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The Tibetan Plateau's alpine ecosystem has been undergoing accelerated climate change and severe vegetation degradation in the past four decades, which has triggered a sharp increase in soil erosion hazards. However, the combined impacts of climate change and vegetation degradation on soil erodibility (K) across geographical and temporal scales remain unclear. Here, we present the first systematic investigation of spatio‐temporal variations in K under different land uses across the southern Tibetan Plateau over the last 35–40 years, and identify the associated driving factors based on a paired resampling campaign conducted in the 1980s and 2020, covering 148 field sites. K‐values derived for the majority of grassland (75.0%) and cropland (66.2%) sites, as well as for a substantial number of forest sites (46.7%) showed a decreasing tendency with time, with average decreases of 31%, 14%, and 5%, respectively. Changes in K were primarily (17.6%) attributed to soil erosion, but were exacerbated by climate change (8.2%). Interestingly, the declines in K resulted in significant decreases in (predicted) soil erosion rates as long as strong disturbances from climate change and human activities were absent. These findings confirm the existence of a negative feedback mechanism between soil erosion and K in most alpine ecosystems on the southern Tibetan Plateau. Our results reveal the extent to which the impact of vegetation degradation on the magnitude of K is enhanced by climate change, thereby providing new insights into the feedback between alpine ecosystems, climate change, and anthropogenic interference. [ABSTRACT FROM AUTHOR]

Fire plays an important role in the Earth system, and is considered an essential control on global vegetation evolution and climate change. However, few Miocene high–resolution fire records have been obtained with which to assess the controls and possible drivers of fire on multiple timescales. Here, we provide a high–resolution charcoal record of the Nanyu section to reconstruct mid–Miocene fire history in the Wushan Basin. Further, we identify and assess the long–term regional fire regime (frequency and intensity) controls and possible drivers by making comparisons with published paleoclimate and paleoenvironmental records (i.e., palynomorphs, magnetic susceptibility, redness, stable isotope, pCO2 and marine δ18O data etc.). We also performed spectral analysis of the charcoal records to investigate possible controls of fire activity on orbital time scales. The analysis results indicate that (a) the reconstructed fire regime exhibits an increase from ∼16 to 13.86 Ma and a significant decrease after ∼13.86 Ma. (b) The steadily increasing regional fire activity during the period of ∼16–13.86 Ma may be caused by increased fuel ignitability and drying climate, whereas significantly decreased fire activity after ∼13.86 Ma is likely attributed to decreased fuel load due to the Mi–3b global cooling event. (c) On orbital time scales, the finding of the Earth's orbital cycles in fire proxy indicates that mid–Miocene fire activity variability in the study area was likely related to Earth's orbital forcing. Key Points: Mid‐Miocene fire history of northeastern Tibetan Plateau was studied based on charcoal concentrationsLong term fire activity variability might be primarily influenced by climatically driven effects on the fuel biomass and flammabilityOn orbital time scales, Earth's orbital forcing might have been a dominant control of regional fire activity variability [ABSTRACT FROM AUTHOR]

Background and Aims: Nitrogen (N2) fixation through endophytic diazotrophs within the non-nodulated plants has been considered a novel source of N inputs in terrestrial ecosystems. However, little is known about the composition and diversity of endophytic diazotrophs within the non-nodulated plants, especially when compared with the diazotrophs in nodulated plants. Methods: High-throughput nifH amplification sequencing was conducted to characterize endophytic diazotrophs within different tissues (leaf, stem, and root) of non-nodulated plants (Salix rehderiana Schneid, S. ernestii Schneid, and Populus purdomii Rehd.) and nodulated plants (Astragalus mahoshanicus and Hippophae rhamnoides L.) which dominate in the newly formed N-limited glacier floodplain in the eastern Qinghai-Tibetan Plateau. Results: We found endophytic diazotrophs, primarily Proteobacteria, in all tissue types of non-nodulated plants and leaf and stem of nodulated plants. The dominant genera were Bradyrhizobium, Ideonella, Azotobacter, and Geobacter. In comparison, diazotrophs within the nodule of leguminous Astragalus mahoshanicus and actinorhizal Hippophae rhamnoides were predominantly of genera Rhizobium and Frankia, respectively. Further, the community composition of diazotrophs was structured by plant species (P = 0.001), tissue types (P = 0.001), and nutrient concentrations (P = 0.001). Leaves of non-nodulated plants exhibited higher Chao1 indices and lower Simpson and Shannon indices than their stem and root, but these were not significantly different among different tissue types of nodulated plants. Conclusions: Endophytic diazotrophs might be prevalent in pioneer plants occurring in the N-limited habitat and have a high degree of host specificity; these findings could help to understand the ability of those pioneer plants to acquire N. [ABSTRACT FROM AUTHOR]

The thermal state of permafrost in the present and future is fundamental to ecosystem evolution, hydrological processes, carbon release and infrastructure integrity in cold regions. In 2011, we initiated a permafrost monitoring network along the China–Russia crude oil pipeline (CRCOP) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. We compiled an integrated dataset of the ground thermal state along the CRCOP route consisting of meteorological data near the southern limit of latitudinal permafrost, ground temperature (GT) data in 20 boreholes with depths of 10.0–60.6 m, soil volumetric liquid water contents (VWCs) and 2D electrical resistivity tomography (ERT) data at different sites. Results demonstrate a permafrost warming during 2011–2020 in the vicinity of the southern limit of latitudinal permafrost, as manifested by rising GTs at almost all depths in response to climate warming. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipelines. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as an insulation layer and thermosyphons. The in situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro–thermal–mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the National Tibetan Plateau/Third Pole Environment Data Center (10.11888/Cryos.tpdc.272357; Li, 2022). [ABSTRACT FROM AUTHOR]

The red clay and loess‐paleosol sediments of the Xiaoshuizi and Halagu planation surfaces of the northeastern Tibetan Plateau (TP) provide insights into the response of paleo‐atmospheric circulation and surface processes to TP uplift and global climate changes. We present silicate Sr‐Nd isotope compositions and bulk sediment grain‐size parameters of the red clay and loess‐paleosol sequences, with the aim of reconstructing changes in the transporting wind systems and sediment source regions. The results indicate that the red clay on the planation surface was transported mainly by the westerlies from the Tarim Basin and the Qilian Mountains, while the loess‐paleosol sediments were transported mainly by the East Asian winter monsoon (EAWM) from the Badain Jaran Desert, Tengger Desert, and Qaidam Basin. These shifts in transport mechanism and source were likely related to major changes in the topography of the TP and the expansion of Northern Hemisphere glaciation since the Middle Pliocene. In addition, we reconstructed the evolution of the paleo‐atmospheric circulation from the Late Miocene to the Middle Pliocene. During the Late Miocene, both the paleo‐EAWM and East Asian summer monsoon (EASM) were weak, and westerly winds dominated the climate of the study area. During the Early Pliocene, both the paleo‐EAWM and EASM exerted an increasing influence on the study area. We ascribe the slight enhancement of the paleo‐EAWM to the gradual growth of the northern TP and the significant enhancement of the paleo‐EASM to global climate changes. Key Points: A major transition in the sediment source and transport dynamic of eolian sediments on the NE TP occurred between the red clay and the overlying loess depositsFrom the Pliocene onward, the paleo‐EAWM and EASM were intensified and exerted an increasing influence on the XSZ planation surfaceThe contribution of the CAO to the XSZ red clay showed an increasing trend from the Late Miocene to the Middle Pliocene [ABSTRACT FROM AUTHOR]

The increase in marine Li isotope composition (δ 7 Li, ∼9‰) since the Cenozoic is possibly related to continental chemical weathering associated with tectonic uplift (e.g., the Tibetan Plateau [TP]). However, the reasons for the spatiotemporal variations of δ 7 Li in the rivers flowing through the TP are still under debate, hindering the understanding of the changes in seawater δ 7 Li. Herein, various geological samples, i.e. river waters, river suspended particulate materials, river sediments, hot springs and silicate rocks, from the Yarlung Tsangpo River basin, the largest river system in the TP, have been analyzed to understand the source and isotopic fractionation of dissolved Li in rivers flowing through high-altitude and tectonic regions. The Yarlung Tsangpo River has an unusually high dissolved Li concentration ([Li] dis) (0.5–313 μg/L, mean 58.4 μg/L, n = 93) and low δ 7 Li dis values (+1.0‰–+14.7‰, mean +6.4‰, n = 92) compared with most river waters. These results can be explained by the input of geothermal water with extremely high [Li] dis (5.5–34.4 mg/L, mean 15.7 mg/L, n = 9) and low δ 7 Li dis (−1.7‰–+3.1‰, mean +1.0‰). Silicate weathering is probably responsible for elevated δ 7 Li dis in river water compared to geothermal water, but the binary mixture model results of silicate weathering and geothermal water do not support this speculation. Ongoing Li isotope fractionation between dissolved loads and secondary minerals has been suggested to be the main reason for the increased δ 7 Li dis in river water. Field study and adsorption experiment results support the view of continuous Li isotope fractionation in rivers. Physical erosion and chemical weathering processes that provide fresh secondary minerals to rivers as well as dissolved Li from geothermal water transported in rivers over long residence times promote Li isotope fractionation. Hence, with the emergence of a continental geothermal system, the tectonic activity may directly or indirectly induce the simultaneous increase in dissolved Li flux and δ 7 Li dis in rivers that eventually flow into the ocean. This can partially explain the increase in seawater δ 7 Li in the Late Cenozoic. • Li isotope composition is analyzed in the largest river system in Tibetan Plateau. • Dissolved load has very high [Li] dis , high Li/Na ratios, and low δ 7 Li dis values. • Geothermal water is responsible for the high [Li] dis and low δ 7 Li dis in river water. • Continental geothermal water increases in the Li flux and δ 7 Li dis in river estuaries. • The results help to explain the increase of seawater δ 7 Li in the late Cenozoic. [ABSTRACT FROM AUTHOR]

The uplift of the Tibetan Plateau (TP) is thought to be closely related to the global climate. For the Yarlung Tsangpo River (YTR), the largest river on the TP, the hot spring input is an important source of solutes. Without considering hot spring input will lead to an overestimation of chemical weathering and CO 2 consumption rate. Two sample series were collected in the basin before and after the monsoon season to evaluate the chemical weathering rates and controlling factors based on the hydrochemical composition. The results of improved forward model indicate that the highest contribution to the total cations comes from rock weathering (59%–99%, average value 93%), of which carbonate dissolution contributes the most (25%–79%, average value 61%), followed by evaporite dissolution (5%–42%, average value 19%) and silicate weathering (1%–29%, average value 13%). The hydrochemistry of tributaries in the middle reaches (Dogxung Tsangpo and Lhasa River) is affected by hot springs significantly, and the maximum contribution reaches 40%. The chemical weathering rates for the sub-basins show a sequence of Lhasa River > Dogxung Tsangpo > Nyang Qu, primarily controlled by lithology and runoff. For the mainstream above the YTR canyon and tributaries in the upper and middle reaches, chemical weathering is controlled by a transport limited regime, and the rest of the basin is governed by a kinetically limited regime. Overall, after deducting the hot spring input from the solutes, the silicate and carbonate weathering rates in the YTR Basin are 1.8 t/km2/yr and 6.3 t/km2/yr, respectively. The atmospheric CO 2 consumption by silicate and carbonate weathering in the YTR Basin accounts for ∼0.17% and ∼0.28% of global, respectively, on ∼0.21% of the global land surface area. The carbon sink caused by chemical weathering and its effect on global carbon cycle in the YTR Basin are insignificant. • Hot spring has high Na and Cl concentration and high Na/Cl ratio in the YTR basin. • Ignoring hot spring, chemical weathering and CO 2 consumption will be overestimated. • Chemical weathering rate is controlled by lithology, runoff, and physical erosion. • The carbon sink caused by chemical weathering in the YTR basin are insignificant. [ABSTRACT FROM AUTHOR]

Alpine treeline ecotones are harsh environment for tree establishment due to low temperature. Tree establishment at treelines requires favorable climate, suitable microsites, and viable seeds. But most researches have been addressed treeline microclimate and its effects on tree regeneration, the knowledge of seed quantity and quality and its controls on seedling recruitment were limited. We measured seed rain, soil seed bank, seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var. smithii (smith fir) along altitudinal gradient, with focus on treeline ecotone in the Sygera Mountains, southeastern Tibetan Plateau. Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate. Seed quantity and seedling recruitment were better in north-facing slope than in south slope. The treeline ecotone above 4200 m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment. The emergence and overwintering rates of transplanting seeds from 3600−3800 m also went down remarkably above 4200 m at north-facing slope. It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment. Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance. This study also provides evidence to support stable treeline position in southeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Thirty-five years ago, the idea of a young Qinghai-Tibetan Plateau was proposed based on a comprehensive investigation on the Qinghai-Tibetan Plateau. This hypothesis suggested that the plateau began to rise from a planation surface (relict surface) that was less than 1000 m high formed during the Miocene to Pliocene. The fast uplift, i.e., the Qingzang Movement, began since ~3.6 Ma, evidenced by massive molasse deposits around the plateau margin and the synchronous occurrence of faulted basins within the plateau. However, later studies challenged this idea and suggested earlier (8, 14 or 35 Ma) formation of the huge plateau topography. Here we reevaluate the Qingzang Movement on the basis of our previous results and in light of new studies in the recent decades. The plateau margin has been subjected to intensive incision by very large drainages and shows the landscape characteristics of an 'infant' stage of the geomorphological cycle. However, these drainages were not formed until 1.7-1.9 Ma; headwater erosion has not yet reached the hinterland of the plateau, so the interior of Tibet is free of significant erosion despite its lofty elevation, and remains an 'old stage' landform. If the mean erosion rate is equivalent to the sum of clastic and soluble discharges of the modern rivers draining the Tibetan Plateau, it should have been worn down to a lowland within 8.6 Ma, ignoring tectonic uplift and isostasy. The massive conglomerate around the plateau margin began to deposit at about 3.6 Ma, indicating an increased relief after that time. Furthermore, the Hipparion fauna sites were widely distributed, and elephants, giraffes, and rhinos were abundant in the Qaidam Basin until the early Pliocene. Cenozoic climate change alone is not able to account for the dense occurrence of Hipparion fauna, unless the paleo-elevation of Tibet was lowered. The rise of Tibet since the Qingzang Movement has had a great influence on the Asian interior aridification. [ABSTRACT FROM AUTHOR]

To investigate climate evolution during the Miocene, especially during the Middle Miocene climate transition on the northeastern Tibetan Plateau, stable oxygen and carbon isotopes of carbonates from a 288-m-thick lacustrine-fluvial sediment sequence covering the period from 17.1 to 6.1 Ma from Tianshui Basin, China, were analyzed. The relatively low stable oxygen isotope values indicate the prevalence of wet climate conditions during the period of 17.1-13.6 Ma, an interval corresponding to the well-known Middle Miocene Climate Optimum. The interval between 13.6 and 11.0 Ma (i.e., the late Middle Miocene) is marked by a progressive increase in the δO values, indicative of a decrease in precipitation, probably linked to the expansion of the East Antarctic Ice Sheet and global cooling since about 14 Ma. The climate in the study area continued to get drier as shown by the enrichment of the heavy oxygen isotope from 11 Ma. We attribute these stepwise climatic changes as revealed by our carbonate δO record from the northeastern Tibetan Plateau to the sustained global cooling that may have reduced moist transport to Central Asia, which in turn led to a permanent aridification. [ABSTRACT FROM AUTHOR]

The siliciclastic sediments of the uppermost section of 185 mcd (meters composite depth) from ODP Site 1146 on the northern continental slope of the South China Sea (SCS) were partitioned according to their sources using end-member modeling on grain-size data. The goal was to evaluate the evolution of the East Asian monsoon over the past 2 million years. The siliciclastic sediments were described as hybrids of four end-members, EM1, EM2, EM3, and EM4, with modal grain sizes of 8-22 μm, 2-8 μm, 31-125 μm, and 4-11 μm, respectively. EM1 and EM3 are interpreted as eolian dust and EM2 and EM4 as fluvial mud. The ratio of eolian dust to fluvial mud ((EM1+EM3)/(EM2+EM4)) is regarded as an indicator of the East Asian monsoon. The variation in this ratio not only shows periodical oscillations consistent with oxygen isotope stages, but also exhibits a phased increasing trend corresponding with the phased uplifts of the Tibetan Plateau, indicating that the evolution of the East Asian Monsoon was controlled not only by glacial-interglacial cycles, but also by the phased uplifts of the Tibetan Plateau during the Quaternary. [ABSTRACT FROM AUTHOR]

The Western Qinling orogenic belt marks the northeastern margin of the Tibetan Plateau. Its late Cenozoic orogenic history is recorded in an excellent sedimentary sequence exposed in the Tianshui sub-basin of the Longzhong basin. According to the magnetostratigraphic analysis from the Yaodian and Lamashan sections, we speculate that the late Cenozoic Tianshui basin accumulated lacustrine/floodplain deposits from ~14.8 to ~2.6 Ma. In addition, detrital apatite fission-track thermochronologic and paleocurrent data reveal that the detritus of the Tianshui basin mostly derived from the Western Qinling and that the youngest population age represents a ~14 Ma volcanic intrusion, which can be related to the lithospheric deformation and uplift of the Tibetan Plateau. Furthermore, two stages of variations in depositional facies and average accumulation rates were attributed to the pulse uplift and deformation of the Western Qinling at 9.2-7.4 and ~3.6 Ma. [ABSTRACT FROM AUTHOR]

An arsenate reductase (Car1) from the Bacteroidetes species Rufibacter tibetensis 1351T was isolated from the Tibetan Plateau. The strain exhibits resistance to arsenite [As(III)] and arsenate [As(V)] and reduces As(V) to As(III). Here we shed light on the mechanism of enzymatic reduction by Car1. AlphaFold2 structure prediction, active site energy minimization, and steady‐state kinetics of wild‐type and mutant enzymes give insight into the catalytic mechanism. Car1 is structurally related to calcineurin‐like metallophosphoesterases (MPPs). It functions as a binuclear metal hydrolase with limited phosphatase activity, particularly relying on the divalent metal Ni2+. As an As(V) reductase, it displays metal promiscuity and is coupled to the thioredoxin redox cycle, requiring the participation of two cysteine residues, Cys74 and Cys76. These findings suggest that Car1 evolved from a common ancestor of extant phosphatases by incorporating a redox function into an existing MPP catalytic site. Its proposed mechanism of arsenate reduction involves Cys74 initiating a nucleophilic attack on arsenate, leading to the formation of a covalent intermediate. Next, a nucleophilic attack of Cys76 leads to the release of As(III) and the formation of a surface‐exposed Cys74‐Cys76 disulfide, ready for reduction by thioredoxin. [ABSTRACT FROM AUTHOR]

The article presents a study which focuses on the regional tectonic tontrols of mineralization in Wuxuefeng Mountains and adjacent regions located in Hoh Xil, an isolated region in the Qinghai-Tibet Plateau in China. It is speculated that Hoh Xil tectonic belt developed a series of fault basins during the Himalayan period and tectogenesis occurred in this period resulted in the concentration of ore-bearing hydrothermal solution.

Assessing flux and primary sources of the atmospheric nitrogen (N) deposition with high spatial resolution remained challenging. The epilithic moss is considered a suitable biological monitor to explore N deposition. Our study presented a detailed analysis of flux and major source contributions of ammonium (NH 4 +) and nitrate (NO 3 −) deposition using N and δ15N signatures of epilithic moss collected densely from the Yangtze River basin. The results showed a more negative δ15N and higher N concentration of the moss in cropland and urban area than in forest and grassland of the basin. A gradient of the estimated N deposition (9.6–34.0 kg ha−1 yr−1) occurred from the Tibetan Plateau to lower reaches, with amount of NH 4 + was approximately three times higher than NO 3 − deposition. The contribution from volatilization to NH 4 + deposition (33.28 ± 8.10%) was less than the contribution from combustion (66.72 ± 8.10%), inconsistent with the traditional findings that N fertilizer and livestock waste are the principal sources of NH 3 emissions. Fossil fuel was the dominant sources of NO 3 − deposition, accounted for 70.22 ± 18.67%. From 2006 to 2019, the source contribution of N deposition in forest remained unchanged, while NH 3 volatilization and fossil fuel emitted NO x in urban areas have increased. Our findings highlighted the importance of combustion sources to N deposition in the Yangtze River basin. [Display omitted] • N deposition was mainly composed of NH 4 + instead of NO 3 − deposition. • Contribution of volatilization was less than combustion sources to NH 4 + deposition. • Fossil fuel was dominant sources to NO 3 − deposition. [ABSTRACT FROM AUTHOR]

Characterized by elevated pCO 2 levels and global warmth, the mid-Miocene climate is a valuable analogue for investigating how the East Asian Summer Monsoon (EASM) may evolve at different time scales. In this paper, we present a quantitative EASM precipitation record with a temporal resolution of ∼14 kyr during the mid-Miocene (∼15.97 to 13.64 Ma) by applying the probabilistic CREST (Climate Reconstruction Software) method to palynological records from the northeast part of the Tibetan Plateau. Reconstructed mid-Miocene EASM precipitation (∼860 mm) was almost twice that of today (∼450 mm), indicating much stronger EASM intensity. The reconstruction shows a gradual long-term decline on which was superimposed a stronger EASM period (∼15.97–14.54 Ma) followed by a relatively stable period (∼14.54–13.84 Ma) and a short period of reduced precipitation (∼13.84–13.64 Ma). The correspondence of EASM precipitation changes with the mid-Miocene climate optimum and west-east thermal gradients in equatorial Pacific suggests these two factors were the main driving forces for EASM evolution from ∼15.97 to 14.54 Ma, whereas the combined impact of global cooling and the northward shift of the Intertropical Convergence Zone is probably responsible for the slight decline of the EASM from ∼14.54 to 13.84 Ma. The weaker EASM between ∼13.84 and 13.64 Ma was most likely a response to the global significant cooling event Mi-3. On orbital time scales, the precipitation records exhibit a dominant ∼400 kyr periodicity, indicating EASM changes were mainly paced by eccentricity via the modulation of precessional amplitude, and the East Antarctic Ice Sheet variations were probably another important driving force. • A high-resolution, quantitative mid-Miocene EASM precipitation record was obtained. • The mean mid-Miocene MAP of ∼860 mm was almost 2 times that of today in NE TP. • Global temperature played key role in long-term mid-Miocene EASM evolution. • West-east thermal gradients in EP, ITCZ are also vital drivers in some intervals. • Orbitally, mid-Miocene EASM variability was dominated by eccentricity forcing. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The <2 μm fraction of Xijin loess includes both wind-blown detrital and in situ pedogenic components. • The pedogenic components are reversely correlated with the >40 μm fraction and global marine oxygen isotope. • The pedogenic components are superior to the magnetic susceptibility for high-resolution reconstruction of the Quaternary climate change in the western Chinese Loess Plateau. Abstract Chinese loess deposits preserve abundant information on the aridification of the Asian interior and Asian monsoon evolution during the Quaternary. Although substantial progress has been made in deciphering the paleoclimatic record of the thick loess deposits in the western Chinese Loess Plateau (CLP), the environmental significance of variations in the magnetic susceptibility (χ) and the ultrafine (<2 μm) grain-size is still unclear when compared with the central CLP. Here, we present high-resolution records of χ, frequency-dependent magnetic susceptibility (χ fd) and grain-size (<2 μm and >40 μm fractions) of the 416-m-long Xijin loess core from the Lanzhou Basin, northeastern Tibetan Plateau. Our results indicate that the <2 μm fraction of the core consists of both detrital dust and material produced during pedogenesis. An integrated analysis of records of χ, χ fd , grain-size (<2 μm) and clay minerals reveals that the pedogenic component of the <2 μm fraction is significantly anti-correlated with the >40 μm fraction and marine oxygen isotope record. Consequently, we conclude that the pedogenic component is a more accurate and sensitive indicator of weathering and soil formation than the χ record, and it is well suited to reconstructing high-resolution Quaternary climatic change in the western CLP. Furthermore, the proportion of the pedogenic component increased systematically over the past 2.2 million years, which may have been primarily caused by long-term global cooling since the Early Pleistocene together with the episodic uplift of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract A comprehensive understanding of the tectonic uplift history of the Tibetan Plateau (TP), a 2000 km wide region with a mean altitude of 4000–5000 m above sea level (asl), is crucial for interpreting global Cenozoic climate change, collisional tectonics and the evolution of the Asian climatic system. However, the timing, degree and extent of the uplift of the TP remain controversial. Here we report new palynological data from Early to Mid-Miocene lacustrine-swamp sediments in the Zeku Basin, northeastern TP. The palynoflora includes 68 palynotaxa at a family or genus level, comprising gymnosperms (16.2%), angiosperms (77.9%), pteridophytes (2.9%) and others (2.9%), and is suggestive of a mixed warm temperate forests of coniferous (e. g., Picea , Abies and Tsuga) and deciduous broadleaved trees (e. g., Ulmus / Zelkova , Betula and Quercus), with some subtropical elements (e. g., Carya and Liquidambar). Three periods of vegetation succession can be recognized from the Caergen Section, indicating a stepwise warming and drying trend from bottom to top. The local palaeoclimatic parameters obtained by applying the Coexistence Approach (CoA) to palynologic assemblages rendered mean annual temperature (MAT) values of 14.2–16.1 °C and mean annual precipitation (MAP) values of 797–1113 mm. This study departs from the traditional application of the CoA, relying on published determination of plant-climate relationships, rather than on data derived from the Paleoflora Database, which is currently not fully open-access. Based on the difference in temperatures between the Early to Mid-Miocene and the present day, and the temperature lapse rate, corrected to take account of Miocene global temperature differences, the estimated palaeoaltitude of the Zeku Basin during the Early to Mid-Miocene was 1200–1400 m asl. This palaeoaltitude estimate suggests that this basin has experienced about 2200–2500 m of uplift since the Early to Mid-Miocene. Findings therefore do not support previous hypotheses that the northeastern TP attained its present altitude before the Miocene. Highlights • We reconstructed Early Miocene vegetation and paleoclimatic changes in the Zeku Basin, based on palynoflora analyses. • Paleovegetation suggested the Zeku Basin's Early Miocene climate was much warmer and more humid than today's. • Local paleoclimatic parameters were quantified by applying the Coexistence Approach (CoA) to the palynologic assemblages. • The Early Miocene paleoaltitude of the Zeku Basin did not exceed 1500 m asl. [ABSTRACT FROM AUTHOR]

• A high resolution, quantitative late Miocene EASM rainfall record was obtained. • The EASM declined from ∼ 10.8 Ma to 7.6 Ma and strengthened from ∼ 7.6 Ma to 6.3 Ma. • Global cooling and paleotopography play key roles in long-term late Miocene EASM evolution. • Late Miocene EASM evolution was dominated by eccentricity forcing in NE TP. Understanding how the East Asian Summer Monsoon (EASM) evolves at different time scales affords a valuable opportunity to reveal the interactions between the hydrosphere, land, oceans and atmosphere. However, the pre-Quaternary evolutionary history and the driving forces that controlled its variability in response to different boundary conditions remain enigmatic. Here, we focus on the late Miocene (∼10.8 to 6.3 Ma) – a period of profound climatic and topographic changes in Asia – and present a quantitative reconstruction of EASM precipitation using the probabilistic CREST (Climate Reconstruction Software) method with a high temporal resolution pollen record from the Tianshui Basin in NE Tibetan Plateau (TP). Our new EASM precipitation record shows a slowly decreasing long-term trend during the period of ∼ 10.8–7.6 Ma, which was followed by a strengthening period from ∼ 7.6 to 6.3 Ma with a large amplitude of precipitation variability. We argue the decrease and increase periods of EASM precipitation were primarily response to late Miocene global cooling and TP uplift after ∼ 8 Ma, respectively. These results are supported by existing climate model simulations, wherein both global climate and paleotopography play key roles in regulating the long-term evolution of late Miocene EASM. On orbital time scales, the precipitation time series exhibit a dominant ∼ 410 kyr eccentricity periodicity, with lower (higher) values intervals corresponding to eccentricity minima (maximum). The synchronous phase of the precipitation and eccentricity records indicate that the eccentricity exerts a dominant influence on the EASM precipitation cycles via its modulation of the precessional amplitude, and the period expansion and contraction of Antarctic ice sheet (AIS) also probably play an important role during that time. Our quantitative late Miocene EASM precipitation records provide new insight into late Miocene EASM precipitation evolution and its relation with global climate, paleotopography, and cryosphere. [ABSTRACT FROM AUTHOR]

The long-term paleoclimate record in Asia and its comparison with the global climate record are of vital importance to understanding the coupling mechanisms between tectonics and climate. However, such long-term climate history in Asia revealed using the biomarker perspective has remained elusive. Here, we reconstruct the Neogene–Quaternary climatic history of the Northeastern (NE) Tibetan Plateau based on the integrated biomarker records of the Tianshui Basin and multiple published data from its surrounding localities. These comprehensive results indicate that the NE Tibetan Plateau did not have a consistent aridity trend until ∼4 Ma. Before 4 Ma, the Neogene climate was generally humid although this pattern was temporarily interrupted by two drying intervals at ∼14.5–∼12.5 and ∼10–∼6 Ma. Each of the two drying intervals and the permanent aridification trend roughly correspond to one phase of global cooling and/or uplift event of the Tibetan Plateau, highlighting the importance and complexity of tectonic–climate interactions. However, our study indicates increasing influence of tectonic uplift on the NE Tibetan Plateau climate since late Pliocene. [ABSTRACT FROM AUTHOR]

Abstract: The Miocene vegetation and climate history of western China remains unclear. However, widely-distributed Miocene sediments of the Tianshui Basin in the NE Tibetan Plateau provide a great potential for deciphering the Miocene vegetation and climate history of this region. This paper presents first sporopollen record from these sediments, covering the period from 17.1 to 6.1Ma. Sporopollen data reveal that temperate, warm-temperate broad-leaved forest of Quercus, Ulmus and Betula dominated the Tianshui region between 17.1 and 14.7Ma, which was replaced by forest or forest-steppe of Ulmus, Artemisia and Betula between 14.7 and 11.7Ma. After a return to a broad-leaved forest of Betula and Quercus during 11.7–8.5Ma, the forest decreased rapidly and was replaced mostly by steppe vegetation (mainly composed of Artemisia, Chenopodiaceae and Poaceae) after 8.5Ma. We interpret the observed vegetation changes as a result of global climate change, which is characterized by global cooling, development of Arctic ice-sheets and permanent El Niño state after the Middle Miocene Climatic Optimum. The rapid development of steppe at about 8.5Ma suggested a permanent drying of the Asian interior at this time, coinciding with the onset of the well-known Hipparion red clay deposition in North China. [Copyright &y& Elsevier]

There have been a number of suggested driving factors for Late Miocene expansion of C 4 plant coverage, including a decline in atmospheric CO 2 concentrations, enhanced aridity and seasonality, shifts in fire regimes, and tectonic uplift. In order to identify and discriminate the driving factors of vegetation changes, continuous records from the same section or basin are required. We present micro-charcoal-based fire history and C 4 vegetation abundance records spanning the Miocene from the Yanwan Section in the Tianshui Basin, on the northeastern Tibetan Plateau (NE TP). Based on statistical analyses, the micro-charcoal concentrations were relatively low before ~10 Ma, and after that time, there was an exponential increase. The C 4 plant abundance shows a strong increase after 8 Ma, about 2 million years after the micro-charcoal concentrations started increasing. We compare our records with published CO 2 , pollen, seasonality, herbivorous mammalian fossil and tectonic records from the same section and basin. We find that C 4 vegetation, fire intensities, and opening landscapes increased simultaneously after 8 Ma. This indicates that a fire-grassland feedback, initially driven by aridification, was the trigger for the Late Miocene expansion of C 4 plants. We speculate that herbivorous mammalian species may also have played a minor role. During the Miocene, there is a trend towards enhanced seasonality and a decline in atmospheric CO 2 concentrations, which were also necessary preconditions for the expansion. • A Miocene micro-charcoal record from northeastern Tibetan Plateau was obtained. • The Miocene fire history was reconstructed based on the micro-charcoal record. • The frequency and intensity of fire activity were correlated to drying. • The intensified fire activity during the late Miocene facilitated C 4 plant expansion. [ABSTRACT FROM AUTHOR]