Redwood Death, Open Sky

By Bruce G. Marcot, Ecology Picture of the Week:

You are in a land of green towers, a grove of old-growth coast redwoods in northern California's Humboldt Redwoods State Park.  As you move through this cathedral forest of iconic pillars, suddenly the canopy opens and the sun shines through.

Look up.  There is a hole in the sky ... more accurately, a canopy gap, formed when one of the old trees died.  

Even dead trees have life.  They are typically referred to as "snags" in U.S. forestry and "wildlife trees" in Canada, and are host to probably hundreds of species of birds, mammals, fungi, insects, and other organisms.  Snags like this one may serve as perching sites for goshawks or other birds of prey ... may provide cavity nests for woodpeckers and then small owls and other "secondary cavity nesters" ... and may even provide habitat for many organisms on the forest floor as the bark sloughs off and the wood disintegrates.  

But it is the gap in the forest canopy that is of interest today.  The gap, even from just this one tree, can radically increase sunlight and temperature and decrease humidity on the immediate forest floor below.  Sun-loving grasses, forbs, shrubs, and even tree seedlings then appear, taking advantage of the newly-created habitat.  This, in turn, provides suitable conditions for many species of birds, insects, and other animals that use the "early successional" forest environment.  

Patches like this naturally occur in old forests.  If you could stroll through this forest and fast-forward in time by decades or centuries, you would see canopy gaps like this one -- formed by trees that die naturally in place or fall over from storms or other causes -- that appear throughout the forest, only to be quickly "healed over" by plants that race to fill the voids.  

So if a tree dies in a forest, it punches a hole in the sky and many organisms benefit.  

  --Bruce G. Marcot

Image and text © Bruce G. Marcot, Ph.D. Research Wildlife Ecologist,
who produces the Ecology Picture of the Week website.