Here are some options, depending on the context:
* A pile of stumps: This is straightforward and descriptive.
* A cluster of stumps: Suggests a group of stumps close together.
* A stand of stumps: Implies a group of stumps in a particular area.
* A field of stumps: For a larger, more widespread collection of stumps.
You could also use a more poetic or metaphorical term, like:
* A graveyard of trees: This emphasizes the loss of the trees.
* A testament to the past: This highlights the history of the area.
Ultimately, the best collective noun depends on the specific situation and the desired effect.