The impacts of climatic factors on radial growth patterns at different stem heights in Schrenk spruce (Picea schrenkiana)

摘要

Key message While radial growth patterns at different stem heights were similar, tree-ring samples collected at breast height showed diminishing chronology strength for detecting climatic signals because of differences in climate responses. In this study, basal area increments (BAI) and tree-ring chronologies for different heights of Schrenk spruce (Picea schrenkiana) in the western Tianshan Mountains were calculated and used to assess the radial growth pattern along the stem. The mean BAI for different stem heights gradually decreased with increasing stem height (1.3 m > 5 m > 10 m > 15 m > 20 m). The five mean BAI series all showed a significant increasing trend since 1961. The mean BAI for the 10 m height showed the fastest increase among the five series. The significant correlations in the original, high-, and low-frequency domains, and the high Gleichlaufigkeit index, indicate coherence among the radial growth patterns for different heights along the stem. A correlation analysis revealed that for three periods (July-September of the previous year, November-December of the previous year, and May-October of the current year) the mean minimum temperature mainly affected the radial growth at the upper positions of the bole, while the relationship between the ring width at breast height and climatic values was clearly weak. The results support the hypothesis that traditional tree-ring sampling at breast height may diminish the strength of tree-ring width chronologies in detecting climatic signals to some extent.