“Fir waves” – the cycle of life and death in White Mountain trees

The always great Something Wild segment on NHPR has a cool discussion of tree patterns in the White Mountains, especially “fir waves.”

When trees growing on this thin soil rock back and forth in the wind, they break their fine feeder roots. As they grow taller, their canopy area exceeds the roots that anchor them.

This factor leads to the “fir wave” phenomenon. That’s the dieback of spruce and fir trees on the upper slopes that occurs over years. As the trees exposed to prevailing winds die, they then expose the trees behind them.

Fir waves have been found to occur only in the northern Appalachians and in the mountains of northern Japan. These slow motion waves include dieback of canopy trees plus new seedlings that regenerate in their wake.

Waves of death and regeneration move an average of three -10 feet per year. They crest and break when they reach the ridgeline above. And the process repeats.

The whole segment is worth a listen (or read the transcript) here.