The moisture content looks perfect N. I do wonder if Thuidium delicatulum could take the place of Spagnum moss for air layering.
Hi D, I suspect most large mosses can be used for air layering, but I have absolutely no evidence... never tried air layering myself. Although Sphagnum is famous for holding the most moisture of all mosses, as far as I know.
I just found this online, from: https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1146&context=bryo-ecol-subchapters
What an article N good find. I have downloaded it to keep. Brilliant read for anybody who sees your posting. Thankyou N.
There is a lot more to read in the document that article is from. I have added the eBook on Bryophyte Ecology to the Plants with Spores (Ferns, Mosses, et al.) Resources | UBC Botanical Garden Forums resource page.