Dear authors,

Thank you for the detailed responses to the issues raised by the reviewers in their reports. Based on this information, a minor revision is required. Please resubmit a revised manuscript that addresses the comments. This revision should also better reflect earlier work in the introduction and discussion (as highlighted by rev1). We are looking forward receiving a revised version.

K Van Oost

A very convincing study which was presented to-the-point. Great to see this formal proof that also thermal fractions remain heterogeneous mixtures of fast and slow cycling SOM. The idea to indeed in future also a priory subdivide SOM into mineral and free OM before engaging in a similar RPO/Py-GC/MS analysis seems very appropriate to me. In doing so we might further discover several less composite thermal fractions.

Just two more points where I see room for improvement.
1° As pointed out by referee 1 conditions for pyrolysis were quite different between the ‘Py-GC-MS’ and off-line pyrolysis for ‘Ramped pyrolysis oxidation’. It should be recognized in the discussion that one cannot just assume that the sequential Py-GC-MS was really able to ‘mimic’ oxidation at various temperatures during ramped pyrolysis oxidation. Of course sources of pyrolysis products (CO2 for RPO and volatilized compounds for Py-GC) will display quite some correspondence but a ‘perfect match’ seems impossible.
2° No interpretation is given on the distinct δ13C of the various thermal fractions. Without this it would in fact be best to omit these data. For instance: why are F1 and F2 that similar in their Δ14C but different in their δ13C? Could this be related to the shift in relative proportions of lipids/lignin/phenols?

Minor comments:
I can certainly follow that the authors refrained from trying to really explain the time series of OM composition. But perhaps you might still want to comment on the following two points: Fig.1 How could you match the lower thermal stability of the >1963 soils with their lower OC%? Seems contradictory. + in in 1973: Δ14C was -27.3 ‰ –> reason?
L117 superscript for -1
L217 studies’
L220 dominant?
L238 something wrong with this sentence here
352 ‘soil comes from’
L252 ‘site’
Fig. 1 Difficult to discern thermograms for the different years: use colour perhaps instead of shades of grey. °C instead of C
Table 2 -> units for τfast and τslow + perhaps in the caption repeat meaning of τ
Table b2 two different notations are used for the fraction of modern C: ‘F modern’ and ‘Fm’ –> keep one.

Thank you for the revisions, we can now proceed to the publication of your work.

Kind regards,

K Van Oost