Timing, patterns and environmental drivers of wood formation in Larix olgensis in Changbai Mountain, Northeast China

BACKGROUND AND AIMS: The temperate montane coniferous forests in Northeast Asia are among the ecosystems most sensitive to ongoing global warming. However, the timing, patterns and environmental controls of wood formation in dominant tree species remain poorly understood. METHODS: In this study, we investigated the intra-annual wood formation of Larix olgensis A. Herry along a 750-1450 m elevational gradient in Changbai Mountain, Northeast China, using weekly microcoring and high-resolution climatic data. Environmental drivers of growth onset, peak and cessation were identified using multiple linear regression models, and the relative contributions of climatic variables to seasonal wood formation were quantified using linear mixed-effects models. KEY RESULTS: We found that for every 100 m increase in elevation, the onset of wood formation was delayed by ∼3.3 days and the growing season shortened by ∼3.5 days. Growth onset was predicted primarily by photoperiod and growing degree days, whereas peak growth was influenced jointly by photoperiod and precipitation. Growth cessation was strongly predicted by photoperiod, with additional contributions from cold degree days and seasonal precipitation. Weekly wood formation was best explained by photoperiod and temperature, with vapour pressure deficit showing a weak but significant positive effect, and soil water content exhibiting a negative relationship to growth. CONCLUSIONS: These findings demonstrate that photoperiod consistently regulates both the timing and seasonal patterns of wood formation in L. olgensis, and that growing degree days and cold degree days play distinct and significant roles in predicting the onset and cessation of secondary growth in spring and autumn, respectively. This study provides valuable insight into the phase-specific climatic controls on wood formation and offers a basis for predicting the response of temperate coniferous forests to future climate change.