Dear Büdel et al.,

All three referees acknowledge the potential interest of your work, but between them, they also raise a number of concerns.
Please carefully revise your manuscript taken into account all these issues, and incorporates the necessary changes in to the new version of the manuscript.

Sincerely
Emilio

Dear Authors,

Thank you for you revised version of the paper. The document have been sent to the original referees, and both highly recommended publication after some minor revisions (small changes) suggested by reviewer 1 (see report).

Sincerely,

Emilio Rodriguez Caballero

# Reviewer 3

General comment
This work deals with the metabolic activity and CO2 gas exchange over time of a cyanobacterial biocrust in the Boodjamulla National Park of Australia. The manuscript has improved after suffer many and substantial modifications from its original version. The abstract and the Introduction are now longer and their wording is better. Methods, in addition to be longer and better written, include modifications in their structure, and the wording and structure of the Results have been modified accordingly. The Discussion has been rewritten, is now longer, including new comparisons, is structured, and includes a section with new content. Conclusion has been rewritten and improved also. In my opinion, the manuscript is very good and ready to be published in its present version except for two small details: the uncertainty about the days in which the CO2 monitoring in field was made and the name of ‘Table 1’ in the page 17 (that table is now ‘Table 2’)

Specific comments
Methods
I agree with the present version except for the uncertainty on the days of the field CO2 monitoring (see below). From the questions I posed in my previous revision and the changes I proposed, those which have not been answered, or accepted, individually have become obsolete because the Methods section has been rewritten. The contents of the Methods section are better structured now in subsections.
Particularly, the text of the section 2.3 of the manuscript (before titled ‘CO2 gas exchange under controlled conditions’, and now titled ‘Environmental manipulations’) has been deeply rewritten and is now more fully explained and much clearer than before. The number of used samples, how prepared, as well as the procedure followed to disentangle the response of NP and DR to variations in light, temperature and water content can be understood now without doubts.
Similarly, the text of the section 2.4 has been lengthened and deeply rewritten too. Only one detail remains unclear: the days in which the one-year field monitoring of CO2 was carried out are not yet explicitly stated. A reader could interpret that measurements were taken every 30 minutes during every day of the year. Was this so or was the field CO2 exchange measured in 34 different days spread between September 2010 and April 2011, as the Table 1 (the table replacing the old figure 3 of the previous version, now removed) seems to suggest?.

Results
I agree with the present version. After the considerable improvement of the wording of Methods section and the modifications in the figure captions, my difficulties with the old figure 4 (now Figure 3) have disappeared.

Discussion
I agree with the present version. I congratulate the authors for the inclusion of new text in the Discussion, for example quoting very recent works and showing the important differences among the CO2 flux as calculated from direct field measurements on biocrusts and that estimated from Eddy Correlation systems. But particularly, for adding a new section on “Reestablishment and resurrection after the dry season”, which constitute an overwhelmingly good response to my previous question about what exactly ‘regrowth’ meant in the conclusions, and questioning whether such a word (now removed) was adequate (since, by default, ‘regrowth’ implies growth, which requires net CO2 assimilation)

Conclusion
I agree with the present version, which is better

References, Tables and Figures
I agree with the present version

Minor remarks
After remove the old figure 3, replacing it by the new Table 1, the other table, on the monthly net primary productivity (old Table 1), remains with the name of ‘Table 1’ in the page 17, although in the main text it appears as Table 2 (line 25, page 6)

Dear Professor Burkhard Büdel

I am pleased to inform you that your paper has been accepted for publication.

Sincerely
Emilio Rodriguez caballero