Tree rings which can record the past climatic events allows for retrospective analyses of climate-growth relationship. Generally, it is assumed that the relationships between tree growth and climate are elevation-independent and age-independent if the biological growth trend related to elevation and age is removed from the tree-ring data. However, if tree growth of different elevations or ages responds differently to climatic conditions, a dendroclimatic analysis based on samples at different elevations or with different ages may be biased in capturing climatic variability throughout the length of the chronology.
In our study, tree cores of Abies faxoniana were taken from three different elevations (High altitude; Middle altitude; Low altitude) to represent the trees growth in Miyaluo of western Sichuan, China (total 132 cores, 37 at Low altitude; 51 at Middle altitude and 44 at High altitude). Three residual chronologies were developed from the cross-dated ring width series using the program ARSTAN, the longest was 170 years (1842-2011). Response analysis showed that the correlation between temperature and chronologies was almost negative, at low altitude there was the highest correlation coefficient. The positive correlation between PDSI (April and May of the current year) and the chronologies of Middle altitude and Low altitude showed that drought stresses inhibited the tree growth. In addition, a significantly positive response to precipitation (April of the current year) found at Low altitude explained that the precipitation was quite important for the tree growth.
Furthermore, analysis of different age classes (old or young) showed that the response of old tree growth to climate change were more obvious than that of the young tree growth. It revealed that climate conditions would affect tree growth differently between different ages. Physiological processes and hydraulic constraints related to tree ages could possibly be the main causes of these age-dependent responses, so the relative sampling strategies should be considered.