ENS de Lyon, UMR 5600 Environnement Ville société, CNRS, Lyon, France.
ENS de Lyon, UMR 5600 Environnement Ville société, CNRS, Lyon, France.
Sci Total Environ. 2024 Nov 20;952:175916. doi: 10.1016/j.scitotenv.2024.175916. Epub 2024 Sep 1.
Riparian trees are particularly vulnerable to drought because they are highly dependent on water availability for their survival. However, the response of riparian tree species to water stress varies depending on regional hydroclimatic conditions, making them unevenly vulnerable to changing drought patterns. Understanding this spatial variability in stress responses requires a comprehensive assessment of water stress across broader spatial and temporal scales. Yet, the precise ecophysiological mechanisms underlying these responses remain poorly linked to remotely sensed indices. To address this gap, the implementation of remote sensing methods coupled with in situ validation is essential to obtain consistent results across diverse spatial and temporal contexts. We conducted a multi-tool analysis combining multispectral and thermal remote sensing indices with in situ ecophysiological measurements at different temporal scales to analyze the responses of white poplar (Populus alba) to seasonal changes in drought along a hydroclimatic gradient. Using this approach, we demonstrate that white poplars along the Rhône River (France) exhibit contrasting responses and behaviors during drought depending on the latitudinal context. White poplars in a Mediterranean climate show rapid stomatal closure to reduce water loss and maintain high minimum water potential levels, although this results in a decrease in remotely sensed greenness. Conversely, white poplars located upstream in a temperate climate show high transpiration and stable greenness but lower minimum water potential and water content. A site in the middle of the gradient has intermediate responses. These results demonstrate that white poplars along a climate gradient can have a range of responses to drought along the iso/anisohydricity continuum. These results are important for future climatic conditions because they show that the same species can have different mechanisms of drought resilience, even in the same river valley. This raises questions regarding how these riparian tree populations will respond to future climatic and hydrological conditions.
河岸树木特别容易受到干旱的影响，因为它们的生存高度依赖于水资源的可用性。然而，河岸树种对水分胁迫的反应因区域水文气候条件而异，这使得它们对不断变化的干旱模式的脆弱性不均衡。要了解这些压力反应的空间变异性，需要在更广泛的时空尺度上对水分胁迫进行全面评估。然而，这些反应背后的确切生理生态机制与遥感指数的联系仍然很差。为了解决这一差距，必须将遥感方法与现场验证相结合，以在不同的空间和时间背景下获得一致的结果。我们进行了多工具分析，结合多光谱和热遥感指数以及不同时间尺度的现场生理生态测量，以分析白杨树（Populus alba）对沿水文气候梯度季节性干旱变化的反应。通过这种方法，我们证明了沿罗纳河（法国）的白杨树在不同的纬度背景下表现出不同的反应和行为。在具有地中海气候的地区，白杨树会迅速关闭气孔以减少水分流失并保持高的最小水势水平，尽管这会导致遥感绿色度下降。相反，位于温带气候上游的白杨树表现出高蒸腾作用和稳定的绿色度，但最小水势和含水量较低。位于梯度中间的一个地点具有中间反应。这些结果表明，沿气候梯度的白杨树可以在等渗/异渗性连续体上对干旱产生一系列反应。这些结果对于未来的气候条件很重要，因为它们表明即使在同一河谷中，同一物种也可能具有不同的抗旱机制。这引发了关于这些河岸树种种群将如何应对未来气候和水文条件的问题。
