Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?
Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?
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DOI：
10.1029/2019gl084749
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发表时间：
2019-12
影响因子：
5.2
通讯作者：
K. C. Pattnayak;J. Tindall;R. Brienen;J. Barichivich;E. Gloor
中科院分区：
文献类型：
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作者：
K. C. Pattnayak;J. Tindall;R. Brienen;J. Barichivich;E. Gloor
大尺度（> - 500 km）降水氧同位素比值（δ18Op）的空间梯度包含有关水文循环的信息。它们是由降水和蒸散发沿气包路径的相互作用产生的，但这些抵消效应很难解开，使土地覆盖变化对δ18Op的影响的量化复杂化。研究表明，利用南美洲热带地区陆地衍生降水示踪剂的气候模式模拟可以定性地解开缠结。然后，我们要么改变自1870年以来观察到的土地覆盖，要么用裸地取代亚马逊森林，以确定结果信号。我们的研究结果表明，历史变化的土地覆盖对年平均δ18O同位素比值梯度的影响很小，不太可能检测到，尽管在旱季有一个明显的信号。此外，水循环变化对亚马逊河流域古记录δ18Op的影响可能被高估了，需要重新解释。
Large‐scale (>500 km) spatial gradients of precipitation oxygen isotope ratios (δ18Op) hold information about the hydrological cycle. They result from the interplay between rainout and evapotranspiration along air‐parcel paths, but these counteracting effects are difficult to disentangle, complicating quantification of the effect of land cover change on δ18Op. We show that disentangling can qualitatively be achieved using climate model simulations with a land‐derived precipitation tracer for tropical South America. We then either vary land cover as observed since 1870 or replace Amazon forests with bare land to determine the resulting signals. Our results indicate that effects of historically changing land cover on annual mean δ18O isotope‐ratio gradients are small and unlikely detectable, although there is a noticeable signal during the dry season. Furthermore, the effect of changes in water recycling on Amazon δ18Op in paleo‐records may have been overestimated and need reinterpretation.