Explain how the retreat of north american glaciers 16,000 years ago influence the distribution of trees.

North American glacier:

About some 15,000 years ago earth faced a catastrophic event of ice age termed as Last Glacial Maximum(LGM), which covered most of the globe. As the northern region of the American continent, along with that most of the region in the European lands. Which made it very hard for the living beings to survive.

Explanation:

Effects on Plants-The process of producing more food was been halted by the severe conditions globally and there were more unfavorable conditions for the plants, as the level and height of ice over the surface was in the range of Km's. As the trees and plants did not had any water available due to low temperature in the region.As most of the Amazon was in scattered form and the rain forests were greatly effected by the ice age, as it covered the surface of the land in the north American region.Due, to too much ice and lack of fertile soil available there were less crop and less trees developed, which caused more severe conditions.

This movement is also referred to as  glacial plucking