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Kisima Ngeda (KN), a spring on the northern margin of saline Lake Eyasi, Tanzania, sustains an Acacia-Hyphaene palm woodland and Typha swamps, while the surrounding vegetation is semi-desert. To study the vegetation changes associated with this spring, which represents a plausible modern analog for the fossil springs documented in the nearby paleoanthropological and archaeological sites of Olduvai Gorge, we analyzed the pollen content of a 43 cm-long sediment core that documents vegetation changes since the last ~1200 years (from cal yrs. C.E. 841 to 2011). Our results show that (1) Hyphaene palms, which require meso-halophytic soil conditions were most abundant in the area of the coring site until cal yrs. C.E. ~1150 when the groundwater supplying the KN spring was likely lower than at present, allowing intrusions of saline lake waters. (2) From cal yrs. C.E. ~1200, a peat began to develop, the palm woodland was replaced by a Mimosaceae woodland, and the increased presence of Typha pollen indicates the presence of more wetlands. (3) From cal yrs. C.E. 1600, the groundwater level of the KN spring increased and reached its highest level in the last 1200 years. (4) Peaks of wetland expansion, which reflect increased groundwater flow and level in response to amplified rainfall in the recharge area (Mt Oldeani, Ngorongoro Highlands), occurred at cal yrs. C.E. ~1200–1400 and ~1650–2011. These outflows of groundwater at Kisima Ngeda were linked to the intensity and frequency of positive Indian Ocean Dipole (IOD) events, which trigger heavy rains in eastern Africa. We conclude that the Kisima Ngeda hydrological system, which has been active for more than 1200 years, responds rapidly to regional climate change driven by changes in the sea surface temperatures (SSTs) of the Indian Ocean. Yet, it is also capable of remaining active during dry intervals as inferred from the Kisima Ngeda record prior to cal yrs. C.E. 1200. Our results support the hypothesis that this type of system helped to maintain Plio-Pleistocene hominin populations and activities in the arid lowlands of the rift on a multi-decennial scale. • Freshwater springs sustain Acacia -palm woodlands near saline Lake Eyasi (N edge). • KN1A pollen record shows Kisima spring woodlands existed since >1200 yrs. • KN1A pollen record infers today is wetter than LIA which was also wetter than MCA. • Fresh groundwater remained easily accessible even during dry periods like MCA. • KN spring likely responds to IOD events and regional precipitation changes. [ABSTRACT FROM AUTHOR]

Abstract: Diverse palynomorphs and phytoliths recovered from coprolites of ovi-caprids (sheep, goat) collected from Yang-Hai Tomb at Xinjiang Province, China, have been used to elucidate the dietary pattern of ancient livestock and to reconstruct the paleovegetation and paleoclimate of this part of northwest China ca. 2500 14C yr BP. Palynological and phytolith data suggest that a rich dry temperate vegetation prevailed in the area during the said period. Climatic conditions and grassland vegetation type of the area are explored using phytolith indices. [Copyright &y& Elsevier]

Based on high-resolution pollen records from lake cores in central Canada, the present study instructed pollen taxa assignations in ecosystem groups and modern analogue technique, reported major results of quantitative reconstructions of vegetation history during the last 1000 years, and discussed the validation of simulated vegetation. The results showed that in central America (115°–95°W, 40°–60°N), best analogue of the modern vegetation is 81% for boreal forest, 72% for parkland, and 94% for grassland-parkland, which are consistent with vegetation distributions of the North American Ecosystem II. Simulations of the past vegetation from the sedimentary pollen showed climate changes during the past 1000 years: it was warm and dry in the Medieval Warm period, cold and wet in the earlier period and cold and dry in the later period of the Little Ice Age. It became obviously increasing warm and drought in the 20th century. The present studies would provide us scientific basis to understand vegetation and climate changes during the last 1000 years in a characteristic region and in 10–100 year time scales. [ABSTRACT FROM AUTHOR]

Abstract: Identification of >40 taxa of plant macrofossils in 14 rodent (Abrocoma) middens collected from 2800 to 3590m elevation at the latitude of Arica, Chile (18°S) provide snapshots of vegetation in the northernmost Atacama Desert over the past 3000 years. Midden floras show considerable stability throughout the late Holocene, which may be due in part to the broad elevational ranges of many perennial species and midden insensitivity to changes in plant community structure. The greatest variability is found in annuals in the Prepuna, a climatically sensitive zone. This variability, however might also arise from the brevity of midden depositional episodes. As the first midden record from the Arica–Parinacota Region (Chile''s northernmost administrative region), this study demonstrates the potential for future midden research in this area. [Copyright &y& Elsevier]

Abstract: The main objective of this paper is to provide researchers that investigate fossil phytolith assemblages and model/data comparisons a new tool for estimating C3/C4 grass composition over time. We tested the reliability of modern soil phytolith assemblages and phytolith indices for tracing the dominance of different grass subfamilies and tree cover density. We analyzed modern soil phytolith assemblages from sites over elevation gradients on Mount Kenya (Kenya), Mount Rungwe and around Lake Masoko (southern Tanzania). These data were compared with available botanical data. A phytolith index named Ic, proved to be an effective proxy of the proportions of Pooideae, Arundinoideae and Bambusoideae grasses (mainly C3 grasses) versus Panicoideae grasses (mainly C4 grasses), increasing with elevation in East-Africa. When tropical mountains are covered by open habitats (e.g. grasses and shrublands), Ic should be a reliable proxy of the C3/C4 grass composition. These results highlight the value of the phytolith index Ic, when interpreting paleo-environmental records from tropical mountains, to: 1) better understand past local and regional C3/C4 grass distributions and associated climatic changes and 2) increase the set of C3/C4 data available for model/data comparisons. [Copyright &y& Elsevier]

Using gas chromatography-mass spectrometry (GC-MS) technique, a series of biomarkers were identified, including n-alkanes, n-alkane-2-ones, isoprenoid etc. from the loess-paleosol samples collected from the S4 and adjacent L5, L4 of the Luochuan loess section, Northwestern China. Based on these data, especially n-alkanes and high-resolution magnetic susceptibility and grain size data, the paleoenvironment and paleovegetation history during S4 was reconstructed. The CPI (Carbon Predominance Index) and correlation between n-alkanes and magnetic susceptibility and grain size data demonstrated that the molecular fossils in paleosol and loess layers can reflect the vegetation condition during the loess-paleosol formation, if the allochthonous organic inputs could be excluded reasonably. The ACL (average chain length) index is correlated well with paleomagnetic susceptibility and grain size variations, displaying their good synchrony with warm and humid climate. However, it relatively lagged behind the paleomagnetic susceptibility and the grain size variations when the climate began to deteriorate. During the formation period of paleosol, the n-alkanes was dominated by C31 homologue, indicating that the primary organic input originated from herbs. Our study also demonstrated that the herbs were more flourish than wood plants in Loess Plateau, especially in the Luochuan area during the warm and humid phase, and there was no typical forest vegetation developed in the studied period. [ABSTRACT FROM AUTHOR]

Sporopollen analysis on a 346 cm peat record at Dahu, Jiangxi, chronologically constrained by 16 AMS 14C datings, provides an opportunity to reconstruct the vegetation evolution stages responding to climate change in South China since the last glacial maximum. The result shows that during 18330–15630 cal a B.P., broad-leaved forest dominated the area, corresponding to mild, cool and fairly humid climate. At the interval of 15630–11600 cal a B.P., several evergreen broad-leaved species appeared within the broad-leaved forest, indicating moderate and humid condition. During early Holocene, broad-leaved evergreen forest community was constructed as Castanopsis/ Lithorcarpus principally developed, suggesting a warm and humid scenario until 6000 cal a B. P. Since 6000 cal a B. P., abrupt forest deterioration happened with an contemporary increase of fern and herb communities, representing a turnover to relatively cool and dry condition and as well, possible impact from human activities. Meanwhile, several relatively cool and dry events can be identified in the sporopollen record, they can be correlated to the North Atlantic Heinrich event, YD and Holocene millennial-scale oscillations, implying that the low latitude climate was coupled with high latitude influences. Moreover, the variations of temperature and humidity since LGM at Dahu were much smaller when compared with the records in north monsoonal China. [ABSTRACT FROM AUTHOR]

Previous studies have found that wetlands prevailed in western Chinese Loess Plateau and pine pollen could reach up to 80% in Qin'an area of the plateau during middle Holocene. It was then deduced that forest vegetation covered Qin'an area in a warm and wet climate during middle Holocene. The proxies of molecule biomarkers from two Holocene sections, a swamp-alluvial loess section and a typical loess-paleosol section are used to reconstruct regional vegetation history. It is found that the heavy-molecular-weight (HMW) homobogues of the n-alkanes in all samples exhibit a pronounced odd-over-even predominance, maximizing at C31 and the abundance of the nC27-alkanes is the lowest in nC27, nC29, nC31, i.e. C27

Abstract: Samples from two lignite seams (Lower Seam, Upper Seam) of the Lavanttal basin (Austria) and additional xylite were investigated for variations in maceral composition, petrography-based facies indicators, bulk geochemical parameters, and molecular composition of hydrocarbons. Both seams originated in a topogenous mire and evolved within a transgressive setting. The final drowning of the mire is indicated by sapropelic shales. Whereas the sapropelic shale overlying the Lower Seam was deposited in a freshwater lake, the sapropelic shale above the Upper Seam represents a brackish lake. Numerous relationships are found between petrography-based facies indicators and the geochemical composition of organic matter. The contents of macerals of the liptinite group are positively correlated with soluble organic matter (SOM) yields and hydrogen index (HI). Consistent with maceral composition and high HI values, enhanced proportions of short-chain n-alkanes, which are predominantly found in algae and microorganisms, are obtained from samples of the sapropelic shales. The final drowning of the mire is reflected by decreasing pristane/phytane ratios, due to the rise in (ground)water table and the establishment of anaerobic conditions, as well as by decreasing ratios of diasterenes/sterenes, indicating increasing pH values in the mire. The degree of gelification of plant tissue (gelification index) is governed by the microbial activity in the mire, as indicated by the hopanes concentration. The differences in floral assemblage during the formation of the Lavanttal lignite seams are reflected by major differences in tissue preservation. Preservation of plant tissue (TPI) in the Lavanttal lignite is obviously controlled by the presence/absence of decay-resistant gymnosperms in the peat-forming vegetation, and additionally influenced by the relative contribution of wood to coal formation. The results provide evidence that valuable information for coal facies characterization could be obtained by petrography-based and geochemical facies indicators. An influence of the floral assemblage (gymnosperms/angiosperms ratio) and of the contribution of algal biomass on carbon isotopic composition of the organic matter (δ 13C=−24.2 to −28.6‰) is proposed. Carbon cycling during biogeochemical decomposition of plant tissue by bacteria is suggested to affect the δ 13C values of the coal. The chemotaxonomical classification of the xylites as gymnosperm remnants, based on the molecular composition of terpenoid biomarkers, is corroborated by the carbon isotopic composition of the xylites (mean δ 13C=−24.1‰) and the extracted cellulose (mean δ 13C=−20.2‰). The higher isotopic difference of about 3.9‰ between cellulose and total organic carbon of the xylites, compared to the difference between cellulose and wood found in modern trees, is explained by the smaller effect of decomposition on δ 13C of cellulose. [Copyright &y& Elsevier]

Abstract: In northern China, the Late Miocene–Pliocene red clay in the eastern Loess Plateau fills a gap of climate records between the well-known loess-soil sequences of the last 2.6 Ma and the Miocene loess-soil sequences from the western Loess Plateau. Previous studies indicate that the red clay is also of wind-blown origin, covering the period from ∼7–8 to ∼2.6 Ma. The red clay therefore provides a good archive to reconstruct paleoecological succession and paleoclimate change. In this study, a palynological investigation was conducted on the late Miocene–Pliocene red clay sequence at Xifeng, central Loess Plateau, which provides new insights into the nature of the evolution of vegetation and climate change from ∼6.2 to ∼2.4 Ma. Our results show that during this period the central Loess Plateau region was covered mainly by a steppe vegetation, indicating long lasting dry climatic condition. Three vegetational zones were recognized during this period. Zone A (∼6.2 to ∼5.8 Ma) is characterized by a steppe ecosystem; Zone B (∼5.8 to ∼4.2 Ma) is characterized by a significant increase of temperate forest plants, indicating a relatively humid regional climate; Zone C (∼4.2 to ∼2.4 Ma) indicates a typical steppe ecosystem. The vegetation shift at about 4.5–3.7 Ma, when the temperate forest plants decrease, the vegetation gradually changed to typical grassland and even to desert steppe. This is interpreted to represent a drying event. The uplift of the Tibetan Plateau at about 4.5 Ma that resulted in the intensification of the monsoon reversal is thought to have played an important role in this significant ecological change. High-latitude cooling may have partially contributed to the climate shift during ∼4.5 to ∼3.7 Ma in the Loess Plateau region, and most likely was the driving force for the ecological shift at about 3.7 Ma. [Copyright &y& Elsevier]

This paper presents an overview of paleoenvironmental changes in East Africa during the late Quaternary based on evidence from pollen, diatoms, microscopic charcoal, and lake level records and associated proxies. The paleoenvironmental records derived from different proxies complement each other to provide a more accurate and complete assessment of the paleoenvironmental changes in East Africa. The records show that the period prior to c. 42,000 14C yr BP was characterized by warm climatic conditions similar to the present. This was followed by a change to cold dry conditions from 42,000 to 30,000 14C yr BP, and cold and moist conditions from 30,000 to 21,000 14C yr BP. Temperatures during the latter period leading to the Last Glacial Maximum (LGM) were probably 2 to 4.1°C lower than the present. Between c. 21,000 and 12,500 14C yr BP East Africa's environment was generally cool, punctuated by two significant episodes of prolonged desiccation. Warm and moist conditions punctuated by rapid climatic changes prevailed in the region during the deglacial and middle Holocene period. Ice core records document two significant and abrupt drought events in the region, one at ∼8300 14C yr BP and the other at 5200 14C yr BP. The onset of a longer and more extensive desiccation period commencing ∼4000 14C yr BP was registered in nearly all sites. The climate of East Africa was generally drier than present during the Medieval Warm Period (MWP) while fairly wet conditions prevailed during the Little Ice Age (LIA) interrupted by three episodes of aridity, more severe than those of more recent times. Whereas this review advances our understanding of climate and vegetational changes in East Africa beyond the Last Glacial Maximum, it also highlights limitations of the paradigms that explain the forcing mechanisms behind the changes. However, unequivocal interpretation of the multiproxy data from East Africa with respect to paleoenvironmental changes becomes extremely complex and challenging especially when the anthropogenic input is considered. [ABSTRACT FROM AUTHOR]

Abstract: The fossil flora from the lower part of the Khuren Dukh Formation (Albian) in the southern part of the Choyr Basin, Mongolia, is characterized by an abundance of ferns and conifers. Occurrence of fossil plants supports the reconstruction of paleovegetation previously estimated by Russian paleobotanists. The “palaeo Choyr Basin” appears to have been covered with fern marsh that was surrounded by conifer forest on the basin slopes or adjacent highlands. [Copyright &y& Elsevier]

Abstract: This article presents a combined pollen and phytolith record of a 1.70-m sediment core from the wetlands of India Muerta (33° 42′ S, 53° 57′ W) in the lowland Pampa (grasslands) of southeastern Uruguay. Six 14C dates and the pollen and phytolith content of the samples permitted the recognition of four distinct climatic periods between 14,850 14C yr B.P. and the present. The Late Pleistocene period (between ca. 14,810 and ca. 10,000 14C yr B.P.) was characterized by drier and cooler conditions indicated by the presence of a C3-dominated grassland. These conditions prevailed until the onset of the warmer and more humid climate of the Holocene around 9450 14C yr B.P. The early Holocene (between around 10,000 and 6620 14C yr B.P.) was characterized by the establishment of wetlands in the region as evidenced by the formation of black peat, the increase in wetland taxa, and the replacement of C3 Pooideae by C4 Panicoideae grasses. During the mid-Holocene, around 6620 14C yr B.P., began a period of environmental change characterized by drier climatic conditions, which resulted in the expansion of halophytic communities in the flat, low-lying areas of the wetlands of India Muerta. About 4020 14C yr B.P. a massive spike of Amaranthaceae/Chenopodiaceae coupled with a radical drop in wetland species indicates another major and more severe period of dryness. After ca. 4000 14C yr B.P., a decrease of halophytic species indicates the onset of more humid and stable climatic conditions, which characterized the late Holocene. The findings reported in this article substantially improve our knowledge of the late Glacial and Holocene climate and vegetation in the region. The data provide a detailed record of the timing and severity of mid-Holocene environmental changes in southeastern South America. Significantly, the mid-Holocene drying trend coincided with major organizational changes in settlement, subsistence, and technology of the pre-Hispanic populations in the region, which gave rise to early Formative societies. This study also represents the first combined pollen and phytolith record for southeastern South America reinforcing the utility of phytoliths as significant indicators of long-term grassland dynamics. [Copyright &y& Elsevier]

Abstract: Two paleoxylologic assemblages and two phytolith assemblages were recovered from Late Pleistocene sediments of El Palmar Formation. These deposits are found in outcrops along the western margin of the Uruguay River. The spectra of taxa obtained in both sets by different methods is complementary. The fossil remains are characterized in terms of floristic composition and paleoclimate. Seven families are recognized: Podostemaceae, Myrtaceae, Anacardiaceae, Mimosoideae, Arecaceae, Poaceace, and Cyperaceae. Sponge siliceous spicules also have been found in these assemblages. The state of preservation of the phytoliths and their weathering degree is analyzed. These studies can be used as a potential paleoecological tool for alluvial sediments. The comparison of fossil assemblages with modern analogs clarifies the paleoecological requirements and composition of two paleocommunities, one dominated by woody forests and the other by palms. The climatic conditions inferred from the reconstructed vegetation and sedimentary deposits indicate a temperate-warm, humid climate. The results constitute the first evidence of the floral diversity of the vegetation in El Palmar National Park during the Late Pleistocene. [Copyright &y& Elsevier]

Abstract: The natural abundance of C3 and C4 plants is affected by multiple environmental factors including temperature, moisture balance and atmospheric pCO2. The relative importance of these factors is a subject of considerable debate, and may vary in different natural ecosystems. Previous studies generally focus on single loess sequences in the Chinese Loess Plateau, and conflicting conclusions on C4/C3 have been reached when studying carbon isotope ratios in carbonate and organic matter. In this paper we report a comprehensive carbon isotopic characterization of total organic carbon (TOC) and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the Chinese Loess Plateau (CLP). The five coring sites encompass large gradients of annual mean temperature (9.2–13.9 °C) and precipitation (402–673 mm), allowing us to assess the controlling mechanisms on C4/C3 plant ratios. Glacial–interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility. Our results demonstrate that increased C4/C3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites. We conclude C4 abundance increases from the last glacial to the Holocene in response to greater monsoon activity and that the C4 expression is suppressed in the cold and drier intervals. [Copyright &y& Elsevier]

Abstract: Palynological contributions for the palaeoenvironmental reconstruction of the Albo-Cenomanian from the Charentes (SW France). The Albo-Cenomanian deposits from the Charentes region (SW France) are characterized by the strong development of brackish and estuarine facies with amberiferous lignitic clays and sands. These facies, which occur in six localities previously studied from a sedimentological and macropalaeontological point of view, exhibit well-preserved palynological assemblages. The studied samples have yielded assemblages dominated by pollen grains of conifers of the genera Araucariacites, Classopollis and Inaperturopollenites, as well as fern spores of Gleicheniaceae and Schizaeaceae. The presence of pollen grains of primitive angiosperms is remarkable in Upper Albian and Lower Cenomanian samples. Furthermore, genus Complexiopollis, which belongs to the Normapolles Group, has been identified in the Upper Cenomanian sample. The picture of the vegetation of the Charentes was determined by two types of coniferous forests. On the one hand, the coastal areas were inhabited by xerophytic trees belonging to the Cheirolepidiaceae, with a rich undergrow constituted by bennettitales, cycads and ferns of the families Gleicheniaceae and Schizaeaceae. On the other hand, open formations of Araucariaceae and Cupressaceae developed in wetter places presenting an understory mainly integrated by ferns. A third plant community composed of ginkgoales in association with primitive angiosperms could develop in riparian places. The studied palynoflora has similarities with other ones from Provence, Vendée, Aquitaine, and Sarthe. This study presents the first reconstruction of palaeovegetation biodiversity and changes between the Uppermost Albian and the basal Upper Cenomanian in the Charentes (SW France). Pour citer cet article : D. Peyrot et al., C. R. Palevol 4 (2005) . [Copyright &y& Elsevier]

Abstract: We present a new stratigraphic (pollen and nonpollen microfossils and charcoal particle) sequence with five AMS dates, covering about the last 9000 yr, of a core collected from the Spanish northern meseta, one of the territories of the Iberian Peninsula for which little paleobotanical information is available. The results support the hypothesis of the permanence of the pine forests, in more or less pure masses or large timber stands, during the Holocene in some Iberian continental zones. The typical substitution in postglacial dynamics of heliophyllous species, such as pines or Cupressaceae, by broadleaf trees did not occur in this inland region. Presumably, factors linked to the substrate, in this case very deep sand dunes covering vast areas, may have contributed to the scarce local competitiveness of the broadleaf trees, which would account for the hegemony of pines in this region. Based on the dynamics of aquatic plants and nonpollen microfossils, an initial phase previous to 7500 14C yr B.P. of high levels in the lake can be identified by high percentages of hydrophytes. A progressive increase in helophytes and the gradual infilling of the lake over the last 5000 yr appear to indicate a phase of aridification similar to those established for the western Mediterranean. Study of charcoal particles, more abundant in the last 2500 yr, has given rise to certain hypotheses regarding the incidence of recurring fires of a local or regional nature. [Copyright &y& Elsevier]

The relationship between the carbon isotopic composition of paleosols and pale-ovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of the carbon isotopic composition of modern soil in this area. A preliminary investigation of the carbon isotopic compositions of the modern soil and the loess/paleosol sequence on the Loess Plateau shows that the carbon isotopic composition of modern soil is consistent with the distribution of modern plants on the Loess Plateau, where the ecosystem is dominated by a mixture of C4 and C3 plants. Comparing the δ 13C values of modern soil and loess-paleosol sequences from the Xunyi profile, we conclude that C3 plants dominated the landscape during loess sediment stages, while C4 plants expanded during paleosol stages. [ABSTRACT FROM AUTHOR]

Sequences of lacustrine sediments developed in intermontane basins in the middle-eastern Shanxi Plateau of China have been investigated in order to reconstruct the paleovegetation and paleoclimate for the middle–late Pliocene. According to the magnetostratigraphy and the fossil assemblages, the lacustrine sediments of Yushe and Taigu Basins were deposited between 5.5 and 2.5 Ma BP. The Zhangcun and Xiaobai Formations are considered to cover a similar period, ranging from 3.5 to 2.5 Ma BP. An increase of Picea and Abies shows that the climate began to become cold after about 4.4 Ma BP. A cold–wet episode, with relatively warm–dry and warm–humid intervals, occurred between 3.6 and 2.5 Ma BP in the Yushe and Taigu Basins. An increase Artemisia, Chenopodiaceae and Ephedra shows that the climate became drier after 2.5 Ma BP. The climate changes of this period probably reflect variations of the East Asian winter and summer monsoons, with an increase winter monsoon activity during the early Pleistocene. [Copyright &y& Elsevier]

We present here the results of a first study comparing modern soil phytolith assemblages with pollen and botanical data at a North Mediterranean site. This work has shown the following limitations and advantages of phytolith analysis for the reconstruction of Mediterranean vegetation:(1) Phytoliths are produced in sufficient quantities for analysis and are well preserved in limestone environments, widespread in the Mediterranean area. (2) Young stands of Quercus ilex and Quercus coccifera, widely distributed in the Mediterranean area do not produce characteristic phytolith types in sufficient quantities to allow the calculation of a reliable index of tree cover density. (3) Pine forests, dominated by Pinus halepensis and Pinus sylvestris, are not recorded in the studied phytolith assemblages. (4) Grassland and shrubland assemblages can be distinguished through their associated phytolith assemblages, in particular by the proportion of crenate phytoliths produced in the short cells of the grass epidermis. (5) The different vegetation groups on the massif cannot be distinguished by pollen analysis. Further studies, comparing modern phytolith assemblages and quantitative vegetation data, should be carried out on forest plots that have been established for several centuries to further assess the role of phytolith analysis in vegetation reconstructions in the Mediterranean region. [Copyright &y& Elsevier]

Site-specific numerical modeling of four sites in two arid alluvial basins within the Nevada Test Site employs a conceptual model of deep arid system hydrodynamics that includes vapor transport, the role of xeric vegetation, and long-term surface boundary transients. Surface boundary sequences, spanning 110 kyr, that best reproduce measured chloride concentration and matric potential profiles from four deep (230-460 m) boreholes concur with independent paleohydrologic and paleoecological records from the region. Simulations constrain a pluvial period associated with infiltration of 2-5 mm yr−1 at 14-13 ka and denote a shift linked to the establishment of desert vegetation at 13-9.5 ka. Retrodicted moisture flux histories inferred from modeling results differ significantly from those determined using the conventional chloride mass balance approach that assumes only downward advection. The modeling approach developed here represents a significant advance in the use of deep vadose zone profile data from arid regions to recover detailed paleohydrologic and current hydrologic information. [ABSTRACT FROM AUTHOR]

Late Pleistocene to Holocene terrestrial climate and vegetation records in the Lower Salmon River Canyon of Idaho are interpreted from the stable isotopic composition of soil carbonates and from aeolian sedimentation frequencies. Carbonate and sediment samples from six sections were processed and analyzed, with the resulting isotopic and grainsize data organized in relation to a normalized time series developed from an associated radiocarbon chronology. This record is interpreted in regards to changes in aridity, temperature and wind speed during the Late Quaternary and is further compared with regional paleoenvironmental records. Lowered δ18O and δ13C concentrations before 20 000 yr BP are interpreted as reflecting Late Wisconsinan cold conditions. After 18 000 yr BP, climatic conditions show warmer periods punctuated by sharp returns to colder temperatures and increased C3 flora by 12 000 yr BP. Higher resolution data show very unstable climatic conditions across the Pleistocene–Holocene boundary, reflected in wide variations in δ18O and δ13C and aeolian sand deposition. During the period between 12 000 and 9000 yr BP, the Lower Salmon River Canyon is thought to have experienced marked seasonality with summers and winters, respectively, warmer and colder than today. This climatic scenario was accompanied by an initial instability in canyon vegetation. Following the establishment of a low-energy floodplain in the canyon after 10 000 yr BP, a pattern of C3-dominant riparian flora appears. During the middle Holocene, climatic and vegetative variability is much reduced from the preceding period. After 4000 yr BP, soil carbonate isotopes reflect a trend toward cooler climate conditions and more mesic vegetation populations. [Copyright &y& Elsevier]

This paper attempts to reconstruct vegetation changes and to infer climate changes during the late Pleistocene and the Holocene in the southeast (Botucatu, Anhembi and Jaguariúna, São Paulo State) and centerwest of Brazil (Pontes e Lacerda, Mato Grosso State). The research approach included the use of carbon isotopes (13C and 14C) in soil organic matter (SOM) and the evaluation of charcoal distribution and its identification at the species level. Soils sampled in this study were located under natural vegetation, along the slopes of small hills. Charcoal was found predominantly between 150 and 50-cm depth, indicating a period of greater frequency of fires in the study areas, between 6000 and 3000 years BP. For the Botucatu, Anhembi and Pontes e Lacerda sites, the δ13C profiles suggest the predominance of C3 plants during the entire Holocene. The 13C patterns obtained at the Jaguariúna site that show a more significant presence of C4 plants compared to the other regions, suggest that this region has been drier than the others during the Holocene. These patterns also indicate the presence of a drier climate compared with present-day conditions at the Jaguariúna region during late Pleistocene until the middle Holocene. This study shows the complexity of vegetation dynamics in the southeast of Brazil during the Holocene. It also shows that the analyses of multiple soil cores representative of the main vegetation communities are necessary for paleovegetation studies. [Copyright &y& Elsevier]

Understanding local-scale paleoecological processes and their driving mechanisms is a major challenge in plant community ecology. However, phytolith records have the potential to retrieve localized signals of the evolution and patterns of past ecosystems. As a case study, we selected a forested region in Northeast China. We first established a modern phytolith reference dataset which enabled numerical estimates to be made of various aspects of the plant community. We then apply the dataset to a phytolith record from a sedimentary profile (HN) from the Changbai mountain region in order to quantitatively reconstruct the evolution of the vegetation since the last deglaciation. The results of partial least squares regression were used demonstrate that modern phytoliths can quantitatively estimate plant community coverage, species diversity and dry weight ratio; three numerical estimates respectively explained 62.3%, 50.3% and 49.5% of the variance. These quantitative relationships can provide reliable modern phytolith analogues for paleoecological reconstructions. The modern phytolith-based vegetation reconstruction indicates that the Changbai mountain region was dominated by forest communities since the late glacial period. The temporal development of the vegetation can be summarized as follows: boreal or coniferous forest, sparse and species-poor → mixed broadleaf-conifer forest, relatively dense and species-rich → mixed broadleaf-conifer forest, dense and species-rich. The phytolith-inferred changes in plant community coverage, dry weight ratio and species diversity correspond well with climatic changes. This supports the view that the environmental background mainly dominates ecosystem evolution, and it also confirms the utility of phytolith records to resolve local paleovegetation patterns and evolution. [ABSTRACT FROM AUTHOR]

In some cases, the oil shale deposited in shallow lakes may be genetically associated with the coal-bearing successions. Although paleovegetation is an important controlling factor for the formation of oil shale- and coal-bearing successions, few studies have focused on their joint characterization. In this study, a total of twenty-one oil shale and coal samples were collected from the upper member of the Lower Cretaceous Muling Formation (K1ml2) in the Laoheishan Basin, and investigated for their bulk geochemical, maceral, palynological, and terpenoid biomarker characteristics, in order to reconstruct the paleovegetation and reveal its influence on the formation of oil shale and coal. The K1ml2 is subdivided into lower, middle, and upper units. The studied oil shale samples from the lower and upper units display a high ash yield (Ad), low total organic carbon (TOC) and sulfur (S) contents, and limited hydrocarbon generation potential. The studied coal samples from the middle unit are characterized by low Ad, and high TOC and low S values, and show significant hydrocarbon generation potential. The paleovegetation during the formation of the lower unit was dominated by mire vegetation, such as shrubs (e.g., Lygodiaceae, Schizaeaceae), tree ferns (e.g., Dicksoniaceae/Cyatheaceae), and coniferous trees (e.g., Podocarpaceae). In the middle unit interval, the paleovegetation was represented by highland vegetation (Pinaceae and Araucariaceae) and peat-forming coniferous plants (e.g., Podocarpaceae, Cupressaceae/Taxodiaceae). Various vegetation, such as herbs (e.g., Osmundaceae), shrubs (e.g., Schizaeaceae), and coniferous trees (e.g., Podocarpaceae) was prosperous during the upper unit interval. Coniferous trees could provide abundant hydrogen-rich materials (e.g., resins) to the mire/lake, which may elevate the hydrogen content in peat/lake sediments, and finally result in higher hydrocarbon generation potential in the coal than in the oil shale. Therefore, the influence of paleovegetation on the formation of oil shale and coal should be fully considered when studying oil shale- and coal-bearing successions. The results also provide guidance for further exploration studies on oil shale and coal in northeast China. [ABSTRACT FROM AUTHOR]

• Paleovegetation seesaw in Brazil is a result of different transition timings since the late Pleistocene. • Stalagmites record soil and vegetation change coupled with atmospheric CO 2 and temperature in Cerrado. • Distinct forcings modulate the δ 13 C and 87Sr/86Sr values in stalagmites from different biomes. Paleovegetation studies in Brazil have been mostly based on pollen analysis and geochemical proxies in lacustrine and soil records. These records, however, are sparsely located in the continent and, in most of the cases, centered over the Holocene, giving a minor picture of past vegetation since the Last Glacial Maximum. Stalagmites have been long used as recorders of paleoprecipitation and monsoon activity over time in tropical and subtropical South America by using δ 18 O analyses, but recently they also showed the potential to record past vegetation and soil changes through the combined use of δ 13 C and 87Sr/86Sr. We utilize this new approach to determine the periods of paleovegetation transition and soil development in the Cerrado (Brazilian savanna) biome from central Brazil. Our results show a coherent period of transition from sparser vegetation and shallower soil above the cave to denser vegetation and thicker soil since the last deglaciation circa 15 ka BP. The timing of this transition is different from the multiproxy evidence found in the Caatinga (dry forest) biome, in northeastern Brazil, circa 4.2 ka BP, resulting in a period of paleovegetation seesaw pattern between central and northeastern regions of Brazil. Additionally, atmospheric pCO 2 and temperature variations may have played a major role on the paleovegetation transition in the Cerrado region whereas precipitation linked to the Intertropical Convergence Zone was the major modulator of paleovegetation in the Caatinga. [ABSTRACT FROM AUTHOR]

In arid and semi-arid climates, soil development is strongly influenced by seasonal patterns and biogenic activity, and often results in pervasive pedogenic horizons consisting of highly concentrated carbonate. In Brazil, such horizons enriched in calcium carbonate are common and relatively well-studied in paleosols of the Upper Cretaceous Marília Formation. However, detailed analyses on the sequence of mineral precipitation phases and the role of organisms in these processes are still lacking. The present work describes eight argillic and calcic horizons characterized by different degrees of carbonate accumulation. Argillic horizons show translocation clay structures and weak to moderate cementation by calcium carbonate. Calcic horizons contain moderate to high carbonate accumulations ranging from powdery coatings to nodular masses of micrite. Carbonate distribution in these horizons is preserved largely as carbonate-cemented macropores produced by such ichnofossils as Planolites, Taenidium, Naktodemasis, Skolithos, Palaeophycus and calcareous rhizocretions. Moreover, stable isotope data, respired soil CO 2 function, and cathodeluminescence (CL) of the paleosol samples were used to evaluate soil paleovegetation, paleoproductivity, and the distinctive stages of calcite precipitation. Stable isotopic analysis suggests that paleovegetation cover in the paleosols was predominantly C 3 -photosynthsizing plants. The relationship between bioturbation indices and soil respiration suggests a positive pattern of paleoproductivity controlled by higher moisture conditions and the increased activity of soil fauna. Finally, CL imaging shows that there were multiple stages of carbonate precipitation with both α-type and β-type fabrics that are interpreted as abiotic and biotic processes during pedogenesis. • Calcic and argillic horizons are described in detail according with carbonate content; • C3 plants are recognized by carbon isotope composition; • Terraphilic and Hygrofillic trace fossils form the paleosols biota; • The relation of substrate colonization and paleosols organisms respiration represent positive paleoproductivity; • Abiotic processes and biotic activities control the pedogenic carbonate accumulation. [ABSTRACT FROM AUTHOR]

In this pater, the paleovegetation and paleoclimate in the Hemudu region of Zhejiang Province during 7000 to 6000 a B. P. are reconstructed. Firstly, using Andersen's method, a correction is made for the percentage of pollens of various plants excavated at Hemudu Site. Secondly, on the basis of the results, the dominant species and constructive species and types of zonal forest vegetation are identified, then the paleovegetation of Holocene Hypsithermal is reconstructed. Finally, by contrasting the above mentioned paleovegetation with the vegetation of Wuyanling Natural Reserve (WYLNR) in south Zhejiang and Dinghushan Natural Reserve (DHSNR) in Guangdong today, and on the analogy of above results, the paleoclimate is also reconstructed. [ABSTRACT FROM AUTHOR]

Paleoenvironmental and paleoclimatic variations experienced by the Mediterranean region during the Miocene Burdigalian-Langhian interval have been investigated through analysis of biomarker signals (n -alkanes and glycerol dialkyl glycerol tetraethers, GDGTs) from slope mudstones of the northern Apennines (Marne di Vicchio Fm). Terrestrial signatures in marine sediments reflected by preserved long-chain n -alkanes with a identifiable odd-over-even carbon number predominance attest to the thermal immaturity of the sedimentary rock. Abundances of n -C 27 , n -C 29 and n -C 31 alkanes, coupled with the carbon isotopic signatures of the n -C 31 homologue suggest that Mediterranean vegetation crossed a transition phase adapting to arid conditions that may favored a shift from woodland to wooded grassland during the Middle Miocene. This ecosystem evolution could have been favored by the passage from warm humid conditions to a warm drier climate, as indicated by GDGT-based TEX 86 and BIT indexes. Strong similarities between these Mediterranean biomarker records and those from the Atlantic (DSDP Sites 94, 516, 608) imply a constant connection of the western Mediterranean to the Atlantic Ocean from ~19 Ma to ~14.5 Ma. • Mediterranean vegetation transition from woodland to grassland during Middle Miocene. • New hydrocarbon biomarker study for the Middle Miocene Mediterranean area. • Ecosystem evolution favored by the passage from warm humid to drier climate condition. • Similar biomarker values between Mediterranean and north Atlantic (IODP SITE 608). • Steady connection of western Mediterranean to Atlantic Ocean from19 Ma to 14.5 Ma. [ABSTRACT FROM AUTHOR]

Long-term paleovegetational records from continental settings help in comprehending regional and global forcing on the abundance of C 3 -C 4 plants in the past. The carbon isotopic composition of soil carbonates (δ13C SC), soil organic matter (δ13C SOM), organic matter occluded in soil carbonate nodules (δ13C NOM) and biomarkers in paleosol organic matter (long-chain fatty acid; δ13C FAME) are often used to estimate changes in the past-vegetational composition. However, it has been observed that depending on the type of proxy, the estimated abundance of C 3 -C 4 plants varies, which can lead to uncertainty in paleovegetational records. Hence, the present study aims to comprehend the factors affecting the δ13C SC , δ13C SOM , δ13C NOM and δ13C FAME values within a paleosol. In this context, available δ13C SC , δ13C SOM , δ13C FAME and newly measured δ13C NOM values from the late Quaternary sequences of the Ganga Plain, India has been used. The abundance of C 4 plants calculated from the δ13C SC and δ13C FAME values is ~2% to 89% higher compared to the δ13C SOM and δ13C NOM values-based estimates. Even with a common source of organic matter, the δ13C SOM values indicate a higher abundance of C 4 plants (~2% to 50%) compared to the estimates from δ13C NOM values. We suggest that the disparity is due to the variation in the response of proxies to perturbations in the paleovegetational regime, growing season condition, and isotopic fractionation during decomposition and incorporation of organic matter into the soil. For example, the organic matter is incorporated into the soil throughout the year and represents average annual biomass, whereas SC precipitates under warmer and often drier condition when the ratio of C 4 to C 3 plant respiration is higher. Additionally, preferential degradation of 13C enriched labile compounds and C 4 plants derived organic matter may lower the δ13C NOM values resulting in an under estimation of C 4 plants in a mixed C 3 -C 4 environment. The higher abundance of C 4 plants estimated from the δ13C FAME values is due to the isotopic fractionation (13C enrichment of ~2‰ to 7‰) during incorporation of plant-derived long-chain fatty acids into the soil. The disparity in the abundance of C 4 plants estimated from δ13C SOM and δ13C NOM values is due to the difference in the preservation of SOM and NOM. Contrary to the NOM (which is in a closed system), SOM in open system within the soil matrix is subjected to 13C enrichment due to the long-term humification of organic matter. Various factors such as grain size and pedogenesis that are inherent to the depositional environment also control the δ13C values of paleosol components. Considering the uncertainties associated with the δ13C values of paleosol components, reporting the absolute abundance of C 4 plants would be uncertain. Therefore, we recommend presenting the relative change in abundance of C 3 -C 4 plants during paleovegetational reconstruction. • Disparity in the abundance of C 4 plants estimated using multiple proxies. • δ13C SC and δ13C FAME values suggest higher C 4 plant than δ13C SOM and δ13C NOM values. • The disparity is linked to the variation in the response of individual proxy. • Soil forming processes affect the isotopic inheritance in paleosol components. • Reporting absolute abundance of C 4 plants would be uncertain. [ABSTRACT FROM AUTHOR]

• Detailed investigation on the δ13C org of the Ganzi loess-paleosol sequence. • Loess δ13C org values in glacial periods are lower than those in interglacial period. • The paleovegetation is mainly dominated by C 3 vegetation since LIG. • The abundance of C3/C4 vegetation has been mainly controlled by climate change. The stable carbon isotope composition of total organic matter (δ13C org) in loess deposits has been widely used as a valuable proxy for reconstructing terrestrial paleovegetation. Aeolian loess is widely distributed on the high Tibetan Plateau (TP); however, little is known about the variability and paleoenvironmental implications of the δ13C org of Tibetan loess. We conducted detailed δ13C org and total organic carbon analyses of the Ganzi loess sequence on the eastern TP since the last interglacial (LIG). Our results indicate that the δ13C org values of loess during glacial periods were lower than those during interglacial periods, with more negative values associated with the cold stages since the LIG on the eastern TP. The reconstruction of vegetation from the δ13C org data indicated that C 3 /C 4 mixed vegetation was dominated by C 3 vegetation, and that the relative abundance of C 4 vegetation during the glacial stages was much lower than that during MIS 5 and MIS 3. The high relative abundance of C 4 plants during MIS 5 and MIS 3 suggested an increased proportion of C 4 plants during the warm period. Since the LIG, the change in the abundance of C 3 /C 4 vegetation in the Ganzi region has been mainly controlled by climate change at the glacial–interglacial scale. The combined effect of temperature, precipitation, and atmospheric CO 2 caused changes in the paleovegetation on the eastern TP. [ABSTRACT FROM AUTHOR]

Previously, Olduvai Bed I excavations revealed Oldowan assemblages <1.85 Ma, mainly in the eastern gorge. New western gorge excavations locate a much older ∼2.0 Ma assemblage between the Coarse Feldspar Crystal Tuff (∼2.015 Ma) and Tuff IA (∼1.98 Ma) of Lower Bed I, predating the oldest eastern gorge DK assemblage below Tuff IB by ∼150 kyr. We characterize this newly discovered fossil and artifact assemblage, adding information on landscape and hominin resource use during the ∼2.3–2.0 Ma period, scarce in Oldowan sites. Assemblage lithics and bones, lithofacies boundaries, and phytolith samples were surveyed and mapped. Sedimentological facies analysis, tephrostratigraphic and sequence stratigraphic principles were applied to reconstruct paleoenvironments and sedimentary processes of sandy claystone (lake), sandstone (fluvial), and sandy diamictite (debris flow) as principal lithofacies. Artifacts, sized, weighed, categorized, were examined for petrography, retouch, and flake scar size. Taxonomic classifications and taphonomic descriptions of faunal remains were made, and phytoliths were categorized based on reference collections. Lithics are dominantly quartzite, mainly debitage and less frequently simple cores, retouched pieces, and percussors. Well-rounded spheroids and retouched flakes are rare. Identifiable taxa, Ceratotherium cf. simum (white rhinoceros) and Equus cf. oldowayensis (extinct zebra), accord with nearby open savanna grasslands, inferred from C 3 grass, mixed and/or alternating with C 4 grass-dominated phytolith assemblages. Palms, sedges, and dicots were also identified from phytoliths. Diatoms and sponge spicules imply nearby freshwater. The assemblage accumulated at the toe of a Ngorongoro Volcano-sourced fan-delta apron of stacked debris flows, fluvials, and tuffs, preserving fossil tree stumps and wooded grassland phytoliths farther upfan. It formed after the climax of Ngorongoro volcanic activity during a Paleolake Olduvai lowstand and was then buried and preserved by lacustrine clays, marking the first of two lake transgressions, signifying wetter climates. Orbital precessional lake cycles were superposed upon multimillennial (∼4.9 kyr) lake fluctuations. • We present a new ∼2 Ma lithics and bone assemblage from the western Olduvai Basin. • The assemblage sits below the Bed I Basalt, 150,000 a older than Upper Bed I DK site. • It's the oldest evidence of Homo exploitation of a savanna paleolandscape at Olduvai. • The assemblage was sited on a fan-delta toe, incised during Lake Olduvai withdrawal. • It was buried by major lake transgression at the end of Ngorongoro fan progradation. [ABSTRACT FROM AUTHOR]

The early Oligocene represents the beginning of the modern icehouse world. To better understand how vegetation and climate changed during this period, we reconstruct quantitively the early Oligocene vegetation and climate by analyzing fossil spore and pollen assemblages from Lühe basin, Yunnan Province, in southwestern China. The reconstructed paleoclimate using Bioclimatic Analysis shows that the mean annual temperature (MAT) ranged from 14.4 to 15.4 °C, the mean annual precipitation (MAP) was 1070.1–1297.8 mm, and the range of mean temperature of coldest quarter (MTCQ) was 6.7 to 7 °C, lower than that of the present day (9.3 °C). The reconstructed regional vegetation indicates a deciduous broadleaved forest mixed with evergreen broadleaved elements. Considering other Paleogene floras in Yunnan, deciduous broadleaved elements dominated in this area from the late Eocene to the early Oligocene. The paleoclimate reconstruction suggests that this vegetation composition may have been controlled mainly by cold winter temperatures. • The first early Oligocene palynoflora in southwestern China is studied. • A deciduous broadleaf forest mixed with evergreen broadleaf elements is reported. • The palaeoclimate of this palynoflora is reconstructed using Bioclimatic analysis. • The vegetation types in SW China may have been controlled by cold winters. [ABSTRACT FROM AUTHOR]