Age- and region-related response of radial growth to climate warming and a warming hiatus

Abstract

For trees in the east from 1980 to 2001 and after 2001 and trees in the west from 1980 to 2001, younger trees responded to precipitation and older trees responded to temperature more strongly. Global warming has now persisted for more than 100 years, but an unusual pause in this rising temperature began in the 2000s, at least for the climate of China. This shift presents an unusual opportunity to investigate possible differences in the radial growth of trees during a climate warming period (1980–2001) and the warming hiatus (after 2001) for different age groups under different moisture conditions. We sampled a total of 304 tree-ring cores of Picea crassifolia in the eastern and western Qilian Mountains, which were divided into four age groups for study. The results indicate that trees of the young group and half-mature group in the wetter eastern region showed insignificant growth trend, while all trees in the drier west showed significant growth reduction related to climate warming. Radial growth of trees in the east showed weak correlation with precipitation, and that in the west positively correlated with precipitation from the previous August–September and current May–June from 1980 to 2001. In contrast, trees in the east positively correlated with precipitation from the previous August–September and current July, and those in the west positively correlated with precipitation from the current April–May during the temperature pause after 2001. Trees in the east showed negative correlation with temperature in the winter dormancy period, and those in the west negatively correlated with temperature from the previous July, November and the current June from 1980 to 2001. Trees in both the east and west showed weak correlations with temperature after 2001. Older trees (> 150 years old) showed a weaker response to precipitation than the younger trees (< 150 years old). In the east, older trees responded to temperature more weakly during the period of climate warming; while in the west, older trees responded to temperature more strongly. If the temperature begins to rise again as it did before 2001, trees in the western region, especially older trees, will suffer more from warming than those in the eastern region. Consequently, older trees in the western Qilian Mountains should be the subject of greater oversight with respect to forest management and protection.