Carbon fraction (CF) of trees is essential for quantifying forest carbon (C) stocks. Considerable attention has been paid to CF variations at various levels with the exception of inter- and intra-growth rings. Herein, the inter- and intra-growth ring variation of CF in Pinus tabuliformis was investigated. Elemental analysis was performed to obtain CF values of the earlywood and latewood in each growth ring of the xylem. Patterns of CF variation at the growth ring level were evaluated using mixed-effect models. The results showed that latewood CF, 50.6 %, was significantly higher than earlywood CF, 49.9 % (p < 0.01). In particular, inter-growth ring variations of CF differed between heartwood and sapwood, as well as between juvenile wood and mature wood. CF values decreased nonlinearly with cambium age toward the heartwood or juvenile wood, with estimated least-squares means of 50.4 % and 51.8 %, respectively. While CF values were almost unaltered in sapwood, and slightly decreased in mature wood, with estimated least-squares means of 50.0 % and 50.2 %, respectively. It indicates that patterns of CF variation between juvenile wood and mature wood are important to estimate the C stock of P. tabuliformis. This research provides insights into C uptake dynamics to support forest management and wood utilization.

中文翻译：

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油松木材碳组分的生长轮间和生长轮内变化

树木的碳分数 (CF) 对于量化森林碳 (C) 储量至关重要。除了生长环间和生长环内之外，各个层面的 CF 变化受到了相当多的关注。在此，CF的生长环间和生长环内变异油松被调查。通过元素分析获得木质部各年轮早材和晚材的CF值。使用混合效应模型评估生长轮水平的 CF 变化模式。结果显示，晚材CF为50.6%，明显高于早材CF为49.9%（p< 0.01）。特别是，心材和边材之间以及幼年木材和成熟木材之间的 CF 连生轮变化不同。 CF 值随着形成层年龄向心材或幼龄材呈非线性下降，估计的最小二乘平均值分别为 50.4% 和 51.8%。而边材的 CF 值几乎没有变化，而成熟木材的 CF 值略有下降，估计的最小二乘平均值分别为 50.0% 和 50.2%。这表明幼龄木材和成熟木材之间的碳纤维变化模式对于估计碳库很重要油松。这项研究提供了对碳吸收动态的见解，以支持森林管理和木材利用。