Climate–growth relationships of Qilian juniper Sabina przewalskii in the Anyemaqen Mountains, Tibet

Abstract

Climate-growth relationships were investigated for 5 mountain slopes of the Anyemaqen Mountains on the northeastern Tibetan Plateau, using a tree-ring width network indicating the chronologies of 20 Qilian junipers Sabina przewalskii. Tree growth is mainly controlled by regional climate conditions, which are modulated by altitudinal factors. The tree growth patterns in this region were classified asccording to a west -east orientation. Temperature and precipitation from August to October of the previous year and May of the current year are the major limiting factors for most chronologies, as indicated by simple correlation analysis. In general, precipitation plays a more important role in governing tree growth than temperature, and tree rings in the east are more sensitive to precipitation than those in the west. Differences in the climate-growth relationship may be caused by varying climate conditions between the western and eastern Anyemaqen Mountains. KEY WORDS: Tree ring · RPCA · Climate-growth relationship · Qilian juniper · Anyemaqen MountainsResale or republication not permitted without written consent of the publisher Clim Res 41: 31-40, 2010 In the region a continental climate dominates, with a short summer and long and cold winters. The mean annual temperature is from 0.5 to 3.9°C, and the warmest mean monthly temperature is from 11.0 to 14.2°C. In the study region annual precipitation is between 450 and 620 mm, with from 56 to 62% of the annual precipitation falling during summer, possibly an indicator of a monsoonal climate (Wang 1988). Temperature and precipitation in the eastern Anyemaqen Mountains are higher than in the western part of the range, i.e. by about 4°C in temperature and 18% in relative humidity.Qilian juniper, one of the dominant species growing on the northeastern TP, is a cold-and drought-tolerant tree species. Pure Qilian juniper forests are mainly distributed on the southern slopes of the Anyemaqen Mountains, at altitudes ranging from 3400 to 3800 m a.s.l. (Fig. 1B). These are the southernmost and highest distribution limits of Qilian junipers (Qinghai Forest Editorial Committee 1993) and are areas sensitive to climate change. (Fig. 1). There were 3 to 5 sampling sites on each sample slope. At each sampling site, 20 to 30 of the largest and presumably oldest trees were sampled. We selected trees that we suspected would be the most influenced by climatic signals, avoiding trees where there had been local disturbances or where trees were too close together and were therefore competing for resources. One or two cores per tree were extracted at approximately breast height (1.3 m) ( Table 1). Chronology developmentAll cores were mounted on slotted wooden boards and polished with different grades of sandpaper (a progressively finer grit), until annual rings could be easily distinguished (Stokes & Smiley 1968). The ring widths were measured using a Velmex measuring system to 0.001 mm. All tree-ring sequences measured were quality checked with the computer program COFECHA ...

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