why does grassland replace forest west of the Mississippi river?

Question

biology, factors determining climate

Answer 1

The main factor is the lower annual precipitation. Grasses don't require as much rainfall as trees do. Other factors that limit growth of trees in grasslands include grazing animals and periodic fires.

Answer 2

The rocky mountains.

These mountains form a barrier to moist air moving southeasterly from the pacific ocean. Grasslands require far less moisture than forests do. Each ecosystem has another means of keeping foreign species from colonizing. Forests are too shady for grass to predominate. On the open plains, tree saplings might sprout, but brush fires are common. Most of the growth of grass takes place right at the surface of the soil. This means it can resprout after a fire. Trees grow mostly from the tips of their branches and fire will kill them. The prarie has one final deterrant to prevent mature trees from growing. Three feet under the sod there is a layer of chalk and lime nearly as hard as cement. This would prevent a tree from forming deep taproots.

Answer 3

try looking up "rain shadow".