After last night’s class I did some more reading about the age ranges of young and old forests. It turns out that a lot of factors contribute to how old a forest will be before it is considered old-growth, including the species of trees present, how often natural phenomona like fires or insect infestations disrupt the forest, and whether or not there are dead trees still standing in the forest.
In most cases, it takes more than 100 years for a forest to be considered old-growth, but some trees can live to be many hundreds of years old. You can read more about it here: https://en.wikipedia.org/wiki/Old-growth_forest
