Spatial and temporal patterns of variations in tree growth over the northeastern Tibetan Plateau during the period AD 1450-2001

Abstract

We analyzed spatial and temporal growth variations of Qilian Junipers over the northeastern Tibetan Plateau (TP) during the period 1450—2001 by applying the empirical orthogonal function (EOF) technique to seven moisture-sensitive tree ring-width chronologies. The first three principal components together explain 78.21% of the total variance. The first principal component (PC1) accounts for 51.58% of the total variance, and represents consistent tree-growth variations in the northeastern TP. The second EOF mode reveals an opposite structure for the southern and northern parts of the northeastern Tibetan Plateau, reflecting the effect of huge topography and associated atmospheric circulation on tree-growth anomalies. The third EOF mode represents an opposite structure for the eastern and western parts of the northeastern Tibetan Plateau, possibly indicating the influence of different branches of atmospheric circulation system in this area. The EOF analysis results of instrumental precipitation data resemble those derived from the seven regional chronologies, providing further support that tree growth is a good indicator of regional precipitation variations. According to the PC1, dry conditions occurred in AD 1450—1510, 1631—1739, 1765—1833, 1866—1883 and 1921—1947, whereas periods of relatively wet years are identified for AD 1511—1630, 1740—1764, 1834—1865, 1884—1920 and 1948—2001. During the past 550 years, 28 years with extreme regional growth depressions was identified. These ring-width extremes generally occurred in century-scale dry periods. The years 1467, 1484, 1641, 1721, and 1928 with extreme tree-growth reductions in the northeastern TP are coeval with severe drought events in eastern China. In addition, the dry intervals or extreme growth depressions generally coincided with cold periods in the northeastern TP and vice versa, implying that the probability of occurrence of wet events in the northeastern TP will be higher in the future under the ongoing global warming.

Tree ring-based annual streamflow reconstruction for the Heihe River in arid northwestern China from ad 575 and its implications for water resource management

“…When viewed alongside a temperature reconstruction for China (Yang et al, 2002; Figure 7c), it can be seen that high-flow conditions generally correspond to warm periods and low-flow conditions generally coincide with cold periods (an exception to this occurs around AD 800). This conclusion is consistent with our previous research, which concluded that dry intervals generally coincide with cold periods in the Qilian Mountains and vice versa (Qin et al, 2011; Yang et al, 2010).…”

Regional extreme climate events on the northeastern Tibetan Plateau since AD 1450 inferred from tree rings

“…QF is a northwestern site in our study area and shows a different pattern: correlations with precipitation for the previous June and July, as well as the current July are significant (pb 0.05). Based on the six chronologies, the spatial precipitation pattern was deduced using empirical orthogonal function (EOF) method (Yang et al, 2010b). The PC1 (the first principal component) shows consistent tree-growth variations and mostly reflects regional precipitation variations, and the PC2 shows a north-south opposite pattern in this area and reflects the effect of huge topography, and the PC3 shows a west-east opposite pattern in this area and reflects the influence of different branches of atmospheric circulation system.…”

Tree‐ring‐based temperature reconstruction for the Wolong Natural Reserve, western Sichuan Plateau of China

“…Those studies have enabled the successful reconstruction of the 3500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau . Key gaps in our understanding of climate change for the Tibetan Plateau still remain, primarily due to sparse coverage of tree-ring sample sites, despite intensified recent efforts (Cook et al, 2010;Yang et al, 2010Yang et al, , 2014. Improved knowledge of these efforts is still needed to create additional climate reconstructions on the Tibetan plateau for regions without sufficient tree-ring data, such as the western Sichuan Plateau.…”

“…Significant progress has been made recently in deriving annually resolved estimates of climatic fluctuations derived from tree-ring data in west Sichuan, and several tree-ring-based temperature reconstructions from various geographical sites of this region are available (Song et al, 2007;Qin et al, 2008;Wu et al, 2008;Li et al, 2011a;Yu et al, 2012). In comparison to the nearby Tibetan Plateau (Bräuning, 2001;Yang et al, 2003Yang et al, , 2009Yang et al, , 2010Zhang et al, 2003;Liang et al, 2008;Fan et al, 2010;Shao et al, 2010;He et al, 2013;Wang et al, 2014), however, the western Sichuan Plateau still receives little attention and only a limited set of tree-ring chronologies have been built Wu et al, 2008;Yu et al, 2012). Increased efforts to obtain new tree-ring archives from the western Sichuan Plateau are recommended to improve our understanding of the spatial and temporal details of climatic variations for this region.…”