干旱对氧气同位素的影响记录在树木环中
Kinzie Bailey1,2,3, Paul Szejner4, Brandon Strange1,2,5
1School of Natural Resources and the Environment, University of Arizona, 1064 East Lowell Street, Tucson, AZ 85721, USA.
Tree physiology
|April 7, 2025
概括
树环中的稳定同位素 (δ18Ocell) 可以揭示过去的用水情况,但干旱性会影响它们的准确性. 这项研究表明,干旱影响氧气交换 (顶峰),影响树木如何记录水源和湿度信号.
科学领域:
- 古气候学和登德罗年代学.
- 同位素地球化学 同位素地球化学
- 植物生理学 植物生理学
背景情况:
- 树木纤维素 (δ18Ocell) 中稳定的氧同位素用于重建树木水源和大气湿度.
- 假设 δ18Ocell 反映降水的假设在树木使用更深水的干旱地区往往是不准确的.
- 氧交换比率 (pex) 影响 δ18Ocell 信号,但通常被视为常数且难以测量.
研究的目的:
- 评估明显的pex (顶峰) 的变化如何影响Ponderosa松 δ18Ocell中的水源和干旱信号的重建.
- 为了研究现场干旱度,顶峰和树环蒸汽压力缺陷 (VPD) 的记录之间的关系.
- 改善 δ18Ocell 中的水源和 VPD 信号的解,特别是在北美季风 (NAM) 等半干旱地区.
主要方法:
- 从NAM地区的七个Ponderosa松树中收集了西水和木纤维素样本.
- 在西水和木纤维素中测量了 δ18O.
- 将测量和建模的 δ18Ocell 值进行比较,以评估顶点变化对环境信号的影响.
主要成果:
- 干旱地区在 δ18Ocell 中代表蒸汽压力缺陷 (VPD) 信号不足,而湿地区则代表过多.
- 表面的顶峰 (apex) 随着地点的干旱程度而变化:高干旱程度 (降水量低,VPD高) 导致高顶峰,反之亦然.
- 干旱度和顶峰之间的关系表明,一种复杂的相互作用影响着树环中的同位素信号忠实性.
结论:
- 现场的干旱程度显著影响表面的峰值 (apex),使得解释 δ18Ocell 作为水源和湿度的直接代理而变得复杂.
- 了解干旱度-顶峰关系对于准确地从树环中重建过去的环境条件至关重要.
- 未来的研究应该考虑顶部的年度环变化,以更好地区分水源和VPD信号,特别是在季风地区.
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