Using plant hydraulic scaling to predict the drought vulnerability of the world's tallest tropical trees

利用植物水力缩放来预测世界上最高的热带树木的干旱脆弱性

• 批准号: NE/V00008X/1
• 负责人: Lindsay Banin
• 金额: $ 2万
• 依托单位: UK CENTRE FOR ECOLOGY & HYDROLOGY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV00008X%2F1
• 关键词: Using; plant; hydraulic; scaling; predict

Tropical rainforests are one of the planets most important stores of carbon, as well as being essential to water cycling at large scales. Within tropical forests the largest trees, with diameters exceeding 70 cm, store between 25-45% of the carbon, yet represent <4% of the total number of trees. These large trees also transport disproportionately more water than smaller individuals do, making them a conservation priority for the future. Large tropical trees are likely to be very old, with many between 200-500 years and some estimated to be >1400 years old. Therefore, they have survived historical extreme climate events, including drought. Yet, recent evidence suggests water transport limitations are likely to make larger trees more vulnerable to the more extreme, more frequent drought events, which are predicted for the future. However, we still do not understand how large trees manage to overcome the huge resistances associated with transporting water such large vertical distances, against gravity, which substantially increase the hydraulic stress the tree experiences in a given climate. This information is essential to understanding how vulnerable these iconic tropical trees will be to the predicted future increases in drought frequency and intensity. Large trees can minimise the effects of increasing resistance to water transport with height through changing multiple leaf and stem hydraulic traits vertically through their stem and canopy. However, data on these vertical changes are rare and do not exist for tropical trees. Consequently, there is limited knowledge concerning whether trees can or cannot compensate for the negative effects being taller has on their water transport capacity and therefore their vulnerability to future drought events.In this project we will combine novel measurements of vertical changes in tree anatomical, structural and hydraulic properties on the world's tallest tropical trees, in two different tropical regions - Amazonia and Borneo - to achieve the following aims:Aim 1: Determine how vertical changes in tree hydraulic and anatomical traits regulate the capacity of tall trees to maintain water transport to their leaves under different environmental conditions.Aim 2: Determine if key structural and architectural properties of tropical trees control the vertical gradients of plant hydraulic and anatomical properties. Aim 3: Determine how accounting for vertical gradients in hydraulic properties in tall tropical trees alters predictions of tropical forest water and carbon cycling.To achieve these aims we will study the tallest tropical trees in the world. This will include trees in Amazonia discovered in 2019 that reach 88.5 m tall, ~30m taller than any other tree recorded in the neotropics. We will compare these to equivalent sized trees in Borneo from the dipterocarp family, the family containing the tallest angiosperm species in the world. On these trees we will measure vertical gradients in hydraulic and anatomical traits on 60 trees varying in height from 20-90 m. These trees will come from eight dominant species in Brazil and Borneo, allowing us to contrast the hydraulic adaptations of trees species from drier, more seasonal climates (Brazil), to those of species that have evolved in wetter, a-seasonal climates (Borneo). To realise the three aims above, our novel vertical hydraulic trait measurements will be combined with measures of whole-tree water transport and storage, tree architectural data derived from state-of-the-art ground-based laser scanning and vegetation models. Combining these techniques will allow us to make a step-change in our current understanding of the limits to water transport in the world's tallest tropical trees and the impact this may have on carbon and water cycling under future climate scenarios.

热带雨林是地球上最重要的碳储存地之一，也是大规模水循环的必要条件。在热带森林中，直径超过70厘米的最大树木储存了25-45%的碳，但占树木总数的不到4%。这些大树也比较小的个体运输更多的水，使它们成为未来的保护重点。大型热带树木可能非常古老，许多在200-500岁之间，有些估计超过1400岁。因此，它们经受住了历史上的极端气候事件，包括干旱。然而，最近的证据表明，水运输的限制可能使较大的树木更容易受到更极端，更频繁的干旱事件的影响，这是预测未来的。然而，我们仍然不明白大型树木如何克服与运输水如此大的垂直距离相关的巨大阻力，对抗重力，这大大增加了树木在给定气候下所经历的水力应力。这些信息对于了解这些标志性的热带树木在预测未来干旱频率和强度增加时的脆弱程度至关重要。大型树木可以通过改变多个叶和茎的水力特性，垂直通过他们的茎和冠层，最大限度地减少随着高度增加对水分运输的阻力的影响。然而，这些垂直变化的数据是罕见的，不存在的热带树木。因此，关于树木是否能够或不能补偿其水分运输能力的负面影响以及未来干旱事件的脆弱性的知识有限。在这个项目中，我们将联合收割机结合对世界上最高的热带树木的解剖学，结构和水力特性的垂直变化的新测量，在两个不同的热带地区-亚马逊河和婆罗洲-实现以下目标：目标1：确定树木水力和解剖特征的垂直变化如何调节高大树木在不同环境条件下维持水分运输到叶片的能力。目标2：确定热带树木的关键结构和建筑特性是否控制植物水力和解剖特性的垂直梯度。目标三：确定热带高大树木水力特性的垂直梯度如何改变热带森林水和碳循环的预测。为了实现这些目标，我们将研究世界上最高的热带树木。这将包括2019年在亚马逊发现的高达88.5米的树木，比新热带地区记录的任何其他树木高约30米。我们将把这些与婆罗洲的龙脑香科的同等大小的树木进行比较，龙脑香科是世界上最高的被子植物。在这些树木上，我们将测量60棵高度从20-90米不等的树木的水力和解剖特征的垂直梯度。这些树木将来自巴西和婆罗洲的八个主要物种，使我们能够对比树木物种从干燥，季节性气候（巴西）到在潮湿，季节性气候（婆罗洲）中进化的物种的水力适应。为了实现上述三个目标，我们新颖的垂直水力特性测量将与全树水分运输和储存的测量，来自最先进的地面激光扫描和植被模型的树木建筑数据相结合。结合这些技术将使我们能够逐步改变我们目前对世界上最高的热带树木的水运输限制的理解，以及这可能对未来气候情景下的碳和水循环产生的影响。