JULY 2016 • NEBRASKAland 35
for ponderosa pine and supported
white spruce forests and grasslands.
Westward during this period, the pines
were forced southward to refuges in
the mountains of southern Arizona
and New Mexico, and into Mexico,
though some stands may have persisted
in sheltered locations farther north.
As the glaciers retreated northward
and the post-glacial climate warmed,
ponderosa pine began to spread out of
its southern refuges. There is evidence
the species reached eastern Colorado
near Fort Collins about 6,000 years
ago and likely migrated into Nebraska
after that. Some botanists, however,
speculate ponderosa pine arrived in our
state as early as 9,000 to 10,000 years
ago.
During its post-glacial residence
here, ponderosa pine expanded its
range southward and eastward, possibly
via river valleys, during cool and moist
periods and retreated during extended
droughts, some which lasted centuries.
The Custer and Garfield county
stands are likely vestiges of one such
expansion.
Shaped by Fire
For eons, fire has shaped nearly all
North American forest types, both
deciduous and coniferous. Ponderosa
pine forests are no exception. Prior
to the arrival of Native Americans
from Siberia about 13,000 years ago,
summer lightning strikes were the
sole fire source. Human-set blazes,
both intentional and accidental,
greatly increased the frequency of
fires throughout North America.
Native Americans burned dense,
Ponderosa pines hug the rocky slopes of the Wildcat Hills in Banner County. Limber pine is the state's only other pine species.
It grows in a single small stand in Kimball County.
