I had similar issues in the past with such open and thin designs.
And while having proper supports where it matter is of great help = they are useless if they fail.
Which seems to be the case in your pics.
Tree supports LOVE to pop off the bed if they get tall and the nozzle keeps dragging over them or bumping into them.
Use a WIDE brim for the model and supports - don’t be shy to use 15 or more mm if required.
Make sure the brim model gap is set to 0 to prevent ripping off.
Apply some liquid glue stick to the plate:
The stick to get glue onto the entire plate then a soft sponge or lintfree cloth MOIST not dripping wet from water.
Wipe over the cold plate to get and even whitish layer - repeat with few drops of water if things get dry to get just a very thin film of glue on the plate.
Have the first layer speed quite slow to allow for a better bonding and do a test print with a not too wasteful model to see how single tree trunk of similar height as in your bog model will hold up.
A bit of flexing above the 10cm is no big deal, layers failing however is and could indicate the print temp being too low or your flow rate not well calibrated.
That is assuming the filament is dry.
If that goes well your big model should come out just fine.