When a tree is cut down, the rings in the trunk can be counted to estimate the tree’s age.
(a tree; is cut down; ) (the rings in the trunk; can be counted; to estimate the tree's age; T:When a tree is cut down) (the rings in the trunk; to estimate; the tree's age)
a tree the rings in the trunk the rings in the trunk
is cut down can be counted to estimate
to estimate the tree's age T:When a tree is cut down
the tree's age