the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 May 2023
Global meta-analysis of water cycling response to plant mixture
Abstract. Plant mixtures maintain irreplaceable ecosystem services through biodiversity conservation, guarantee food security, and buffer climate change. However, the effects of plant mixing on the water cycle remain poorly understood despite the significance of the water cycle in maintaining life on Earth. Here, we conducted a meta-analysis using a global data set of 1,631 paired observations from 88 publications to explore how plant mixtures affect seven critical water cycle processes (soil water content, runoff, infiltration, soil evaporation, canopy transpiration, throughfall, and water use efficiency). We found that plant mixtures reduced mean soil water content (1.5 %), runoff (12.3 %), and soil evaporation (7.8 %), while improving soil infiltration (42.7 %), leaf transpiration (13.5 %), and water use efficiency (40.9 %). The effect size of plant mixtures greatly depended on ecosystem types; crop mixtures significantly reduced soil evaporation (10.7 %) and runoff (22.1 %), whereas mixed forest and agroforestry systems significantly enhanced soil infiltration rates. Moreover, the effect size of the plant mixture also varied with climate (mean annual precipitation), soil properties (organic matter content, bulk density, and total nitrogen content), and management practices (crop type, fertilization, and irrigation). In plant minutes, resource complementarity, abiotic facilitation and biotic feedback may be the underlying mechanisms that regulate water cycle. This work highlights the importance of plant mixtures in facilitating positive water cycles and provide insights into the establishment of sustainable artificial ecosystems.
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RC1: 'Comment on egusphere-2023-719', Ning Chen, 17 Jul 2023
This meta-analysis work analyzed how does plant mixture affect land surface water cycle. This topic is very important and this work is timely to inform what is the situation. The authors collected a very good data, and the methodological framework is robust. Therefore, this is a nice and solid work. I'm glad to read it at this stage. I have no big major concern except several technical points.
Line 28: I would like to remove “global”, as plants play their roles mainly in the local - regional scales, and their effects are largely limited in the global scale.
Line 38: remove the dot
line 40: what does the “this” mean is unclear, rephrase please
line 50-51: it’s unclear what is “the region”? clarify
Line 80-82: it will be better to write the search expression in a formal way, which will benefit reproduction
line 103: please provide details about the data source
Line 167: replace these abbreviation names with “water cycle” or similar words, to make it simpler and clearer
line 188: “at” → “among”
line 189: in the topsoil (0-20 cm) in deeper soil? An “and” is missing here?
Figure 10: legend within each panel is not necessary. It’s better to remove them to keep the figure more concise
Citation: https://doi.org/10.5194/egusphere-2023-719-RC1 -
AC1: 'Reply on RC1', Xiaodong Gao, 25 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC1-supplement.pdf
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AC1: 'Reply on RC1', Xiaodong Gao, 25 Jul 2023
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CC1: 'Comment on egusphere-2023-719', Yakun Tang, 22 Jul 2023
This paper investigates the effect of plant mixture on water cycle process. The authors perform a meta-analysis, using 1631 paired observations (monocultures-mixtures) from 88 published studies. They conclude that, compared to monoculture, plant species mixtures can promote positive hydrological processes by improving plant water use and reducing unproductive water consumption. Given the relatively fewer information on hydrological processes in relation to plant mixture in previous studies, compared to biomass and soil properties, the study is of great interest. However, the descriptions of statistical analyses are incomplete, and the explanations of how to analyze the effects of mean annual precipitation and temperature on the relationship between plant mixtures and water cycling, as well as the roles of other influencing factors, are unclear. In the discussion, the mechanisms underlying the impact of plant mixtures on hydrological processes are mainly attributed to complementarity and interspecific facilitation, with selection effects and complementarity effects also mentioned. These theories form the foundation for understanding the relationship between biodiversity and ecosystem functions. However, the article does not effectively integrate these theories with the research results.
Citation: https://doi.org/10.5194/egusphere-2023-719-CC1 -
AC2: 'Reply on CC1', Xiaodong Gao, 25 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC2-supplement.pdf
-
AC2: 'Reply on CC1', Xiaodong Gao, 25 Jul 2023
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RC2: 'Comment on egusphere-2023-719', Anonymous Referee #2, 22 Sep 2023
This meta-analysis examines the effects of plant mixtures on various processes of the water cycle and how these effects differ among ecosystem types, climate conditions, soil properties, and management practices. The authors report that plant mixtures have both positive and negative impacts, depending on the water cycle process considered and that the effect size of plant mixtures strongly depend on ecosystem types considered as well es soil and climatic factors.
While the topic of the study is highly interesting, I have some major concerns:
- The distribution of the vegetation types and also of the water cycle processes considered is highly unbalanced. The purpose of a global meta-analysis becomes questionable when there are fewer than 10 grassland studies included and for some processes, fewer than 10 publications are available (as noted in my specific comment). The limited number of publications makes it challenging to derive meaningful results, especially when comparing processes across different ecosystem types. I recommend either expanding the number of studies in the meta-analysis or focusing on ecosystems with a substantial number of studies (such as forests, agroforestry, and croplands). If the latter option is chosen, please update the title accordingly.
- It is not clear what is a monoculture in agroforestry. “Agroforestry refers to any of a broad range of land use practices where pasture or crops are integrated with trees and shrubs [https://en.wikipedia.org/wiki/Agroforestry]. In forests it is likely the dominating tree species in a plantation. However, this needs to be defined/explained. Thus, further explanations and definitions are needed, and probably the authors need to re-evaluate the studies.
- In addition, the text needs linguistic revision. In particular, the use of scientific terms and the presentation of graphics are sometimes a bit sloppy. I have listed some, but not all, typos and incorrectly used terms below.
Specific comments:
Ls13-14: Please rephrase. Since meta analyses are based on many publications, some understanding how plant mixtures impact the water cycle is already there. But, are there contrasting findings, or could findings be generalized, even over different vegetation types?
L17: In terms of functions such as transpiration “increasing” is likely more appropriated that “improved”
L22: Do you mean “mixtures” instead of “minutes”?
L23: “impact” or similar is more appropriated than “regulate”
L24: What is a “positive water cycle”? please rephrase.
L35: What is meant by “Plant mixtures […] not only promote species recruitment”? Maybe remove as not related to the study.
L38: Remove dot before the references.
Ls42-45: Unclear, what is meant by negative effects, if the result of higher diversity is improved soil water availability. Please elaborate on this.
L44: Strange wording “overproduction of mixtures”. Do you mean overyielding?
L48: Table 1 does not show that “most studies have focused only on the effects of plant mixtures on individual or several of these water cycle processes”. Please correct.
Ls50-52: It would be beneficial if some specific examples of regional differences in the relationship between plant diversity and water cycle processes were presented in the introduction.
L63 (and L 235): Misleading citation, Lange et al. 2015 and Chen et al. 2020 reported on increases soil organic matter content with plant diversity. Effects on soil water holding capacity are not assessed/discussed.
Ls63-65: I disagree with this sentence. I think there is a good in-depth understanding of how plant diversity impacts biological and physical ecosystem properties, which in turn affect the water cycle. A global meta-study can increase the knowledge of general patterns and drivers among regions and vegetation types as well as differences among them.
Ls86-92: Based on Figure 1, 4 and Table S1, the ecosystem types and the water cycle processes are very unbalanced in this meta analyses. For instance, only a few grasslands are included in this study and just a few studies that investigate soil evaporation (7), throughfall (3), leaf transpiration (7). Though, it is possible to calculate effect sizes based on only a few studies/observations, I think this is a caveat for a general global meta-analysis.
L99: “seed” or “species” sown?
L99: Please elaborate on the rationale and methods of the simulations.
L101: Add “along the soil profile” after measurement interval.
L105: Please rephrase. SOC is a component of the soil organic matter, not vice versa.
L106: What does “available” mean, “plant available”? Maybe use “mineral” instead.
L142: Do you mean “maximum likelihood” instead of “restricted likelihood“.
L162: This seems a bit selective. Based on Figure 4, only water use efficiency was different in croplands from grassland, but see my earlier comment the unbalanced number of studies for ecosystems.
Ls163-164: Unclear. Please rephrase.
L189: Unclear. Please rephrase.
Ls189-190: Unclear. Please rephrase. What exactly does the significant interaction term between MAT and sampling depth tell; different directions, different slopes?
L211: Not clear what kind of plant communities were compared when assessing the effect of legumes on the diversity effect: non-legume monocultures vs non-legume mixtures, legume monocultures vs legume mixtures, non-legume monocultures vs. legume mixtures,… This should be defined.
L239: Delete “and”.
Ls257-262: I suggest to remove the section on biotic interactions/facilitation, as this is not considered in this study and some more elaborated discussions on how biotic interactions impact water processes are needed.
Figures and Tables: Please provide information on the abbreviations in all figures (e.g. missing in Figure 2 and Figure S3, Table S1), so that all figures can be understood on a stand-alone basis.
Figure 2: Please rephrase the captions, unclear.
Figure 3b: I am wondering if the trendline would be similar, if the single observation at 15 years is not included. The huge confidence interval is also remarkable.
Figures 5 & 6: What is the “relative weight”, how and why was it calculated? Also, the red lines in most panels do not properly represent the distribution of points (observations), in particular in the panels 100-200mm and 200-500mm. Please explain.
Figure 9: Check letters on the panels. In the captions, add carbon to “soil organic content”.
Table S1: Typo in the captions: should be “throughfall”. Also, three of the 88 studies do not have any entry in the responses of water cycle processes to plant mixtures? In addition, I strongly suggest to include information on ecosystem types, the studies deal with.
Citation: https://doi.org/10.5194/egusphere-2023-719-RC2 -
AC3: 'Reply on RC2', Xiaodong Gao, 25 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC3-supplement.pdf
Status: closed
-
RC1: 'Comment on egusphere-2023-719', Ning Chen, 17 Jul 2023
This meta-analysis work analyzed how does plant mixture affect land surface water cycle. This topic is very important and this work is timely to inform what is the situation. The authors collected a very good data, and the methodological framework is robust. Therefore, this is a nice and solid work. I'm glad to read it at this stage. I have no big major concern except several technical points.
Line 28: I would like to remove “global”, as plants play their roles mainly in the local - regional scales, and their effects are largely limited in the global scale.
Line 38: remove the dot
line 40: what does the “this” mean is unclear, rephrase please
line 50-51: it’s unclear what is “the region”? clarify
Line 80-82: it will be better to write the search expression in a formal way, which will benefit reproduction
line 103: please provide details about the data source
Line 167: replace these abbreviation names with “water cycle” or similar words, to make it simpler and clearer
line 188: “at” → “among”
line 189: in the topsoil (0-20 cm) in deeper soil? An “and” is missing here?
Figure 10: legend within each panel is not necessary. It’s better to remove them to keep the figure more concise
Citation: https://doi.org/10.5194/egusphere-2023-719-RC1 -
AC1: 'Reply on RC1', Xiaodong Gao, 25 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Xiaodong Gao, 25 Jul 2023
-
CC1: 'Comment on egusphere-2023-719', Yakun Tang, 22 Jul 2023
This paper investigates the effect of plant mixture on water cycle process. The authors perform a meta-analysis, using 1631 paired observations (monocultures-mixtures) from 88 published studies. They conclude that, compared to monoculture, plant species mixtures can promote positive hydrological processes by improving plant water use and reducing unproductive water consumption. Given the relatively fewer information on hydrological processes in relation to plant mixture in previous studies, compared to biomass and soil properties, the study is of great interest. However, the descriptions of statistical analyses are incomplete, and the explanations of how to analyze the effects of mean annual precipitation and temperature on the relationship between plant mixtures and water cycling, as well as the roles of other influencing factors, are unclear. In the discussion, the mechanisms underlying the impact of plant mixtures on hydrological processes are mainly attributed to complementarity and interspecific facilitation, with selection effects and complementarity effects also mentioned. These theories form the foundation for understanding the relationship between biodiversity and ecosystem functions. However, the article does not effectively integrate these theories with the research results.
Citation: https://doi.org/10.5194/egusphere-2023-719-CC1 -
AC2: 'Reply on CC1', Xiaodong Gao, 25 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC2-supplement.pdf
-
AC2: 'Reply on CC1', Xiaodong Gao, 25 Jul 2023
-
RC2: 'Comment on egusphere-2023-719', Anonymous Referee #2, 22 Sep 2023
This meta-analysis examines the effects of plant mixtures on various processes of the water cycle and how these effects differ among ecosystem types, climate conditions, soil properties, and management practices. The authors report that plant mixtures have both positive and negative impacts, depending on the water cycle process considered and that the effect size of plant mixtures strongly depend on ecosystem types considered as well es soil and climatic factors.
While the topic of the study is highly interesting, I have some major concerns:
- The distribution of the vegetation types and also of the water cycle processes considered is highly unbalanced. The purpose of a global meta-analysis becomes questionable when there are fewer than 10 grassland studies included and for some processes, fewer than 10 publications are available (as noted in my specific comment). The limited number of publications makes it challenging to derive meaningful results, especially when comparing processes across different ecosystem types. I recommend either expanding the number of studies in the meta-analysis or focusing on ecosystems with a substantial number of studies (such as forests, agroforestry, and croplands). If the latter option is chosen, please update the title accordingly.
- It is not clear what is a monoculture in agroforestry. “Agroforestry refers to any of a broad range of land use practices where pasture or crops are integrated with trees and shrubs [https://en.wikipedia.org/wiki/Agroforestry]. In forests it is likely the dominating tree species in a plantation. However, this needs to be defined/explained. Thus, further explanations and definitions are needed, and probably the authors need to re-evaluate the studies.
- In addition, the text needs linguistic revision. In particular, the use of scientific terms and the presentation of graphics are sometimes a bit sloppy. I have listed some, but not all, typos and incorrectly used terms below.
Specific comments:
Ls13-14: Please rephrase. Since meta analyses are based on many publications, some understanding how plant mixtures impact the water cycle is already there. But, are there contrasting findings, or could findings be generalized, even over different vegetation types?
L17: In terms of functions such as transpiration “increasing” is likely more appropriated that “improved”
L22: Do you mean “mixtures” instead of “minutes”?
L23: “impact” or similar is more appropriated than “regulate”
L24: What is a “positive water cycle”? please rephrase.
L35: What is meant by “Plant mixtures […] not only promote species recruitment”? Maybe remove as not related to the study.
L38: Remove dot before the references.
Ls42-45: Unclear, what is meant by negative effects, if the result of higher diversity is improved soil water availability. Please elaborate on this.
L44: Strange wording “overproduction of mixtures”. Do you mean overyielding?
L48: Table 1 does not show that “most studies have focused only on the effects of plant mixtures on individual or several of these water cycle processes”. Please correct.
Ls50-52: It would be beneficial if some specific examples of regional differences in the relationship between plant diversity and water cycle processes were presented in the introduction.
L63 (and L 235): Misleading citation, Lange et al. 2015 and Chen et al. 2020 reported on increases soil organic matter content with plant diversity. Effects on soil water holding capacity are not assessed/discussed.
Ls63-65: I disagree with this sentence. I think there is a good in-depth understanding of how plant diversity impacts biological and physical ecosystem properties, which in turn affect the water cycle. A global meta-study can increase the knowledge of general patterns and drivers among regions and vegetation types as well as differences among them.
Ls86-92: Based on Figure 1, 4 and Table S1, the ecosystem types and the water cycle processes are very unbalanced in this meta analyses. For instance, only a few grasslands are included in this study and just a few studies that investigate soil evaporation (7), throughfall (3), leaf transpiration (7). Though, it is possible to calculate effect sizes based on only a few studies/observations, I think this is a caveat for a general global meta-analysis.
L99: “seed” or “species” sown?
L99: Please elaborate on the rationale and methods of the simulations.
L101: Add “along the soil profile” after measurement interval.
L105: Please rephrase. SOC is a component of the soil organic matter, not vice versa.
L106: What does “available” mean, “plant available”? Maybe use “mineral” instead.
L142: Do you mean “maximum likelihood” instead of “restricted likelihood“.
L162: This seems a bit selective. Based on Figure 4, only water use efficiency was different in croplands from grassland, but see my earlier comment the unbalanced number of studies for ecosystems.
Ls163-164: Unclear. Please rephrase.
L189: Unclear. Please rephrase.
Ls189-190: Unclear. Please rephrase. What exactly does the significant interaction term between MAT and sampling depth tell; different directions, different slopes?
L211: Not clear what kind of plant communities were compared when assessing the effect of legumes on the diversity effect: non-legume monocultures vs non-legume mixtures, legume monocultures vs legume mixtures, non-legume monocultures vs. legume mixtures,… This should be defined.
L239: Delete “and”.
Ls257-262: I suggest to remove the section on biotic interactions/facilitation, as this is not considered in this study and some more elaborated discussions on how biotic interactions impact water processes are needed.
Figures and Tables: Please provide information on the abbreviations in all figures (e.g. missing in Figure 2 and Figure S3, Table S1), so that all figures can be understood on a stand-alone basis.
Figure 2: Please rephrase the captions, unclear.
Figure 3b: I am wondering if the trendline would be similar, if the single observation at 15 years is not included. The huge confidence interval is also remarkable.
Figures 5 & 6: What is the “relative weight”, how and why was it calculated? Also, the red lines in most panels do not properly represent the distribution of points (observations), in particular in the panels 100-200mm and 200-500mm. Please explain.
Figure 9: Check letters on the panels. In the captions, add carbon to “soil organic content”.
Table S1: Typo in the captions: should be “throughfall”. Also, three of the 88 studies do not have any entry in the responses of water cycle processes to plant mixtures? In addition, I strongly suggest to include information on ecosystem types, the studies deal with.
Citation: https://doi.org/10.5194/egusphere-2023-719-RC2 -
AC3: 'Reply on RC2', Xiaodong Gao, 25 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-719/egusphere-2023-719-AC3-supplement.pdf
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