| How
Old is a Tree? |
From the
time a tree starts life as a seedling, it begins to record
its own age through a series of light and dark circular growth
rings in its trunk. The dark rings are caused by rapid spring growth
with larger cells; the dark rings will provide an accurate record
of the tree’s age. Thick rings indicate a year of good rainfall,
while thin rings show a time of drought.
In this cross-section
example, some historical events that have taken place during
the life of
some of Pittsburgh’s oldest
trees are highlighted.
|
| 1758: This
tree was just a sapling when General John Forbes defeated the
French at Ft. Duquesne and re-named it Ft. Pitt in honor of British
Prime Minister William Pitt. |
1851: Our
growing young tree saw the simple beginnings
of the Pennsylvania Railroad, a line extending from Pittsburgh to Turtle Creek |
| 1900: Now
a mature tree, it continued to grow with giant, industrial Pittsburgh,
the world leader at the turn of the century in the
production of steel, glass and aluminum. |
| 1936: When
the city was inundated with the great St. Patrick’s Day
Flood, this tree towered over the watery ruins of Downtown Pittsburgh. |
| 2001: The
tree trembled when Three Rivers Stadium was demolished, but now
stands tall as Pittsburgh has become a leading information
and technology center. |
