the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Post-flooding disturbance recovery promotes carbon capture in riparian zones
- 1School of Earth and Planetary, University of Chinese Academy of Sciences, Beijing, 100049, China
- 2State Key Laboratory for Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, 100875, China
- 3Department of Environmental Science, Policy and Management, University of California, Berkeley, 94704, USA
- 4Yale School of the Environment, Yale University, New Haven, 06511, USA
- 5Institute of Wetland Ecology & Clone Ecology; Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Thaizhou, 318000, China
- Yihong Zhu and Ruihua Liu contributed equally to this paper.
- 1School of Earth and Planetary, University of Chinese Academy of Sciences, Beijing, 100049, China
- 2State Key Laboratory for Water Environment Simulation, School of Environment, Beijing Normal University, Beijing, 100875, China
- 3Department of Environmental Science, Policy and Management, University of California, Berkeley, 94704, USA
- 4Yale School of the Environment, Yale University, New Haven, 06511, USA
- 5Institute of Wetland Ecology & Clone Ecology; Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Thaizhou, 318000, China
- Yihong Zhu and Ruihua Liu contributed equally to this paper.
Abstract. Vegetation, water, and carbon dioxide have complex interactions on carbon mitigation in vegetation-water ecosystems. As one of the major global change drivers of carbon sequestration, water disturbance is a fundamental but poorly discussed topic to date. The riparian zone is a representative highly dynamic vegetation-water carbon capture system. Unfortunately, its global carbon offset functionality is remarkably underestimated. This study examines the daily CO2 perturbations in the riparian zone with two-year in-situ observations along the Lijiang River. We show that the riparian zone transformed from a carbon source to carbon sink after recovery from flooding. Consequently, a quantitative global riparian carbon offset model is proposed. Based on the intensity of flooding submergence and post-flooding vegetation coverage, ~0.11Gt·year-1 CO2 is captured following flooding, and 0.53 Gt·year-1 more CO2 is captured due to flooding, which is equivalent to 9.1 % of the global forest carbon sequestration. This finding shed new light on the quantitative modelling of the riparian carbon cycle under flooding disturbance, underlining the importance of the proper restoration of riparian systems to achieve global carbon offset.
Yihong Zhu et al.
Status: final response (author comments only)
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RC1: 'Comment on bg-2022-175', Anonymous Referee #1, 11 Sep 2022
This study evaluates how carbon fluxes of river riparian areas seasonally respond to flooding by investigating the CO2 and dissolved carbon fluxes during pre- and post-flooding seasons. The methods were generally well established and results were generally well discussed. In particular, authors discussed how vegetation and the post-flooding change of riparian vegetation species and richness affect/determines net carbon fluxes in river riparian areas. I think this could be a valuable contribution to this area.
One thing that might be ambiguous to audience is that authors use terms like “pre-flooding”, “flooding” and “post-flooding” to describe their measurements in different seasons. This might be a bit misleading because floods often refer to short-term events. Considering authors evaluated these carbon fluxes on a seasonal base, I’d suggest authors changes these expressions to pre-flooding seasons, flooding seasons and post-flooding seasons instead.
I have only a few minor comments on the rest of the manuscript. See below,
Line 174: in different seasons
Line 175: we first reviewed the diel cycle.
Line 176: change “the terrestrial area” to “riparian soils” or “riparian area”, same below
Line 183: “terrestrial area with vegetation” to “riparian area with vegetation”
Line 200-203: the sentence repeat line 186-188. Consider delete one of them
Line 241: is the water-air carbon flux (Fig. 2b).
Line 285-286: no need to capitalize first letters
Line 313: needs further analysis
Line 332: the riparian zone thus has …
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AC1: 'Reply on RC1', Huai Zhang, 24 Nov 2022
The comment was uploaded in the form of a supplement: https://bg.copernicus.org/preprints/bg-2022-175/bg-2022-175-AC1-supplement.pdf
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AC1: 'Reply on RC1', Huai Zhang, 24 Nov 2022
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RC2: 'Comment on bg-2022-175', Anonymous Referee #2, 31 Oct 2022
The authors studied the effects of flooding on carbon emissions and sinks in the riparian zone. They measured field CO2 flux and developed a model to simulate the riparian carbon emissions. Although multiple methods applied, I am not convinced by the data yet. The introduction is not comprehensive, methods lack some important information, the results and discussions are not convincible. At the current stage, I think it is not suitable for publishing. There are also some comments need to be considered:
- Please correct the reference “Xunhua et al., 1998”. The first name and last name were switched.
- Lines 39-44, flooding submergence could cause anoxic conditions, which favors the reduction reactions. Thus, methane should be released more than carbon dioxide and are more important?
- Line 58, a space was missed in the unit mg·m-2 h-1.
- Introduction is too short to summarize the recent research progress in riparian carbon cycle. More information are needed about riparian soil properties, CO2 and CH4 emissions, vegetation, and some modelling work.
- Line 86, province?
- The information of sediment or soil should be added, including soil pH, total organic carbon/nitrogen content, etc.
- Section 2.2.1, the setup of static chamber and gas sampling are not clear for me. Do you have a base for the chamber? How to seal the chamber during the non-flood periods? The gas samples were taken every four hours, and the chamber were always closed during this time? If it is so, did the temperature inside of the chamber change a lot? How did you calibrate the flux data with temperature?
- The detailed information of gas chromatography should be introduced.
- The statistical method of multiple comparisons should be given.
- Equation 2, the unit of each parameter should be clarified. How did you calculate the D and p value?
- Section 2.3.2, why did you compare with the CO2 flux of global forests?
- Where is the daily CO2 flux in different months?
- Lines 180-183, is that due to the effects of climate? Without exclusion of the climate effects, I think you can’t reach the conclusion that “in post-flooding season, the terrestrial area with vegetation sequestrates carbon for a longer time”.
- Figure 1, the standard deviation/error of the data should be provided.
- Lines 189-194, you should calculate accumulated CO2 emissions rather use the average value. Otherwise, I think you can’t get the conclusion that “the riparian zone acted overall as a carbon sink”.
- Table 3, the whole plant species can be shown in the supplementary data.
- Section 3.5, how did you verify the model data?
- The unit should be kept the same through the manuscript. For example, the CO2 flux is expressed as g·m-2 d-1, g·m-2 year-1, and mg·m-2 h-1.
- Figure 5, the unit should be Gg·m-2 year-1?
- Section 3.6, how did you upscale the site CO2 flux to a global/regional CO2 flux? Did you consider the effects of temperature, vegetation, seasonal changes, variations of soils etc.? If not, it is hard to believe the data.
- Lines 357-361, again, you couldn’t conclude a net emission by using the average flux data.
- Section 4.3, I didn’t find any data of microbiology. So please delete this part.
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AC2: 'Reply on RC2', Huai Zhang, 24 Nov 2022
The comment was uploaded in the form of a supplement: https://bg.copernicus.org/preprints/bg-2022-175/bg-2022-175-AC2-supplement.pdf
Yihong Zhu et al.
Yihong Zhu et al.
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