You can [[botanize]] but you can not [[forage]] on steppe tiles.
You can dig or pack steppe away. Dropping [[pile of dirt|dirt]] also destroys the steppe tile. You can convert a [[Dirt dirt tile|dirt]] tile into a steppe tile by planting [[mixed grass]] botanized from other steppe tiles. Steppe spreads onto dirt tiles on its own, but slower than [[grass]].
Planting steppe with [[mixed grass]] is treated like planting any other [[flower]] type. As such, the success rate of planting [[mixed grass]] is influenced by the [[Nature|nature]] subskill, [[gardening]].