Turning up the heat in a northern hardwood: Response of soils and trees to summer and winter climate change

气候变化正在威胁着森林提供各种服务的能力，其中包括导致冬季变暖和土壤冻融循环增加，夏季变干和变暖，给植物造成水分压力。加拿大致力于维护能够适应当前和即将发生的全球变化的森林。为了预测森林对气候变化的反应，科学家们最近认识到，不仅需要建立基于区域气候的模型，还需要建立基于树种之间、树木与土壤之间相互作用的重组以及可能的反馈的模型。本研究计划的长期目标是在气候变化下，表征加拿大东部温带落叶林中土壤-植物相互关系和养分循环。未来5年，该研究项目将继续加强森林对气候变化响应的预测框架，开展新的野外操作试验，评估生长季土壤变暖和冬季积雪减少对温带落叶森林北部边界土壤碳动态的影响。为此，将在不同处理下测量土壤有机碳水平、形式和稳定性的变化，土壤微生物生物量的有机碳，土壤呼吸，凋落叶分解速率，细根生物量产量和微生物群落以及溶解有机碳浸出率，这些处理包括生长季节土壤增温，冬季除雪，两者结合和参考（对照）样地。还将评估使用离子交换树脂和传统土壤化学提取方法的土壤养分有效性，以及种子发芽率、幼苗存活率、生长、水分利用、叶面营养和根菌根真菌的关联。由于场地位置、复制地块的数量、生长季节和冬季气候变化都是实验测试的事实，以及树木与土壤在补充和幼树生长阶段的相互作用是在田间实验气候变化下研究的，这些实验与其他地方不匹配。因此，这个研究项目是一个非常独特和重要的研究项目：(1)测量和估计森林的当前和未来状态和动态；(2)改进森林对气候变化响应的模拟模型，从而确定可能的最佳气候变化适应战略；(3)培训HQPs，以进一步了解气候变化下的森林功能，并将这些知识传授给参与森林管理决策的公共和私营森林部门。

Climate change is threatening the capacity of forests to provide its various services by causing, among other events, milder winters and increased freeze-thaw cycling in the soil and drier and warmer summers that create water stress for plants. Canada is committed to maintaining forests that are resilient to current and imminent global change. To forecast forest response to climate change, scientists have recently recognized the need to develop models not just based on regional climates, but also based on the reorganization of interactions between tree species and between trees and soils as well as possible feedbacks. The long-term objective of this research program is to characterize soil-plant interrelationships and nutrient cycling in eastern Canadian temperate deciduous forests under a changing climate. In the next 5 years, the research program will continue to strengthen the predictive framework of the response of forests to climate change by running novel manipulative field experiments to assess how soil warming during the growing season and decreased snow cover during winter affect soil carbon dynamics at the northern limit of temperate deciduous forests. To do so, changes in soil organic carbon levels, forms and stability, organic carbon from soil microbial biomass, soil respiration, leaf litter decomposition rates, fine root biomass production and microbial communities and dissolved organic carbon leaching rates will be measured under various treatments which include growing season soil warming only, winter snow removal only, a combination of both and reference (control) plots. Soil nutrient availability using ion-exchange resins and conventional soil chemical extraction methods as well as seed germination rates, seedling survival, growth, water use, foliar nutrition and root mycorrhizal fungi associations will also be assessed. These experiments are not matched elsewhere due to site location, number of replicated plots, the fact that both growing season and winter climate change are experimentally tested and that interactions between trees and soils at recruitment and juvenile growth stages are investigated under experimental climate change in the field. This research program is thus a very unique and essential piece of research for: (1) measuring present and estimating future states and dynamics of forests, (2) improving simulation models of forest response to climate change and thus pin-pointing the best possible adaptation strategies to climate change, and (3) training HQPs to gain further understanding of forest functioning under a changing climate and transfer this knowledge to the public and private forest sectors involved in forest management decision-making.