A funny thing happened to ponderosa pine
and other tree species during the last ice age. As the ice
sheet advanced, the tree was forced either south into Mexico
or to the Pacific Coast to find warmer climates. Gradually,
the trees evolved independently and differentiated into subspecies.
The trees in Mexico developed needles in groups of 2 while
the trees from the West Coast developed needles in groups
of 3. When the ice sheets retreated ponderosa pine again spread
to the east and north. On the Helena National Forest the two
subspecies meet around the Continental Divide and that is
why ponderosa pine in this area have either needles in bunches
of 2 or 3. We are at the meeting zone of the two subspecies
of ponderosa pine.
When ponderosa pine is young its bark
is brownish black and the tree is sometimes called “bull
pine”. When the tree grows older the bark changes to
a yellowish color and develops a plate like structure. The
bark looks somewhat like a jigsaw puzzle with its plates,
which do serve a purpose.
If the tree catches fire these plates pop
off as the bark burns. The tree in effect is shedding its
burning bark. This adaptation, along with the great thickness
of the bark, allows the tree to be very resistant to low intensity
fire.
The tree has needles from 3 to 5 inches long
that occur in groups of 2 or 3. The cones of the ponderosa
are about as large as a baseball and can be identified by
sharp points at the end of the cone scale.
Ponderosa pine has been affected by fire suppression.
By putting fires out in the forest for the last hundred years
we have encouraged the build up of fuels and younger trees.
We call the younger trees “ladder fuels” because
they can carry a wildfire into the canopy of the mature forest.
Ponderosa pine is not adapted to survive crown fires, and
a fire of this intensity may kill even the large and old trees.
As ponderosa pine forests have become increasingly
thick the amount of shade on the forest floor has increased.
In some areas there is now too much shade for ponderosa pine
to prosper because it needs full sunlight to grow. Douglas
fir seedlings need shade to survive, and in some areas
the Douglas fir is taking over forests that used to be predominantly
ponderosa pine.
Ponderosa pine is a valuable tree for lumber
purposes from making paper to building houses. Artificial
vanilla is made from the bark of ponderosa pine. Old yellow
barked ponderosa sometimes smell of vanilla. |
