Effect of Grazing Intensities on Soil N2O Emissions from an Alpine Meadow of Zoige Plateau in China
Round 1
Reviewer 1 Report
General statements
Since N2O is one of the major GHGs, there is a strong need to study N2O emissions under different land uses, not only in arable land. So the topic of the Manuscript is up-to-date, but there is a need to clarify in many places and to answer some question. It would be also nice to put a map of the region into the MS, since it is not clear which is Zoige plateau and Qinghai-Tibetan Plateau. The Introduction part should be strengthened with the effect of different driving factors (such as pH, water filled pore space, etc) on N2O emissions. In the Materials and Methods section the description of the treatments (2.2) should be clarified. Since N2O emission is very variable in space and time, I am not sure that statements in the Discussion part are well established on the base of monthly measurements. The English style of the MS must be also improved in some places.
Specific comments
Abstract
Line 21: Please put the word “nitrous-oxide” before N2O. This is the first place in the MS where the abbreviation is occurred.
Line 22: The expression “ three-intensities grazing treatments” sounds a bit strange. In fact, there is four intensity, because there is a control as well. Please rephrase the sentence.
Line 24: Please change “ under the grazing intensities” to “under different grazing intensities”.
Line 25: N2O cannot be collected by chamber, since chamber is the method, not the way of sample collection. Please correct it.
Line 26-28: Please rephrase the sentence.
Line 29: What is “grazing land”? The mean value of the three grazing treatments? Please specify it.
Introduction
Lines 41: I would change “grassland ecosystem is” to “grassland ecosystems are”. It would be also nice to put into the sentence that what percent of China is grassland.
Line 56: I wouldn’t use the word “believed” in this context.
Materials and Methods
Lines 75-81: I would put the information from 3.1 into this section. The information about the seasonal changes in meteorological factors are not results, should be placed into the study site description.
Line 86: The treatment G0 must be also mentioned in the abstract.
Lines 87-90: This sentence is hard to understand. What does it mean that different grazing intensities from G0 to G1.6 was settled as…. What unit of measure is hm2? Why the numbers are not in ascending order? How many yaks were grazed in G1.2?
Line 112: How far is this meteorological station from the experimental site?
Line 124: How often, in how many replicates was pH measured?
Line 125? How volumetric water content was measured?
Results
Lines 145-153: Please put this paragraph into the Materials and Methods part.
Line 166: Please sign in Table 1 that there is no significant difference between treatments in pH, NH4+-N and bulk density (put superscript “a” letter to everywhere).
Figure 2: The dots shouldn’t be linked, since it is not a continuous measurement.
Line 182: What does grazing land mean? The average of the three grazed treatments? Please specify it.
Line 200: I would say driving factors instead of impact factors.
Line 207: How can be a relationship between N2O emission and pH in the treatments, if there was no difference in pH values in the treatments?
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper concerns studies on level of N2O emission in effect of grazing intensities in condition of alpine meadow in China. Emission of N2O as a greenhouse gas emmitted to the atmosphere is a big problem. However, about 70 % of this gas is produced in soils, in that in agricultural soils. Therefore more and more attention is payd for looking for sources of its emission. From this reason the aim of presented manuscript is proper and useful. After the reading this manuscript I have some questions and comments: 1. I understand that during the 2 years of the experiment its location was the same and the soil factors in 2013 and 2014 were the same (?) 2. I am not sure if there were not significant differences between the both years in aspects the data presented in Figure 3. Therefore I am not sure if the Authors could calculte the total mean for N2O emission. 3. I did not find any logical trends in soil factors in grasslands in dependency on grazing intensities in exception of aboveground biomass. 4. This experiment was conducted only 2 years which were characterized with different weater condition and, as we know, these factors have very important effect on the level of N2O emission from the soil. Therefore the data presented in the Figure 3 and 4 are quite different. It’s hard to explain obtained results when the soil or/and weather conditions in both years of studies are not the same. It is important because 2014 was warmer and more humid than 2013. From this reason this experiment should be conducted 3 years. 5. In my opinion this paper needs some more time for improvment.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Thanks for considering to review this paper.
The paper is interesting for the readers and can be helpful for the local livestock production of cattle and sheep, but it need some improvements.
Here are the may concern:
1: Abstract: please highlight the novelty of your paper, i can not find difference in your and others paper.
2. (2.4.1 Climatic factors) Please mention the number of climatic/meteorological regions you considered in your study.
3. (2.4.2 Soil Characteristics Analysis): Can you put google map or some thing like that because it will show the exact sampling points for soil?
4. (2.4.3 Aboveground Biomass) Question 2 also can be applied here.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
The authors conducted a two-year experiment concerning the measurements of N2O emissions
from areas with different intensity of yak grazing.
The work has a structure appropriate for scientific articles,
is written in a correct and understandable language
and concerns the current problem variability of greenhouse gas emissions.
Please find below some comments:
L84: I think, light to high intensities should be defined more precisely.
The text says that 3 yaks were grazed for the intensity of G0.7 and G1.6.
So how did these intensities differ?
L142: Citation needed for SPSS 21.0.
The research area is extensive.
Did the authors consider the differences in soil properties before starting the study?
Particularly large differences are observed for the P, DOC and WFPS variables.
I wonder if it is possible that they do not depend on the intensity of the grazing.
Indeed, one gets the impression that in this study there are factors
other than the intensity of grazing, which influence N2O emissions.
These may not be the weather or at least not the percipitation
(the correlation between rainfall and N20 flux is not significant)
but the differences exist e.g. between 2013 and 2014.
in the paper there is no clear answer as to how the grazing situation influences the N2O emission.
Perhaps the authors will suggest what can be done to obtain such an answer, e.g. in the final conclusions.
L239: Could you please check if this is true i.e.
"Peak of N2O emission was ... likely due to the freezing and thawing process"
Was it not observed in 2014?
L305: The use of the term "long term" to denote research conducted over two years is exaggerated.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Since there is a session in the Results part about the effect of different driving factors on soil N2O emission, the Introduction part should be strengthened with the effect of these driving factors (such as pH, water filled pore space, etc) on N2O emissions. I suggested it in the first course of the reviewing process but the suggestion was ignored. It would be nice to do it.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The submitted new version of manuscript is improved what indicates that Authors tried to work on the text. Although my comments in the first review concerned too short time of this experiment but I can find in it some interesting observations and results. I hope they be helpful for the practical management of meadows in this part of China in aspect of the best numer of yacks per area of meadow and the protection of environment against N2O emission.
On the end I not sure if in the line 203 presented value 0.085 shoud not be as minus (-0.085) (?).
Author Response
Please see the attachment.
Author Response File: Author Response.docx
