Palaeovegetation Reconstruction Research Articles

Quaternary plant macrofossils from Robertson Cave, Naracoorte, South Australia: vegetative remains

Recently discovered fossils from Naracoorte Caves have enabled reconstruction of the local palaeovegetation of the Naracoorte region and improved understanding of floristic changes that occurred during the Quaternary. Here, we describe taxa represented by macrofossils of vegetative remains extracted from the Robertson Cave sediment deposit, approximately 820–24,230 years BP. Three non-angiosperm (Racopilum cuspidigerum var. convalutaceum, Pteridium esculentum and Callitris sp.) and five angiosperm taxa (Allocasuarina verticillata, Hibbertia sp., Acacia sp., Eucalyptus sp. and Banksia marginata) representing eight families were identified. Allocasuarina verticillata, Acacia sp. and Eucalyptus sp. are also known from previously identified reproductive structures. These plant species grew in the Naracoorte region during the Quaternary and add to the existing database for future plant identification and palaeovegetation reconstruction. Rachel A. Atkins* [rachel.atkins@adelaide.edu.au ], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Robert S. Hill [bob.hill@adelaide.edu.au ], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Kathryn E. Hill [kathryn@debillenvironmental.com.au ], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and DeBill Environmental, 13 Hawkesbury Ave, Kilburn, South Australia 5084, Australia; Samantha E.M. Munroe [Samantha.Munroe@csiro.au ], Commonwealth Scientific and Industrial Research Organisation (CSIRO), Environment, Townsville, Queensland 4811, Australia; Elizabeth H. Reed [liz.reed@adelaide.edu.au ], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia.

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.

Using pollen in turbidites for vegetation reconstructions

ABSTRACTTurbidites, deposited by sub‐aqueous gravity flows, are common in sedimentary archives worldwide and present a unique challenge and opportunity when reconstructing past vegetation through pollen analysis. When sampling pollen from a sediment core for palaeovegetation records, it is common practice to target background sediments (i.e. pelagic sediment) and avoid sampling turbidites, as they are presumed to portray a misleading picture of past vegetation. This assumption stems from our limited understanding of pollen abundance and distribution through turbidites, meaning that palynologists overlook deposits that could potentially be used to reconstruct past vegetation and climate. We present pollen assemblage and sedimentological data from four recent (<150 years) deep marine turbidite deposits from the Hikurangi Subduction Margin, Aotearoa‐New Zealand, with the aim of understanding the abundance and distribution of pollen in fine‐grained turbidites. We find that pollen is diluted in the bases of turbidites, but despite this dilution, the proportions of different pollen taxa remain consistent through each turbidite. These results confirm that pollen can be sampled from turbidites for palaeovegetation reconstructions and that sampling the fine‐grained upper parts of turbidites will provide the best pollen recovery.

Forest or grassland? Late Pliocene vegetation and climate of the Yushe Basin, Northern China

The Pliocene warm period is regarded as an analogue of future warming, and quantitative reconstruction of palaeovegetation and palaeoclimate during this period is helpful for predicting vegetation and climate changes in the future. Here, we quantitatively reconstructed the late Pliocene vegetation and climate based on phytolith assemblages from the Upper Zhangcun Formation in the Yushe Basin, Northern China. The results show that the vegetation was dominated by grasses with few trees, which conflicts with the pollen assemblage results. The possible reason for this contradiction is that phytoliths tend to mirror local, shoreline vegetation (grasses with few aquatic plants), while pollen tend to mirror both local and regional vegetation (trees in surrounding mountains and piedmont, grasses on lakeshores and aquatic plants in wetlands) in a small structurally confined lake. The phytolith-based quantitative reconstruction of mean annual precipitation (812–1673 mm) and warm season precipitation (417–1197 mm) provides values that are higher than those at present, revealing an increase in Asian monsoon rainfall during the late Pliocene, which is consistent with the pollen results, although the reconstructed vegetation is different. This study highlights the usefulness of phytoliths in reconstructing Cenozoic vegetation and climate and underlines the importance of landforms in determining phytolith and pollen assemblages in sediments.

Floral Diversity of South Karanpura Basin, Jharkhand, India and their Palaeoclimatic Implication with Special Reference to Palaeoenvironment

Abstract The palaeofloristic study of Gondwana sediments recovered from Religara area, South Karanpura Basin illustrates the macrofloral diversity in the area. Three distinct megafloral assemblages I, II, III are reported from freshly exposed coaly shale and carbonaceous shale layers of lower Barakar, upper Barakar and Raniganj formations of the basin. The assemblage comprises 72 species and thirteen genera of which 28 are newly reported species, which clearly exemplifies the macrofloral diversity over Permian Period in the studied area. The retrieved floral assemblages justified the existence of two interrelated ecosystems i.e., terrestrial and marshy. A gradual shifting of leaf morphology in reticulate leaves of order Glossopteridales illustrates biostratigraphic age as well as the shifting of climate during the deposition of sediments. The dominance of narrow mesh Glossopteris flora with the presence of typical Karharbari flora in the lowermost fossil horizon, illustrating the biostratigraphic age as late Artinskian (lower Barakar Formation). Likewise, the middle and upper floristic zones are dominated by Glossopteris of intermediate mesh form and broad mesh form suggesting biostratigraphic age as Kungurian (upper Barakar) and Wordian-Changhsingian (Raniganj) respectively. Deposition of in-situ Vertebraria depicts the autochthonous coal deposits and existence of some patches of palaeosol in the investigated location. The present investigation aims to infer the biostratigraphy, palaeoclimate, palaeoenvironment, palaeovegetational reconstruction of the basin during late Artinskian –Kungurian and Wordian- Changhsingian times.

Quaternary plant macrofossils from Robertson Cave, Naracoorte, South Australia: reproductive structures

The World Heritage Naracoorte Caves in southeastern South Australia are important palaeontological sites known primarily for their diverse vertebrate fossils. Some of the caves also contain well-preserved Quaternary plant macrofossils, but little palaeobotanical research has been undertaken to date. Here, we describe the angiosperm plant taxa represented by macrofossils of reproductive structures that have been extracted from the Robertson Cave sediment deposit; this has an age range of 820–24,230 years BP. We identified 29 angiosperm taxa representing 20 families. These represent some of the plant species that grew in the Naracoorte region during the Quaternary, and form a database for future plant identification and palaeovegetation reconstructions. Rachel A. Atkins [rachel.atkins@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Robert S. Hill [bob.hill@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia; Kathryn E. Hill [kathryn@debillenvironmental.com.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia and DeBill Environmental, 13 Hawkesbury Ave, Kilburn, South Australia 5084, Australia; Samantha E.M. Munroe [Samantha.Munroe@csiro.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005; Elizabeth H. Reed [liz.reed@adelaide.edu.au], School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia, Environment Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia, and Earth and Biological Sciences (Palaeontology), South Australian Museum, Adelaide, South Australia 5000, Australia.

Largest fossil logs of Paraphyllanthoxylon-type from the Eastern Hemisphere (Upper Cretaceous, Czech Republic)

The fossil genus Paraphyllanthoxylon is known from many localities around the world. In some cases, the fossilized logs can reach quite large proportions. We present the findings of large fossil logs (the two biggest logs have diameter 98 cm, length minimally 11 m, estimated height 34 m, and diameter 93 cm, length 7 m, estimated height 32.5 m) with Paraphyllanthoxylon type of wood from the Klikov Formation (Turonian–Santonian) in South Bohemia (Czech Republic). These are the largest documented logs from the Eastern Hemisphere from Upper Cretaceous. Our study clarifies for the first time the geological context of fossil wood finds from the South Bohemian Basins. The fossiliferous strata represent a bedload sedimentation in a series of low-sinuosity, braided stream channels. The palaeovegetation reconstruction indicates that trees of Paraphyllanthoxylon-type apparently dominated at the locality, but platanoids and plants of Normapolles complex were also present. No distinct growth ring boundaries were seen, but there were variations in vessel frequency. These changes in wood anatomy were unique and probably associated with rare events in the ecosystem, perhaps a major flood.

Stable isotope analysis of carnivores from the Turkana Basin, Kenya: Evidence for temporally-mixed fossil assemblages

Stable isotope palaeoecology of fossil mammals is a key research tool for understanding the environmental context of hominin evolution in the Plio-Pleistocene of Africa. Well studied mammal groups include bovids, suids, equids, proboscideans and primates, but to date there has been no in-depth study of modern and fossil carnivores. Here we produce an Africa-wide oxygen and carbon enamel isotope dataset for modern carnivores and compare it with fossil carnivore data sampled from the Plio-Pleistocene Omo Group of the Turkana Basin, Kenya. Comparison of modern carnivore carbon isotopes with satellite images of land cover indicates that carnivore δ13C is related to the proportion of woody cover in the local environment. Modern carnivore oxygen isotopes are strongly influenced by the δ18O of meteoric water, through drinking from standing water and through prey body fluids. Carbon isotope data from fossil carnivores shows close agreement with palaeovegetation reconstructions from δ13C of palaeosol carbonates from the same geological Members, and a similar long-term trend in δ13C values through time (4 Ma to 1 Ma), reflecting a gradual increase in the proportion of C4 grasses in the Turkana Basin. This increase in the δ13C of large carnivores is consistent with the evidence from other mammalian groups for an increase in the proportion of grazers compared to browsers and mixed feeders during this time interval. Two distinct trends within oxygen versus carbon isotope space indicates that the fossil carnivores lived during two distinct climatic regimes – one in which palaeo-lake Turkana was freshwater, and one in which the lake resembled its modern-day hyperalkaline state. These two climatic states most likely represent the end-members of precessionally-driven rainfall extremes over the Ethiopian Highlands. This indicates that each studied faunal assemblage from the Omo Group is a time- and climate-averaged palimpsest; this has significant implications for the interpretation of environmental signals and community palaeoecology derived from Turkana Basin fossil mammals, including early hominins.

Forest Steppe-Like Vegetation Near Cherskiy (West Beringia) During the Early Pleistocene Olyorian Period Reconstructed Using Plant Macrofossils

The lower Kolyma region is known for rich Early Olyorian large mammal assemblages including plesiomorphic musk ox, reindeer, horse, broad-fronted moose, steppe mammoth and cave bear. Data on the vegetation in zonal habitats from the Olyorian period are, in contrast, scarce. Earlier palynological results from classical Olyorian sites indicated predominant grassland vegetation with scattered larch occurrences but are, due to limited taxonomical resolution, uncertain. Plant macrofossil data were, so far, only available from azonal, aquatic habitats. Here, we describe Olyorian palaeo-vegetation from an exposure near Cherskiy, Nizhnekolymsky District, Sakha Republic, Russia. The macrofossil-based reconstruction of palaeo-vegetation revealed the existence of an open forest steppe comprising a mosaic of sparse larch groves in a dry grassland composed of tundra steppes, degraded meadow steppes and saline meadows. In the larch groves, light demanding shrubs and dwarf shrubs such as shrub birch (Betula cf. fruticosa, B. nana ssp. exilis), raspberry (Rubus idaeus), cowberry (Vaccinium vitis-idaea), and crowberry (Empetrum nigrum) formed the understory. Ruderal pioneer plants point to open ground as result of disturbances, possibly due to the activity of large herbivores. The nitrophytic ruderal species Urtica dioica, in particular, suggests locally increased nutrient supply from animal excretions. Also, the abundant remains of Chenopodium cf. prostratum might be explained by disturbances and nutrient enrichment, but Chenopodium is also characteristic of salt accumulation in the soil owing to high evaporation under arid conditions, which are also indicated by alkali grass (Puccinellia sp.). The presence of trees and shrubs indicates interglacial-like temperature conditions but the dominance of dry grassland species and the occurrence of facultatively halophytic plants (Chenopodium prostratum, Puccinellia sp.) suggests aridity, which is more typical of cold stages. During the early Pleistocene, i.e., prior to the Early-Middle Pleistocene transition (EMPT) culminating around 900 ka ago, the duration of climate cycles was shorter and the amplitude of climate fluctuations was smaller. Ice-rich permafrost formed only after the EMPT during increasingly extreme cold stages, and, during warm stages, its thawing resulted in paludification of the active layer. Prior to the EMPT, the climate in West Beringia was constantly relatively dry, more or less moderate and more stable than thereafter. In contrast to modern tundra and northern taiga in the study region, dry habitats apparently prevailed during the time of deposition of the plant macro-remains.

Vegetation history of SE Sicily from feudal land management to post-war agricultural industrialization

A new marine pollen record from SE Sicily is presented. The pollen study was done at a sub-decadal resolution to assess the role and extent of human impact in driving regional environmental and land cover changes over the last four hundred years. The combination of palaeoecological evidence and historical documents provides a detailed report of the main ecological dynamics in relation to socio-economic events, past land use, and land management regulations in Sicily. Our palaeovegetational reconstruction reveals a remarkably stable landscape, preserved by traditional land use practices that have persisted through the long-lasting feudal history of Sicily. After centuries of human-induced environmental stability, an abrupt change in vegetation structure occurred around 1950 AD, reflecting the modern land use policies and agricultural reforms following the Second World War. This vegetational breakpoint in SE Sicily corresponds to a suggested date for the onset of the Anthropocene.

Spatial distribution and environmental significance of phytoliths in the surface soil of the Xilingol Grassland in Inner Mongolia, China

Reconstruction of grassland ecosystems and their vegetation succession is an important issue in palaeoenvironmental research. Phytoliths and pollen are two common proxies for palaeovegetation reconstruction, and their importance can be evaluated based on investigations of the relationships between modern vegetation and phytolith/pollen assemblages in surface-soil samples. The correlations between phytolith assemblages and environmental variables were analysed based on 34 surface-soil samples from the Xilingol Grassland, Inner Mongolia, North China, and a palynological analysis was carried out on the same samples, enabling a comparison between their sensitivity to vegetation and climate change. The results show that the phytolith assemblages mainly consist of blocky and rondel phytoliths, while other short-cell phytolith types, such as saddle and bilobate types, are scarce. The pollen assemblages were characterised by a high abundance of Artemisia and Amaranthaceae. Canonical correspondence analysis (CCA) indicated that the most important environmental factors affecting the distribution of phytoliths are altitude and latitude, while the mean warmest monthly temperature (MWMT) and altitude were the most significant environmental factors affecting the distribution of the pollen assemblages. CCA of the phytoliths and pollen assemblages separated both samples into two groups: broadleaf forest/scrub and steppe/meadow groups, but it appeared that phytoliths were more sensitive in arid grasslands. This case study could be used as a baseline for interpreting fossil phytolith/pollen assemblages from the grasslands of Inner Mongolia and indicates that multiproxy analysis of the same samples can provide reliable information on palaeovegetation and palaeoclimate reconstruction.

Modern pollen and vegetation relationships in a mangrove tidal creek, South Andaman, Andaman & Nicobar Islands, India and their palaeoecological implications

This paper presents the first modern pollen, non-pollen palynomorphs and grain size data from a pristine mangrove tidal creek on the South Andaman Island, Andaman and Nicobar Islands, India. The surface sediment samples were collected from different mangrove environments of the Wright Myo Creek, South Andaman to study the relationship between the pollen-spore data and present vegetation cover. Results show that pollen from local vegetation more abundant, whereas regional vegetation surrounding the depositional site is poorly represented. Heritiera littoralis, Ceriops tagal, Excoecaria agallocha and Bruguiera gymnorrhiza are markedly abundant in the landward zone. The transitional and seaward pollen assemblages are characterized by Rhizophora mucronata, Avicennia marina and Bruguiera gymnorrhiza pollen types. Pollen from mangroves are locally restricted and reflect the distributions of the source plants and mangrove types. However, the greatest concentrations of allochthonous taxa of evergreen, deciduous and montane components are derived from the surrounding lands. This area receives high rainfall during monsoon favouring long distribution of palynomorphs i.e. allochthonous species from hinterland to the depositional site through connecting drainage system. Abundance of non-pollen palynomorphs suggest not only humid as well as wet conditions, but also the particular salinity and pH characteristics of mangrove types in the area. Such relationships were evident in the Redundancy Analysis (RDA), which revealed that the first two axes of the RDA with self-values of 0.63 and 0.06 respectively explained 68.4% of data variation and 95.2% of the correlation between pollen and the environment. Additionally, the RDA analysis between Non-Pollen Palynomorph (NPP) data and the environmental variables showed that the first and second axes with self-values of 0.60 and 0.04 respectively, explained 68.4% and 96.1% of NPP data variance, respectively. The granulometric analysis clearly indicates that sand fraction is maximum towards sea, whereas suspended sediments (silt and clay) are significantly higher towards transitional and landward zones. This is well corroborated with pollen preservation in this area. At the mouth of the creek, strong hydrodynamic flow and low pollen percentages is observed, while abundant pollen are noticed in the suspended sediments probably due to weak hydrodynamic forces towards land. Therefore, the effects on pollen assemblages from sediment dynamic conditions must be taken into consideration during the reconstruction of palaeovegetation and palaeoclimate. The presented dataset provides new information on modern pollen assemblages and their relationship to the vegetation types and environmental conditions, which can also be effectively applied to other mangrove ecosystems of South and South East Asian regions to reconstruct palaeovegetation and palaeoclimatic changes.

Terpenoids in surface soils from different ecosystems on the Tibetan Plateau

Realizing the potential of terpenoid biomarkers as an unequivocal land ecosystem and floral diversity indicator calls for work to establish a direct link between the terpenoids extracted from the plants and those found in the underlying soils. To this end, we have characterized the triterpenoid profile of soils and vegetation along two altitudinal transects representing very different ecosystems. The first transect, comprising 31 sample sites, was on the eastern slopes of Mt Gongga (eastern Tibetan Plateau) rising from 1230 m to 4500 m above sea level, an area with a temperate monsoonal climate. The second transect, sampling 29 sites, was on the northern slopes of Mt West Kunlun, a region characterized by montane desert, meadow and alpine steppe (located between 1300 m and 5050 m above sea level). The dominant terpenoid biomarkers (polycyclic triterpenoids of the taraxerane, oleanane, friedelane, ursane, lupane, glutinane and lanostane series) identified in the soils were found to be consistent with the overlying vegetation. However, the discovery of some unusual triterpenoids, including the pentacyclic triterpene 3-methyl ethers (PTMEs), D:A-friedo-2,3-secoolean-2,3-dioic acid, methyl 3β-acetoxylup-20(29)-en-28-oate, 24-methylenecycloartan-3-one, 9,19-cyclolanostan-3-yl 24-methylene acetate, 3α-methoxy-9β-lanosta-7,24-dien-26,23-olide and 3α-methoxy-9β-lanost-7-en-26,23-olide in the Gongga soils, does not match the current vegetation and may be indicative of a long vanished forest-type vegetation. Thus, soil biomarkers may be a useful tool in the reconstruction of palaeo-vegetation.

An evaluation of soil phytoliths for reconstructing plant communities and palaeoclimate in the northern temperate region

AbstractPhytoliths can act as efficient carriers of information about palaeovegetation and palaeoclimatic conditions, but the representativeness of soil phytoliths from palaeoecological sediments has not been fully understood. In this study, phytolith assemblages in topsoils and associated plant communities at 55 sites in Northeast China were compared. The results indicate that samples from herbaceous and woody communities could be reliably differentiated by topsoil phytoliths. Notably, different phytolith types exhibit varying degrees of representational bias in terms of the aboveground plant community. Some morphotypes (e.g., bilobate, rondel and lanceolate) over‐represent the richness of the corresponding plant; some morphotypes, including microhair, conical epidermal, silicified stomata and epidermal phytoliths, under‐represent the parent plant abundance; additional morphotypes (e.g., elongate, saddle and trapeziform sinuate) are consistent with the changes of associated plants. Based on the representational bias, we calibrated the percentages of topsoil phytoliths and established a phytolith‐based transfer function for precipitation in Northeast China. A palaeoclimate reconstruction in the Changbai Mountains (in the eastern part of Northeast China) based on the above phytolith‐based transfer function for precipitation shows that the region has gone through continuous climatic changes since the late glacial period: from cold and dry conditions to warm and dry conditions, then to warm and wet conditions, and finally to cool and dry conditions. The phytolith‐based reconstructed climate changes since the late glacial period correspond well to those reconstructed by other records from the same stratigraphic profile, and our phytolith‐based climatic reconstruction also confirms the reliability of abrupt cold climatic shifts at 8.2, 6.8, 5.6, 4.6 and 4.2 ka. In conclusion, our results provide the basis for the reliability of phytoliths for reconstructing climatic changes in the northern temperate region.Highlights Calibrating soil phytolith assemblages for any quantitative palaeovegetation reconstruction using phytoliths is necessary. Phytolith morphotypes in topsoils may over‐ or under‐represent or agree with the abundance of modern plant taxa. Phytolith‐based climatic reconstruction corresponds well with the abrupt climate changes evident since the Late Glacial period and other proxy records.

Evaluation of the potential of surface pollen spectra from caves in SW China for vegetation reconstruction

Pollen analysis is rarely applied to cave sediments because of the complex range of processes influencing the origin, transport and taphonomy of pollen grains in caves. In order to evaluate the potential of pollen spectra from within caves for vegetation reconstruction, we compared the modern pollen from the interior and exterior of four caves in Guangxi and Guizhou, in southwestern China. The results show that the pollen spectra from within the sack-shaped caves, and from the front and middle of a long, narrow caves, were similar to those outside the caves, and therefore that the pollen spectra from these caves can reliably be used for palaeovegetation reconstruction. Wind is the major transport medium for the pollen entering caves, but animals may be additional transport medium. In addition, cave geometry is likely to be responsible for the observed spatial distribution of pollen concentrations in caves. In long, narrow caves, the entrance is the optimum sampling location for pollen analysis; however, in sack-shaped caves an optimum sampling location cannot be specified due to the gradient in pollen concentration between the entrance and the rear, together with its irregular distribution.

Relative pollen productivity estimates for alpine meadow vegetation, northeastern Tibetan Plateau

A promising method of reconstructing past vegetation from pollen records uses mathematical models of the relationship between pollen and vegetation. These can be calibrated using the extended R-value (ERV) approach on datasets of modern pollen assemblages and related vegetation surveys. This study presents the results of calibrating the pollen-vegetation models for non-arboreal pollen types in alpine meadow habitats on the Tibetan Plateau. Surface soil samples were analysed for pollen and the surrounding vegetation was recorded at 30 randomly located sites in the Zoige basin, northeastern Tibetan Plateau. ERV analysis found that the most reliable results were obtained when using ERV sub-models 1 and 2, and distance-weighting the vegetation data by applying the taxon-specific Prentice–Sutton method. The relevant source area of pollen for these soil samples was found to be ca. 200 m. Relative pollen productivities (RPP) of 15 non-arboreal taxa were estimated relative to Cyperaceae (RPPCyp). The taxa can be divided into three groups according to their RPPs, those with high RPPCyp values > 1.68 (Thalictrum, Artemisia, Caryophyllaceae, Chenopodiaceae and Plantago), those with moderate values (0.42–0.62) (Taraxacum-type, Apiaceae, Polygonum and Aster-type), and those with low values < 0.4 (Gentianaceae, Potentilla, Brassicaceae, Saussurea-type and Poaceae). The RPP values obtained from our study differ from those of previous studies in other parts of China, and form the basis for future reconstruction of palaeovegetation on the Tibetan Plateau through model-based methods, such as the Landscape Reconstruction Algorithm, or Multiple Scenario Approach.

Effect of pedogenesis on the stable isotopic composition of calcretes and n‐alkanes: Implications for palaeoenvironmental reconstruction

AbstractIn a fluvial system, depending on sub‐aerial exposure, non‐pedogenic pond calcretes can be modified into pedogenic calcretes. The present study attempts to understand the effect of sub‐aerial exposure and pedogenesis on calcretes using carbon and oxygen isotopic composition. For this purpose, two profiles (profile‐A and profile‐B) from the same stratigraphic level in Rayka from the western part of India were selected. The profiles are separated by a distance of 500 m and showed differences in calcrete characteristics. In profile‐A, the calcretes showed pedogenic features (root traces and void filling spar) whereas calcretes in profile‐B showed non‐pedogenic characteristics (fine laminations). However, some of the calcretes in profile‐A exhibited remnants of fine laminations suggesting that initially the calcretes had a non‐pedogenic origin but were modified due to pedogenesis. In profile‐A, the carbon and oxygen isotope values of pedogenic calcrete (δ13CPC and δ18OPC) showed more variation compared with non‐pedogenic pond calcretes (δ13CSPC and δ18OSPC) in profile‐B. The δ13CPC and δ13CSPC values exhibited a spread of 3·0‰ and 1·3‰, respectively, and δ18OPC and δ18OSPC values showed a spread of 2·3‰ and 1·3‰, respectively. The differences in the isotopic composition between the two profiles suggest that pedogenesis controlled the isotopic inheritance in calcretes. In addition, the carbon isotopic composition of organic matter (δ13COM) and n‐alkanes (δ13Cn‐alk) that forms the basis of palaeovegetational reconstruction have also been measured to understand the effect of pedogenesis on organic matter in both of the profiles. The average δ13COM values in profile‐A and profile‐B are −23·4‰ and −21·1‰, respectively. The disparity in δ13COM values is a result of the difference in the sources and preservation of organic matter. However, the δ13Cn‐alk values show a similar trend in profile‐A and profile‐B, indicating that sources of n‐alkanes are the same in both of the profiles and δ13Cn‐alk values are unaffected by the pedogenic modifications.

Large-scale vegetation history in China and its response to climate change since the Last Glacial Maximum

Large-scale palaeovegetation reconstruction plays a critical role in improving our understanding of the response of vegetation to climate change and in reducing the uncertainty in predictions of vegetation change under global warming scenarios. Here, we present quantitative vegetation reconstructions for China since the Last Glacial Maximum (LGM), using 286 selected fossil pollen records analyzed using the biomization method. The results show that from 23 to 19 ka (1 ka = 1000 cal yr BP), steppe and desert expanded southeastwards, dominating northern China, whereas forest in eastern China shrank southwards to near the middle and lower reaches of the Yangtze River; the percentage of forested sites at this time was the lowest during the studied interval. Forest then developed gradually during 18–12 ka. During the early and middle Holocene, tropical seasonal forest, broad-leaved evergreen/warm mixed forest, and temperate deciduous forest shifted northwards by 2°, 4° and 5° in latitude, respectively, relative to today, and then declined in the late Holocene. In detail, forest flourished in the middle Holocene (9–4 ka) in semi-arid and semi-humid northern China, whereas it reached a maximum in the early and middle Holocene (11.5–6 ka) in humid southern China. Our results suggest that although forest throughout China exhibited the expected response to the evolution of the East Asian summer monsoon, precipitation exerted a more significant effect on vegetation change in northern China, whereas temperature and precipitation played a more important role in southern China. Our results are a potentially useful reference for assessing future vegetation dynamics under global warming scenarios.

Quantifying regional vegetation changes in China during three contrasting temperature intervals since the last glacial maximum

The need to reduce the uncertainty of predictions of vegetation change under global warming highlights the importance of understanding the vegetation patterns and possible mechanisms of vegetation response during past warming intervals. Here, we present quantitative regional vegetation reconstructions for China during the Last Glacial Maximum (LGM, 18 ± 2 14C kyr B.P.), early Holocene (EH, 8.5 ± 0.5 14C kyr B.P.), and mid-Holocene (MH, 6 ± 0.5 14C kyr B.P.), using the biomization method and based on 249 pollen records. In addition, we used an inverse vegetation modeling approach to investigate the effect of climate change and CO2 concentration on the observed vegetation changes. The results demonstrate that during the LGM, steppe expanded southeastwards, reaching the present-day temperate deciduous forest (TEDE) zone; in contrast, the forest in eastern China underwent a substantial southward retreat and its percentage reached a minimum. The warm mixed forest (WAMF) and TEDE shifted southwards of ∼10° N relative to today, and tropical seasonal rain forest (TSFO) was almost absent. In addition, the forest-steppe boundary shifted southwards to near the middle and lower reaches of the Yangtze River. During the EH and MH, the TSFO, WAMF, and TEDE exhibited respective northward shifts of 2°, 4° and 5° relative to today. In MH, the percentage of forest sites increased and reached a maximum, and the forest-steppe boundary had shifted northwestwards to near the present-day 300 mm isohyet. Our palaeovegetation reconstructions and model sensitivity experiments suggest that temperature was the dominant factor controlling the vegetation distribution during the LGM, while precipitation became increasingly more important during the Holocene throughout China. We further show that precipitation was the primary factor controlling palaeovegetation distribution in northern China, while temperature became increasingly more important in southern China. Our findings are potentially important for understanding the evolution of vegetation in China in response to ongoing global warming.

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.