A large stand of aspen trees that are genetically identical individuals produced by vegetative reproduction is called a clonal colony or a clonal stand.

Here's why:

* Vegetative reproduction: Aspen trees reproduce asexually through root suckers. This means a new tree grows from the roots of an existing tree, creating a genetically identical copy.

* Clonal colony: The term refers to a group of organisms that are genetically identical and have originated from a single ancestor through asexual reproduction.

So, a stand of aspen trees that all share the same DNA and have been produced through root suckers form a clonal colony, often referred to as a clonal stand.