Dry season rainfall as a source of transpired water in a seasonal, evergreen forest in the western Amazon region inferred by water stable isotopes
Dry season rainfall as a source of transpired water in a seasonal, evergreen forest in the western Amazon region inferred by water stable isotopes
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DOI：
10.3389/frwa.2022.886558
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发表时间：
2022-09-23
影响因子：
2.9
通讯作者：
Aguiar, Renata Goncalves
中科院分区：
文献类型：
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作者：
Borma, Laura De Simone;Demetrio, Wilian Carlo;Aguiar, Renata Goncalves
目前的工作旨在调查潜在的水源植物在一个地区的万年青森林位于亚马逊河流域西部（Rebio贾鲁）。我们使用天然丰富的水同位素-δ H-2和δ O-18-在干旱期开始时（2016年5月）和干旱期结束时（2016年10月）追踪植物的主要水源/在严重的厄尔尼诺干旱（ENSO 2015/16）之后过渡到湿润期（2016年10月）。土壤样品收集在土壤剖面高达4米深。2016年5月和10月，从18棵树（14种）中采集了植物样本。2015年9月至2017年2月期间收集了雨水和河水样本。我们发现，在干旱期/向湿润期过渡的结束时（即，2016年10月），平均植物木质部信号更丰富（δ H-2：-20.0 +/- 8.1 ppm; δ O-18：-1.13 +/- 1.88 ppm）（δ H-2：-36.7 +/- 5.6 ppm; δ O-18：-3.50 +/- 1.30 ppm），干旱期开始。2016年5月平均同位素土壤信号（δ H-2：-35.4 +/- 5.90千分之一; δ O-18：-5.19 +/- 0.70千分之一）比10月份略有减少（δ H-2：-27.6 +/-13.8 ‰; δ O-18：-4.35 +/-1.73 ‰），并且通常比木质部信号更耗尽。在双同位素空间中，木质部信号在干旱期开始时遵循的降雨信号的湿润期，而木质部信号在干旱期结束/过渡到湿润期遵循的信号的旱季降雨，这表明植物大多蒸腾最近的雨水。与预期相反的是，我们没有发现在木质部信号的土壤孔隙中存储的水的证据，这表明，以满足干旱期的水分需求，植物不使用从过去的时期存储在土壤层中的水。
The present work aimed to investigate the potential sources of water for plants in an area of evergreen forest located in western Amazonia (Rebio Jaru). We used a natural abundance of water isotopes-delta H-2 and delta O-18-to trace the main source of water to plants at the beginning of the dry period (May 2016) and at the end of the dry period/transition to the wet period (October 2016) following a severe El Nino drought (ENSO 2015/16). Soil samples were collected in a soil profile up to 4 m depth. Plant samples from 18 trees (14 species) were collected in May and in October 2016. Rainwater and river water samples were collected between September 2015 and February 2017. We found that, at the end of the dry period/transition to the wet period (i.e., October 2016), the average plant xylem signal was more enriched (delta H-2: -20.0 +/- 8.1 parts per thousand; delta O-18: -1.13 +/- 1.88 parts per thousand) than in May 2016 (delta H-2: -36.7 +/- 5.6 parts per thousand; delta O-18: -3.50 +/- 1.30 parts per thousand), the onset of the dry period. The averaged isotopic soil signal in May 2016 (delta H-2: -35.4 +/- 5.90 parts per thousand; delta O-18: -5.19 +/- 0.70 parts per thousand) is slightly more depleted than in October (delta H-2: -27.6 +/- 13.8 parts per thousand; delta O-18: -4.35 +/- 1.73 parts per thousand) and, in general, more depleted than the xylem signal. In the dual isotope space, the xylem signal at the beginning of the dry period follows the rainfall signal of the wet period, while the xylem signal at the end of the dry period/transition to the wet period follows the signal of the dry season rainfall, suggesting that plants mostly transpire recent rainwater. Contrary to what was expected, we did not find evidence in the xylem signal of the water stored in the soil pores, which suggests that to meet to the water demands of the dry period, plants do not use the water from past periods stored in the soil layers.