Flat Leaf Biome Identification

Does anyone know what biome creates these flat areas of leaves? They seem to appear most in stacked layers of rock/leaf/air. I suspect it might be the cave type or the cave type overlapping with a biome. Of course, I didn’t make any notes about the biomes I picked, so any tips would be great!

looks to me like an effect of autumn when the leaves fall but in biome form.

do some caves have leafy floor that seem independent from what is on surface ?

Yeah, it’s pretty! It’s just everywhere on this sovereign and I’d kind of like to avoid it in the future.