By most definitions, both are Wood-y, and trees are taller than (X), with some species being able to be either. More importantly, I think there needs to be definitions of herbaceous plant biomes, like grassland or equivalent, as well as differentiation between a barrens that is covered with moss or other non-vascular plants, and barrens that have nothing. Also, consider: Grassland ↔ Savannah ↔ Shrubland ↔ Woodland ↔ Forest.