Dawadi, B.

Eckstein, D.

Liang, Eryuan

Wang, Y.

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Shrub and tree growth in southeast Tibet: new information for dendroclimatology   E. Liang1, Y Wang1, B Dawadi1, 2, D Eckstein3  1 Institute of Tibetan Plateau Reserch, Chinese Academy of Science, Beijing, China 2 Central Department of Hydrology and Meteorology, Tribhuvan University, Kathmandu, Nepal 3 Department of Wood Science, University of Hamburg, Hamburg, Germany liangey@itpcas.ac.cn   High-elevation Tibetan Plateau provides an excellent platform to investigate responses of tree or shrub growth to extreme environments. However, little is known about their adaptation to climate change across a large latitudinal scale. Along two latitudinal transects across the eastern and central Tibetan Plateau, variations in growth of timberline trees and shrubs and their responses to climate were investigated. Along the eastern Tibetan Plateau, timberline tree growth was, in general, controlled by summer temperature as well as winter temperature. In particular, timberline tree growth was limited by summer minimum temperature, as reported for Juniperus przewalskii on the northeastern Tibetan Plateau, Picea likiangensis var. balfouriana in southern Qinghai, Abies georgei var. smithii, Picea likiangensis var. balfouriana and Rhododendron nivale in southeastern Tibet [1-4]. We should mention that the growth of rhododendron shows a climatic signal to those of Abies georgei var. smithii at timberline.   However, along another transect ranging from central Nepal via Nam Co Lake in central Tibet and the middle of Qaidam to the Qilian Mountains, the responses of tree growth to climate are different from those along the eastern Tibetan Plateau. Despite its high elevation (4000 m a.s.l.), the radial growth of Betula utilis shows strong signals (positive) of pre-monsoon precipitation, while March-May temperature is negatively correlated with tree growth due to the fact that high temperature can increase evaporation [5]. Unlike dwarf shrubs in the circum-arctic tundra ecosystem which positively respond to above-average temperature in the growing season, moisture turned out to be growth limiting for the dwarf shrub Juniperus pingii var. wilsonii, particularly the loss of moisture caused by high maximum temperatures in May–June [6]. Populus euphratica is a key species of Tugai forests in the central Asian deserts. In the Qaidam Basin, its growth was persistently positively correlated with temperature from previous September to current August although not significant throughout. The annual precipitation of around 41 mm can not exert any significant effect on Euphrates poplar growth in view of the extremely high annual evaporation of 2150 mm. Water in the nearby Tuolahai River is limited to the period from June-September. The positive correlation of tree growth with spring/early summer temperature indicates that the riparian Euphrates poplar trees may benefit from an increasing river runoff due to an advanced and accelerated snow and glacier melting [7]. In the central Qilian Mountains, the growth of Picea crassifolia was strongly limited by precipitation or moisture in May-June, being similar with Juniperus pingii var. wilsonii around the Nam Co Lake. In spite of the high elevation on the central Tibetan Plateau, the growth of trees or shrubs was primarily controlled by moisture. These studies provide useful information for understanding the adaptation of trees and shrubs to extreme environments.   [1] E. Liang, X. Shao, D. Eckstein, L. Huang and  X. Liu. For. Ecol. Manag. 236, 268 (2006) [2] E. Liang Y, X. Shao and N. Qin. Glob. Planet. Change 61, 313 (2008) [3] E. Liang and D. Eckstein. Ann. Bot. 104, 665 (2009)  [4] E. Liang, X. Shao and Y Xu. Theor Appl Clim. 98, 9 (2009) [5] B. Dawadi, E Liang, L. Tian, L.P. Devkota and T. Yao. Quat. Int. 283, 72 (2013) [6] E. Liang, X. Lu, R. Ren, X. Li, L. Zhu and D. Eckstein. Ann Bot 109, 721 (2012) [7] E. Liang, P. Ren, S. Zhang, X. Shao and D. Eckstein D. Trees 27, 447 (2013)   ---------------------------------- Key words: Tree ring, dendroecology, dendroclimatology, timberline, alpine shrub, latitudinal transects, climatic change 

Shrub and tree growth in southeast Tibet: new information for dendroclimatology

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Shrub and tree growth in southeast Tibet: new information for dendroclimatology

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