TY - JOUR A1 - Herzschuh, Ulrike A1 - Birks, H. John B. A1 - Liu, Xingqi A1 - Kubatzki, Claudia A1 - Lohmann, Gerrit T1 - Retracted: What caused the mid-Holocene forest decline on the eastern Tibet-Qinghai Plateau? N2 - Aim: Atmospheric CO2 concentrations depend, in part, on the amount of biomass locked up in terrestrial vegetation. Information on the causes of a broad-scale vegetation transition and associated loss of biomass is thus of critical interest for understanding global palaeoclimatic changes. Pollen records from the north-eastern Tibet-Qinghai Plateau reveal a dramatic and extensive forest decline beginning c. 6000 cal. yr bp. The aim of this study is to elucidate the causes of this regional-scale change from high-biomass forest to low-biomass steppe on the Tibet-Qinghai Plateau during the second half of the Holocene. Location: Our study focuses on the north-eastern Tibet-Qinghai Plateau. Stratigraphical data used are from Qinghai Lake (3200 m a.s.l., 36 degrees 32'-37 degrees 15' N, 99 degrees 36'-100 degrees 47' E). Methods: We apply a modern pollen-precipitation transfer function from the eastern and north-eastern Tibet-Qinghai Plateau to fossil pollen spectra from Qinghai Lake to reconstruct annual precipitation changes during the Holocene. The reconstructions are compared to a stable oxygen-isotope record from the same sediment core and to results from two transient climate model simulations. Results: The pollen-based precipitation reconstruction covering the Holocene parallels moisture changes inferred from the stable oxygen-isotope record. Furthermore, these results are in close agreement with simulated model-based past annual precipitation changes. Main conclusions: In the light of these data and the model results, we conclude that it is not necessary to attribute the broad-scale forest decline to human activity. Climate change as a result of changes in the intensity of the East Asian Summer Monsoon in the mid-Holocene is the most parsimonious explanation for the widespread forest decline on the Tibet-Qinghai Plateau. Moreover, climate feedback from a reduced forest cover accentuates increasingly drier conditions in the area, indicating complex vegetation-climate interactions during this major ecological change. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=1466-822X U6 - https://doi.org/10.1111/j.1466-8238.2009.00501.x SN - 1466-822X ER - TY - JOUR A1 - Wang, Yongbo A1 - Liu, Xingqi A1 - Herzschuh, Ulrike A1 - Yang, Xiangdong A1 - Birks, H. John B. A1 - Zhang, Enlou A1 - Tong, Guobang T1 - Temporally changing drivers for late-Holocene vegetation changes on the northern Tibetan Plateau JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Fossil pollen records have been widely used as indicators of past changes in vegetation and variations in climate. The driving mechanisms behind these vegetation changes have, however, remained unclear. In order to evaluate vegetation changes that have occurred in the northern part of the Tibetan Plateau and the possible drivers behind these changes, we have applied a moving-window Redundancy Analysis (RDA) to high resolution (10-15 years) pollen and sedimentary data from Lake Kusai covering the last 3770 years. Our analyses reveal frequent fluctuations in the relative abundances of alpine steppe and alpine desert components. The sedimentary proxies (including total organic carbon content, total inorganic carbon content, and "end-member" indices from grain-size analyses) that explain statistically some of the changes in the pollen assemblage vary significantly with time, most probably reflecting multiple underlying driving processes. Climate appears to have had an important influence on vegetation changes when conditions were relatively wet and stable. However, a gradual decrease in vegetation cover was identified after 1500 cal a BP, after which the vegetation appears to have been affected more by extreme events such as dust-storms or fluvial erosion than by general climatic trends. Furthermore, pollen spectra over the last 600 years are shown by Procrustes analysis to be statistically different from those recovered from older samples, which we attribute to increased human impact that resulted in unprecedented changes to the vegetation composition. Overall, changes in vegetation and climate on the northern part of the Tibetan Plateau appear to have roughly followed the evolution of the Asian Summer Monsoon. After taking into account the highly significant millennial (1512 years) periodicity revealed by time-series analysis, the regional vegetation and climate changes also show variations that appear to match variations in the mid-latitude westerlies. KW - Asian Summer Monsoon KW - Late-Holocene KW - Pollen KW - Procrustes analysis KW - Redundancy analysis KW - Tibetan Plateau KW - Vegetation KW - Westerlies Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.06.022 SN - 0031-0182 VL - 353 IS - 8 SP - 10 EP - 20 PB - Elsevier CY - Amsterdam ER -