Seeing the fruit for the trees in Borneo: responding to an unpredictable community-level fruiting event

东南亚的热带森林最近受到了巨大的压力，原因是有选择的伐木和广泛的清除油棕榈种植。因此，人们对利用自然再生或积极恢复处理来恢复退化森林产生了兴趣。然而，东南亚热带森林树木的生殖生物学限制了对这些方法有效性的研究，因为大多数大型树冠树木很少开花和结果。这些零星的大规模繁殖事件负责建立新的幼苗群体，这些幼苗长大后成为下一代成年树冠树，关键是要发现这些间歇性的再生尝试在因伐木而退化的森林中是否与在原始森林中一样成功，以及在实施植树和砍伐攀缘植物等处理的森林中，导致幼苗补充的过程是否得到有效恢复。然而，由于这些再生事件发生得如此罕见和不可预测，因此很难将其纳入传统的研究规划周期，尽管在树木生命周期早期发生的事件对未来森林至关重要。在这个项目中，我们将在马来西亚的沙巴迅速建立采样点，我们知道，自2010年以来，2019年5月开始了树冠树木的大规模开花。我们的目标是比较的数量和多样性的水果和幼苗在这个桅杆事件中产生的主要（未受干扰，未记录）的森林，并在相邻的森林已被记录，要么留下自然再生或恢复种植树苗，并保持他们五年的攀缘切割。由于砍伐森林的恢复始于20多年前，在某些情况下，最初的一批种植幼苗现在是大型树冠树木，可能在今年的繁殖活动中首次贡献种子和幼苗。我们还将测量决定植物如何捕获和利用资源的性状的表达，如三种类型森林中最常见的物种的光和营养物质，这将决定恢复森林中建立的幼苗群落的功能是否与未受干扰的原始森林中的功能更相似，而不是在伐木后自然再生的森林中。这项研究的一个重点是树冠和紧急树木，龙脑香科，这是有针对性的伐木的优势家庭的物种。采伐森林具有较低的密度大的繁殖成熟的dipterocarp个人，恢复的一个关键目标是重新建立这个家庭的优势和多样性，种植和维护dipterocarp幼苗。龙脑香属植物具有热带森林树木植物群的一个不寻常的特征，即它们与根定殖外生菌根真菌（ECM）形成互惠关系，而森林中的大多数其他物种与丛枝菌根（AM）形成不同类型的根关系。我们最近的研究表明，ECM幼苗受益于接近高密度的ECM成人，可能是因为他们交换资源，通过一个共同的地下真菌网络，因为ECM物种抑制根病原体。相比之下，AM幼苗有较低的生存时，位于同一物种的高密度的成人。我们的项目的最后一个目的是测试是否ECM物种的高成人密度的有益影响是减少在采伐森林ECM成人的密度低得多，以及这些影响是否被抵消恢复。因此，这项研究将有助于了解东南亚森林在桅杆事件期间如何再生，以及伐木的负面影响是否可以通过恢复来减轻。

Southeast Asian tropical forests have been subjected to recent intense pressure due to selective logging and widespread clearance for Oil Palm cultivation. Consequently there is an emerging interest in restoring degraded forests using either natural regeneration or active restoration treatments. However, the reproductive biology of Southeast Asian tropical forest trees limits research on the effectiveness of these approaches, because most large canopy trees only flower and fruit very rarely. These sporadic mass reproductive events are responsible for establishing new cohorts of seedlings that grow up to become the next generation of adult canopy trees, and it is critical to discover whether the success of these episodic attempts at regeneration is as great in forests that have been degraded by logging as they are in primary forests, and whether the processes leading to seedling recruitment are restored effectively in forests where treatments such as tree planting and climber cutting have been applied. However, because these regeneration events occur so infrequently and unpredictably it is very difficult to incorporate them into the conventional planning cycle for research, despite the critical importance of the events that occur early in the life cycle of trees to future forests. In this project we will rapidly establish sampling sites in Sabah, Malaysia, where we know that a mass flowering of canopy trees was initiated in May 2019, for the first time since 2010. We aim to compare the amount and diversity of fruits and seedlings produced during this masting event in primary (undisturbed, unlogged) forests, and in adjacent forests that have been logged and either left to regenerate naturally or restored by planting tree seedlings and maintaining them for five years by climber cutting. Because the restoration of logged forests began more than 20 years ago, the original cohort of planted seedlings are now, in some cases, large canopy trees that may contribute seeds and seedlings for the first time during the reproductive event this year. We will also measure the expression of traits that determine how plants capture and use resources such as light and nutrients for the most common species that occur in each of the three types of forest, which will determine whether the community of seedlings that establish in the restored forests functions in a more similar way to that in the undisturbed primary forest than in the forests left to regenerate naturally after logging. A key focus on this study will be on species of the dominant family of canopy and emergent trees, the Dipterocarpaceae, which are targeted for logging. Logged forests possess a lower density of large reproductively mature dipterocarp individuals, and a key aim of restoration is to re-establish the dominance and diversity of this family by planting and maintaining dipterocarp seedlings. Dipterocarps possess an unusual trait for the tree flora of tropical forests, which is that they form mutualistic associations with root-colonising ectomycorrhizal fungi (ECM), whereas most other species in the forest form a different type of root association with arbuscular mycorrhizas (AM). Our recent research has shown that ECM seedlings benefit from proximity to a high density of ECM adults, possibly because they exchange resources through a common below-ground fungal network and because ECM species suppress root pathogens. In contrast, AM seedlings have lower survival when located close to a high density of adults of the same species. A final aim of our project is to test whether the beneficial effects of high adult density for ECM species is reduced in logged forests where the density of ECM adults is much lower, and whether these effects are offset by restoration. This research will therefore contribute results that are vital to understanding how Southeast Asian forests regenerate during masting events, and whether the negative effects of logging can be mitigated by restoration.