the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Nov 2023
Regulating effects of mixed-cultivated grasslands in surface water conservation and soil erosion reduction along with restoration of alpine degraded hillsides
Yulei Ma
Jesús Rodrigo-Comino
Manuel López-Vicente
Gao-Lin Wu
Abstract. Vegetation restoration is among the most effective measures for controlling runoff and soil erosion resulting from human activity. Nevertheless, few studies have been undertaken to analyze the effects of plant restoration on maintaining the stability of the hydrological cycle, especially, in alpine degraded hillsides where mixed-cultivated grasslands predominate in the landscape. In this research, we conducted in situ monitoring using runoff plots to investigate the impact of three strategies, each combining two grass species per plot (three species in total), on a 20-degree slope, assessing the activation and volume of surface runoff and soil loss in alpine degraded hillsides over three years (2019, 2020 and 2022). A severely degraded meadow plot was used as control. The findings indicated that mixed-cultivated grasslands can effectively manage runoff and reduce soil loss as planting ages increase. Between 2019 and 2022, the values of the runoff reduction ratio decreased for Deschampsia cespitosa and Elymus nutans (DE), Poa pratensis L.cv. Qinghai and Elymus nutans (PE), and Poa pratensis L.cv. Qinghai and Deschampsia cespitosa and (PD) from -79.3 % to -115.4 %, from -130.4 % to -156.1 %, and from -48.5 % to -87.6 %, respectively. On the contrary, the mean sediment concentration reduction ratio increased from -120.9 to 55.8 % (in DE), from 112.4 to 59.7 % (in PE), and from -94.3 to 62.1 % (in PD). This implies that protective measures should be prioritized during the initial planting stage of cultivated grasslands in alpine degraded hillsides. The key factors affecting soil loss and runoff were rainfall amount, duration and intensity (60-min intensity). We conclude that the results of this study can serve as scientific guides to design efficient policy decisions for planning the most effective vegetation restoration in the severely degraded hillside alpine meadows.
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Yulei Ma et al.
Status: open (until 28 Dec 2023)
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RC1: 'Comment on hess-2023-257', Corinna Gall, 14 Nov 2023
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The study by Yulei Ma et al. deals with a very interesting topic, namely the influence of different combinations of grass species on runoff formation and soil erosion to derive effective grassland restoration strategies. For this purpose, surface runoff and sediment discharge were measured under natural rainfall over a period of four years for three different mixed-cultivated grasslands and one severely degraded meadow as a control. Furthermore, precipitation, soil and vegetation characteristics were recorded in order to determine the most important factors that additionally influence runoff and soil erosion.
Overall, the manuscript is in good order and comprehensibly written. However, the abstract as well as the results and discussion section should be revised with the following comments.
I would also like to suggest changing the title of the study, as the term "surface water conservation" is not clear and also not explained in the text.
Abstract
In the present form of the abstract, the problem of the study is not clear and the presentation of the main results is also difficult for the reader to understand, as runoff reduction ratio and sediment concentration ratio are not common parameters in erosion research. Since these parameters will be explained later, I think it is acceptable to use them in the study, but in the abstract I would recommend presenting the results in a generally understandable way to increase the impact of the abstract.
Line 20: The term “maintain the stability of the hydrological cycle” is only once used in the abstract and never again in the study itself, which is confusing. Especially at the beginning of the abstract the meaning of this term is not clear.
Line 22: Please clarify by adding “restoration strategies”.
Line 26: What do you mean with “manage runoff” here?
Introduction
The introduction is well structured, so that the objective of the study can be derived from the comprehensibly presented problems of alpine grassland ecosystems.
Line 92: Remove one “the”.
Line 97: Please add “soil characteristics” for clarification.
Line 123: Please write out the abbreviations of the three mixed-cultivated grassland types in the introduction again. For example, “SDM” was never explained before in the text.
Materials and methods
The methods section is very detailed and precisely written so that no questions remain unanswered.
Line 147: Do you mean “epipedon” here? Also check the caption of Figure 1 (line 626 + 628); please also correct here “SEM”.
Line 148: Clarify the reference to Fig. 1b and Fig. 1c.
Line 150: Why is this value shown as a multiplication?
Line 161: Shouldn't the grass species reduce soil erosion and increase surface runoff? Please clarify.
Line 241: Lower the bracket after “cm3”.
Line 245: Remove “cohesion” one time.
Results
The presentation of the results in the figures is clear and comprehensible. However, the results in the text are partially generalized in comparison to the information in the figures. Here, attention should be paid to indicating in the text whether differences are significant or non-significant.
In my perspective, there is also one important result of the study that has not yet been mentioned. I guess that you selected three different grass mixtures because you originally assumed that there would be differences in runoff and soil erosion due to their different structural properties, which you also described in your study. However, there were no measurable differences between the grass mixtures, which is also an important result that should be mentioned and discussed!
Line 272: Since increased runoff and reduced soil erosion is the desired outcome, a word other than "dramatically" would be more appropriate here.
Lines 279-281: According to Fig. 3b there is no significant difference between SDM and the grass-mixtures for 2019 regarding soil erosion and also in 2022 the differences in soil erosion are not significant between treatments. However, you can state a lower soil erosion for all treatments in 2022 compared to 2020, and for 2019 for the treatments PE and PD. Please be more precise here.
Line 292-294: According to Fig. 4a this statement is true for the treatments DE and PE, but not PD. Please do not generalize the results for all treatments and be more precise.
Line 301: According to Fig 4d the mean values of RRSR are somewhere between 50 and 0. Please make it clear what is meant here.
Figure 1: Please correct the typos in the figure caption.
Figure 5: Please check that the technical terms in the figure correspond to those in the caption. Why are the median lines are missing in these boxplots? It would be better coordinated if the median values were also shown in this figure.
Discussion
Consider to include a discussion about the missing difference in runoff and soil erosion of the three selected grassland mixtures. If this part is missing from the discussion, the question arises as to why three different grass mixtures were chosen in the first place.
Line 372: What does the "more" refer to?
Lines 374-384: This part is more suitable for section 4.2 where you discuss the effects of grassland community characteristics on runoff and soil loss.
Citation: https://doi.org/10.5194/hess-2023-257-RC1
Yulei Ma et al.
Yulei Ma et al.
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