Climate sensitivity of regional carbon stocks in Canada's western boreal forest

加拿大西部北方森林区域碳储量的气候敏感性

• 批准号: RGPIN-2021-02521
• 负责人: Vanderwel, Mark
• 金额: $ 2.91万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741926
• 关键词: Climate; sensitivity; regional; carbon; stocks

Canada's western boreal forest stores vast amounts of carbon. Stretching from Manitoba to the Yukon, the managed portion of this forest region contains the equivalent of about 130 years' worth of national greenhouse gas emissions and represents a globally significant carbon pool. However, increases in aridity in recent decades have caused region-wide losses of forest carbon as moisture stress has both reduced productivity (slowed tree growth) and increased mortality. These changes pose a significant threat as warming temperatures and greater aridity together exacerbate the risk of fire, predispose trees to attack by insect pests, reduce supplies of merchantable timber, and trigger damaging climate change feedbacks when carbon stocks are released to the atmosphere. Over the next five years, we will use a coordinated set of field studies and modelling experiments to: (1) evaluate how effects of water availability on the growth and mortality of individual trees vary among species, with local competition, and with site conditions; (2) assess how climatic variation in productivity and biomass turnover within forest stands influence rates of biomass accumulation over time; (3) project how the current species composition, stem size distribution, and carbon density of forest stands across the region are expected to change under future climate and disturbance scenarios. My students and I will establish a network of 400 sites across three major boreal ecozones in western Canada. At each of these sites we will conduct aerial surveys with an unmanned aerial vehicle, and use year-to-year changes in the resulting imagery to measure annual rates of tree growth and mortality. We will use these data to develop statistical models for how climatic factors influence the productivity and mortality of individual trees and larger stands in different ways. We will then incorporate these relationships into an individual-based forest simulator to project how differences in tree growth and mortality translate into changes in forest structure and composition over time. Finally, we will run model-based experiments with this simulator to evaluate how increases in moisture stress affect regional carbon balance, forest structure, and species composition over the 21st century. This research program will provide a clearer understanding of carbon dynamics across a major Canadian forest region for which there is currently little data. Although the conventional thinking is that these forests are a net carbon sink, model projections based on extensive new data could reveal their potential to become a carbon source if moisture stress increases as expected over the coming decades. A better understanding of the sensitivity of the western boreal forest to climate change would resolve important uncertainties concerning its influence on Canada's national greenhouse gas emissions and the global carbon-climate system.

加拿大西部的北方森林储存着大量的碳。从马尼托巴省延伸到育空地区，这片森林地区的管理部分包含了大约130年的全国温室气体排放量，代表了一个全球重要的碳库。然而，近几十年来干旱的增加造成了整个区域的森林碳损失，因为水分胁迫降低了生产力（减缓了树木的生长）并增加了死亡率。这些变化构成了重大威胁，因为气温升高和更严重的干旱共同加剧了火灾风险，使树木容易受到害虫的袭击，减少了商品木材的供应，并在碳储量释放到大气中时引发破坏性的气候变化反馈。在未来五年内，我们将采用一系列协调的实地研究和模拟实验：(1)评估水分供应对不同树种、本地竞争和场地条件下单株树木生长和死亡的影响；(2)评估林分生产力和生物量周转量的气候变化如何随时间影响生物量积累速率；(3)预测在未来气候和干扰情景下，整个区域林分的物种组成、茎粗分布和碳密度将如何变化。我和我的学生将在加拿大西部三个主要的北方生态区建立一个400个站点的网络。在这些地点，我们将使用无人驾驶飞行器进行空中调查，并使用所得到的图像的年变化来测量树木的年增长率和死亡率。我们将利用这些数据来开发统计模型，以了解气候因素如何以不同的方式影响单株树木和大型林分的生产力和死亡率。然后，我们将把这些关系纳入一个基于个体的森林模拟器，以预测树木生长和死亡率的差异如何随着时间的推移转化为森林结构和组成的变化。最后，我们将利用该模拟器进行基于模型的实验，以评估21世纪水分胁迫的增加如何影响区域碳平衡、森林结构和物种组成。这个研究项目将对加拿大主要森林地区的碳动态有一个更清晰的了解，目前这方面的数据很少。虽然传统的想法是这些森林是一个净碳汇，但基于大量新数据的模式预测可能显示，如果未来几十年水分压力如预期的那样增加，它们可能成为一个碳源。更好地了解西部北方森林对气候变化的敏感性，将解决有关其对加拿大国家温室气体排放和全球碳气候系统影响的重大不确定性。