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We present radiometric 81Kr dating results for ice samples collected at the outlets of the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau. This first application of 81Kr dating on midlatitude glacier ice was made possible by recent advances in Atom Trap Trace Analysis, particularly a reduction in the required sample size down to 1 μL STP of krypton. Eight ice blocks were sampled from the bottom of the glacier at three different sites along the southern edges. The 81Kr data yield upper age limits in the range of 15–74 ka (90% confidence level). This is an order of magnitude lower than the ages exceeding 500 ka which the previous 36Cl data suggest for the bottom of the Guliya ice core. It is also significantly lower than the widely used chronology up to 110 ka established for the upper part of the core based on ice δ18O. Plain Language Summary: The oldest ice that has ever been found outside of the polar regions is from the bottom of the Guliya ice cap in the western Kunlun mountains on the Tibetan Plateau. Previous dating results from the Guliya ice core, drilled in 1992, indicate that the bottom ice is more than 500,000 years old. However, due to the lack of alternative dating methods in that time range, the age scale of the Guliya ice core has so far not been checked independently. In this work we present dating results for the Guliya ice cap with a new dating method for ice based on the radioactive decay of the extremely rare krypton isotope 81Kr. Eight ice samples were retrieved at three different margin sites of the Guliya ice cap, where the old bottom ice is expected to resurface. The 81Kr measurements for these samples yield upper age limits in the range of 15–74 ka, which is significantly lower than the previous dating results for the ice core. Key Points: Radiometric 81Kr dating of bottom ice from the Guliya ice cap is presented81Kr data yield upper age limits in the range of 15–74 ka81Kr results are difficult to reconcile with ages previously obtained for the Guliya ice core based on 36Cl and δ18O [ABSTRACT FROM AUTHOR]

Against the background of global climate warming, the relationship between plant communities in high-cold ecosystems and environmental gradients has attracted much attention. We investigated the relationship between the distribution of plant communities and environmental factors in a semi-arid region of the Qinghai-Tibet Plateau. We analyzed the effects of environmental factors on the distribution of plant communities using two-way indicator species analysis and canonical correspondence analysis. The most important factor explaining the distribution of plant communities was the depth of the active layer of permafrost (denoted as PF), followed by soil water content at 40-cm soil depth. There was a strong correlation between these two factors. With changes in the PF, the dominant species in plant communities showed an obvious transition. The indices of species richness and species diversity decreased markedly with increasing PF, whereas biomass and vegetation coverage showed weaker responses to changes in the PF. The distribution structure for plant communities in this area mainly results from changes in the PF. Furthermore, the PF has remarkable and important effects on the characteristics of the plant community. [ABSTRACT FROM AUTHOR]