Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Considering climate change, there is no consensus on the impact of global warming on forest growth. Therefore, it is crucial to investigate the effects of climate change on tree radial growth. However, in arid eastern central Asia, the large-spatial scale radial growth-climate relationship remains poorly understood. In this study, we collected radial growth data from 13 Siberian larch (Larix sibirica) plots along an altitudinal gradient (1100–2200 m a.s.l.) in the Altai Mountains, China. Principal component analysis (PCA), bootstrapped correlation, and linear regression were conducted to detect and quantify the effects of climatic factors on radial growth and to reveal the spatial variation in the radial growth-climate relationship. Results showed that chronologies were clustered into low- and high-altitude groups. In the low-altitude group, the self-calibrating Palmer Drought Severity Index (scPDSI) in current April showed a strong positive impact on radial growth, while the previous September mean temperature and diurnal temperature range in previous July both significantly negatively affected radial growth. These three climate variables explained 63% of radial growth variance. Among them, the scPDSI, with a relative importance of 63%, was the primary limiting factor. In the high-altitude group, the current January maximum temperature and previous July precipitation were significantly negatively correlated with radial growth, while the June minimum temperature was significantly positively correlated with radial growth. These three climatic factors together contributed to 38% variance in radial growth. Furthermore, the plot-specific relationship between climate variables and radial growth varied significantly with different altitudes. As the climate becomes wetting and warming in the Altai Mountains, our result suggests that the radial growth might benefit in an altitude between 1800 and 1900 m a.s.l., where temperature and precipitation were both positively correlated with radial growth. These findings will provide a basis for sustainable forest management under global climate change.