Atlas of paleoclimates and paleoenvironments of the Northern Hemisphere: Late Pleistocene, Holocene

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How old is pastoralism in Tibet? An ecological approach to the making of a Tibetan landscape

How old is the human footprint in the world's largest alpine ecosystem? A review of multiproxy records from the Tibetan Plateau from the ecologists' viewpoint

We use a data set of 35 surface pollen samples from lake sediments, moss polsters and top soils on the north-eastern Tibetan Plateau to explore the relationship between modern pollen assemblages and contemporary vegetation patterns. The surface pollen transect spanned four vegetation zones––alpine meadow, steppe, steppe desert and desert––under different climatic/elevational conditions. Relative representation (Rrel) values and Principal Components Analysis (PCA) were used to determine the relationships between modern pollen and vegetation and regional climate gradients. The results show that the main vegetation zones along the regional and elevational transects can be distinguished by their modern pollen spectra. Relative to Poaceae, a high representation of Artemisia, Nitraria and Chenopodiaceae was found, while Cyperaceae and Gentiana showed values in the middle range, and Ranunculaceae, Asteraceae, Ephedra and Fabaceae had low relative representation values. PCA results indicate a high correlation between the biogeoclimatic zones and annual precipitation and annual temperature and July temperature. The Artemisia/Chenopodiaceae ratio and the Artemisia/Cyperaceae ratio are useful tools for qualitative and semi-quantitative palaeoenvironmental reconstruction on the north-eastern Tibetan Plateau. Surface lake sediments are found to have different palynomorph spectra from moss cushion and soil samples, reflecting the larger pollen source area in the contemporary vegetation for lakes.

Modern pollen representation of source vegetation in the Qaidam Basin and surrounding mountains, north-eastern Tibetan Plateau

The history of late Holocene glacier fluctuations in eastern Tibet was studied by determining the ages of trees growing on glacier deposits. Maximum tree ages yield minimum ages of AD 1760 and 1780 for moraine formation at the maximum extent of the ‘Little Ice Age’ glacier advances in two glacier forefields. Subsequent moraines could be dated to the beginning of the nineteenth and the beginning of the twentieth century. Larch trees from a third glacier forefield in southeastern Tibet show evidence of glacier activity from 1580 to 1590, from the end of the eighteenth to the beginning of the nineteenth century and from 1860 to 1880. One glacier at Mt Gyalaperi recently advanced in both 1951 and 1987. Periods of glacier advances can partly be correlated with periods of growth reductions in chronologies of total ring width and maximum latewood density derived from trees growing on slopes above the glacier valleys. Correlation functions with meteorological data suggest that maximum latewood density of subalpin...

Tree-ring evidence of ‘Little Ice Age’ glacier advances in southern Tibet

The basis for valid paleoecological investigations is a profound know ledge of the evolution of climate. Moreover, paleoclimatological studies enable us — perhaps — to draw conclusions as to the future development of climate, provided the reasons for and the possible periodicity of changes in climate during the past are understood. So paleoclimatology has become an intensively investigated discipline. Of course it should be known whether the solar irradiance is variable or not (WILLSON et al. 1981, KERR 1982), and tectonic uplifting or down- warping may play an important role in the evaluation of possible climatic influences on the biosphere. So it is worthwhile to note that according to VOZOVIK (1976) the mean elevation of the watersheds in the Central Caucasus Mts. increased from late Pliocene times (Lower Akchagyl: 2000 m), and from the very beginning of the Pleistocene (Upper Akchagyl, 2700 m) to the Middle Pleistocene (end of the Apsheron, 3500 m), to 4400 m in recent times. The same topic has been analyzed by ALESHINSKAYA et al. (1976 a,b) in regard of the Tien Shan Mts., in connection with changes in synchronous paleoecological conditions. Other important boundary conditions are the surface areas of the inland ice-masses (for the last glaciation see DENTON and HUGHES 1981; for the whole of the Pleistocene, the continental shelf areas included: GROSVALt) 1983), as well as the changes in the CO2-content of the global atmosphere in an interglacial-glacial-interglacial cycle.

https://link.springer.com/content/pdf/10.1007%2F978-3-642-48633-3_20.pdf

h.c. Burkhard Frenzel

Papers

The History of Flora and Vegetation During the Quaternary