Ecological stability during the LGM and the mid-Holocene in the Alpine Steppes of Tibet? Georg Miehe a, ⁎, Sabine Miehe a , Kerstin Bach a , Jürgen Kluge a , Karsten Wesche b , Yang Yongping c , Liu Jianquan d a Faculty of Geography, University of Marburg, Deutschhausstraße 10, D-35032 Marburg, Germany b Senckenberg Museum of Natural History Görlitz, PoB 300 154, D-02806 Goerlitz, Germany, Germany c Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, PR China d Institute of Molecular Ecology, MOE Key Laboratory of Arid and Grassland Ecology, School of Life Science, Lanzhou University, Lanzhou 730000, Gansu, PR China abstract article info Article history: Received 22 December 2010 Available online 13 July 2011 Keywords: Steppe Qinghai–Tibet Plateau Grazing Endemics LGM Mid-Holocene optimum Arid and Alpine ecosystems are known for extreme environmental changes during the Late Quaternary. We hypothesize that the world's largest Alpine arid ecosystem however, the Alpine Steppes of the Tibetan highlands, remained ecologically stable during the LGM and the mid-Holocene. This hypothesis is tested by distributional range of plant species, plant life forms and rate of endemism. The set of character species has a precipitation gradient between 50 and 350 mm/a, testifying for resilience to precipitation changes. 83% of the species have a wider vertical range than 1000 m used as a proxy for resilience to temperature changes. 30% of the species are endemic with 10 endemic genera, including plate-shaped cushions as a unique plant life form. These findings are in line with palaeo-ecological proxies (δ 18 O, pollen) allowing the assumption that Alpine Steppes persisted during the LGM with 3 to 4 K lower summer temperatures. During the mid-Holocene, forests could have replaced Alpine Steppes in the upper catchments of the Huang He, Yangtze, Mekong, Salween and Yarlung Zhangbo, but not in the interior basins of the north-western highlands, because the basins were then flooded, suppressing forests and supporting the environmental stability of this arid Alpine grassland biome. © 2011 University of Washington. Published by Elsevier Inc. All rights reserved. Introduction Quaternary biogeography has so far restricted ecologically stable areas to humid rugged escarpments of tropical mountains (Fjeldså, 1994). In contrast, arid and Alpine biomes are well known to be particularly sensitive to environmental changes (e.g. Körner, 1999; Kuper and Kröpelin, 2006). The Alpine Steppes of the Tibetan highlands are the world's largest Alpine arid biome. Therefore it can be assumed that this Alpine biome of the old world's desert belt underwent incisive environmental changes since the Last Glacial Maximum. The herewith connected radiation feedback effects to changing surface properties are of undisputed relevance for Global Change Scenarios because they act as a highly-elevated heat source for global circulation (cf. Shi et al., 2001; Duan and Wu, 2005). Supposing that palaeo scenarios are helpful in predicting the future we present here an ecology approach based on the present flora and vegetation of the northwestern Tibetan highlands. Palaeo-environmental scenarios are highly diverging. For the Last Glacial Maximum an ice-sheet is suggested (Kuhle, 2001) or isolated little extended mountain glaciations (Derbyshire et al., 1991; Lehmkuhl and Owen, 2005; Owen, 2009) and desert (Herzschuh et al., 2006; Herzschuh and Liu, 2007; Ni et al., 2010). In contrast to these scenarios, Petit-Maire and Bouysse (2002) suggest both steppe with continuous permafrost for the LGM and the mid-Holocene optimum, whereas forests are supposed during MIS 3 (Herzschuh and Liu, 2007), the mid-Holocene (Mosbrugger et al., 2007) or the IPPC A2 scenario (Böhner and Lehmkuhl, 2005). Our approach is based on 253 floristically complete vegetation records linked with climatic data thus providing the first data set of the altitudinal and hygric distribution ranges for the plant species and life forms of the Alpine Steppes, serving as a 1) temperature- and 2) humidity-related proxy for palaeo scenarios. Endemism plays a key role in validating palaeo scenarios (Fjeldså and Lovett, 1997; Dynesius and Jansson, 2000). The higher the number and rank of endemism is, the less extinguishing effects of climatic changes can be supposed. Therefore 3) we introduce here for the first time a LGM scenario based on endemic plant taxa and plant life forms of the Alpine Steppe biome. Additionally, 4) we use the analysis of plant life forms as well as a further proxy to test ecological stability hypothesizing that a high rate of specifically adapted plant life forms reflect the stability of environmental conditions. The main purpose of the floristic analyses therefore is to determine the percentage of endemic plants and Quaternary Research 76 (2011) 243–252 ⁎ Corresponding author. Fax: + 49 6421 2828950. E-mail address: miehe@staff.uni-marburg.de (G. Miehe). 0033-5894/$ – see front matter © 2011 University of Washington. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.yqres.2011.06.002 Contents lists available at ScienceDirect Quaternary Research journal homepage: www.elsevier.com/locate/yqres