Evaluating the role of local and landscape factors on the resilience of mixed-species forest ecosystems under climate uncertainty

在北方和亚北方混交林中，针叶树和落叶树之间的相互作用需要竞争有限的资源，如光、水和养分。然而，在某些情况下，假设存在多个物种以促进树木的生长。我的研究旨在提高我们对竞争或便利化条件的理解，以及随之而来的对长期森林动态、森林对干扰的恢复能力以及提供森林生态系统服务(如木材生产、碳储存和生物多样性)的影响。特别是，我将重点测试物种之间的相互作用如何在新颖的未来气候条件下发生变化。*我和我的学生将研究森林的组成和结构如何影响树木生长所必需的资源的可用性。通过评估资源可获得性在年内和年间的变化，我们将深入了解何时何地对资源的竞争将是最重要的，以及预计的气候变化将如何改变竞争或便利化的盛行。树木和森林的发展预计不仅会受到当前生长环境的影响，还会受到过去环境条件的影响。我们将测试针叶树种和落叶树种对过去环境条件的敏感性差异，以提高我们对当前生长条件将如何影响森林对干扰和气候相关压力(如干旱)的脆弱性的理解。具体地说，我们将检验这一假设，即在某些条件下，混交林对环境变化和极端天气事件的适应能力更强。*混交林的长期动态假设是由景观干扰、包括气候在内的环境条件以及干扰时森林的发展状态相互作用所驱动的。然而，气候变化可能会改变物种的相对竞争能力，以及不同干扰类型的流行和强度。因此，关于这些因素的相对重要性及其相互作用在未来气候条件下将如何变化，仍存在很大的不确定性。使用基于过程的森林模型，我们将研究驱动混合物种森林动态的机制，并预测这些过程将如何在未来发生变化。我们还将测试不同森林管理做法的时机和强度如何影响林分和景观尺度上的混交林的动态。具体地说，我们将评估森林管理是否能够提高森林对气候变化的适应能力，并测试如何最有效地权衡短期和长期管理目标，以在未来气候不确定的情况下保持森林生态系统服务的多样性。

In boreal and sub-boreal mixed-species forests, interactions between coniferous and deciduous trees entail competition for limiting resources, such as light, water and nutrients. However, under some conditions the presence of multiple species is hypothesized to facilitate tree growth. My research aims to improve our understanding of the conditions under which competition or facilitation will occur, and what the concomitant impacts on long-term forest dynamics, the resilience of forests to disturbances, and the provision of forest ecosystem services, such as timber production, carbon storage and biodiversity will be. In particular, I will focus on testing how interactions between species are projected to change under novel future climate conditions.***My students and I will examine how forest composition and structure impacts the availability of resources essential for tree growth. By evaluating how resource availability changes within and between years, we will gain insights into where and when competition for resources will be most important, and how projected changes in climate will alter the prevalence of competition or facilitation. Tree and forest development is expected to be influenced not only by the current growth environment, but also by past environmental conditions. We will test for differences in the sensitivity of conifers and deciduous species to past environmental conditions to improve our understanding of how current growth conditions will influence the vulnerability of forests to disturbances and climate-dependent stress, such as drought. Specifically, we will test the hypothesis that under some conditions, mixed-species forest will be more resilient to environmental change and extreme weather events.***The long-term dynamics of mixed-species forests are hypothesized to be driven by the interplay of landscape disturbances, environmental conditions including climate, and the developmental state of the forest at the time of disturbance. However, climate change will likely alter the relative competitive ability of species, and the prevalence and intensity of different disturbance types. Therefore, large uncertainty remains regarding how the relative importance of each of these factors, and their interactions, will change under future climate conditions. Using process-based forest models we will examine the mechanisms that drive mixed-species forest dynamics, and project how these processes will change in the future. We will also test how the timing and intensity of different forest management practices influences the dynamics of mixed-species forests at stand and landscape scales. Specifically we will evaluate if forest management can increase the resilience of forests to climate changes, and test how to most effectively trade-off short- and long-term management goals to maintain a diversity of forest ecosystem services under future climate uncertainty.