A colony of space travelers makes their way to their new home planet. After landing and establishing their base camp, a wood worker begins to cut down trees and notices that none of the trees have more than 12 rings. Curiously he explores the country side for several days and can find no trees with more than 12 rings (dead or alive).
I want the character to conclude that there is a pending extinction level event that will happen again, and this evidence is proof it has happened before.
I can't think of what kind of event would leave new trees to grow but leave no old trees behind.
To clarify some of the questions asked in comments.
- He finds no trees older than 12 rings and a ring represents one solar year on that planet.
- The trees are biologically similar to trees on Earth.
- He does find dead and fallen trees but none that have more than 12 rings.
- There are no remains of trees older than 12 solar years ago.
- There are no fossilized remains of older trees.
I'm looking for an event that happened 12 years ago that made all the trees disappear. At this point I haven't figured out how he'll know the event will happen again, but I guess that depends upon what kind of event it is.