Nature Horizons requires Mantle and Biolith.

Nature Horizons is a mod that add new trees to the overworld to spice up your world.

Nature Horizons add the following tree:

• aspen, found in the aspen forest and old growth aspen forest
• black walnut, found in the aspen forest and old growth aspen forest
• blackwood, found in the savanna biomes
• juniper, found in badlands biomes
• pine, found in taiga biomes(replace vanilla spruce pine tree)
• redwood, found in old growth redwood taiga

as you noticed the mod also add 3 biomes: aspen forest, old growth aspen forest and the old growth redwood taiga

additionally black walnut leaves drop hard walnut and juniper leaves drop juniper berry.

hard walnut need to be be cracked against a hard block to be edible(see nature_horizons:can_break_hard_walnut tag)