Using seven well-replicated Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies developed at Zongwulong and Shalike Mts. in the northeastern part of the Qaidam Basin annual precipitation from previous July to current June in the recent 1000 years was reconstructed for Delingha. The reconstruction can capture 63.1% of precipitation variance and the equation was stable over time. For the reconstructed precipitation, wet periods occurred in AD1520-1633 and 1933-2001, whereas dry intervals in 1429-1519 and 1634-1741. In addition, the magnitude in precipitation variation was lower before 1430 with about 15 mm, but it increased to 30 mm during the period of 1430 to 1850. After 1850, the precipitation variance decreased again. In contrast to the increase in temperature, a decrease in annual precipitation was evident since the 1990s. The agreement in low-frequency variation between the reconstruction and the glacier accumulation and particulate content in Dunde ice cores during the recent several hundred years suggested that the precipitation reconstructed in this study was rather reliable, and represented a regional signal. This 1000-year reconstruction could benefit our understanding of climatic variation in decadal to century-scale in this region, and provide basic data to climate models and to prediction of future climate in the 21st century. Keywords: northeastern part of the Qaidam Basin, tree-ring width series of Qilian juniper, precipitation reconstruction in 1000 years.

Birch (Betula) trees and forests are found across much of the temperate and boreal zones of the Northern Hemisphere. Yet, despite being an ecologically significant genus, it is not well studied compared to other genera like Pinus, Picea, Larix, Juniperus, Quercus, or Fagus. In the Himalayas, Himalayan birch (Betula utilis) is a widespread broadleaf timberline species that survives in mountain rain shadows via access to water from snowmelt. Because precipitation in the Nepalese Himalayas decreases with increasing elevation, we hypothesized that the growth of birch at the upper timberlines between 3900 and 4150 m above sea level is primarily limited by moisture availability rather than by low temperature. To examine this assumption, a total of 292 increment cores from 211 birch trees at nine timberline sites were taken for dendroecological analysis. The synchronous occurrence of narrow rings and the high interseries correlations within and among sites evidenced a reliable cross‐dating and a common climatic signal in the tree‐ring width variations. From March to May, all nine tree‐ring‐width site chronologies showed a strong positive response to total precipitation and a less‐strong negative response to temperature. During the instrumental meteorological record (from 1960 to the present), years with a high percentage of locally missing rings coincided with dry and warm pre‐monsoon seasons. Moreover, periods of below‐average growth are in phase with well‐known drought events all over monsoon Asia, showing additional evidence that Himalayan birch growth at the upper timberlines is persistently limited by moisture availability. Our study describes the rare case of a drought‐induced alpine timberline that is comprised of a broadleaf tree species.

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