Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

Abstract

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes.

A 3,500-year tree-ring record of annual precipitation on the northeastern Tibetan Plateau

“…The interpretation of a dominant moisture control on tree growth in this region is supported by a number of previous studies (16,(19)(20)(21)(22). Interpreting local tree growth for this species as a predominant response to interannual variability of prior July to current-year June precipitation is consistent with the results of refs.…”

Growth–climate relationships along an elevation gradient on a southeast-facing mountain slope in the semi-arid eastern Qaidam Basin, northeastern Tibetan Plateau

“…Our results confirmed previous studies in this region that strong precipitation signals can be found in tree-ring data obtained from sites close to the upper treelines Liu et al 2006;Qin et al 2013). For example, in Qin et al (2013), correlations with previous July- Fig.…”

“…However, they did not observe persistently enhanced relationships to temperature at the upper treeline sites. This pattern was confirmed by a recent study by Qin et al (2013) in Delingha, approximately 130 km to the northwest of Dulan, who found that growth of Qilian junipers sampled at the upper treeline (4020 m) was still mainly controlled by precipitation. Peng et al (2008) also found that precipitation was an important limiting factor for upper treeline sites located on the drier west-facing slopes in the A'nyêmaqên Mountains.…”

“…Table 1 summarizes the general characteristics of the ten chronologies for the full chronologies (Table 1b) and chronology statistics for the common period 1801-2010 (Table 1c). Comparing our chronologies with other Qilian juniper chronologies in this region (e.g., Zhang et al 2003;Sheppard et al 2004;Yin et al 2008;Zhu et al 2008;Liu et al 2009;Gao et al 2013;Qin et al 2013;Yang et al 2013), both the mean sensitivity and signal-to-noise ratio (SNR) values are in the mid-to upper-range of the reported values, while the between-tree rbar and all-series rbar values are somewhat lower than those reported in other studies (Table 1c). Also lower are the percentages of variance explained by PC1, probably as a result of our sampling strategy of coring trees of all ages (Table 1c).…”

“…Based on the findings by Liu et al (2006) and Qin et al (2013), it is expected that the tree-ring series sampled at different elevations have strong covariation patterns at this site. To discern the distribution of variances among the interrelated series, rotated principal component analysis (RPCA) was used to identify orthogonal modes of variation patterns representing tree growth patterns unique at different elevations, in a way similar to applications of RPCA in climate regionalization (Richman 1986;White et al 1991).…”