Boreal forests, vital carbon sinks storing about 32% of the world's forest carbon, face significant threats from climate change. In west-central Canada, studies have primarily focused on the impacts of forest fires and water availability on forest biomass. However, the effects of rising atmospheric CO and climate warming, particularly in relation to spatial variations in mean annual temperature (MAT), remain less understood. Our comprehensive study utilizes data from 871 permanent sample plots, encompassing 208,961 trees across western boreal forests of Canada over 50 years. Our findings reveal a net biomass increase of 0.052 Mg ha yr per degree increase in plot MAT. Two-thirds of this increase can be attributed to reduced mortality rates at higher MATs. Notably, warmer regions showed a more pronounced decrease in growth with stand age, suggesting that younger forests might benefit more from climate warming compared to mature ones. We identified a MAT threshold of 3 °C, beyond which forests show net biomass increase with rising CO, while colder forests exhibit a decline. Future projections indicate that net biomass change in northeastern regions in our study area, particularly above 56° N, may experience adverse effects from increasing CO levels, while southwestern regions could benefit. Besides, in some regions south of 52°N under the 2041–2070 SSP5–8.5 scenario, where predicted temperatures exceed historical maximums, the potential instability and unpredictability of biomass-climate-CO relationships under such extreme conditions should be noted. Our study underscores the complex interplay between climate change factors and boreal forest biomass, highlighting the need for tailored forestry management strategies that consider these spatial and dynamic patterns.

中文翻译：

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加拿大西部北方森林对全球环境变化响应的空间变化


北方森林是重要的碳汇，储存了世界森林碳的约 32%，面临着气候变化的重大威胁。在加拿大中西部，研究主要集中在森林火灾和水资源供应对森林生物量的影响。然而，大气二氧化碳浓度上升和气候变暖的影响，特别是与年平均温度（MAT）空间变化相关的影响，人们仍然知之甚少。我们的综合研究利用了 871 个永久样地的数据，涵盖加拿大西部北方森林 50 年来的 208,961 棵树。我们的研究结果表明，地块 MAT 每增加一度，净生物量增加 0.052 毫克公顷。其中三分之二的增长可归因于较高 MAT 下死亡率的降低。值得注意的是，较温暖的地区随着林龄的增长表现出更明显的生长下降，这表明与成熟的森林相比，年轻的森林可能从气候变暖中受益更多。我们确定了 3 °C 的 MAT 阈值，超过该阈值，森林的净生物量会随着二氧化碳的上升而增加，而较冷的森林则会出现下降。未来的预测表明，我们研究区域的东北地区（特别是北纬 56°以上）的净生物量变化可能会因二氧化碳浓度增加而受到不利影响，而西南地区则可能受益。此外，在2041-2070 SSP5-8.5情景下，在北纬52°以南的一些地区，预测温度超过历史最高温度，应注意在这种极端条件下生物量-气候-CO关系的潜在不稳定性和不可预测性。我们的研究强调了气候变化因素与北方森林生物量之间复杂的相互作用，强调需要制定考虑这些空间和动态模式的定制林业管理策略。