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The upper Yellow River valley in the northeastern Qinghai–Tibetan Plateau (QTP) is an important corridor for prehistoric migration to the hinterland plateau. However, most studies have focused on the Neolithic Age, with limited evidence for earlier periods. The Shalongka (SLK) site on the northeastern QTP spans the Epipaleolithic to Bronze Age and contains cultural deposits, so provides a good basis for unraveling the evolutionary history of the human-land relationship. In this study, we sampled the 420-cm-thick section T1406E at the SLK site and undertook lithologic stratigraphic description and analysis of grain size, redness, magnetic susceptibility, geochemical elements, pollen and charcoal. Dating control was provided by accelerated mass spectrometry 14C and optically stimulated luminescence methods. Results show that SLK site was affected by the local fluvial sedimentary environment. The absolute dating results of the SLK site have revealed that humans occupied the site during the Epipaleolithic (8.5–7.3 cal ka BP), Yangshao culture (5.9–5.1 ka) and Qijia Culture (4.1–3.9 cal ka BP). Pollen analysis showed that the humans lived in a landscape that was predominated by forest-steppe. Consolidating with multidisciplinary evidence, we learned that Epipaleolithic sites were occupied by microlithic hunter-gatherers and comprised by relatively fixed seasonal central campsites, and their mobility was significantly decreased from the early to late period. Subsequently, farmers of the Yangshao culture migrated from the low elevation (Chinese Loess Plateau) to the upper Yellow River valleys on the QTP and founded the earliest settlement villages (~5.9 ka) on the QTP. People of the Qijia culture adopted diversified survival strategies under the settled lifestyle. In all, we infered that SLK site may play an important role in the communication and integration between different people and cultures. [ABSTRACT FROM AUTHOR]

• New dataset of modern fungal spores on the Tibetan Plateau. • Fungal spore assemblages indicative of vegetation communities. • Eight reliable dung-indicator fungal spore-types identified. • Total concentration of coprophilous fungi can be used to diagnose grazing pressure. • Vital modern analog data for fossil fungal spore studies on the Tibetan Plateau. Recent research on the Qinghai-Tibetan Plateau (QTP) has focused on the human-land relationship and its evolution through time; fossil fungal spores are promising proxies for recovering information on paleoecological changes and ancient anthropogenic activity. Modern analog fungal spore datasets are crucial for accurate paleoecological interpretation of fossil fungal spores, however, these are lacking for the QTP. In this study, we analyzed 130 modern samples of topsoil and herbivore dung from eastern QTP to assess fungal assemblages in different habitats and vegetational communities. The results indicate that fungal spores in different types of domestic herbivore dung samples are quite similar and dominated by Sporormiella spp., Urocystis sp., Sordaria spp., Pleospora spp., QTPF-01 (Qinghai-Tibetan Plateau Fungi). Topsoil samples, collected from different vegetation zones, show more variation. Savoryella spp. is the dominant taxon in cropland samples, while Meliola spp. and Coniochaeta spp. are well associated with alpine forest environments. Fungal spore assemblages in alpine shrub, alpine meadow, and alpine steppe are mostly dominated by Glomus spp., together with Savoryella spp., Valsaria sp., Entorrhiza spp., and QTPF-03. Comparison of fungal assemblages in herbivore dung and topsoil samples suggests that Sporormiella spp., Urocystis sp., Sordaria spp., Pleospora spp., QTPF-01, Podospora spp., Delitschia A., and QTPF-07 are the most reliable dung indicators. The total concentration of coprophilous fungal spores is sensitive to grazing pressure and can be used to diagnose the intensity of pastoralism on the QTP. Our work provides vital modern analog data for fossil fungal spore studies on the QTP. [ABSTRACT FROM AUTHOR]

• Wet climate prevailed during the middle Holocene. • Grazing activities affected the composition of plant communities since 3.5 ka. • Agricultural cultivation intensified since 2.2 ka in Qinghai Lake Basin. The Qinghai Lake basin (QLB) is an ideal region to explore the interaction between climate change, vegetation evolution, and anthropogenic activities during the Holocene epoch. This is due to the basin's particular sensitivity to global climate changes along with its densely distributed archeological sites, present since the last deglaciation. To date, a full understanding of the lakeshore terrestrial fossil pollen record is lacking and few studies have explored the human signals in the pollen spectra of the northeast Qinghai-Tibetan Plateau. Here, we present fossil pollen and charcoal records from over 8500 years ago obtained from a high resolution-dated aeolian section in the southeastern margin of the QLB. These results show that the pollen spectra are dominated by herbaceous and shrubby pollen taxa, while arboreal pollen taxa are rare. From approximately 8.5–7.2 ka, Artemisia - and Poaceae- dominated temperate steppe developed in the region, suggesting relatively warm and dry climatic conditions. Comparatively, regional vegetation shifted to Cyperaceae-dominated alpine meadow from approximately 7.2–3.4 ka, which reflected cooler and wetter climatic conditions. Thereafter, the amount of Asteraceae, Artemisia , and Chenopodiaceae notably increased from approximately 3.4–1.8 ka, suggesting that temperate steppe dominated the region under relative drier climate. Noticeably, an interval between approximately 1.8–0.6 ka was characterized by an increase of Hippophae pollen, reflecting a comparatively warmer episode; alpine meadow then reoccupied the region since approximately 0.6 ka. Combining the variations of charcoal concentrations (20–50 µm and >50 µm) with human-related pollen taxa (Aster -type, Chenopodiaceae, Plantago , and Hordeum -type), we inferred that prehistoric humans were extensively using fire for hunting and subsistence during 7.2–3.5 ka, which strongly impacted the local vegetation during the middle Holocene; regional grazing activities intensified and caused grassland degradation since approximately 3.5 ka, which manifested with a significant increase in Aster -type and Chenopodiaceae pollen. After this period, Hordeum -type pollen as well as charcoal concentration of >50 µm increased significantly since approximately 2.2 ka, suggesting an intensifying agricultural cultivation in the region. [ABSTRACT FROM AUTHOR]

Salt lakes on the Qinghai-Tibetan Plateau (QTP) are remarkable for Li-rich brines. Along with the surging demand of Li, the Li-rich brines in salt lakes on the QTP are of great importance for China's Li supply. Previous studies reported the geological, geographical, geochemical signatures of numerous salt lakes on the QTP; however, conclusive work and the internal relationships among the hydrochemistry, distribution and geological setting of Li-rich salt lakes are still inadequate. In this study, major and trace (Li, B) ionic compositions of 74 Li-rich salt lakes on the QTP were reviewed. The Li-rich brines cover various hydrochemical types (carbonate, sodium sulfate, magnesium sulfate, and chloride types) and present horizontal zoning from the southwest to the northeast along with the stronger aridity. The Li concentrations and Mg/Li ratios in these salt lakes range from 23 to 2895 mg/L, 0.0 to 1549.4, respectively. The distribution of these salt lakes is close to the major suture zones. Geothermal water is proposed to be the dominant source of Li in the investigated salt lakes, while weathering of Li-bearing sediments and igneous rocks, and brine migration provide a minor part of Li. Four factors (sufficient Li sources, arid climate, endorheic basin and time) should be considered for the formation of Li-rich brines in salt lakes on the QTP. [ABSTRACT FROM AUTHOR]

The Rb/Sr ratio is an important indicator of weathering intensity in both lacustrine and loess sediments because of the inertness of the Rb element and the activity of the Sr element during the weathering process. Generally, the environmental interpretation of Rb/Sr ratio proxy in lacustrine sediments is contrary to that in the loess-paleosol sequence: it shows a negative correlation between the Rb/Sr ratio and chemical weathering intensity in lacustrine sediments, but shows a positive pattern in the loess-paleosol sequence. However, in this study, we investigated the Rb/Sr ratio of a lacustrine core (ISL1A) from Qarhan Salt Lake (QSL) in eastern Qaidam Basin (QB), and found the Rb/Sr ratio indicated a positive correlation with regional precipitation. This pattern is similar to that of the loess-paleosol sequence rather than the lacustrine sediments. According to grain size statistics and the comparison of Rb/Sr ratio with other proxies (halite and calcite contents, grain size, and F values of grain size discriminant function), we preliminarily proposed that the abundant input of aeolian materials, transported by the strong northwest wind, cause these unexpected Rb/Sr ratio fluctuations in the ISL1A core. The comparison between background Rb and Sr elemental data of relevant regions and these of the core indicated the aeolian origin of Rb/Sr ratio in the lacustrine sediments, and the Rb and Sr elemental composition probably represents the geochemical characteristics of the dust source area. The Sr-Nd isotopic composition indicates that the erosive paleo-lake strata in western QB could be the origin of aeolian materials in lacustrine sediments in the QSL, as well as the loess deposits in Dulan County, Qinghai Lake Basin, and Xining Basin. The regional correlation between proxies of the ISL1A core and other aeolian records also supports the aeolian origin of detrital input in the core. Finally, we propose that the origin of the detrital input must be distinguished before the Rb/Sr ratio is applied as a weathering intensity proxy in lacustrine sediments, especially in arid basins. [ABSTRACT FROM AUTHOR]