Overall quality/General comments

This paper presents and describes a new data synthesis product for field collections of vegetation, active layer, and fire severity measurements from the Alaskan tundra. This dataset is particularly useful to the scientific community because 1) these areas are rapidly changing in response to climate change and permafrost thaw, 2) access to tundra regions is difficult and thus empirical datasets are sparse compared to other biomes (and housed in different data repositories), and 3) Alaska in particular is a tundra “hotspot” given observations of fire activity in this region of the past ~70 years. Data was collected for this synthesis from direct contact with PIs, existing repositories, and literature searches.

The authors have done an excellent job of filtering, harmonizing, and organizing the disparate datasets into a cohesive structure. What makes the dataset the most useful is that it can be used in different ways depending on research question. For example, one can identify a location of interest, see the data available at that site, and then go back to the original publication or dataset. That in and of itself makes the data compilation extremely useful to Arctic researchers. Furthermore, the synthesis itself is organized by most commonly measured variables, which allows users to quickly collect data for larger comparative questions (e.g., a metric in one region compared to another, or one time period to another), comparisons to other datasets (e.g., measurements compared to remote sensing data), and comparisons between variables (e.g., relationships between fire occurrence and vegetation turnover). This type of flexibility is wonderful for scientists working in this region to start to design new research projects and generate new hypotheses.

Overall, I see no issues with this manuscript as written. There is a clear explanation of the what the dataset has in it, how the data were organized, how it might be used by researchers, what is missing in the data, and potential issues with sampling design differences. The only thing I would like to see added is a description of whether or not this database will be open to new submissions in the future and if so, how it will be maintained.

Specific/Technical Comments:

In terms of technical issues, the paper is well-written, and the figures are informative and designed well, and the paper is structured in a logical way. I see nothing that needs to be edited for clarity, as the paper is very easy to read.  I appreciated reading such a well-conceived paper!

Review of  “A synthesized field survey database of vegetation and active layer properties for the Alaskan tundra (1972-2020)” by SHU et al.

The authors went to considerable efforts to compile this data base from 37 datasets originating from field measurements by different authors working in the tundra zones of Alaska over 50 years. Almost 200 000 data points were compiled and located with their geographic coordinates and the observed/measured data on vegetation cover (mostly structural), basic soil properties, active layer thickness were uniformized and compiled. In addition, the authors overlay the remote sensing mapping data of wildfires from the Alaska Large Fire Database (ALFD), thus allowing for future research to be carried on the impact of fires on the ecosystems. Some sites were surveyed by their authors after one or more fires (post-fires), other between fires and some before fires (pre-fire). An index of fire severity is also one data in the file (the dNBR attribute). The paper (supporting text) for this new, integrated, SATFiD data file, presents the compilation methodology, the “averaging” approach that was sometimes used to uniformize the data collected by different field researchers applying different survey methods with unequal precision. All considered, this is important work.

The authors state three objectives for their work: “(1) Gather datasets and synthesize them in a way that will facilitate further analysis by investigators and promote synthesis research efforts, (2) deepen our understanding of ecosystem processes within the Alaskan tundra, particularly fire-vegetation-permafrost interactions, and (3) identify areas of interest for future research where knowledge is lacking or there is great potential for follow-up research to study change and long-term trends.” I suggest to add a fourth one: to provide basic data on properties of the components of the ecosystem such as soil physical properties, active layer thickness, organic layers, water content, vegetation composition and dynamics,  as measured parameters for modelers to validate their simulations as well as for providing a better understanding of processes for their modelling. The authors are conscious that the data compiled in the different regions of the Alaskan tundra provide “snapshots” of the state of the vegetation and basic soil conditions at the time the various surveys were carried on the field. Maybe, this should be explained in a stronger statement in the text. We understand that fires are a major factor that may have induced ecological changes and that revisiting the field sites shall allow to assess its impacts of ecosystems. However, fire is only one factor of change. For instances climate change is also associated with shrub dynamics and snow cover variations, a factor not part of the dataset. Active layer thickness, surface erosion and deposition, organic layer growth (particularly through moss cover thickening) have also varied over the past 50 years. Therefore, although providing fundamental basic information, the SATFiD data will need to be used with some circumspection.

Here are a few editing and technical comments:

• Line 36: “exceptionally rapid rates of warming”, exceptional relative to what? Maybe just say very rapid.
• Line 54: I suggest replacing “biological changes” by ecological changes.
• Line 73: I suggest replacing “strong warming” by fast or rapid warming
• Line 80: replace “expeditions” by field work or field surveys
• Line 81: “The Alaskan tundra is an important component of the Arctic tundra biome…” Maybe say differently like.. represents an important fraction of the Arctic tundra with an area over 8.5 million km² and shares similarities with other Arctic regions.
• Line 86: I suggest replace “included” by inventoried.
• Line 97: delete “we argue that”, not necessary.
• Table 2: last procedure: daily calculation. Unclear to me. Do you mean repeat measurements over a long time period, i.e. months, years?? As it is written now I understand that the mean of a small number of measurements taken within one day is considered a daily mean..?!. Maybe I misunderstand… For instances, are temperature data taken over time with dataloggers averaged daily?
• Figures 5 and 6. I suggest you reorganize the figures and captions so as not to repeat a and c in both figures.