbon isotope composition of BC and soil organic carbon (SOC) (%BC, %SOC, δ13CBC and δ13CSOC) in 29 topsoil samples from the central and southeastern QTP. In general, the %SOC and %BC of topsoil show generally similar variations, indicating a common controlling factor for SOC and BC production, i.e., vegetation. The relatively small BC/SOC ratios fall in the range of BC/OC for pyrogenic particles from biomass burning, indicating a minor contribution of BC from fossil fuel combustion. The δ13CSOC of topsoil can effectively indicate local vegetation in the QTP. The δ13CBC and δ13CSOC are positively correlated, whereas the δ13CBC values are more negative than those of δ13CSOC. This could due to fire season and fractionation processes during post-deposition, but not carbon isotope fractionation during combustion or exogenous BC input. Therefore, BC in topsoil of the QTP mainly records ‘local’ environmental information, and the δ13CBC can be used in paleovegetation reconstruction in combination with the local climate.

Leaf wax &amp;lt;i&amp;gt;n&amp;lt;/i&amp;gt;-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation

Abstract. Long-chain n-alkanes originate from leaf waxes of higher terrestrial plants, they are relatively resistant against physical and chemical degradation and are preserved in sediment archives for at least millennial timescales. Since their homologue patterns discriminate between vegetation forms, they were increasingly used for paleovegetation reconstructions during the last years. However, before any robust interpretation of the long-chain n-alkane patterns in sediment archives, reference samples from modern vegetation and topsoil material should be investigated at a regional scale. Apart from some temperate and tropical regions, such systematic regional studies on modern plant and topsoil material are still largely lacking.To test the potential of leaf wax-derived n-alkane patterns for paleoenvironmental studies in the semi-humid to semi-arid central southern Caucasus region, we investigated the influence of different vegetation forms on the leaf wax n-alkane signal in modern plants and topsoil material (0–5 cm) from eastern Georgia. We sampled (i) sites with grassland/herbs that included steppe, cultivated grassland and meadows, and (ii) sites that are dominated by deciduous hornbeam forests.The results show that long-chain n-alkanes originate from leaf waxes of higher terrestrial plants and that their homologue pattern allow to discriminate between different vegetation forms: n-Alkanes derived from sites with grassland/herbs are mainly dominated by C31, while n-alkanes derived from sites with deciduous trees/shrubs show high abundances of C29. Thus, long-chain n-alkanes have a great potential when used for regional paleovegetation reconstructions. Moreover, the n-alkane distributions of the topsoils do not show correlations with mean annual temperatures and precipitation along the investigated transect. As degradation of organic matter can affect the leaf wax n-alkane distribution, we further present an updated end-member model that includes our results, accounts for degradation effects and enables semi-quantitative reconstructions of past vegetation changes in the central southern Caucasus region.

Reconstruction of paleovegetation and paleoecology from the Early Cretaceous sporomorphs of Bougaz-1 well, northeast Sinai, Egypt

A WELL-preserved, diverse sporomorph assemblage of 62 species belonging to 39 genera has been recorded in two Cretaceous (Aptian/Albian) samples recovered from depths 3105m and 3117m in the Bougaz-1 well, northeast Sinai. The identified 62 species consist of 20 genera and 27 species of pteridophytic fern spores, nine genera and 15 species of gymnosperm pollen, and 10 genera and 20 species of angiosperm pollen. A correlation of the encountered sporomorphs and their parent plant affinities (classes, orders and families) has been attempted in order to give an image of the past vegetation in this part of Egypt. Vegetation reconstruction demonstrates a mixed forest which is represented by a mixture of ferns, gymnosperms and angiosperms. A remarkable abundance of pteridophytic fern spores with other hygrophilous elements such as Afropollis pollen seems to indicate paleoclimatic trends towards warm humid conditions during the Aptian/Albian period in the studied area. This climatic preference is also confirmed by the low frequencies of conifer vegetation such as Araucariaceae, Cheirolepidiaceae and genetalean pollen (Ephedripites) which were predominant on the topographically higher and relatively xeric environments.

Carbon isotopic composition of branched tetraether membrane lipids in a loess-paleosol sequence and its geochemical significance

Carbon isotopes of organic matter have been widely used in quantitative reconstruction of paleovegetation and paleoclimate since they are sensitive to vegetation and environmental changes. However, the effect of transformation of soil organic matter after burial remains unclear. The carbon isotopes of brGDGTs, which were likely produced by heterotrophic bacteria in soil or peat, provide an opportunity to fill this gap. In this study, we investigated the stable carbon isotopic composition of brGDGT-derived alkane spanning the last 60 kyr in the Lantian loess-paleosol sequence from the southern Chinese Loess Plateau, as well as its relationship with δ13C values of total organic carbon (TOC) and other established climatic proxies. The results show that the δ13C values of brGDGTs were slightly depleted (ca. 1–2‰) relative to TOC, and a good linear relationship between them was observed. These support a heterotrophic lifestyle of brGDGT-producing bacteria and suggest that δ13C values of brGDGTs may have potential use in paleovegetation reconstruction. The similar variations between δ13C values of brGDGTs and TOC in the soil core also suggest that the effect of soil organic matter transformation after burial may have limited impact on the environmental significance of δ13C values of TOC. In comparison with δ13C values of the TOC, the widely used proxy for past vegetation changes, the δ13C values of brGDGTs seem more specific and sensitive in the Lantian profile due to its specific origin and stable chemical structure.

Assessment and calibration of representational bias in soil phytolith assemblages in Northeast China and its implications for paleovegetation reconstruction

AbstractThe assessment and calibration of representational bias in modern soil phytolith assemblages provide the basis for improving interpretation of fossil phytolith assemblages. We studied soil phytolith representation by comparing phytoliths from living plant communities with those from paired surface soils, representing 39 plant communities in Northeast China. Together with the use of representation indices, the 34 and 30 soil morphotypes observed in forest and grassland samples, respectively, were both classified into the following four groups: “Associated types” were similarly represented in soils and in the corresponding species inventory data; “Over-represented types” and “Under-represented types” were respectively over- and under-represented in soils compared to the inventory data; and, in the case of “Special types,” the relationship with the parent plants was unclear. In addition, the diagnostic types exhibited different degrees of representation, while the most common morphotypes were equally represented between grassland samples and forest samples. On this basis, a comparison between the original and corrected soil phytolith indices of the additional 29 soil samples was conducted. The soil phytoliths frequencies corrected by R-values differed between plots with differing plant compositions, and were moderately consistent with actual plant richness in the plot inventory data. We therefore confirmed that R-values are a promising means of correcting soil phytoliths for representational bias in temperate regions. The corrected soil phytoliths can be used to reliably reflect vegetation variability. Overall, our study provides an improved understanding of soil phytolith representation and offers a potential method for improving the accuracy of paleovegetation reconstruction.

Herbaceous phytoliths from forest and grassland in Northeast China: Potential significance for determining past forest–grassland boundaries

Phytoliths are a useful tool for reconstructing paleovegetation and paleoenvironments and grass short cell phytoliths (GSCPs), in particular, can provide important paleoenvironmental information. Although herbaceous phytoliths from non-grass species in forests also provide important paleovegetation information, they have not been investigated in as much detail as GSCPs, especially in Northeast China. In this study, we examined herbaceous phytolith morphotypes and assemblages from both forested and grassland areas in NE China, comprising three vegetation types. The phytoliths in 60 herbaceous quadrats were divided into seven morphotype groups. Cross-shaped phytoliths, bilobate type-C with long shank and papillate echinate morphotypes were only observed in grassland (GRA); complex saddle and bilobate type-A were only observed in non-understory vegetation in forested areas (NON); and phytoliths with scrobiculate decoration, elongate curved, silicified stoma (F), silicified stoma (D), globular granulate and oblong ruminate were only observed in forest understory (UND). Papillate (39.7%) was the dominant phytolith type in UND assemblages, and bilobate was dominant in NON (27.2%) and GRA (55.0%). According to the results of Discriminant Analysis (DA) and Detrended Correspondence Analysis (DCA), there was no similarity between UND and GRA, while NON had similarities with both UND and GRA. We conclude that herbaceous phytolith morphotypes and assemblages from forest and grassland in NE China are substantially different, which potentially enables their use for paleovegetation reconstruction in the region. Overall, our findings provide a new approach for determining past forest–grassland boundaries in NE China.

Palynological assemblage from the Deccan Volcanic Province, central India: Insights into early history of angiosperms and the terminal Cretaceous paleogeography of peninsular India

Sedimentary deposits of the Deccan Volcanic Province (DVP), of central India are rich in fossil flora and fauna. Based on a new palynological study of Infratrappean deposits from a borehole succession located in the Ashtona village, Yeotmal District, Maharashtra (Wardha Basin), this paper attempts a reconstruction of the Late Cretaceous paleovegetation, paleoecology, depositional environment and paleogeography of central India prior to Deccan volcanism, and also seeks to evaluate the early history and timing of the angiosperm diversification relative to the Cretaceous-Paleogene (K-Pg) transition. The stratigraphic age of the Infratrappean sequence was determined on the basis of several index palynomorphs (Aquilapollenites, Jigansupollis), Azolla cretacea, Gabonisporis sp, Scollardia conferta of Maastrichtian age. Two new pollen species (Dipterocarpuspollenites cretacea sp. nov., Retiacolpites pigafettaensis sp. nov., and one new dinoflagellate species (Pierceites deccanensis sp. nov.) are described in this study. The numerical abundance of the mangrove pollen Spinizonocolpites pollen (Nypa), combined with the dinoflagellate cyst Pierceites deccanensis, indicates a brackish marine depositional setting close to low-lying coastal forests in central India during the Late Cretaceous. Furthermore, the new evidence presented here from an inland location in the Deccan province strongly suggests the existence of a shallow marine embayment in central India during the late Maastrichtian, which extended from the east coast through the Godavari rift zone, thus adding significantly to the previously described marine signatures from the Upper Cretaceous sequence of Rajahmundry area on the south-eastern coast of peninsular India. The Late Cretaceous fossil pollen of Dipterocarpaceae documented here provides compelling evidence for the evolution of these tropical rain forest elements in the insular India and their dispersal to south east Asia after the initiation of India-Asia collision, consistent with the Out of India hypothesis. The new palynomorph assemblage also has significant implications for our understanding of the floral response to the initiation of Deccan volcanism.

Lignin in the Organic Matter of the Soils of the Russian Plain as Biomarker of Palaeoenvironment

It has been shown by the methods of biochemistry, nuclear magnetic resonance, and isotope geochemistry that the proportions of lignin phenols may be used as molecular traces of paleovegetation due to their biochemical and physiological specificity and high resistance to decomposition. Lignin structures have been detected in soils and in iron–manganese concretions. The comparison of the 13C NMR spectra of native lignin preparations isolated from different woody and herbaceous species with those of soil humic acids makes it possible to identify many characteristic shifts of lignin nature in humic acids at 56, 102, 115, 119, 131, 147, 151–152, 160, and 166 ppm. The information role of biomarker has been tested at the reconstruction of paleovegetation in the uplands of the Russian Plain. The representativeness of information has been increased using the isotope analysis (δ13C) and the radiocarbon dating; a new parameter—the composition of lignin phenols—has been introduced to the existing system of biomarkers.

Subrecent pollen spectra of the southern part of Zabaikalskii krai as a methodological basis for the reconstruction of paleovegetation.

Subrecent pollen spectra of the southern part of Zabaikalskii krai as a methodological basis for the reconstruction of paleovegetation.