Dear Dr. Bouriaud,

both reviewer evaluated the study and found the presented data set and modeling approach as a valuable contribution for the estimate of annual aboveground carbon uptake by wood biomass considering the interannual variation of wood density and its negative correlation with tree-ring width.

I have carefully read the comments of both reviewers and their major and minor concerns and checked how those were considered in the author’s responses. In most cases their concerns were adequately addressed and changes incorporated in the manuscript following the suggestions of both reviewers.

A still opened question is the correlation of ring width and wood density presented in figure 1b with is fundamental for the error estimates of interannual wood biomass production . Both reviewers suggest, and I agree with them, that the correlation of ring width and wood density follows a non-linear trend. A linear regression model, even presenting a high square coherency, does not fit well to the presented relationship. For instance, an increase in ring width from 6 mm to 8 mm does not significantly reduce wood density anymore (wood density stays constant at values of about 300 kg m-3). I do not understand why a non-linear relationship (i.e., negative exponential) can be used in the modeling approach, which for my understanding would result in better predictions of the annual biomass increment depending on the volume increment. What would be the difference of a non-linear regression model between ring width and wood density and the model approach used in the MCMC?

Addressing this opened question I am pleased to accept "Influence of wood density in tree-ring based annual productivity assessments and its errors in Norway spruce" for publication in Biogeosciences.

Best regards,
Jochen Schöngart

Dear Dr. Bouriaud,

I am pleased to accept bg-2015-102 "Influence of wood density in tree-ring based annual productivity assessments and its errors in Norway spruce" for publication in BIOGEOSCIENCES after some technical corrections which are indicated below.

The revision has answered the issues raised by the reviewers and editor, and I found the manuscript much improved in terms of clarity.

Best regards,

Jochen Schongart
(Associated Editor of Biogeosciences)

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Technical corrections of bg-2015-102

P. 17/L. 491: Should be “periods”.

Table 1:

Delete the dot between "kg" and "m-3" in the columns "RMSE" and "Bias".

Supplements:

Please indicate the unit "years" in the column "age" of Supplement S1: Sampling plot location, stand and tree characteristics.

Please present the units of the parameters in the same line.