Mixed Forest plantations for climate Change mitigation and adaptation

森林景观恢复与造林作为减缓气候变化的重要契机，近年来受到国际社会的广泛关注。因此，它在许多政治倡议中占有突出地位，如欧盟绿色协议和波恩挑战。然而，由气候变化引起的生物和非生物压力的持续增加使森林受到威胁。面对气候变化，森林的适应和减缓最终是联系在一起的，因为从长远来看，森林固碳(C)的能力取决于树木应对多种压力的能力。越来越多的证据表明，混交林人工林，即几种树种混合的人工林，在固碳方面更有效，同时也能更好地应对碳相关的压力。因此，混合人工林为缓解和适应气候变化提供了一个重要的基于自然的解决方案。然而，单一栽培仍然主导着世界上的森林种植园。土地所有者和利益相关者明显抵制混合人工林的原因需要在未来的森林政策中加以确定和解决，以促进更具抗cc能力的混交林人工林的大规模扩张。阻碍混合人工林大规模扩张的一个可能因素是从业者和决策者缺乏科学证据。利用全球森林生物多样性实验网络（TreeDivNet），我们将以一种双赢的方式，对树木多样性、物种特性和管理（间伐和施肥）如何影响混交林人工林减轻（碳固载）和适应（干旱和草木恢复力）碳排放的潜力提供机制理解。此外，我们将把这些知识转化为可被从业人员和决策者广泛采用的指导方针。TreeDivNet网络包括26个遍布全球的实验，种植了大约120万棵树。所有这些实验都基于一个共同的、统计上合理的设计，该设计允许检测树木多样性、管理和森林生态系统功能（包括碳封存）之间的因果关系。MixForChange的功能和机制重点以及网络中嵌入的对比环境背景将使我们能够将研究结果扩展到案例研究之外，为广泛环境下的混合种植园管理提供基于证据的指导方针。此外，MixForChange将在一个共同框架内以前所未有的规模分析混合种植园减缓和适应气候变化潜力与实现利益攸关方目标之间的协同作用和权衡。通过在各级管理和治理中大力关注知识转移和能力建设，将确保MixForChange的社会影响。MixForChange将为促进混交林种植园作为基于自然的解决方案来对抗CC做出重要贡献。

Forest landscape restoration and afforestation have recently received much international attention as a crucial opportunity for mitigating climate change (CC). Therefore, it features prominently in many political initiatives such as the EU Green Deal and the Bonn Challenge. Yet, the ongoing increase in biotic and abiotic stress driven by CC puts forests under threat. In the face of CC, adaptation and mitigation by forests are ultimately linked, because the ability of forests to sequester carbon (C) in the long run depends on the ability of trees to cope with multiple stresses. A growing body of evidence suggests that mixed forest plantations, i.e., plantations where several tree species are mixed, are more efficient in sequestrating C, while better coping with CC-related stress. Mixed plantations thus represent an opportunity for an important nature-based solution for CC mitigation and adaptation. However, monocultures still dominate the world’s forest plantations. The reasons for the apparent resistance to mixed plantations among landowners and stakeholders need to be identified and addressed in future forest policies to promote the large-scale expansion of more CC-resilient mixed forest plantations. One of the possible factors that may have prevented the expansion of mixed plantations at large scales is insufficient scientific evidence for practitioners and policy-makers. Using a global network of forest biodiversity experiments (TreeDivNet), we will provide a mechanistic understanding of how tree diversity, species identities and management (thinning and fertilization) influence both the potential of mixed forest plantations to mitigate (C sequestration) and adapt (drought and herbivory resilience) to CC, in a win-win approach. In addition, we will translate this knowledge into guidelines that can be widely adopted by practitioners and policy-makers. The TreeDivNet network comprises 26 experiments spread across the globe, with ca. 1.2M planted trees. All these experiments were based on a common, statistically sound design that allows detection of causal relationships between tree diversity, management and forest ecosystem functioning (incl. C sequestration). The functional and mechanistic focus of MixForChange and the contrasting environmental contexts embedded in the network will allow us to scale-up our findings beyond case studies to provide evidence-based guidelines for mixed plantation management in a broad range of environments. Moreover, MixForChange will analyse in a common framework, and at unprecedented scale, synergies and trade-offs between the CC mitigation and adaptation potential of mixed plantations and the fulfilment of stakeholders’ objectives. The societal impact of MixForChange will be ensured by a strong focus on knowledge transfer and capacity-building at all levels of management and governance. MixForChange will make an important contribution to promoting mixed forest plantations as nature-based solutions to fight CC.