Controls on leaf water hydrogen and oxygen isotopes: A local investigation across seasons and altitude
- 1State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
- 2National Observation and Research Station of Earth Critical Zone on the Loess Plateau of Shaanxi, Xi’an, 710061, China
- 3Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
- 4State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, 610065, Chengdu, China
- 5Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, 710054, China
- 6College of resources and environmental engineering, Ludong University, 264025, Yantai, China
- 1State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
- 2National Observation and Research Station of Earth Critical Zone on the Loess Plateau of Shaanxi, Xi’an, 710061, China
- 3Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
- 4State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, 610065, Chengdu, China
- 5Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, 710054, China
- 6College of resources and environmental engineering, Ludong University, 264025, Yantai, China
Abstract. The stable oxygen (δ18Oleaf) and hydrogen (δ2Hleaf) isotopes of leaf water act as a bridge that connects hydroclimate to plant-derived organic matter. However, it remains unclear whether the source water (i.e., twig water, soil water, and precipitation) or meteorological parameters (i.e., temperature, relative humidity, and precipitation) are the dominant controls on δ18Oleaf and δ2Hleaf. Here, we reported seasonal analysis of δ18Oleaf and δ2Hleaf together with isotopes from potential source waters and meteorological parameters along an elevation transect on the Chinese Loess Plateau. We found that δ2Hleaf values were more closely correlated with source water isotopes than δ18Oleaf values, whereas δ18Oleaf and δ2Hleaf values were similarly correlated with meteorological parameters. Dual-isotope analysis showed that the δ18Oleaf and δ2Hleaf values were closely correlated because of their similar altitudinal and seasonal responses, and so generated a well-defined isotope line relative to the local meteoric water line (LMWL). We also compared the measured δ18Oleaf and δ2Hleaf values with predicted values by the Craig-Gordon model, and found no significant differences between them. We demonstrate that the first-order control on δ18Oleaf and δ2Hleaf values was the source water, and the second-order control was the enrichment associated with biochemical and environmental factors.
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Jinzhao Liu et al.
Status: open (until 01 Sep 2022)
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RC1: 'Comment on hess-2022-246', Anonymous Referee #1, 30 Jul 2022
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I appreciate the Editor to give me a chance to review the paper.
The manuscript “Controls on leaf water hydrogen and oxygen isotopes: A local investigation across seasons and altitude” presents a dataset on analysis of δ18Oleaf and δ2Hleaf together with isotopes from potential source waters and meteorological parameters along an elevation transect on the Chinese Loess Plateau. The research topic is important and within the scope of the journal.
But it seems a bit simple and not systematic in the content. The manuscript at present lacks novel results or theory that would provide a significant advance in this field.
1) The main conclusion of this paper has been confirmed by previous studiesï¼ the first-order control on δ18O leaf and δ2Hleaf values was the source waterï¼and the second-order control was the enrichment associated with biochemical and environmental factorsï¼Cernusak et al., 2016; Barbour et al., 2017; Munksgaard et al., 2017). The experimental design and results of the paper are not innovative.
2) A large number of studies have shown that the enrichment associated with plant transpiration is an important factor affecting δ18Oleaf and δ2Hleaf values. However, the authors did not carry out research and discussion in this paper.
3)Plants and soils were sampled in May, July, and September 2020 (In the experimental design). Why only choose this three months? Is it persuasive?
4ï¼Besides, what is the specific sampling interval?
5) Why only one or two deciduous and coniferous trees were chosen in each plot?
6) There are large differences in population and altitude between sampling points 5-8(Fig.1). But there is no weather station here.
7) In 4.1ï¼these results argued with the recent global meta-analysis thatδ18Oleaf and δ2Hleaf values reflect climatic parameters (i.e., RH and temperature) differently. What are the reasons for the controversial conclusion?
8) It seems a bit simple in the conclusion. It needs a stronger ending for the conclusion. Besides, it is suggested to supplement the existing deficiencies and prospects.
Jinzhao Liu et al.
Jinzhao Liu et al.
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