Ecological stability during the LGM and the mid-Holocene in the Alpine Steppes of Tibet?

Abstract

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 (δ18O, 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.

Vascular plants at extreme elevations in eastern Ladakh, northwest Himalayas

“…The species in this study region are not threatened equally as there are great differences in their ecological tolerance. A similar conclusion was made for alpine communities of the Tibetan highlands by Miehe et al (2011), who noted the wide thermal and hygric ranges of many key species and considered this arid alpine biome resilient to climatic changes. In conclusion, these findings, combined with the presence of 12…”

Cosmogenic 10Be surface exposure dating and glacier reconstruction for the Last Glacial Maximum in the Quemuqu Valley, western Nyainqentanglha Mountains, south Tibet

“…For example, Miehe et al . () proposed that alpine steppes persisted in the LGM with 3–4 °C depression in summer temperature, based on biogeographic data from the alpine steppes of the TP. Using biogeographic and phylogenetic data from Trechus and juniper tree haplotypes, Schmidt et al .…”

Last Glacial climate reconstruction by exploring glacier sensitivity to climate on the southeastern slope of the western Nyaiqentanglha Shan, Tibetan Plateau

“…During the Late Quaternary, the western Nyaiqentanglha Shan was intensively glaciated, and many moraines were formed and preserved in the glaciated valleys (Li and others, 1986;Owen and others, 2005;Chevalier and others, 2011;Dong and others, 2014). Two sets of moraines are present near valley mouths on the southeastern slope of the western Nyaiqentanglha Shan (Fig.…”

“…Using the monthly averaged temperatures at the Dangxiong Station and the linear monthly temperature lapse rates (Table 2), we calculate the monthly temperature grids in the model domain. When modeling the glacier mass balance on the western Nyainqentanglha Shan, both Caidong and Sorteberg (2010) and Zhao and others (2014) adopted a precipitation-elevation gradient of 5%/100 m from the observations of Li and others (1986) in the region. Here we use the precipitation-elevation gradient of 5%/100 m and the monthly precipitations at Dangxiong station to calculate the monthly precipitation grids for the model domain.…”