the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Hydrological effects of evapotranspiration in the Qilian Mountains forest belt
Yinying Jiao
Dongdong Qiu
Yuwei Liu
Lei Wang
Siyu Lu
Gaojia Meng
Xinrui Lin
Rui Li
Qinqin Wang
Longhu Chen
Niu Sun
Abstract. Mountainous areas are the main water-producing and source areas of rivers. Global climate change is transforming the distribution of plants and forms of water use. Therefore, a clear understanding of evapotranspiration in mountainous forest zone is key for understanding the ecohydrological effect of vegetation and its influence on the water cycle of the watershed. We quantified the evapotranspiration processes in the forest belts of the Qilian Mountains as well as their contribution to runoff yield and concentration based on precipitation, soil water, and plant water samples and experimental data. The study showed that transpiration of Qinghai spruce accounted for the highest proportion of evapotranspiration in the entire Qinghai spruce forest ecosystem, with an average of 79 %, which means that transpiration is much greater than evaporation. Soil water content and air humidity were the dominant factors influencing evapotranspiration in Qinghai spruce forest belts. The growing season of Qinghai spruce is characterized by greater evapotranspiration than precipitation in each month. Consequently, the forest zone does not yield flows in the eastern part of the Qilian Mountains. The warming of global temperatures and human activities are likely to trigger shifts in the distribution areas and evapotranspiration regimes of Qinghai spruce, which in turn will lead to a change in water resource patterns in the basin.
Yinying Jiao et al.
Status: final response (author comments only)
- RC1: 'Comment on hess-2022-375', Anonymous Referee #1, 30 Mar 2023
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RC2: 'Comment on hess-2022-375', Anonymous Referee #2, 14 May 2023
General comment
The authors of this manuscript aimed to assess the role of transpiration, compared to other water fluxes, in a spruce forest in the Qilian Mountains, China. In their analyses, the authors exploited the usefulness of stable isotopes of hydrogen and oxygen to investigate water fluxes in the soil-plant-atmosphere continuum.
Although this manuscript may be interesting for the readers of Hydrology and Earth System Sciences, the current version presents a poor description of the sampling approaches and laboratory methodologies, and the dataset does not seem sufficient to support the main findings (only a growing season was considered, and the authors collected only 7 xylem samples). Furthermore, the authors should have determined the uncertainty in their estimates, in order to assess the impacts on the main results.
In terms of presentation quality, the manuscript would benefit from a thorough revision of the English by a native speaker, and the authors should upload high-resolution figures with labels that are readable.
Specific comments
- Section 1: I think the introduction lacks some paragraphs describing the usefulness of stable isotopes of hydrogen and oxygen to investigate water fluxes in the soil-plant-atmosphere continuum. Furthermore, the novelty of this work is not clear (it seems a case study, but there are many like this one), and the specific objectives and/or the research questions should be clearly addressed.
- Section 2: The authors should add the area of the catchment and of the study site (it is unclear whether it is a subcatchment, a hillslope or a plot), and more specific topographic characteristics (e.g., elevation range, slope, aspect etc.). Lithology, soil type and texture should be described as well.
- Section 3.1: In this section, the authors should provide clear and detailed information about meteorological data and water sample collection. About meteorological data, the authors should clarify whether the station is located in the study site (is it representative of the local meteorological conditions?) and the temporal resolution of the measurements. About water samples, details should include temporal (monthly, weekly, daily or event timescale?) and spatial resolution (how many locations for each water source? At which elevation?), as well as depth for soil water samples (and how many locations?) and xylem samples (how many trees and locations were considered?). Furthermore, in this section the authors should describe the methodological approaches used for precipitation collection (what kind of collector was used?) and extraction of water samples from soil and plants (what kind of plant tissue was collected?).
- Section 3: This section also lacks a paragraph reporting how water samples were transported and stored before isotopic analyses, and details about laboratory analyses. These details should include the methodology used for isotopic analyses of the different water samples, the uncertainty in the isotopic measurements, any information about protocols used to ensure the quality of the analyses.
- In Section 3.3.5 and 3.3.6, the authors should clarify if they have assessed the uncertainty in their estimations, for instance, by error propagation and based on the uncertainty in the isotopic analyses and isotopic variability among various samples.
- Table 1: The number of xylem water samples (only 7) used for this study is too low. I think these few samples alone cannot support findings and the conclusions.
- Figure 3a: The authors report soil depths here, but they should have described those sampling depths in a previous section. Furthermore, the authors should clearly explain why soil depth varies for various sampling times.
- Figure 7: The authors should indicate the uncertainty in their estimates, clearly in the text and by error bars in this figure.
- I do not understand the purpose of Section 5.2 and the title does not reflect the content of the section.Technical corrections
- Figure 1: Labels are difficult to read. I suggest increasing their size and resolution.
- Line 107: “Water isotopes…were observed” is an unusual phrasing; please change the verb.
- Figure 2: Again, labels are difficult to read. I suggest increasing their size and resolution.
- Figure 3, 4, 5 and 7: Please increase the size of the labels.
- Figure 8a: The legend is unreadable; please increase the size and the resolution of the labels.Citation: https://doi.org/10.5194/hess-2022-375-RC2
Yinying Jiao et al.
Yinying Jiao et al.
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