AFIRE - Assessing ENSO-induced Fire Impacts in tropical Rainforest Ecosystems

热带森林储存了世界上一半以上的森林碳，生产了所有陆地系统三分之一以上的生产力。它们也是生物多样性的热点，拥有世界上很大比例的陆地动植物。然而，越来越多的证据表明，由于与人为森林干扰(如农业、伐木、火灾和碎片化)和极端气候事件有关的多重压力，热带森林履行重要生态系统服务(即固碳和生物多样性保护)的能力已大大降低。在这些骚乱中，火灾是最大的威胁。热带雨林并没有与火共同进化，物种也没有适应火或火给森林带来的变化。然而，今天，引火源在大多数人工改造地区很常见，因为许多生活在热带森林中的当地农民传统上使用火作为一种管理技术，为种植准备土地。选择性采伐和碎片化增加了剩余森林的易燃性，加剧了这一问题。至关重要的是，在严重干旱期间，火灾更有可能逃离目标区域，进入周围的森林。这正是2015-16年厄尔尼诺南方涛动(ENSO)期间发生的情况-被认为是有记录以来最强的三次事件之一。漫长的旱季让亚马逊和东南亚热带雨林的数千场大火失控。具体地说，在巴西亚马逊地区，2015年底发生了超过8.7万起火灾事件，比2014年(非ENSO年)增加了48%。因此，大范围的野火影响了我们在帕拉州圣塔伦地区附近的20块永久土地中的一半，幸运的是，其他10块土地没有被烧毁。可持续亚马逊网络(SAN)在2010年沿着森林修改的梯度建立了这些地块，自2014年以来，英国和巴西科学家的一个联合项目(ECOFOR)一直在该地区开展研究。因此，我们在这里提出的工作得益于关于碳动态和植物功能特征的独特和详细的火灾前信息(来自ECOFOR)，以及三个不同的分类群(鸟类、粪甲虫和植物)的分布和次级种子传播过程(来自SAN)。独一无二的是，我们的永久地块网络是在2015年火灾之前沿着现有的森林修改梯度建立的，使我们能够对不同森林干扰类别的火灾影响进行第一次严格评估。使用详细的火灾前数据检查火灾影响的能力使我们能够发展三个主要的研究途径，跨越人类修改的森林干扰梯度：(1)非常严重的野火对植物群落和碳动态的影响，因此评估哪些植物功能特征可以预测物种的死亡、存活和补充；(2)调查火灾对森林动物(即鸟类和屎甲虫)和相关种子传播过程的影响；(3)详细了解当前极端ENSO事件的规模和影响，探索遥感信息与地面措施之间的关系。遥感产品与火灾严重程度的实际测量之间的更好联系将使我们能够扩大整个区域的碳排放和生物多样性损失估计。火灾的结果至关重要，因为随着气候变化，世界各地的热带森林可能会受到更干燥、更热、更长的旱季的威胁。我们的发现将有助于制定缓解战略，以管理未来由ENSO引发的干旱和严重野火对热带森林的影响。我们还预计，火灾现场将成为对热带野火影响的长期研究的基础。

Tropical forests store more than a half of the world's forest carbon and produce over one third of the productivity of all terrestrial systems. They are also biodiversity hotspots, and host a large proportion of the world's terrestrial flora and fauna. However, growing evidence shows that the ability of tropical forests to perform important ecosystem services (i.e. carbon sequestration and biodiversity conservation) has been dramatically reduced by multiple pressures associated with human-induced forest disturbances (e.g. agriculture, logging, fire and fragmentation) and extreme climate events. Of these disturbances, fire represents of the greatest threats. Rainforests have not co-evolved with fire, and species have not adapted to withstand fire or the changes it imposes on the forests. Yet today, ignition sources are common in most human-modified regions, as many local farmers living within tropical forests traditionally use fire as a management technique to prepare their land for planting. This is compounded by selective logging and fragmentation, which increase the flammability of the remaining forests. Critically, fires are much more likely to escape their target area and enter the surrounding forests during severe drought events.This is exactly what happened during the current 2015-16 El Niño Southern Oscillation (ENSO) - considered one of the three strongest events ever recorded. The prolonged dry season allowed thousands of fires to get out of control in Amazonian and SE Asian tropical rainforests. Specifically in the Brazilian Amazon, the end of 2015 was marked by over 87,000 fire events, a 48% increase in relation to 2014 (a non-ENSO year). As a result, the widespread wildfires affected half of our 20 permanent plots near the Santarém region in the state of Pará, while fortunately preserving the other ten plots unburned. The Sustainable Amazon Network (SAN) has established these plots along a gradient of forest modification in 2010, and since 2014 a joint project between UK and Brazilian scientists (ECOFOR) has been carrying out research in this region. Consequently, the work we are proposing here benefits from unique and detailed pre-fire information on carbon dynamics and plant functional traits (from ECOFOR) as well as the distribution of three distinct taxa (birds, dung beetles and plants) and secondary seed dispersal processes (from SAN). Uniquely our network of permanent plots is established along an existing gradient of forest modification before the 2015 fires, allowing us to undertake the first rigorous evaluation of fire effects across different forest disturbance classes. This ability to examine fire impacts using detailed pre-fire data allows us to develop three major avenues of research across a human-modified gradient of forest disturbances: (1) the impacts of very severe wildfires on plant communities and carbon dynamics, assessing therefore which plant functional traits may predict species mortality, survival and recruitment; (2) an investigation into the fire impacts on forest fauna (i.e. birds and dung beetles) and associated seed dispersal processes; and (3) the development of a detailed understanding of scale and impacts of the current extreme ENSO-event, exploring the relationship between remote sensing information and ground-based measures. The better linkages between remote-sensing products and actual measures of fire severity will allow us to scale up the carbon emission and biodiversity loss estimates across the whole region. The results fo AFIRE are critically important, as tropical forests around the world may be threatened by drier, hotter and longer dry seasons with climate change. Our findings will help inform mitigation strategies to manage the impacts of future ENSO-mediated droughts and severe wildfires on tropical forests. We also expect AFIRE plots to form the basis of much longer-term research on the impacts of tropical wildfire