The role of fire in the carbon dynamics of the boreal forest II. - Eurasia model simulations of historical fire disturbance and carbon dynamics (1000-2002).

The boreal forest contains large reserves of carbon, and across this region wildfire is a common occurrence. To improve the understanding of how wildfire influences the carbon dynamics of this region, methods were developed to incorporate the spatial and temporal effects of fire into the Terrestrial ecosystem Model (TEM). The historical role of fire on carbon dynamics of the boreal region was evaluated within the context of ecosystem responses to changing atmospheric CO2 and climate. These results show that the role of historical fire on boreal carbon dynamics resulted in a net carbon sink; however, fire plays a major role in the interannual and decadal scale variation of source/sink relationships. To estimate the effects of future fire on boreal carbondynamics, spatially and temporally explicit empirical relationships between climate andfire were quantified. Fuel moisture, monthly severity rating, and air temperature explained a significant proportion of observed variability in annual area burned. These relationships were used to estimate annual area burned for future scenarios of climate change and were coupled to TEM to evaluate the role of future fire on the carbon dynamics of the North American boreal region for the 21st Century. Simulations with TEM indicate that boreal North America is a carbon sink in response to CO2 fertilization, climate variability, and fire, but an increase in fire leads to a decrease in the sink strength. While this study highlights the importance of fire on carbon dynamics in the boreal region, there are uncertainties in the effects of fire in TEM simulations. These uncertainties are associated with sparse fire data for northern Eurasia, uncertainty in estimating carbon consumption, and difficulty in verifying assumptions about the representation of fires that occurred prior to the start of the historical fire record. Future studies should incorporate the role of dynamic vegetation to more accurately represent post-fire successional processes, incorporate fire severity parameters that change in time and space, and integrate the role of other disturbances and their interactions with future fire regimes.

北方针叶林（boreal forest）蕴藏着大量碳储量，且该区域野火频发。为深化对野火如何影响该区域碳动态的认知，研究人员开发了将野火的时空效应纳入陆地生态系统模型（Terrestrial ecosystem Model, TEM）的方法。本研究在生态系统对大气CO₂与气候变化的响应这一框架下，评估了历史野火对北方针叶林区域碳动态的作用。研究结果表明，历史野火对北方针叶林碳动态的作用最终形成了净碳汇；但野火在年际与年代际尺度的源汇关系变化中扮演着核心角色。为预估未来野火对北方针叶林碳动态的影响，本研究量化了气候与野火间具有明确时空特征的经验关联。燃料湿度、月度火烈度评级与气温能够解释观测到的年度过火面积变异中的绝大部分。利用上述经验关联，研究人员对未来气候变化情景下的年度过火面积进行了预估，并将其与陆地生态系统模型耦合，以评估21世纪未来野火对北美北方针叶林区域碳动态的作用。陆地生态系统模型的模拟结果显示，受CO₂肥化效应、气候波动与野火的共同影响，北美北方针叶林整体表现为碳汇，但野火活动的增强会导致碳汇强度下降。尽管本研究凸显了野火对北方针叶林碳动态的重要性，但陆地生态系统模型的野火效应模拟仍存在诸多不确定性。这些不确定性源于欧亚大陆北部野火数据匮乏、碳消耗量估算存在偏差，以及难以验证历史野火记录起始之前野火表征相关假设的合理性。未来研究应纳入动态植被模块，以更精准地复现火后生态演替过程；引入随时空动态变化的火烈度参数；并整合其他干扰因子的作用及其与未来野火格局的相互作用。