Globally, increasing drought-induced tree mortality rates under climate change are projected to have far-reaching effects on forest ecosystems. Among these forest systems, the boreal forest is considered a ‘tipping element’ of the Earth's climate system. This forest biome plays a critical role in ecosystem services, structures and functions while being highly sensitive to drought stress. Although process-based models are important tools in ecological research, very few have yet been developed that integrate advanced physiological mechanisms to simulate drought-induced mortality in boreal forests. Accordingly, based on the process-based TRIPLEX model, this study introduces the new TRIPLEX-Mortality submodule for the Canadian boreal forests at the stand level, that for the first time successfully incorporates two advanced drought-induced physiological mortality mechanisms (i.e., hydraulic failure and carbon starvation). To calibrate and validate the model, 73 permanent sample plots (PSPs) were selected across Canada's boreal forests. Results confirm a good agreement between simulated mortality and mortality observations (R²=0.79; P<0.01; IA=0.94), demonstrating good model performance in simulating drought-induced mortality in boreal forests. Sensitivity analysis indicated that parameter sensitivity increased as drought intensified, and the shape parameter ($c$) for calculating percentage loss of conductivity (PLC) was the most sensitive parameter (average SI = -3.51) to simulate tree mortality. Furthermore, the results of model input sensitivity analysis also showed that the model can capture changes in mortality under different drought scenarios. Consequently, our model is suitable for simulating drought-induced mortality in boreal forests while also providing new insight into improving model simulations for tree mortality and associated carbon dynamics in a progressively warmer and drier world.

在全球范围内，气候变化导致干旱引起的树木死亡率增加，预计将对森林生态系统产生深远的影响。在这些森林系统中，北方森林被认为是地球气候系统的“引爆要素”。这种森林生物群落在生态系统服务、结构和功能方面发挥着关键作用，同时对干旱压力高度敏感。尽管基于过程的模型是生态研究中的重要工具，但很少有人开发出整合先进的生理机制来模拟北方森林干旱引起的死亡的模型。因此，基于基于过程的 TRIPLEX 模型，本研究在林分级别为加拿大北方森林引入了新的 TRIPLEX-死亡率子模块，这是第一次成功地结合了两种先进的干旱引起的生理死亡机制（即水力衰竭和碳饥饿）。为了校准和验证模型，在加拿大北方森林中选择了 73 个永久样本地块 (PSP)。结果证实了模拟死亡率和死亡率观察结果之间的良好一致性（R ² =0.79；P <0.01；IA=0.94)，表明模型在模拟北方森林干旱引起的死亡率方面表现良好。敏感性分析表明，参数敏感性随着干旱加剧而增加，形状参数（$C$) 用于计算电导率损失百分比 (PLC) 是模拟树木死亡率的最敏感参数（平均 SI = -3.51）。此外，模型输入敏感性分析的结果还表明，该模型可以捕捉不同干旱情景下死亡率的变化。因此，我们的模型适用于模拟北方森林中干旱引起的死亡率，同时也为改进对逐渐变暖和干燥世界中树木死亡率和相关碳动态的模型模拟提供了新的见解。