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

在全球范围内，几乎所有现存热带森林的一半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和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森林正在再生的了解要少得多。至关重要的是，随着未受干扰森林的面积越来越小，近年来受干扰森林的经济和社会重要性变得越来越大。然而，人们对这些森林的恢复能力，即它们通过抵抗破坏和迅速恢复来应对短期扰动（如enso引起的干旱）的能力知之甚少。如果我们要管理热带森林，无论是从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在地方到区域尺度上对周期性干旱作出反应。只有这样，我们才能制定明确考虑到干旱影响的政策和做法，并保护这些脆弱生态系统带来的经济和社会效益。为了提供政策制定者和从业者更好地规划森林管理战略的证据，我们将使用地面和卫星遥感相结合的方法，研究当前ENSO干旱对东南亚婆罗洲砍伐和退化森林的影响。在实地研究中，我们将通过扰动梯度考察树木对干旱的反应，利用20世纪90年代中期在最后一次影响该地区的ENSO大干旱时建立的森林清查样地网络。2014年，作为对受干扰森林采伐后恢复的长期研究的一部分，这些地块被重新审视，因此代表了一个独特的自然实验室，可以比较enso引起的森林结构、组成和生态系统功能在不同土地利用梯度上的变化，并解决采伐干扰和干旱的相互作用。在18个月的项目中，我们将对25个地块进行至少四次重访。在每个样地，我们将测量各种叶片性状、冠层结构和树木死亡率。这将由英国和马来西亚研究助理组成的联合小组完成，他们将在马来西亚大学的设施中收获叶子并分析叶子的化学特性。此外，我们将收集树叶的光谱反射率测量值。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的森林对当前干旱的反应。特别是，我们将利用新的Sentinel-2地球观测卫星生成当前干旱影响的区域地图，同时还将根据NOAA AVHRR图像生成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一致性，确定先前的干扰或其他因素是否会影响森林对干旱事件的恢复力。最后，我们将通过安装在无人机上的传感器的观测来跟踪冠层结构和组成的变化，从中我们将研究藤本植物/树木组成的动态，这些组成在干旱条件下似乎会发生变化。我们将与项目合作伙伴——东南亚雨林研究计划（southeast Asian Rainforest Research Programme）和二叠纪全球（Permian Global）——合作，与负责东南亚地区森林管理的行动者组成网络。我们将通过传播活动来实现这一目标，包括在马来西亚举办一个讲习班，在那里将展示当前ENSO对东南亚森林影响的证据，并提供一个论坛，讨论如何最好地调整森林管理政策和实践，以适应未来的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.