The authors attempted to discuss nitrogen turnover with N isotopic enrichment of ammonia. First of all, what does the “nitrogen turnover” mean here? Please define in the text.
In the manuscript the authors reported the results in the top, side and core of the piles. In the experimental part of the manuscript, the authors should present how they obtained the top, side and core samples. And how many top, side and core samples each run? More details are needed for the experiment part.
Statistical analysis: the authors altogether performed three runs. As you used Tukey’s multiple range comparison tests to separate the means, what are “the means” here? Are they “means” of different samples each run (if yes, also how many samples?)? Or “mean” among the three runs?
It seems that the results of the three runs were not so consistent with each other. The authors better present some comments or explanations about this.
Also the authors should be serious about the comments by one rewires. It is not a good answer to claim that “here we cannot put the ammonia volatilization in the equation because we did not measure the 15NH4 of the volatilized ammonia”.
For the Keeling plot analysis or the interpretation of isotopic enrichment, since initial organic N or NH4+ may convert to NO2- and NO3-, is this kind of conversion a factor influencing the isotopic fractioning other than the NH3 volatilization?
The authors better have a native English speaker to check the English writing. Although I am not a native English speaker, I can find some grammatical or typo errors. Below are some examples: Page 7578 line 9: “significant high” should be “significantly higher”; Page 7581 line 13: “One cm”?