Thread:GandalftheTurquoise/@comment-25012056-20151007101104/@comment-27723099-20151029210417

This "SET_..." seems to control it. I guess every biome has a type (NORMAL, NORMAL_OAK, NORMAL_SPRUCE, NORMAL_OAK_SPRUCE, FOREST, MOUNTAINS, or SWAMP) defined in the biome code.