Building Tools to Reconstruct Forest Disturbances

气候变化是森林生态系统面临的最大挑战。自然干扰的频率和严重程度将随着气候变暖而增加，如野火、昆虫暴发和风灾。因此，必须了解森林如何应对过去的干扰，以预测它们将如何应对未来的条件。古生态和树生态方法是重建森林动态、干扰机制和生物-非生物相互作用的主要工具。到目前为止，树生态和古生态研究主要集中于野火，而其他干扰往往被忽视(例如，千年规模的昆虫暴发和历史收获)，尽管它们被认为是森林结构和动态的主要驱动因素。这一认识差距源于缺乏可靠的代理或方法论办法来重现过去发生的情况和严重程度。我的研究的长期目标是提高我们在多个时间和空间尺度上对森林干扰机制的理解。这项为期5年的计划旨在利用新的树生态和古生态方法重建温带-北方森林界面的自然(昆虫爆发及其与野火的相互作用)和人为(收获)干扰制度。具体目标是：(1)利用回收的原木驱动样本重建过去300至400年间的昆虫暴发及其与火灾的相互作用；(2)利用亚化石样本和历史档案重建在历史收获期间适用的收获标准(物种、年龄、直径)，并确定其对工业化前森林的影响；(3)利用鳞翅目鳞片重建千年的昆虫暴发历史。实现这些目标有赖于三种方法。(I)我将恢复在历史伐木过程中砍伐的亚化石树木，以重建过去的昆虫暴发、火灾制度和历史收成。我将使用树枝生态学来研究保存在选定的北方湖泊缺氧区的亚化石原木。(2)通过在收集的原木驱动器样本上确定历史伐木公司的标识类型，并结合历史档案的使用，我将对过去的森林采伐模式进行地理参考。(3)我将应用我的新的和最近测试的古指示器--鳞翅目鳞片--对加拿大东部森林中的两种主要的鳞翅目食叶动物(云杉芽虫和森林帐篷毛虫)进行千年尺度的重建。该方案将极大地推进森林干扰的重建，这对于更现实地预测未来森林生态系统对气候变化下的干扰的反应是至关重要的。

Climate change is the greatest challenge facing forest ecosystems. The frequency and the severity of natural disturbances, such as wildfire, insect outbreaks, and windthrow, will increase with warming. Therefore, it is essential to understand how forests have responded to past disturbances to predict how they will react to future conditions. Paleoecological and dendroecological approaches are the main tools for reconstructing forest dynamics, disturbance regimes, and biotic-abiotic interactions. To date, dendroecological and paleoecological research has focused mainly on wildfires, whereas other disturbances have often been neglected (e.g., insect outbreaks at the millennial scale and historical harvesting) despite being known as major drivers of forest structure and dynamics. This knowledge gap stems from the absence of reliable proxies or methodological approaches for reconstructing their past occurrence and severity. The long-term objective of my research is to improve our understanding of forest disturbance regimes at multiple temporal and spatial scales. This 5-year program aims to reconstruct the natural (insect outbreaks and their interaction with wildfires) and anthropogenic (harvesting) disturbance regimes in the temperate-boreal forest interface using novel dendroecological and paleoecological methods. The specific objectives are to (1) reconstruct insect outbreaks and their interactions with fire regimes over the last 300 to 400 years using recovered log-drive samples; (2) reconstruct, using subfossil samples and historical archives, the harvest criteria (species, age, diameter) applied during historical harvests and determine their impact on the pre-industrial forest; and (3) reconstruct the millennial history of insect outbreaks using lepidopteran scales. Attaining these objectives relies on three approaches. (i) I will recover subfossil trees felled during historical log drives to reconstruct past insect outbreaks, fire regimes, and historical harvests. I will use dendroecology to study subfossil logs preserved in the anoxic zone of selected boreal lakes. (ii) By identifying the logotypes of historical logging companies on the collected log-drive samples combined with the use of historical archives, I will georeference past forest harvesting patterns. (iii) I will apply my novel and recently tested paleoindicator, lepidopteran scales, to produce a millennial-scale reconstruction of the two main lepidopteran defoliator species in eastern Canadian forests (spruce budworm and the forest tent caterpillar). This program will significantly advance the reconstruction of forest disturbances that is essential to provide a more realistic projection of future forest ecosystem response to disturbance under climate change.