With 450,000 kmKobresia (syn. Carex) pygmaea dominated pastures in the eastern Tibetan highlands are the world's largest pastoral alpine ecosystem forming a durable turf cover at 3000-6000 m a.s.l. Kobresia's resilience and competitiveness is based on dwarf habit, predominantly below-ground allocation of photo assimilates, mixture of seed production and clonal growth, and high genetic diversity. Kobresia growth is co-limited by livestock-mediated nutrient withdrawal and, in the drier parts of the plateau, low rainfall during the short and cold growing season. Overstocking has caused pasture degradation and soil deterioration over most parts of the Tibetan highlands and is the basis for this man-made ecosystem. Natural autocyclic processes of turf destruction and soil erosion are initiated through polygonal turf cover cracking, and accelerated by soil-dwelling endemic small mammals in the absence of predators. The major consequences of vegetation cover deterioration include the release of large amounts of C, earlier diurnal formation of clouds, and decreased surface temperatures. These effects decrease the recovery potential of Kobresia pastures and make them more vulnerable to anthropogenic pressure and climate change. Traditional migratory rangeland management was sustainable over millennia, and possibly still offers the best strategy to conserve and possibly increase C stocks in the Kobresia turf.

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A detailed chronology has been obtained for a loess section at Yuanbao, situated at the northwestern edge of the Chinese Loess Plateau. The ages were obtained by the measurement of the optically stimulated luminescence (OSL) from coarse-silt-sized quartz grains. These ages showed that deposition at this site was continuous from 17 ka to the present, but that there was a decrease in the sedimentation rate from 0.60 to 0.10 m/ka at 13.489/1.15 ka, and this is proposed as the location of the Pleistocene/Holocene (P/H) boundary. A change in OSL sensitivity occurs at this depth. The depth and sharpness of this boundary is compared with the change obtained in low-field magnetic susceptibility (MS) measurements on 65 samples from the section. The MS changes gradually over 1.9 m and thus does not provide an easily discernible boundary. The new OSL-based sedimentation rates are used to calculate the mass accumulation rates for the Holocene and the end of the Pleistocene.Peer reviewe

The establishment and evolution of the Asian monsoons and arid interior have been linked to uplift of the Tibetan Plateau, retreat of the inland proto-Paratethys Sea and global cooling during the Cenozoic. However, the respective role of these driving mechanisms remains poorly constrained. This is partly due to a lack of continental records covering the key Eocene epoch marked by the onset of Tibetan Plateau uplift, proto-Paratethys Sea incursions and long-term global cooling. In this study, we reconstruct paleoenvironments in the Xining Basin, NE Tibet, to show a long-term drying of the Asian continental interior from the early Eocene to the Oligocene. Superimposed on this trend are three alternations between arid mudflat and wetter saline lake intervals, which are interpreted to reflect atmospheric moisture fluctuations in the basin. We date these fluctuations using magnetostratigraphy and the radiometric age of an intercalated tuff layer. The first saline lake interval is tentatively constrained to the late Paleocene-early Eocene. The other two are firmly dated between ∼46 Ma (top magnetochron C21n) and ∼41 Ma (base C18r) and between ∼40 Ma (base C18n) and ∼37 Ma (top C17n). Remarkably, these phases correlate in time with highstands of the proto-Paratethys Sea. This strongly suggests that these sea incursions enhanced westerly moisture supply as far inland as the Xining Basin. We conclude that the proto-Paratethys Sea constituted a key driver of Asian climate and should be considered in model and proxy interpretations.

The onset of modern central Asian atmospheric circulation is traditionally linked to the interplay of surface uplift of the Mongolian and Tibetan-Himalayan orogens, retreat of the Paratethys sea from central Asia and Cenozoic global cooling. Although the role of these players has not yet been unravelled, the vast dust deposits of central China support the presence of arid conditions and modern atmospheric pathways for the last 25 million years (Myr). Here, we present provenance data from older (42–33 Myr) dust deposits, at a time when the Tibetan Plateau was less developed, the Paratethys sea still present in central Asia and atmospheric pCO2 much higher. Our results show that dust sources and near-surface atmospheric circulation have changed little since at least 42 Myr. Our findings indicate that the locus of central Asian high pressures and concurrent aridity is a resilient feature only modulated by mountain building, global cooling and sea retreat.

Qinghai Lake is of significance for paleoclimate research because it lies in a pivotal region that is influenced by both the mid‐latitude Westerlies and the low‐latitude Asian summer monsoon (ASM). Most published lake level histories of Qinghai Lake are interpreted from drill‐core proxies. Here we combine geomorphic shoreline investigations with optically stimulated luminescence dating to constrain lake level variations since the last deglacial. The results indicate that two periods of highstands occurred during the last deglacial (∼16–14.9 and ∼12.6–12.2 ka), and that lake levels were 6–7.4 m higher than at present. Lake levels dropped abruptly during the Younger Dryas, and were generally low with frequent fluctuations during the early Holocene. Qinghai Lake reached its highest Holocene level, 9.1 m higher than modern, at ∼5 ka, and has regressed during the past 2 ka. We propose that high lake levels during the last deglacial were due mainly to melting glacial and permafrost waters, supplemented by enhanced Westerlies precipitation and decreased evaporation during Heinrich Event 1 (∼16–14.9 ka) and increased ASM rainfall during the Bølling–Alleröd warm period (∼14–12 ka). Lake level fluctuations during the Holocene were generally in accordance with moisture variations in the marginal monsoon zones of inland China.

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