the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
10 Jan 2022
10 Jan 2022
Inter- and intra-event rainfall partitioning dynamics of two typical xerophytic shrubs in the Loess Plateau of China
- 1State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- 2University of Chinese Academy of Sciences, Beijing 100049, China
- 3State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China
- 4National Observation and Research Station of Earth Critical Zone on the Loess Plateau in Shaanxi, Xi’an 710061, China
- 1State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- 2University of Chinese Academy of Sciences, Beijing 100049, China
- 3State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China
- 4National Observation and Research Station of Earth Critical Zone on the Loess Plateau in Shaanxi, Xi’an 710061, China
Abstract. Rainfall is known as the main water replenishment in dryland ecosystem, and rainfall partitioning by vegetation reshapes the spatial and temporal distribution patterns of rainwater entry into the soil. The dynamics of rainfall partitioning have been extensively studied at the inter-event scale, yet very few studies have explored its finer intra-event dynamics and the relating driving factors for shrubs. Here, we conducted a concurrent in-depth investigation of rainfall partitioning at inter- and intra-event scales for two typical xerophytic shrubs (Caragana korshinskii and Salix psammophila) in the Liudaogou catchment of the Loess Plateau, China. The event throughfall (TF), stemflow (SF), and interception loss (IC) and their temporal variations within the rainfall event as well as the meteorological factors and vegetation characteristics were systematically measured during the 2014–2015 rainy seasons. The C. korshinskii had significantly higher SF percentage (9.2 %) and lower IC percentage (21.4 %) compared to S. psammophila (3.8 % and 29.5 %, respectively) (p < 0.05), but their TF percentages were not significantly different (69.4 % vs. 66.7 %). At the intra-event scale, TF and SF of S. psammophila was initiated (0.1 vs. 0.3 h and 0.7 vs. 0.8 h) and peaked (1.8 vs. 2.0 h and 2.1 vs. 2.2 h) more quickly, and TF of S. psammophila lasted longer (5.2 vs. 4.8 h), delivered more intensely (4.3 vs. 3.8 mm∙h−1), whereas SF of C. korshinskii lasted longer (4.6 vs. 4.1 h), delivered more intensely (753.8 vs. 471.2 mm∙h−1). For both shrubs, rainfall amount was the most significant factor influencing inter-event rainfall partitioning, and rainfall intensity and duration controlled the intra-event TF and SF variables. The C. korshinskii with larger branch angle, more small branches and smaller canopy area, has an advantage to produce stemflow more efficiently over S. psammophila. The S. psammophila has lower canopy water storage capacity to generate and peak throughfall and stemflow earlier, and it has larger aboveground biomass and total canopy water storage of individual plant to produce higher interception loss compared to C. korshinskii. These findings contribute to the fine characterization of shrub-dominated eco-hydrological processes, and improve the accuracy of water balance estimation in dryland ecosystem.
Jinxia An et al.
Status: open (until 07 Mar 2022)
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RC1: 'Reviewer comments on hess-2022-4', David Dunkerley, 17 Jan 2022
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This paper explores a little further data from the same field observations as were discussed previously by some of the same authors in their 2019 HESS paper Temporally dependent effects of rainfall characteristics on inter- and intra-event branch-scale stemflow variability in two xerophytic shrubs (Yuan et al. 2019).
[Yuan, C., Gao, G., Fu, B., He, D., Duan, X., & Wei, X. (2019). Temporally dependent effects of rainfall characteristics on inter- and intra-event branch-scale stemflow variability in two xerophytic shrubs. Hydrol. Earth Syst. Sci., 23(10), 4077-4095. doi:10.5194/hess-23-4077-2019].
The same two species of shrubs are studied, and the field observations analysed here come from the same 2014-2015 data collection as were analysed by Yuan et al. (2019). The field data collection appears to have been one and the same for both papers.
Both Yuan et al. (2019) and the present ms. (An et al.) seek to explore the role of rainfall variability and plant architecture on stemflow, throughfall, and interception, paying attention to how these work at intra-event timescales. Their ability to do this is however hampered by their reliance on rainfall observations that were aggregated and logged only every 10 minutes. This is hardly sufficient temporal resolution to permit analysis of time lags before the commencement of stemflow, and various other analyses that the authors seek to make.
Given that the two papers explore the same shrub taxa in the same field area during the same two years (2014-2015), and that both explore the intra-event workings of stemflow and throughfall, I think that a key requirement is for the Introduction to make it clear and explicit how the present paper differs in scope and results from the earlier paper of Yuan et al. (2019). The earlier paper appears to have focussed more strongly on branch-scale mechanisms, but a clear distinction requires very careful reading and differences in data processing make it very difficult indeed to see what is new in the current ms.
In particular, in their Introduction (and perhaps also in a covering letter to accompany their submission) the authors should highlight what can be learned about stemflow and throughfall in the two shrub taxa that was not already demonstrated by Yuan et al. (2019). I think that it would be helpful for the authors to compare and contrast what was learned by Yuan et al. (2019) and what similarities or differences emerge in the present study (An et al.).
In other respects the paper seems entirely routine, containing nothing new in method, theory, or argument. I do think that the authors should evaluate the adequacy f their data and field sampling, however. Do the 38 rainfall events in two years form a sufficiently large sample of events? Does sampling of just four branches (line 202) represent a sufficiently large sample? What is the evidence for this being the case? And only a single individual plant of each species was used to measure throughfall and stemflow dynamics (line 198). How was the single individual selected? Is a sample of one really sufficient to draw meaningful conclusions concerning the entire species, as the authors do? These matters and similar considerations should be discussed and critically evaluated. As the paper stands, the authors merely report that they studied only a single shrub of each species but provide no evaluation of whether this is a sufficient and representative sample. (In the same vein, the use of aggregated, 10-minute rainfall amounts warrants critical comment by the authors. The authors should also report fully and properly the characteristics of the rainfall events that they monitored. To judge from the data in Yuan et al. (2019) these were mostly rather brief - from one to a few hours. But the present ms. (An et al.) does not even mention the event duration (nor, for instance, whether the rain was during daylight hours or at night - which is surely relevant to evaporative losses and hence to interception amounts). All of this must be corrected in a revision to the current ms. Some evidence of the nature of just four rainfall events can be found in Figure 5 but this is hardly sufficient.
David Dunkerley
Faculty of Science
Monash University-
AC1: 'Reply on RC1', Guangyao Gao, 18 Jan 2022
reply
Dear Pro. David Dunkerley,
Thank you very much for the prompt review on our manuscript (hess-2022-4). I want to give a quick reply to your comments about the novelty of this work. We will submit a detailed reply later.
In your comments, you stated that "Both Yuan et al. (2019) and the present ms. (An et al.) seek to explore the role of rainfall variability and plant architecture on stemflow, throughfall, and interception, paying attention to how these work at intra-event timescales." Actually, this work is greatly different from Yuan et al. (2019) which only studied the branch-scale stemflow (only one of the rainfall partitioning processes). We can see it from the title of Yuan et al. (2019), i.e., "Yuan, C., Gao, G., Fu, B., He, D., Duan, X., & Wei, X. (2019). Temporally dependent effects of rainfall characteristics on inter- and intra-event branch-scale stemflow variability in two xerophytic shrubs. Hydrol. Earth Syst. Sci., 23(10), 4077-4095. "
This work conducted a concurrent in-depth investigation of throughfall, stemflow, and interception at inter- and intra-event scales for two typical xerophytic shrubs. To our best knowledge, there was no study to investigate the intra-event variations of all the rainfall partitioning components (throughfall, stemflow, and interception loss) for shrubs. This is the main novelty of this study.
Best regards!
Guangyao Gao
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AC1: 'Reply on RC1', Guangyao Gao, 18 Jan 2022
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RC2: 'Comment on hess-2022-4', Anonymous Referee #2, 18 Jan 2022
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Reviewer comments to hess-2022-4
Rainfall partitioning (interception loss, throughfall, and stemflow) is an old theme in the field of forest hydrology, and numerous studies have been done on quantified rainfall partitioning and their influencing factors at event scale. Nevertheless, the relevant studies are lacking for shrubs of drylands, and the intra-event dynamics have been less explored. An et al. characterized and quantified the rainfall partitioning of two xerophytic shrubs at both inter-event and intra-event scale in the Loess Plateau of China. What's really interesting to me is their concurrent finer investigation (10 min) on the intertwined rainfall partitioning processes. It seems that another paper by some of the same authors has been published in HESS (Yuan et al., 2019, 23(10): 4077-4095) in digging into the branch-scale dynamics of stemflow (only one of the rainfall partitioning processes). In my view, this study steps further and provides a full view of the reciprocal dynamics among interception loss, throughfall, and stemflow at the shrub-scale and thereby discussed the underlying mechanisms. In this sense, this study adds some new insights into rainfall partitioning and has the potential for a better understanding of the shrub-dominated eco-hydrological processes in drylands. Of course, the authors should explicitly explain the difference between two papers. Moreover, this paper is in general well-written; the experimental design and data analysis are normal and acceptable; results and discussion are informative. I have some moderate/minor comments that are required before considering the manuscript for publication.
- L49: Water loss due to interception evaporates but not transpires back to atmosphere. “transpiration” here is NOT a correct term for interception loss.
- L133: A citation is missed for Flora of China.
- L271: What does values such as “11.1±8 mm”? Mean±SD or Mean±SE? Better explain for the first time as they appear.
- L305-311: Are the thresholds for the generation of TF and SF derived from regression equations comparable to or in the range of that measured using tipping bucket rain gage? A brief discussion somewhere in the Discussion section is desirable.
- L370: significantly → significant
- L404-414: The authors contributed the significant higher IC % in C. korshinskii than in S. psammophila to the higher water storage of S. psammophila. However, they used the absolute values (4.9 L versus 6.0 L) but not the normalized ones. Surely, a large canopy tends to absorb more rainwater than a small canopy, but that does necessarily mean that the large canopy has a higher capacity in retaining rainwater. Actually, the intercepts (0.92 for C. korshinskii and 1.15 for S. psammophila) in the fitted formulas between interception loss (mm) and rainfall amount (mm) in Figure 4e are indicative that C. korshinskii has a lower canopy water storage, hence a potential lower interception loss.
- L443-447: I would like to argue with the authors that the dynamic characteristics for TF such as TFI, TFI10, LETF, TFD, LGTF and LMTF are just different variables indicating the behaviors of TF but not the reasons for the generation of TF. Those variables are results but not the reasons. That means, according to those variables, it is reasonable to say which variables are indicative of an earlier or later generation of TF, but they are not the reasons that a shrub species is “beneficial to the generation of TF”. This is also the case for SF.
- The authors made a detailed description of intra-event rainfall partitioning dynamics. I suggest that they elaborate more on the potential ecological implications.
Jinxia An et al.
Jinxia An et al.
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