Not sure this is what you're looking for, but I think the USFS has sometimes used a "scenic integrity" scale to capture something like naturalness (e.g. glossary of [1], p. 165; see also [2]). But maybe the US case is a bit unique given the recency of settlement/colonization, which can give a tempting reference point for thinking about naturalness, e.g. [3].

[1] https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fseprd589689.pdf

[2] https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fseprd657375.pdf

[3] Gimmi, U., & Radeloff, V. C. (2013). Assessing naturalness in northern Great Lakes forests based on historical land-cover and vegetation changes. Environmental management, 52(2), 481-492.

Thank you Logan, very interesting!

No proposed alternative indicator from my side, but I thought it may be of interest to refer to our recent review study on Old-growth forests in Europe, which also discussed the naturalness indicator and the difficulty of interpreting related data from Forest Europe:

O’Brien, L., Schuck, A., Fraccaroli, C., Pötzelsberger, E., Winkel, G., Lindner, M., (2021) Protecting old-growth forests in Europe - a review of scientific evidence to inform policy implementation. Final report. European Forest Institute, p. 104.

Book Protecting old-growth forests in Europe A review of scientif...

Thanks Marcus! Have read it already. Congratulations, and will surely refer to it. Best regards, Stefanie

Hello Stefanie,

or do you mean hemerobie approach like stated in

Article Hemeroby as an impact category indicator for the integration...

Yes and no. I am looking for a feasible alternative to hermerobie studies which are very costly and often not repeated.

Hello Stefanie,

if you have Biodiversity Data you can look for:

Müller, J.; Bußler, H.; Bense, U.; Brustel, H.; Flechtner, G.; Fowles, A.; Kahlen, M.; Möller, G.; Mühle, H.; Schmidl, J.; Zabransky, P. (2005): Ur- wald relict species-Saproxylic beetles indicating structural qualities and habitat tradition – Urwaldrelikt-Arten - Xylobionte Käfer als Indikato- ren für Strukturqualität und Habitattradtion. Waldökologie online 2, S. 106–113

or

Christensen, M., Heilmann-Clausen, J., Walleyn, R., & Adamcik, S. (2005). Wood-inhabiting fungi as indicators of nature value in European beech forests. Monitoring and Indicators of Forest Biodiversity in Europe–From Ideas to Operationality, 229.

Nitare (red.) 2000. Signalarter. Indikatorer på skyddsvärd skog. Flora över kryptogamer. Skogstyrelsens Förlag. Jönköping.

Blaschke, M., Helfer, W., Ostrow, H., Hahn, C., Loy, H., Bußler, H., & Krieglsteiner, L. (2009). Naturnähezeiger–Holz bewohnende Pilze als Indikatoren für Strukturqualität im Wald. Natur und Landschaft, 84(12), 560-566.

Thanks for the information and literature references. But this data on certain species is obtainable only with high human and financial resources. Would prefer to rely on nationally available data from e.g. NFIs.

We have tried to estimate the return to old-growth based on nine different parameters related to forest composition, structure, and functions by comparing old-grwoth with formerly managed stands. However, the variation within each indicator is very large in old-growth stands, hence it is really difficult to quantify old-growthiness (or naturalness). This is our paper, fyi: Article The long way back: Development of Central European mountain ...

Best regards,

Dominik

Dear Stefanie,

In Denmark, the UNA-Index is used (Møller, 2003). You may find the actual assessment scheme with the indicators under the heading 'Bilag 4' in the document under following link:

https://naturstyrelsen.dk/media/nst/66971/skovstruktur.pdf

If you need any help understanding the Danish, send me a pm.

Kind regards,

Joost de Koning

Thanks both of you for the interesting information!

Here's what the Czech old-growth forest people use:

https://pralesy.cz/databanka-metodika

You can find their criteria as a pdf in Tabulka 1. Alas all in Czech, but you maybe Google translate or one of the authors could help.

regards

Peter szabo

Thanks Peter! It worked well to translate it with google translate. Much appreciated! Best regards, Stefanie

We use quantity and quality of dead wood as an indicator of forest naturalness. https://www.sciencedirect.com/science/article/abs/pii/S0378112715002868?via%3Dihub

Dear Stefanie, you might be interested in this paper (it is in press in Diversity and Distributions) : https://www.biorxiv.org/content/10.1101/2021.02.08.430252v4

It precisely uses NFI data, but requires good training data.

Regards, Yoan

Thank you Yoan, very interesting. What if you don't know the time of the last harvesting?

Stefanie Linser you could go in a different direction if you wanted to investigate this question at a broad spatial scale. For example, you could use the Montréal Process indicator of forest fragmentation to quantify and examine trajectories for "core" forest (i.e., forest at the center of a completely forested landscape), under the assumption that core forest has a high degree of naturalness simply because it's intact forest cover and not adjacent to other fragmenting land covers. This is a simplification, of course, and there are issues of spatial resolution, neighborhood size for analysis, etc. Article The United States’ Implementation of the Montréal Process In...

Thanks Frank for this interesting approach to assess naturalness via fragmentation. However, in Europe the forest area is rather highly fragmented, at least outside the alpine forest areas and we need indication on naturalness for the whole forest area. But fragmentation could at least be part of a potential index including management, protection and further biodiversity related data. Thanks and best regards! PS: Thanks for the paper reference. The Special Issue on C&I for SFM https://www.mdpi.com/journal/forests/special_issues/Criteria_Indicators is great!

Dear Stefanie, it might be interesting for you to take a look at the

"Old-Growth-Indicator"

Article Quantifying old-growthness of lowland European beech forests...

Great, thanks Maria!

Article A quantitative indicator framework for stand level evaluatio...

Thanks Wouter! Impressive how many indicators have actually been measured at the field/stand level, but I think than most of them are not feasible at national level. Too costly and too much expertise needed...

Dear Stefanie, the assessment of the naturalness of forests (I consider the term itself problematic, however) should include the criterion of the completeness of the species inventory of recent larger mammals that can influence forest structure and biodiversity. Also, whether their "natural" activity is restricted by hunting or other measures. Where possible, consideration should also be given to whether or not natural processes such as mass reproduction of bark beetles (Scolytidae) are allowed, because such processes are of very high importance for the biodiversity of forests. Common forestry practices and legal regimes, at least at the regional level, could be used for the assessment.

Thanks Jürgen, very interesting. I agree with species inventory of larger mammals. However, also small species are of relevance, particularly threatened species (beetles, insects, invasive plant and animal species) and here it is extremely difficult to obtain national data, as the monitoring requires experts for the monitoring. And thanks also for the reminder on qualitative indicators like forestry practices and legal regimes. indeed relevant. Thanks!

It all depends on the baseline you set. Few suggestions:

(1) post-war,

this is what many people do. Please explain, why. Imo it makes no sense. We are talking about naturalness.

(ii) c 1800, end of pre-industrial period. Until then, domestic grazers and draught-animals shaped open and wooded landscape in a relatvely near-natural way. No artificial border between forest and the open. Most rivers still unregulated, wetlands undrained.

(iii) c 8.000 - 10.000 BP

Large herbivores going extinct. Before that they exerted quite some power on landscape and translocated seeds, fertilisers and minerals.

P.S.: Why should a dense forest be natural after shooting out all the deer before?