I grew up there, it’s a tundra/prairie biome. I grew up in the he’ll creek formation area though so lots of buttes. Any trees were largely planted by settlers.
It’s quite beautiful in its own right. Just avoid the eastern part of the state, that bits flat as a board and about as boring.
Where I grew up in nd tree lines were more for wind breaks than described here.
Here’s a bit a little south of Mandan, https://maps.app.goo.gl/fkns9wFp8NsnCvFy9
Trees don’t really do well around here. And bear in mind this is the more woodsy part of nd. Past this it’s mostly grasslands even more.