i wouldnt do so, u say ur trees there are long and strong and decades old , ur plants will be little and weak in beginning and some days or weeks old.....
think noone can tell you because only you have this soil, u will only know if u try, probably it will also work, probably good or not so good,
but there is also the chance that you import something that dont harms the trees but your plants, and then you sit there at the end with nothing and was weeks busy with the plants......
dont know what u have to pay for soil, here it cost 7-8 euros for 50 liter light soil from atami/biobizz/plagron etc..... and if i think what i get out of it at the end its really no problem to pay that little price in the beginning.....
...if you ask from the organic aspect, that you want to know 100% where it comes from and that there is really non-organic shit inside, then i would sterilize it by heating and use later some ecto/endo/bacteria soil innoculent to get life back in there
but also want to know if someone have tried out forest soil with sterilization, because i live next to forest, can imagine that you have to dig a little bit deeper for some good soil ready to use...