Long-Term Cultivation of Fruit Plantations Decreases Mineralization and Nitrification Rates in Calcareous Soil in the Karst Region in Southwestern China

Round 1

Reviewer 1 Report

Review “Long-term cultivation of fruit crops decreases mineralization and nitrification rates in calcareous  soil in the Karst region in southwestern China”

General comments

The article studied the effect of the transformation of the tropical forest to woody crops, on the properties of the soil, especially soil organic carbon, soil nitrogen and the mineralization of soil N

The field trial is valuable since a sufficiently long period of time has elapsed to observe clear effects on the organic matter of the soil.

The description of soil analysis method need be improve, with inclusion of method for water holding capacity determination.   

The results are correctly presented and described. The discussion in general is adequate, although when authors interpreting the increase in the clay fraction of the soil, it is not adequately explained what causes this increase, which in turn is associated with changes in the mineralization of N

In general it is an article that is suitable for Forest, after making the proposed corrections

Specific comments

Line 21, 28 29 please change “clay content” see below  

Line 154, Indicate analysis method for determination of Water hoding capacity (WHC) or If WHC is calculated from soil texture date then include the description of this method

Line 248 Please review the figure captions, I think that there is a mistake

Line 242, please review significance level “(0.5)”

Line 248 please review significance level “(0.5)”

Line 275 please include description of AOB acronim

Line 284, 287, the expression “clay content” is a important issue that must be clarified by authors.

According to the methods description , texture determination employed by the author  any pretreatmet was employed for eliminate the soil organic matter.  

In consecuence, when soil texture is determined some clay particles are forming aggregates. The soil organic matter is a cementing agent for this agreggates and when the soil organic matter disappears, the clay particles disaggregate. These sil or sand-size aggregates are disaggregated and therefore silt or sand-size particles are also reduced.

Therefore, the authors should not refer to the “clay content” of the soil but rather the “disaggregated clay” present in the soil.  

Author Response

Q1 Lines 21, 28 29 284, 287, the expression “clay content” is an important issue that must be clarified by authors. According to the methods description, texture determination employed by the author any pretreatment was employed for eliminate the soil organic matter. In consequence, when soil texture is determined some clay particles are forming aggregates. The soil organic matter is a cementing agent for this aggregate and when the soil organic matter disappears, the clay particles disaggregate. These soil or sand-size aggregates are disaggregated and therefore silt or sand-size particles are also reduced. Therefore, the authors should not refer to the “clay content” of the soil but rather the “disaggregated clay” present in the soil.  

Response: Thanks for your valuable suggestion. For textural analyses, soil samples (< 2 mm) were pre-treated with hydrogen peroxide (H2O2) and hydrochloric acid (HCH) to remove organic material and carbonates, respectively, and subsequently sodium hydroxide (NaOH) solution was added as a dispersion agent. All samples were then dispersed in an ultrasonic bath and the particle-size distribution (clay, silt and sand) of the suspensions was determined using an LS-230 laser particle characterization analyzer. Actually, “clay content” in this study is the “disaggregated clay”. We think that the “clay content” can represent the meaning of “disaggregated clay” after adding the specific description of soil texture. Thus, we still use “clay content” to characterize soil texture.

Q2 Line 154 Indicate analysis method for determination of Water hoding capacity (WHC) or If WHC is calculated from soil texture date then include the description of this method.

Response: We clarified the determination method of water holding capacity and soil texture in detail.

Q3 Line 248 Please review the figure captions, I think that there is a mistake

Response: We have revised this point.

Q4 Line 242, please review significance level “(0.5)”. Line 248 please review significance level “(0.5)”

Response: We have revised this point.

Q5 Line 275 please include description of AOB acronym.

Response: The AOB acronym has been firstly shown in Introduction section. Please see line 77 in revised manuscript without changes marked.

Reviewer 2 Report

The authors investigate mineralization and nitrification rate changes due to the long-term cultivation of fruit crops in the Karst region of southwestern China.

The study deals with the influence of soil organic carbon and total N contents, calcium concentrations, cation exchange capacity, water holding capacity, pH, and soil texture on mineralization and nitrification rate.

In general, the manuscript is well-written, and the information provided would be interest of the Forests journal’ readership.

The introduction is well built, the aim of the study is relevant from scientific and economic reasons as well. The experiment was well-designed, figures and tables are high quality, informative, and well structured, site description is thoroughly written. Formatting of the text is mixed somehow, Introduction and Results are justify, Materials and Methods are left-aligned. Materials and methods are properly detailed. Results are clear, the authors did an excellent analysis of their collected data.

I have only a few minor comments to the authors that could be addressed prior to publication.

Below Figure 3. the title of Figure 4. can be seen too. In this case, the title of Figure 3 is wrong or Figure 4. is missing.

The other comment is to line 198-199 “Compared with the forest soils, long- term fruit crop cultivation increased clay and sand contents, with significant differences observed between the forest and crop sites at the Jianhui and Guilin sites (P < 0.05).” But in Table 1. Sand content decreased significantly in Jianshui and Guilin and did not change in Pingguo.

Some specific comments are below:

Line 99. In Figure 1. the names of sites are Guilin, Guohua, Jianshui. In Table 1 Pingguo is told, in Figures 2. and 3. Guohua. Little bit confusing although it can be identified from the text that Guohoa is in Pingguo county.

Line 169. Equation symbol somehow is misplaced. The numbering of equations is non-uniform.

Line 200. Consider the respelling of Jianshui.

Line 239. Consider respelling of such.

Line 402. Nitrogen should be N.

Line 325., 335., 354., Consider reformat reference.

Author Response

Q1 Below Figure 3. the title of Figure 4. can be seen too. In this case, the title of Figure 3 is wrong or Figure 4. is missing.

    Response: We have revised this point.

Q2 The other comment is to line 198-199 “Compared with the forest soils, long- term fruit crop cultivation increased clay and sand contents, with significant differences observed between the forest and crop sites at the Jianhui and Guilin sites (P < 0.05).” But in Table 1. Sand content decreased significantly in Jianshui and Guilin and did not change in Pingguo.

    Response: Thanks for your attention. We have revised this point; please see lines 205‒207 in revised manuscript without changes marked.

Q3 Line 99. In Figure 1. the names of sites are Guilin, Guohua, Jianshui. In Table 1 Pingguo is told, in Figures 2. and 3. Guohua. Little bit confusing although it can be identified from the text that Guohoa is in Pingguo county.

    Response: We have uniformly used “Pingguo” as the site name.

Line 169. Equation symbol somehow is misplaced. The numbering of equations is non-uniform.

   Response: We have revised this point.

Line 200. Consider the respelling of Jianshui.

   Response: We have revised this point.

Line 239. Consider respelling of such.

   Response: We have revised this point.

Line 402. Nitrogen should be N.

   Response: We have revised this point.

Line 325., 335., 354.,.

   Response: We have revised references.