the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Aug 2024
Terracing Increases Organic Carbon Content in the Loess Plateau
Abstract. Aim: Terracing is widely distributed in mountainous and hilly areas around the world and can be effective in inhibiting soil erosion, increasing soil moisture, improving soil quality and potentially having a positive impact on soil carbon pools.
Methods: To understand the impact of agricultural activities and ecological restoration measures on changes in soil carbon pools in terraced areas, we set up an observation system in typical terraces on the Loess Plateau and soil samples were gathered from 0–100 cm depth in terraces (containing different crops and different ecological restoration vegetation) and slopes.
Results: The results show that terracing can effectively increase soil organic carbon (SOC) content (7.7 g∙kg−1 in terraced cropland > 4.9 g∙kg−1 in sloping cropland). Changes in the organic carbon content of the terracing is mainly due to improvements in soil and water conservation capacity and agricultural activities, loss of soil organic carbon due to short-term abandonment and an increase in soil organic carbon due to replanting of fruit trees and crops. The choice of tree species in afforestation policies has also led to differences in soil organic carbon. Pinus tabuliformis Carr. has the highest SOC content (9.8 g∙kg−1).
Conclusions: The SOC content in 0–100 cm of terraced fields planted with wheat was 1.5 times higher than that of sloping fields planted with wheat. Compared with sloping land, terrace construction significantly increased the SOC content of cultivated land, especially in the top soil layer (0–30 cm), and converting some sloping land into terraces would enhance the carbon sequestration capacity. This study has significant implications for agricultural management and ecological restoration in the terraced areas of the Loess Plateau and contributes to the development of rational policies for carbon sequestration on arable land in terraced areas.
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RC1: 'Comment on egusphere-2024-2047', Anonymous Referee #1, 30 Aug 2024
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Land-terracing activities have been widely developed in mountainous and hilly areas mainly in China and the world other places in order to inhibit soil erosion, increase soil moisture, and improve the soil qualities. This study seems to be a systematic work to well understand the impact of agricultural activities and ecological restoration measures on changes in soil carbon pools in terraced areas. as my assessment, this study has significant implications for agricultural management and ecological restoration in the terraced areas of the Loess Plateau in China and even instruct for the world other countries. Thus, I recommend acceptance for publication and also encourage authors well address and improve the shortcomings for the whole text in consideration on my suggestions below:
1) In the whole text, many places about Loess Plateau should be limited in China.
2) Please briefly introduce the history of land terracing activities in the Loess Plateau. Different from other countries, Chinese terracing policy has a long history. I am wondering whether there has a correlation between the soil carbon variation and terracing time or not.
3) Widely terracing lands have been distributed almost all over the Loess Plateau and covering many kinds of climate types. In this text, a small county of Zhuanglang was selected as research area. Please give an evaluation on its representativeness of terracing lands. I think the climate changes should also play important roles for SOC variation even the similar terracing condition.
4) The SOC content of the abandoned apple tree terraces were lower than that of the in-use apple tree terraces. Generally, this seems to be contradicted with the observed facts in the world. I think it may be collected with seasonal fertilizers addition.
5) The key scientific issues seem to be clear. However, I didn’t catch what are the main novelties of this study. Please summarized some sentences to well address them at the end of the introduction section.
Citation: https://doi.org/10.5194/egusphere-2024-2047-RC1 -
RC2: 'Comment on egusphere-2024-2047', Anonymous Referee #2, 04 Oct 2024
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This manuscript investigates the effect of terracing on soil organic carbon (SOC) dynamics in the Loess Plateau region, with a focus on the impacts of different vegetation types (wheat, apple, grassland, trees, etc.). Given the global significance of agricultural terraces and the urgent need to develop management practices that can sequester atmospheric carbon as SOC, this topic is valuable and interesting. However, I have identified several issues that prevent me from giving a positive evaluation of this manuscript.
Major concerns:
The manuscript discussed the mechanisms through which terracing and vegetation types impact SOC dynamics, identified various potential factors such as water content, soil fertility, erosion reduction, roots, biomass, and crops (see sections 4.2 and 4.3). However, none of these factors were measured in this study—only SOC content was assessed for all samples (as seen in all figures and tables, which only present SOC content data). This approach significantly reduces the value of the paper and introduces considerable uncertainty in the discussions and conclusions. Could the authors include additional data in their current analysis, such as nutrients, root biomass, slope gradients, and bulk density, to better support their interpretations? Without such data, the value of current manuscript is difficult to discern.
Your Discussion has focused on the effects of terrace abandonment on SOC content (section 4.2), but within your analysis, only 5 out of 77 sites are abandoned terraces (only considered apple tree), this is unfortunately not ideal.
You sampled 77 terraced sites but only 7 slopes as the non-terraced control. 7 slopes are under wheat and grassland, which is also not comparable as the terraced slopes. But I totally understand that in this region it’s very difficult/maybe impossible to find non-terraces slopes. One solution might be trying to find reference samples from the global products with high resolution if it’s possible. Or author could consider revise this paper by only focusing on the effect of difference vegetation types in terraces systems?
More minor comments:
Abstract: I’m not sure if the format of abstract meets the requirement of BG journal. Please check
Line 27 changes in organic carbon content in terraces is mainly driven by the improved soil and water….
Line 45 is is?
Line 62 maintain soil fertility and increase…
Line 64. conversion of terraces into slopes?? I think it’s another way around…
Line 72 sloping soils? -> soils in sloping land
Line 81 but also
Line 98-99 I don’t understand this sentence
Line 102 By the end of 2012, there were 37,100 km2 of terraced fields on the Loess Plateau. please add a reference
Line 110 to be clearer: we gathered soil samples from terraces and non-terraced slopes,
Line 147 please check this sentence
Line 188 0.7 g kg-1, report sd/se along with your mean value
Line 237-240 sentence is too long
Conclusion: some statements are not supported by data -> see major comments
Citation: https://doi.org/10.5194/egusphere-2024-2047-RC2
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