Deforestation for Agriculture Temporarily Improved Soil Quality and Soil Organic Carbon Stocks

Round 1

Reviewer 1 Report

The topic is interesting and rarely mentioned in publications.

However, the methodology lacks data essential for the evaluation of the material as a whole.

Information on the particle size distribution is necessary to determine whether the research objects are comparable. Especially due to the large distance (2 km) between the facilities.

The operations performed after termination of the poplar plantation and the tillage (P-W and W systems) should also be described in detail. then it will be possible to refer to the obtained results and their discussion.

The text is technically good, only a minor citation error has been noted: line 284 is [32, 37, 37]

 

Author Response

Dear Editor,

Thank you for giving us the opportunity to submit the major revised manuscript. We have modified the manuscript accordingly, and detailed corrections are listed below point by point:

 

• Themethodology lacks data essential for the evaluation of the material as a whole.

√  The total soil samples number was 45, we only did three repetitions, but we collected 5 points and combined into a composite sample for each sample. And the distance of each plot was greater than 100 m within the same system.

• Information on the particle size distribution is necessary to determine whether the research objects are comparable. Especially due to the large distance (2 km) between the facilities.

√  We have added the information about this study site in Figure 1, the area of poplar plantation was more than 20 hectares, we could not find a wheat field so closer.

• The operations performed after termination of the poplar plantation and the tillage (P-W and W systems) should also be described in detail. then it will be possible to refer to the obtained results and their discussion.

√  We have added the information in the abstract and 2.2. Experimental design and soil sampling. We have clarified the difference between P-W and W systems. P-W: a summer maize and followed by winter wheat field after deforestation one year of a poplar plantation, W: a wheat-maize rotation field applied for decades.

• The text is technically good, only a minor citation error has been noted: line 284 is [32, 37, 37]

√  We made a mistake on the citation, it should be [32, 36, 37], we have checked carefully and changed it. Thanks a lot for your kindly reminding.

Author Response File: Author Response.doc

Reviewer 2 Report

Review evaluation for “forests-1530109” Deforestation for agriculture temporarily improved soil quality and soil organic carbon stocks by Wang et al. This manuscript examined the effect of land use conversion and agricultural activities on soil properties. Initially, it was an interesting topic and attracted great attention. However, I found some parts of the manuscript and Materials and Methods were designed wrongly (mainly the soil sampling parts and also analysis). I think the results are biased and contain high uncertainty due to the low number of soil samples. Practically and logically, it is wired significant differences only one year after the land use conversion in some soil properties, which need at least 4-5 years or even more to show detectable changes. SO I recommend a major revision to the authors and expect an intensive revision mainly in the M&M section. Additionally, please find detailed comments were listed below.

L17: “deforestation have not been thoroughly examined” this topic is intensively examined in worldwide. This is one example of the bibliometric analysis in land use change “Environmental Science and Pollution Research” https://doi.org/10.1007/s11356-018-2866-5” which shows how was the tends of the topic in previous decades.

L18-19: what is the difference between “, a wheat (Triticum aestivum L.)“ and “and a wheat field,” land uses. Please clarify them.

L21: The results showed that soil bulk……….

L22: Similarly, the soil organic………

L21-22: the authors reported that “The soil bulk density and pH decreased, and the soil total nitrogen, total phosphorus, and total potassium contents increased considerably compared with the poplar plantation” and simultaneously in line 26 reported that “there was considerable nitrogen limitation in the system after deforestation”. It is a contradictory result. Additionally, in line 21 mentioned after deforestation, soil bulk density decreased, so why does it need to compact soil again? Moreover, soil compaction in any format is harmful and a disadvantage for soil productivity.

L23-24: Obviously, this increment in SOC stock in the subsoil is not due to deforestation. It is clear it is due to the poplar plantation (roots, …..). Logically the increase or any changes in some soil parameters only after one year of cultivation is strange (the changes can happen to soil EC faster than others).

L27-28: “improving the soil fertility and stability of SOC stocks” how did the authors conclude that adding nitrogen and soil compaction will increase soil fertility and SOC stock?

Why did the results of the two fields of wheat not compare?

L33: on earth,

L41: it is not true to limit the soil quality only to SOC. Although SOC plays an important role in soil quality, several other soil properties are important in soil quality. Please see the following published papers for the role of the other soil properties

https://doi.org/10.1016/j.geoderma.2019.114139

https://doi.org/10.1016/j.ejsobi.2019.103119

L43-44: The accumulation of SOC content is not only limited to the mentioned factors. In fact, the controlling factors of SOC initially depend on the study area scale. For example, the main drivers in farm and local scales could be topography, parent material, management and vegetation, and land cover; however, in regional, provincial, and country scales, the controlling factors can be land cover and climatic factors, geology, and so on. Therefore, listing the SOC controlling factors without revealing the spatial extend might convey wrong information to readers. See the recent studies in SOC, its spatial distribution, and local and regional controlling factors.

https://doi.org/10.1016/j.geodrs.2020.e00256

https://doi.org/10.1016/j.geoderma.2018.09.006

https://doi.org/10.1016/j.catena.2021.105723

L83: “a poplar plantation (P–W), and a wheat field (W)” please define the differences clearly. Maybe by adding the duration of cultivation for (W), it will be clear to the authors.

L93-101: I suggest to the authors include Figure 1, which shows the study area, defines the region for different land uses and adds the digital elevation map for the whole region.

L104: how about the cultivation history for “a wheat field (W)”? It is really important to know the past history and duration of cultivation. Is it a monoculture or rotation culture?

L108: compound fertilizers, are included which fertilizers?

L110-119: how many soil samples were selected for each land use? It is really helpful to include the sampling locations in Figure 1 which is proposed above.   

L113-114: These numbers of soil samples are insufficient.

L15-127: TK, TP, and TN were used for the first time. Please add full names for them.

L132: “ith”

L137: “(n = 3)” it represents the number of soil samples?

In Figure 1. Some letters were missed. In Figure 1a, it seems there is a significant difference between bulk density for depths of 0-10 and 60-100 cm. please recheck. In Figure 1b, it seems the letters were placed wrongly. For instance, there is a significant difference between 0-10 and 60-100 while the mean for 40-60 is higher than 60-100 cm but no significant difference with 0-10 cm.

L192: Figure 2a. How is it possible to increase SOC only one year after deforestation? The turnover rate for SOC is defiantly more than 1 year. Before wet combustion, plant residue and debris, and everything above 2mm were excluded. Practically with one growing season (cultivation), should not see such big differences with the natural land cover.

L326-328: what do you think these differences could be due to the error during the laboratory measurements? In this study, only a few samples were analyzed, so the chance of error is high.

L343: “soil permeability and soil respiration greatly improved after deforestation,” how this conclude? The soil permeability and soil pore did not measure!

 

L363: the increment in TN is mainly due to the application of fertilizers.

L392-393: unclear sentence. Please reformulate.

L394 “TP, and TK increased significantly” Inconsistent with L397 “that nitrogen was limited in the study area”

L399: “soil BD increased the activity of soil microorganisms” how did you measure soil microorganisms’ activities? And this result did not support by the text.

Author Response

Dear Editor,

 

Thank you for giving us the opportunity to submit the major revised manuscript. We have modified the manuscript accordingly, and detailed corrections are listed below point by point:

 

• L17: “deforestation have not been thoroughly examined” this topic is intensively examined in worldwide. This is one example of the bibliometric analysis in land use change “Environmental Science and Pollution Research” https://doi.org/10.1007/s11356-018-2866-5” which shows how was the tends of the topic in previous decades.

√  We have changed the sentence, we did not clarify the meanings before, we wanted to expound that there were only a few studies on the change in soil properties in the initial period after deforestation. Most studies prefer to the long term.

• L18-19: what is the difference between“, a wheat (Triticum aestivum L.)“ and “and a wheat field,” land uses. Please clarify them.

√  We have clarified the difference between P-W and W systems. P-W: a summer maize and followed by winter wheat field after deforestation one year of a poplar plantation, W: a wheat-maize rotation field applied for decades.

• L21-22: the authors reported that “The soil bulk density and pH decreased, and the soil total nitrogen, total phosphorus, and total potassium contents increased considerably compared with the poplar plantation” and simultaneously in line 26 reported that “there was considerable nitrogen limitation in the system after deforestation”. It is a contradictory result. Additionally, in line 21 mentioned after deforestation, soil bulk density decreased, so why does it need to compact soil again? Moreover, soil compaction in any format is harmful and a disadvantage for soil productivity.

√  We agree with your opinions, and we have changed the sentences, although the soil total nitrogen increased, the C:N ratio increased in the system after deforestation compared with other systems, so we thought there was nitrogen limitation in the system after deforestation.

 

   We have deleted the “compacting the soil”, although soil compaction was harmful for soil productivity, we thought it could restrain the soil microbial activity, and then reduce the decomposition of organic carbon before.

• L23-24: Obviously, this increment in SOC stock in the subsoil is not due to deforestation. It is clear it is due to the poplar plantation(roots, …..). Logically the increase or any changes in some soil parameters only after one year of cultivation is strange (the changes can happen to soil EC faster than others).

√  Compare with the poplar plantation system, the SOC stock in the subsoil was increased in the system after deforestation, the roots biomass of the poplar plantation system and the system after deforestation should be the same. So we though these differences were caused by deforestation. And we discussed it in L352-360. We also added the explanation for the increase in deep soil organic carbon.

   The study site was located in the eastern coastal area of China, sandy loam soil is prevalent in this area. The soil has fewer particles and better air permeability, the annual variation of soil organic carbon fluctuated greatly. The figure below shows the annual variation of organic carbon in our study site. This maybe the reason for the great changes in a year. （We can not upload figures in this table, we provided in the word）

https://doi.org/10.1016/j.catena.2018.07.032

• “improving the soil fertility and stability of SOC stocks” how did the authors conclude that adding nitrogenand soil compaction will increase soil fertility and SOC stock?

√  In this study, the soil is sandy, the soil permeability is strong, soil compaction will restrain the soil microbial activity, but this only is beneficial to soil organic carbon sequestration.

We have changed the sentence, the meaning before maybe confuse the readers.The higher soil C:N ratio indicated that the unstable components made up a more significant proportion of the organic matter, which would increase the soil carbon mineralization rates(Lu, X.; Mao, Q.; Wang, Z.; Mori, T.; Mo, J.; Su, F.; Pang, Z., Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest. Forests 2021, 12 (6). https://doi.org/10.3390/f12060734).

And Guo et al., (2019) suggested that combinations of N and P fertilizers will be beneficial to SOC storage and increase SOC stabilization in agroforestry systems. So we thought adding nitrogen would be beneficial to SOC storage. (Guo, J.; Wang, B.; Wang, G.; Wu, Y.; Cao, F. Afforestation and agroforestry enhance soil nutrient status and carbon sequestration capacity in eastern China. Land Degrad. Dev. 2019, 31 (3), 392-403. https://doi.org/10.1002/ldr.3457).

• Why did the results of the two fields of wheat not compare?

√  We mainly want to focus on what happens to forest land after deforestation, so more on the difference between after deforestation and before deforestation. We discussed the differences between P,P-W and W in L337-349, we thought it was obvious and clear, and not very important. So we did not pay too much attention on it.

• L33: on earth

√  We have changed the letter, but we also found some articles presented in this style.

https://doi.org/10.1029/2019GB006461

https://doi.org/10.1002/ecy.1879

• L41: it is not true to limit the soil quality only to SOC. Although SOC plays an important role in soil quality, several other soil properties are important in soil quality. Please see the following published papers for the role of the other soil properties

https://doi.org/10.1016/j.geoderma.2019.114139

https://doi.org/10.1016/j.ejsobi.2019.103119

√  We are sorry that the sentence we wrote is not precise, now we have checked it and added some words in L43, thanks a lot.

• L43-44: The accumulation of SOC content is not only limited to the mentioned factors. In fact, the controlling factors of SOC initially depend on the study area scale. For example, the main drivers in farm and local scales could be topography, parent material, management and vegetation, and land cover; however, in regional, provincial, and country scales, the controlling factors can be land cover and climatic factors, geology, and so on. Therefore, listing the SOC controlling factors without revealing the spatial extend might convey wrong information to readers. See the recent studies in SOC, its spatial distribution, and local and regional controlling factors.

https://doi.org/10.1016/j.geodrs.2020.e00256

https://doi.org/10.1016/j.geoderma.2018.09.006

https://doi.org/10.1016/j.catena.2021.105723

√  We have added the information in L45-46 according to your suggestion. Thanks a lot.

• L83: “a poplar plantation (P–W), and a wheat field (W)” please define the differences clearly. Maybe by adding the duration of cultivation for (W), it will be clear to the authors.

√  We have changed the description of P-W system in L86-87, and we have added the information in the abstract and 2.2. Experimental design and soil sampling to define the differences clearly between P–W and W systems.

• L93-101: I suggestto the authors include Figure 1, which shows the study area, defines the region for different land uses and adds the digital elevation map for the whole region.

√  We have added the the study area in Figure 1, thanks for your suggestions.

• L104: how about the cultivation history for “a wheat field(W)”? It is really important to know the past history and duration of cultivation. Is it a monoculture or rotation culture?

√  We have added the information in the abstract and 2.2. Experimental design and soil sampling. We have clarified the difference between P-W and W systems. P-W: a summer maize and followed by winter wheat field after deforestation one year of a poplar plantation, W: a wheat-maize rotation field applied for decades.

• L108: compound fertilizers, are included which fertilizers?

√  We have asked local farmers about the compound fertilizers, and we are very sorry that we made a mistake about fertilization times, we have changed it in L120. Thanks for your reminding.

• L110-119: how many soil samples were selected for each land use? It is really helpful to include the sampling locations in Figure 1 which is proposed above.   

√  The total soil samples number was 45, we are very sorry that we did not

describe it clearly in our manuscript, we have added the information in 2.2. Experimental design and soil sampling.

• L113-114: These numbers of soil samples are insufficient.

√  The total soil samples number was 45, we only did three repetitions, but we collected 5 points and combined into a composite sample for each sample. And the distance of each plot was greater than 100 m within the same system.

• L15-127: TK, TP, and TN were used for the first time. Please add full names for them.

√  We have checked it and added the information in L137-139, thanks for your reminding.

• L132: “ith”

√  We have checked it and changed the mistake, thanks a lot.

• L137: “(n = 3)” it representsthe number of soil samples?

√  We are very sorry that we did not describe it clearly in our manuscript，(n = 3) represents three replicates for each soil sample.

• In Figure 1. Some letters were missed. In Figure 1a, it seems there is a significant difference between bulk density for depths of 0-10 and 60-100 cm. please recheck. In Figure 1b, it seems the letters were placed wrongly. For instance, there is a significant difference between 0-10 and 60-100 while the mean for 40-60 is higher than 60-100 cm but no significant difference with 0-10 cm.

√  We have checked carefully in figure 1. We did not add the letters about significant difference for depths. The letters indicated significant differences among planting systems for the same soil layer. The information maybe not very clear, but we added them blow the figure.

If required, we can add the letters about significant difference for depths.

• L192: Figure 2a. How is it possible to increase SOC only one year after deforestation? The turnover rate for SOC is defiantly more than 1 year. Before wet combustion, plant residue and debris, and everything above 2mm were excluded. Practically with one growing season (cultivation), should not see such big differences with the natural land cover.

√  We have discussed in the reply for comment 4, the SOC content in our study site changed greatly due to the sandy soil.

• L326-328: what do you think these differences could be due to the error during the laboratory measurements? In this study, only a few samples were analyzed, so the chance of error is high.

√  The total soil samples number was 45, we only did three repetitions, but we collected 5 points and combined into a composite sample for each sample. And the distance of each plot was greater than 100 m within the same system. The differences between the three duplicate samples were within acceptable limits.

• L343: “soil permeabilityand soil respiration greatly improved after deforestation,” how this conclude? The soil permeability and soil pore did not measure!

√  We have added the soil porosity in Figure 2, but we did not have date about the soil respiration.

• L363: the increment in TNis mainly due to the application of fertilizers.

√  We do not understand your comment in L363, the increment of TN might be mainly due to the application of fertilizers in the topsoil, but the C:N ratio also changed in the subsoil, we thought land-use changes also affected the C:N ratio.

• L392-393: unclear sentence. Please reformulate.

√  We have checked carefully and reformulate the sentence.

• L394 “TP, and TK increased significantly” Inconsistent with L397 “that nitrogen was limited in the study area”

√  We have deleted the sentence “and the limitation of nitrogen was particularly significant in the P–W system”, we thought although the soil total nitrogen increased, the C:N ratio increased in the system after deforestation compared with other systems, so we thought there was nitrogen limitation in the system after deforestation.

• L399: “soil BD increased the activity of soil microorganisms” how did you measure soil microorganisms’ activities? And this result did not support by the text.

√  Normally, the increase of soil BD in the same soil type will lead to the decrease of soil porosity, Wang et, al.(2020) considered that

the decrease in oxygen will decrease the diversity of soil microorganisms. So we thought the decrease in soil BD increased the activity of soil microorganisms. We have changed soil BD to soil porosity.

(Wang, Y., Liu, L., Tian, Y., Wu, X., Yang, J., Luo, Y., Li, H., Awasthi, M.K., Zhao, Z., 2020. Temporal and spatial variation of soil microorganisms and nutrient under white clover cover. Soil and Tillage Research 202, 104666.. doi:10.1016/j.still.2020.104666)

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

The manuscript has been sufficiently improved

Reviewer 2 Report

The authors revised the manuscript and answered all previous concerns accurately.