A global understanding of forest-savanna transitions

全球对森林-稀树草原转变的理解

• 批准号: 2890074
• 金额: --
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2890074
• 关键词: global; understanding; forest; savanna; transitions

Savannas dominate the tropics, and often occur in areas which could be forest, given the rainfall and soils. Why savannas are where they are, and how that might change under climate change has long preoccupied scientists, but a general understanding has yet to be developed. Remote sensing offers a way to address this problem, and new data sets from lidar and radar sensors in particular, have the potential to describe and explain savanna-forest transitions globally. Given the importance of these ecosystems for local people, carbon cycling and biodiversity, this understanding is vital for responding to the climate and biodiversity crises. In this PhD you will use these new remote sensing data and machine learning to understand how and why savannas transition into forests and how this is changing. You will map and classify the world's savanna-forest transitions and test what determines their location and temporal stability. Theoretical models suggest that both gradual and abrupt transitions between savannas and forest can occur, depending on the traits of trees. However, in the real world, it is not clear why in some places, gradual transitions occur, whilst in other, there is a mosaic of sparse savanna and closed forest. Nor do we understand how stable these patterns will be under climate change, changes to herbivory (such as the loss of elephants) and CO2 fertilisation. Filling these gaps in our knowledge is important because savannas are thought to be particularly sensitive to climate change: they are expected to both be a globally important carbon sink, and to change rapidly as CO2 fertilisation allows trees to outcompete grasses. Which factors control savanna[1]forest boundaries, and how these factors will respond to climate change and other environmental changes, will therefore be vital for the future of savannas.

稀树草原在热带地区占主导地位，考虑到降雨量和土壤，通常出现在可能成为森林的地区。稀树草原为什么会出现在现在的位置，以及在气候变化下稀树草原会如何变化，长期以来一直是科学家们关注的焦点，但尚未形成普遍的理解。遥感提供了解决这一问题的方法，特别是来自激光雷达和雷达传感器的新数据集有可能描述和解释全球稀树草原-森林的转变。鉴于这些生态系统对当地人、碳循环和生物多样性的重要性，这种理解对于应对气候和生物多样性危机至关重要。在本博士课程中，您将使用这些新的遥感数据和机器学习来了解稀树草原如何以及为何转变为森林以及这种情况如何变化。您将绘制世界稀树草原-森林过渡区的地图并对其进行分类，并测试决定其位置和时间稳定性的因素。理论模型表明，稀树草原和森林之间可能会发生逐渐和突然的转变，具体取决于树木的特征。然而，在现实世界中，尚不清楚为什么在某些地方会发生逐渐过渡，而在另一些地方却出现稀疏的稀树草原和封闭的森林。我们也不了解这些模式在气候变化、食草动物的变化（例如大象的消失）和二氧化碳施肥的情况下有多稳定。填补我们知识上的空白非常重要，因为稀树草原被认为对气候变化特别敏感：它们预计将成为全球重要的碳汇，并且随着二氧化碳施肥使树木在竞争中胜过草类而迅速发生变化。因此，哪些因素控制稀树草原[1]森林边界，以及这些因素如何应对气候变化和其他环境变化，对于稀树草原的未来至关重要。