Human-Altered Water and Carbon Cycles in the Lake Yangzong Basin since the Yuan Dynasty

Round 1

Reviewer 1 Report

The manuscript entitled Anthropogenic activities altered water and carbon cycle in the Lake Yangzong Basin since the Yuan Dynasty, essentially consists of the study of a 10.2 m sediment core that allows us to reconstruct the history of Lake Yangzong during the last 13,400 years. The authors applied X-ray fluorescence spectroscopy (XRF) to scan elements continuously in a 10.2 m sediment core from this lake. Using X-ray fluorescence spectroscopy (XRF) to scan elements continuously in a 10.2 m sediment core from this lake. By combining correlation analysis, principal component analysis (PCA), core chronology, and total organic carbon (TOC) content, we reconstructed the historical sequence of geochemical element contents in the Lake Yangzong catchment over the past 13,000 years.

The water in the lake comes from rain and also from the drainage channeled by the small rivers that flow into the lake. In addition to water, these contributions have contributed to providing sediments that come from the rocky substrate. However the authors have neglected to include any information about the geology of the area. However the authors have neglected to include detailed information on the geology of the area. We barely know from reading the manuscript that it is primarily composed of Permian, Carboniferous, and Devonian limestone.

But nothing else. It would be interesting to better understand the relationship between rocky substrate and sediments, the total chemical composition of these rocks and thus be able to correlate it with the main elements they provide in Table 1 of the manuscript.

According to the authors of the elements that have been analyzed in the sediment core, elements such as Fe, Ti, Rb, Zr, and Mn represent terrestrial detrital materials and Ca and Sr represent endogenous materials produced by chemical and biological processes within the lake .

Without knowing the composition of the elements of the rocks that are in the path of the water currents that converge in the lake, it is difficult to make this statement. It is, from the erosion of these rocks, for more than 13,000 years that the sedimentary filling of the lake has occurred.

Likewise, not having differentiated the type (isotope) of carbon and considering that everything analyzed in the sedimentary core as formed inside the lake is inaccurate, or at least doubtful.

It is surprising that in a calcareous area like that there cannot be some classic paleoclimatic criterion: study of the pollen record in the same sedimentary column used, study of speleothems with oxygen isotopes. We consider that using history from the geochemical elements in the Lake Yangzong catchment over the past 13,000 years.

Only after comparing the palynological data obtained in the sedimentary column or the O16/O18 oxygen isotope data would it be possible to try to deduce the relationship between climate and anthropic action in the area.

In my opinion, knowledge of the rocks that exist in the area should be provided with their elemental chemical analysis to know the origin of the elements analyzed using X-ray fluorescence spectroscopy (XRF) to scan elements.

The different C isotopes existing in the sedimentary record should be differentiated since not all of them come from organic or geochemical activity in the lake.

The interpretation made by the authors of the manuscript is too simplified since there is no biunivocal relationship between anthropic action and natural action in the sedimentary environment of the lake itself.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The main subject of the manuscript and the described area and recorded changes are quite interesting. It would be interesting and useful if biotic proxies were studied as well.

My main concern is that there is no data analysis - correlation, PCA, preparation of plots/graphs....  described in the Materials and methods, what must be corrected.

In the Results, there were sentences belonging to the Discussion. This also must be corrected.

This and some additional minor corrections are in the revised version of MS.

Comments for author File: Comments.pdf

Author Response

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Reviewer 3 Report

I am not satisfied with the title of the paper. It is a descriptive sentence which is not normal.

I am not sure about the low cost of XRF which is stated in L 76, particularly in developing countries.

L93: 1388 AD …

Fig.1: The legend is not readable! What is the full name of YZH-1? What is the time of the land use map? Is the elevation from the mean sea level? The YunNan is not used similarly to the MS text. In addition, I cannot distinguish where it is exactly on the map, because the symbol is not distinguishable with the study basin.

L124-128: Why one point was used for sampling?  The nine samples were measured at one time, why? Are they sampled from one depth? Why was this sampling not conducted for different depths?

L130-136: Are these depths also used for sediment sampling?

L142-144: Please describe the importance of the analysis of nine study elements.

L144: The LoI is done for how many min or hr? L155: what is this unit? (mm a-1)

L173: The methodology didn’t explain what means of the significant correlation.

Table 1: I think you should clarify that the results are related to the correlation coefficient!

L193: check the end of the sentence.

L195-196: delete. It is related to the methodology.

The limitations of the study and the suggestions for future research should be described.

Bests

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript has been satisfactorily corrected, eliminating some of the inconcretions that existed in the initial draft. For me, it would obviously be a good improvement to add paleobotanical data that would improve the results of the paleoclimatic reconstruction of the conditions both in the lagoon and in the immediate surroundings of the lake. Even so, the geochemical work is sufficiently indicative of the variations in environmental conditions during the time represented by the sedimentary sequence studied. I recommend publishing later an expanded version of this work complemented by a paleopalynological study of the time interval represented by the survey. It would contribute to better understanding the variations in the environment, especially in the vegetation cover and in the anthropic activities in the area.

Author Response

Thank you for your encouraging comments.