The role of complementarity and facilitation in influencing tree community resilience

全球变化因素，如昆虫和病原体的非本地入侵以及气候变化，正在对世界上许多地区的许多树种的生长和生存以及许多森林生态系统的功能产生不利影响。目前的研究表明，混合树种可以更好地应对应激环境事件。然而，在什么类型的林分和环境条件下使用什么类型的混合物，以最大限度地提高森林对自然和人类诱导的压力的复原力，几乎是未知的。在这个发现研究计划中，我打算测试几个假设，即森林的组成和结构如何与基本共存机制相互作用，以促进(或不促进)树木和森林对许多不同的永久性和/或间歇性压力单独或联合作用的抗性和恢复(这两种衡量弹性的指标)。我将使用受控野外实验和在受管理和未受管理的森林中设置的永久地块相结合的方法来研究这些问题。我将与研究生和博士后密切合作，并与来自世界各地的科学家合作回答这些问题。一项雄心勃勃的新田间实验目前正在加拿大魁北克省里彭附近建立，其中各种树种的混合生长在不同的密度和空间布置中，以在受控的环境中测试其中一些假设。来自25个以上国际树木多样性实验的数据也将被用来测试在广泛的气候条件和树种混合情况下，树木多样性如何影响森林对各种压力的恢复能力。将使用60多个国家在各种环境条件下管理的森林和天然森林建立的小规模和大规模永久地块，以增加我们调查结果的实际相关性，并检验我们调查结果的普遍性。这项研究的结果将被用来设计新的管理方法，以提高树木面对全球变化的韧性和存活率，从城市公园和花园、农作物和受管理的森林到广阔的林地保护区。更好地了解保持或增加树木多样性和林分复杂性的好处，为我们在管理和恢复日益新颖和紧张的生态系统方面面临越来越大的挑战，开辟了许多可能的应用领域。

Global change factors such as non-native invasion of insects and pathogens as well as climate change are negatively affecting the growth and survival of many tree species and functioning of many forest ecosystems in a great number of regions in the world. Current studies indicate that mixtures of tree species can better cope with stressful environmental events. However, what types of mixtures to use under what types of stand and environmental conditions to maximise forest resilience to natural and human-induced stressors are mostly unknown. In this discovery research program, I intend to test several hypotheses regarding how forest composition and structure are interacting with basic coexistence mechanisms to promote (or not) both tree and forest resistance and recovery (both measures of resilience) to many different permanent and/or intermittent stressors acting alone or in conjunction. I will use a combination of controlled field experiments and permanent plots set in managed and unmanaged forests to investigate these questions. I will work closely with graduate students and Post-Docs and collaborate with scientists from around the world to answer these questions.An ambitious new field experiment where various mixtures of tree species grown in different densities and spatial arrangements is currently being established near Ripon in Quebec, Canada, to test some of these hypotheses in a controlled setting. Data from more than 25 international tree-diversity experiments will also be used to test how tree diversity affects forest resilience to various stressors in a wide set of climatic conditions and tree species mixtures. Small and large scale permanent plots established in managed and natural forests in a wide range of environmental conditions from more than 60 countries will be used to increase the practical relevance of our findings and to test the generality of our findings. The growth and mortality at the tree and plot scales will be studied in relation to known recent climatic and biotic stressors that have occurred.The results of this study will be used to design novel management approaches for increasing the resilience and survival of trees facing global change from urban parks and gardens, agricultural crops, and managed forests to vast protected areas of forested land. A better understanding of the benefits of maintaining or increasing tree diversity and stand complexity opens up many possible applications as we face the increasing challenge of managing and restoring increasingly novel and stressed ecosystems.