Old-growth forest, Warren County, within the Hearts Content Scenic Area of Allegheny National Forest.
Note the large white pine in the foreground. White pines are among the largest trees in the tract. They arose several centuries ago after a large, canopy-opening disturbance (such as windthrow or a wildfire) flooded the forest floor with enough light for the trees to germinate.
Today, the white pine component is declining; the canopy of hemlocks and American beeches casts deep shade on the forest floor, preventing the white pines from germinating. If more American beeches succumb to beech bark disease, and if the hemlock woolly adelgid reaches the tract, the resulting canopy breaks will likely promote white pine regeneration.