Well, that still doesn't really have anything to do with the forests themselves.
I don't see how it doesn't have anything to do with the forests themselves. The culture which is creating this series has a very old, proud tradition of believing that forests (and all life really) are as alive as they are because of spirits which live inside each being with some spirits being relatively more powerful than others. And, more particularly, the forest is seen as one of THE chief dwelling places of spirits.
It's not as if the trees and other plants are inhabited by spirits and tries to attack Link, it's just ghosts and spirits that happens to reside in a forest.
You misunderstand me. The spirits do not have to occupy the things which they represent. The forest is seen as a location of for lack of a better word, mystical power that is home to many a spirit. The fact they happen to reside in the forest is the reason I'm telling you it fits in with a lot of Eastern and Western lore.
None of the spirits and ghost of the Forest Temple has any actual ties to the temple or the theme of "Forest", they might as well have been in the Shadow Temple, or another dungeon from another game.
As I have pointed out to you already, spirits and ghosts themselves are intricately linked to the theme of "Forest". They could have been elsewhere, just like I could be called Frankenweenie instead of Misty, but I am not called by that and these appearances are in the Forest Temple (it's literally called the Forest Temple.)
The only enemies from the Forest Temple that doesn't appear in the Shadow Temple are Octoroks, Skullwalltulas and Deku Babas, none of which are undead in any way.
O_O which lists of enemies are you comparing?
Shadow Temple:
Beamos, Floormaster, Gibdo,
Keese, Like Like, Red Bubble, ReDead,
Stalfos, Wallmaster, Skulltulla, Golden Skulltula,Dead Hand, Big Boss: Bongo Bongo.
Forest Temple: Ganon, Amy, Beth,
Big Deku Baba, Blue Bubble,
Deku, Baba, Floormaster, Joelle,
Gold Skultulla, Green Bubble, Meg,
Octorok, Skulltula, Skullwatulas, Stalfos, Wallmaster, Wolfos.
I'll cross out any that are shared.
Now I'll cross out any that aren't undead or are planty seeming.
and hey, since I've already got the page open, let's compare the traps located in them too.
Shadow Temple: Blade Trap, Floor Spikes, Fire Eye, Guillotine, Poison Water, Wall Spikes, Whirling Scythe.
Forest Temple: ----
So based on this list it seems there are undead enemies which appear in the forest temple which do not appear in the Shadow temple. Even if I discount the Poe Sisters, which I think a bit unfair seeing as they would be some of the spirits my argument rests on, but even so, I still have Blue and Green Bubbles in the Forest Temple.
More interestingly, I look to the Shadow Temple and I see a whole manner of nasty undead that do not appear in the Forest Temple despite the fact they so easily could: Red Bubble, ReDead, Dead Hang, Like Like, Gibdo, Bongo Bongo himself isn't much like Ganon who appears from a painting. (Note, paintings are usually made from natural substances found in forests, framed by wood, made from either animal skins or paper (which comes from trees). The Forest Dungeon has only spirits appearing, while Shadow Temple has true undead.
Other than that, it's just the Poe Sisters and Phantom Ganon, which could easily been placed in the Shadow Temple.
The creatures which appear in the Shadow Temple are unnatural, malevolent, and given the setting of a place that is trying to kill you (see all the traps) would not necessarily belong. Phantom Ganon himself seems to best comprise the difference, after all, Ganon is not dead. This is merely a phantom of him. The Poe Sisters are restless souls and spirits which you put to rest while the Shadow Temple you're killing these animated undead creatures.
and I do agree with you on the temples themselves, their themes are vastly different, but the enemies that appear in the Forest Temple doesn't really have any ties to the theme of Forest, or even haunted forest for that matter. The Forest Temple might as well have been called the Mountain Temple and been placed up on a mountain top and the enemies would still fit the theme of the temple.
On your own list, you have a jungle man, a venus fly trap wannabe, another venus fly trap wannabe, a moth, a I don't even know what Gohma is...I'd say some sort of anthropod like the wiki does, but even that seems a stretch for how it is usually drawn, and something we think is a large version of another man eating plant.
The jungle man's claim to fame is being a jungle man who dances around and summons insects and fire to do his bidding isn't that correct? Dunno, he doesn't seem particularly significant to the forest unless we're accepting the lore of the world. He could just as easily be in a mountain area summoning fire and insects to do his bidding. Insects live pretty much everywhere that isn't cold. He must be one of those ones that's saved by his dungeon being exactly what everyone imagines when they hear forest.
And Gohma, I mean, like I said, unless I'm accepting that he belongs there....what even is he? And why couldn't he appear anywhere else? He doesn't seem to have anything that particularly demands him to be in the forest. I mean, I guess his temple is pretty foresty...it's a spirit and very large tree. But nothing about him himself seems in keeping with the theme.
I'll give you the three variations on the same concept of man-eating plant and the giant moth as being clearly forest related, but if you're keeping jungle man and gohma on that list I really don't see how they couldn't belong anywhere else.