Spatio-TEmporal Dynamics of Forest Response to ENSO Drought (STEED)

在全球范围内，几乎一半剩余的热带森林被分配用于木材生产，这表明这些森林对许多国家来说是巨大的经济资产。此外，这些森林还提供重要的社会和生态系统服务，从食物来源到减缓气候变化，并从碳抵消计划中产生收入。与未受干扰的森林相比，人们对以前砍伐和退化的正在再生的森林的了解要少得多。关键的是，随着未受干扰的森林面积越来越小，近年来受干扰森林的经济和社会重要性变得更大。然而，这些森林的复原力，即它们通过抵抗破坏和迅速恢复来应对短期扰动(例如，ENSO引发的干旱)的能力，人们了解得很少。如果我们要管理热带森林，无论是最初的开发还是随后的恢复，我们都需要更好地了解这些系统如何应对地方和区域范围内的周期性干旱。只有到那时，我们才能制定政策和实践，明确考虑干旱的影响，并保护从这些脆弱的生态系统中获得的经济和社会利益。为了提供证据，使决策者和实践者能够更好地规划森林管理战略，我们将结合地面和卫星遥感方法，研究当前ENSO干旱对东南亚婆罗洲伐木和退化森林的影响。在实地，我们将利用上世纪90年代中期影响该地区的最后一次重大ENSO干旱时建立的森林调查样地网络，研究树木对干扰梯度上的干旱的反应。2014年，作为对受干扰森林采伐后恢复的长期研究的一部分，重新考察了这些地块，因此是一个独特的天然实验室，用于比较ENSO引起的土地利用梯度上森林结构、组成和生态系统功能的变化，并处理采伐干扰和干旱的相互作用。在18个月的项目中，我们将至少重访25个地块四次。在每一块土地上，我们将测量各种树叶特征、树冠结构和树木死亡率。这项工作将由英国和马来西亚的研究助理组成的联合团队完成，他们将在马来西亚大学的设施中采集树叶并分析树叶的化学特性。此外，我们还将收集树叶的光谱反射测量结果。这将使我们能够扩大我们的实地观测，使用多光谱卫星图像来绘制更广泛地区对当前干旱的森林反应图。特别是，我们将利用新的哨兵2号地球观测卫星来生成当前干旱影响的区域范围地图，同时还将从NOAA AVHRR图像中生成20年时间序列干旱指数。后者将提供与非干旱条件相比森林对干旱的时间反应的证据，而前者将使我们能够绘制森林反应的空间连贯性，确定先前的干扰或其他因素是否影响森林对干旱事件的复原力。最后，我们将通过无人机安装的传感器的观测来跟踪树冠结构和组成的变化，从中我们将检查藤本植物/树木组成的动态，这些变化似乎在干旱条件下发生变化。我们将与我们的项目合作伙伴东南亚雨林研究计划和二叠纪全球组织合作，与负责整个东南亚地区森林管理的行为者网络接触。为此，我们将开展宣传活动，包括在马来西亚举办一次研讨会，会上将提出当前ENSO对东南亚森林的影响的证据，并提供一个论坛，讨论如何最好地使森林管理政策和做法适应未来的ENSO事件。

Globally, almost half of all remaining tropical forest is allocated for timber production, illustrating the enormous economic asset that these forests represent to many nations. Additionally, these forests provide important societal and ecosystem services, from being sources of food through to climate change mitigation and generating income from carbon offset schemes. Compared to undisturbed forests, much less is known about previously logged and degraded forests that are regenerating. Critically, with increasingly smaller areas of undisturbed forest remaining, the economic and societal importance of disturbed forests has become greater in recent years. However, the resilience of these forests i.e. their capacity to respond to short-term perturbations (e.g. ENSO-induced drought) by resisting damage and recovering quickly, is poorly understood. If we are to manage tropical forests, both in terms of their initial exploitation and subsequent rehabilitation, we need to better understand how these systems respond to periodic drought at local to regional scales. Only then can we develop policies and practice that explicitly take into account the impacts of drought and protect the economic and societal benefits derived from these fragile ecosystems.To provide the evidence from which policy makers and practitioners can better plan forest management strategies we will examine the impact of the current ENSO drought on logged and degraded forests in Borneo, SE Asia, using a combination of ground-based and satellite remote sensing methods. In the field we will examine the response of trees to drought across a disturbance gradient, making use of a network of forest inventory plots that were established in the mid-1990s at the time of the last major ENSO drought to affect the region. In 2014 these plots were revisited as part of a long-term study into post-logging recovery of disturbed forests and as such represent a unique natural laboratory for comparing ENSO-induced changes in forest structure, composition and ecosystem functioning across a land-use gradient and addressing the interactions of logging disturbance and drought. We will revisit 25 plots at least four times during the 18 month project. At each plot we will measure a variety of leaf traits, canopy structure and tree mortality. This will be done by a joint team of UK and Malaysian research assistants who will harvest leaves and analyse leaf chemical properties in facilities at the Universiti of Malaysia.Additionally we will collect spectral reflectance measurements from the leaves. This will allow us to scale up our field observations to use multispectral satellite images to map forest response to the current drought across wider regions. In particular, we will make use of the new Sentinel-2 earth observing satellite to generate region-wide maps of current drought impact, whilst also producing a 20 year time-series drought index from NOAA AVHRR imagery. The latter will provide evidence of the temporal response of the forest to drought in comparison with non-drought conditions, whilst the former will allow us to map the spatial coherence of forest response, determining whether prior disturbance or other factors affect the resilience of forests to drought events. Finally, we will track changes in canopy structure and composition through observations from UAV-mounted sensors, from which we will examine the dynamics of liana/tree composition, which appear to change during drought conditions.With our project partners, the South East Asian Rainforest Research Programme and Permian Global, we will engage with a network of actors who are responsible for forest management across the SE Asia region. We will do this through dissemination activities including a workshop in Malaysia, where will present evidence of the impact of the current ENSO on SE Asian forests and provide a forum for discussion on how best to adapt forest management policy and practice to future ENSO events.