The last two are a mix of trees and open land transition ecosystems between boreal and tundra in the north, and boreal and grassland in the south.
(The last two; are; a mix of trees and open land transition ecosystems between boreal and tundra in the north, and boreal and grassland in the south)
The last two
are
a mix of trees and open land transition ecosystems between boreal and tundra in the north, and boreal and grassland in the south