Growth rate determines the superior xylem growth of Siberian spruce over Siberian larch in the southern Altai Mountains, Northwest China

Key message

Despite the better performance in wood growth compared with Siberian larch, Siberian spruce may be more vulnerable to ongoing climate change.

Abstract

Understanding the species-specific wood formation kinetics is critical to assess forest growth and carbon sequestration under climate warming; however, such knowledge is still scarce in the fragile forest ecosystems of arid and semi-arid central Asia. Here, we monitored wood formation in two dominant tree species Siberian spruce (Picea obovata Ledeb.) and Siberian larch (Larix sibirica Ledeb.) during 2018 and 2019 at two sites in the southern Altai Mountains, northwest China, and aimed to describe the intra-annual dynamics of wood formation and to understand the annual variation in growth and carbon sequestration of these two species. Results show that the differences in wood production between species were remarkable. Siberian spruce produced 68.5–87.6 cells year⁻¹ at an average rate of 0.82–0.95 cells day⁻¹, about twofold higher than Siberian larch. The differences between species in terms of the onset, cessation timing, and duration of cell production were marginal. Cell production of both species started from mid-May to early June, ceased from early to mid-August, and lasted for about 64 to 70 days. The higher growth rate of spruce led to greater wood production compared to larch. The longer growing seasons induced by climate warming may not result in increased forest growth, thereby failing to enhance carbon sequestration in arid and semi-arid taiga of Central Asia.