Forests in the Far North of Ontario (FNO), Canada, are likely the least studied in North America, and quantifying their current and future carbon (C) stocks is the first step in assessing their potential role in climate change mitigation. Although the FNO forests are unmanaged, the latter task is made more important by growing interest in developing the region’s natural resources, primarily for timber harvesting. In this study, we used a combination of field and remotely sensed observations with a land surface model to estimate forest C stocks in the FNO forests and to project their future dynamics. The specific objective was to simulate historical C stocks for 1901–2014 and future C stocks for 2015–2100 for five shared socioeconomic pathway (SSP) scenarios selected as high priority scenarios for the 6th Assessment Report on Climate Change. Carbon stocks in live vegetation in the FNO forests remained relatively stable between 1901 and 2014 while soil organic carbon (SOC) stocks steadily declined, losing about 16% of their initial value. At the end of the historical simulation (in 2014), the stocks were estimated at 19.8, 46.4, and 66.2 tCha−1 in live vegetation, SOC, and total ecosystem pools, respectively. Projections for 2015–2100 indicated effectively no substantial change in SOC stocks, while live vegetation C stocks increased, accelerating their growth in the second half of the twenty-first century. These results were consistent among all simulated SSP scenarios. Consequently, increase in total forest ecosystem C stocks by 2100 ranged from 16.7 to 20.7% of their value in 2015. Simulations with and without wildfires showed the strong effect of fire on forest C stock dynamics during 2015–2100: inclusion of wildfires reduced the live vegetation increase by half while increasing the SOC pool due to higher turnover of vegetation C to SOC. Forest ecosystem C stock estimates at the end of historical simulation period were at the lower end but within the range of values reported in the literature for northern boreal forests. These estimates may be treated as conservatively low since the area included in the estimates is poorly studied and some of the forests may be on peat deposits rather than mineral soils. Future C stocks were projected to increase in all simulated SSP scenarios, especially in the second half of the twenty-first century. Thus, during the projected period forest ecosystems of the FNO are likely to act as a C sink. In light of growing interest in developing natural resources in the FNO, collecting more data on the status and dynamics of its forests is needed to verify the above-presented estimates and design management activities that would maintain their projected C sink status.

中文翻译：

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加拿大安大略省北部森林的历史和未来碳储量

加拿大安大略省远北地区 (FNO) 的森林可能是北美研究最少的地区，量化其当前和未来的碳 (C) 储量是评估其在减缓气候变化方面的潜在作用的第一步。尽管 FNO 森林不受管理，但由于人们对开发该地区自然资源（主要用于木材采伐）的兴趣日益浓厚，后一项任务变得更加重要。在这项研究中，我们将实地和遥感观测与地表模型相结合，以估计 FNO 森林中的森林碳储量并预测它们的未来动态。具体目标是模拟 1901-2014 年的历史碳库和 2015-2100 年的未来碳库，其中五种共享社会经济路径 (SSP) 情景被选为第六次气候变化评估报告的高优先级情景。FNO 森林中活植被的碳储量在 1901 年至 2014 年间保持相对稳定，而土壤有机碳 (SOC) 储量稳步下降，损失了其初始值的 16% 左右。在历史模拟结束时（2014 年），活植被、SOC 和总生态系统库中的存量估计分别为 19.8、46.4 和 66.2 tCha-1。2015-2100 年的预测表明 SOC 储量实际上没有实质性变化，而活植被 C 储量增加，在 21 世纪下半叶加速了它们的增长。这些结果在所有模拟的 SSP 场景中都是一致的。因此，到 2100 年，森林生态系统碳库总量的增加幅度为 2015 年价值的 16.7% 至 20.7%。有和没有野火的模拟显示了 2015-2100 年火灾对森林碳库动态的强烈影响：包括野火使活植被增加减少了一半，同时由于植被 C 到 SOC 的更高周转率而增加了 SOC 库。历史模拟期结束时的森林生态系统碳库估计值处于低端，但在北方北方森林文献中报告的值范围内。这些估计可能被视为保守的低值，因为估计中包含的区域研究不足，并且一些森林可能位于泥炭沉积而不是矿质土壤上。在所有模拟的 SSP 情景中，预计未来的碳储量都会增加，尤其是在 21 世纪下半叶。因此，在预测期间，FNO 的森林生态系统可能充当碳汇。鉴于对开发 FNO 自然资源的兴趣日益增加，需要收集更多有关其森林状况和动态的数据，以验证上述估算和设计管理活动，以保持其预计的碳汇状态。