Topography- and species-dependent growth responses of Sabina przewalskii and Picea crassifolia to climate on the northeast Tibetan Plateau

Dendroecological techniques were used to examine the relationships between topographic aspects, climatic variation and radial growth of Qilian juniper (Sabina przewalskii Kom.) and Qinghai spruce (Picea crassifolia Kom.) on the northeast Tibetan Plateau. Both tree species exhibit a lower growth rate, a larger interannual growth variability and a higher percentage of missing rings on the west- than east-facing slopes. The two tree-ring chronologies of the west-facing slope are positively correlated with monthly precipitation and relative air humidity, but negatively correlated with monthly maximum temperature in prior July–September and current May–June, suggesting a severe limitation of moisture availability on tree growth. On both topographic aspects, the two tree species show a significant and positive correlation with winter temperature. In comparison, the two tree-ring chronologies of the east-facing slope are positively related to July temperature. Interspecific differences in climatic responses can only be seen by a different strength of the climatic signal. Overall, the biophysical setting is critical in determining the nature of growth responses to climate. This study might provide useful information for looking forward in ecological forecasting of where and how possible future climate change will affect subalpine forests on the northeast Tibetan Plateau.