Pruning can encourage the early formation of knot-free wood with high economic value. However, few studies have assessed the costs and benefits of production in order to determine the optimal pruning design. The concept of a functional crown provides reasonable guidance for pruning, but there is no objective method of determining the functional crown. Semimonthly measurements of leaf traits and photosynthetic characteristics and the corresponding environmental conditions were conducted for young Larix olgensis plantations throughout the entire growing season. The dynamic crown net photosynthetic rate (A_n) was simulated by comprehensively considering the leaf mass per area, photosynthetically active radiation, air temperature (T_air), vapor pressure deficit and leaf position within the crown (relative depth into the crown, RDINC). The precision (P) was estimated to be 95.5%, indicating that our model performed well in predicting the dynamic crown A_n for young Larix olgensis plantations. The net primary productivity (NPP) of each whorl of the tree crown was calculated by numerically integrating the instantaneous A_n. The net carbon contribution from branches to the tree was obtained by subtracting the annual carbon increment from the NPP. The results showed that some live branches in the lower crown contributed negatively to the trunk, indicating that pruning should not focus only on dead branches. Thus, the lower boundary of the functional crown (LBFC) provides a valuable guideline for pruning treatments. Considering that the LBFC will shift upward as the tree grows, we suggest that advanced pruning techniques be applied to reduce costs and minimize labor.

修剪可以鼓励早期形成具有高经济价值的无结木材。但是，很少有研究评估生产的成本和收益以确定最佳的修剪设计。功能性牙冠的概念为修剪提供了合理的指导，但是没有确定功能性牙冠的客观方法。在整个生长季节中，对落叶松幼龄人工林每半个月进行一次叶片性状和光合特性及相应环境条件的测量。通过综合考虑单位面积的叶片质量，光合有效辐射，气温（T _air）来模拟动态树冠净光合速率（A _n）），蒸气压不足和树冠内的叶片位置（进入树冠的相对深度，RDINC）。精度（P）估计为95.5％，这表明我们的模型在预测落叶松幼林动态冠冠A _n方面表现良好。通过对瞬时A _n进行数值积分，计算出树冠各轮的净初级生产力（NPP）。通过从NPP中减去年度碳增量，可以得出树枝对树木的净碳贡献。结果表明，下冠的一些活枝对树干有负面影响，表明修剪不应该只集中在枯枝上。因此，功能性牙冠的下边界（LBFC）为修剪治疗提供了宝贵的指导。考虑到LBFC将随着树的生长而向上移动，我们建议使用先进的修剪技术以降低成本并最大程度地减少人工。