My Favorite Tree

In reading Aldo Leopold's Sand County Almanac, I came to a line that struck a chord with me.  Leopold wrote, "The only conclusion I have ever reached about trees is that I love all trees, but I am in love with pines."  I understood exactly what he meant.  Although my love extends to all trees, and especially each and every pine, I have a favorite among the pines.

The whitebark pine is a member of a tree that began in the Old World.  They aren't as tall and graceful as a Ponderosa, or as plentiful as a Douglas fir or Lodgepole, but they are tenacious and tough.  They grow slowly, hitting full reproductive stride at 70-100 years old and living up to 1,500 years.  Whitebark pines live in high elevations--often over 9,000 feet where few other plants can grow.  This habitat leads to great benefits both immediately around the pine and much further down the slope.  Whitebark pines are often the first tree to grow at high elevations--other trees can't handle the amount of snow, hard wind, or poor soil.  However, once these pines are established they improve the soil and provide shade needed for other plants to grow.  This shade also slows the rate the winter snow melts resulting in less flooding downstream, a longer flow of water to riparian (wet) areas, and more consistent water for humans using the water for agriculture or hot showers.  High on the rocky slopes, areas that have whitebark pine have more biodiversity--both plant and animal--than areas without the tree.

Animals like the grizzly bear, the red squirrel, and Clark's nutcracker depend on the seeds from the cones for winter survival.  The grizzly eats the nuts to put on needed weight for hibernation while smaller animals hide seeds for eating all winter long.  Whitebark pine cone production varies and on years with a low number of cones there are more human bear conflicts as bears, unable to find food in high elevations, search for it in low elevations closer to people.  

Clark's nutcracker has an especially important role.  Many birds and small animals will inadvertently plant a few bushes throughout the course of their lives as they collect seeds.  A Clark's nutcracker, however, will plant an entire forest.  This bird, named for Meriwether Lewis of the Lewis and Clark Expedition, is the key to the growth of whitebark pine seedlings.  The pine's cones do not naturally open to release seeds.  The nutcracker opens the cone with his built in multi-purpose tool, otherwise known as a beak.  He uses it as a  chisel, tweezers, storage compartment, hoe, and planter.  Early in the harvest the bird eat the pine nuts, as the season progresses he caches them miles in all directions.  He will fill the pouch under his tongue with as many as 80 seeds and travel to select a cache.  One bird was seen hiding 35,000 seeds in 9,500 different places.  The Clark's nutcracker has an incredible spatial memory--all winter he's travels back to the places he cached seeds.  But in a good year, he won't eat every seed he stored.

Two years pass.

Then, fully matured and with enough moisture in the soil, a new whitebark pine seedling will sprout.  Because the seeds are often plucked from the tree before they are fully grown.  It will take another year or two for the embryo to develop completely and then for the seed coat to get worn down for germination.  Whitebark pine is one of the few trees that has "seed banks".  In other words, because it takes a couple of years for seeds to germinate there can still be a lot of new seedlings after a year of low pine cone production. Often many trunks grow from the same spot--one of the 9,500 places a mouthful of seeds was hidden.  Without the Clark's nutcrackers, the cones would remain closed and the seeds locked inside the cones.

Today, there are concerns about the future of whitebark pine because of climate change (warming makes other trees able to grow in high elevations pushing whitebark pines out), the invasive white pine blister rust (infecting 20% of the whitebarks in the Greater Yellowstone Area), and the native mountain pine beetle (30-40% of mature whitebarks in the area are dead).  The Yellowstone area is one of the last strongholds for whitebark pine.  It is a keystone species in the ecosystem providing life to its plant and animal neighbors nearby as well as those--including humans--far down from its rocky slopes.

I didn't know all of this when I fell in love with the tree.  I only saw the graceful five-needle clusters and a tree growing in the toughest of conditions.  I still love those clusters, but each time I learn a new piece of this pine's story, I am amazed by how it survives, thrives, and provides for all organisms near it.  And I haven't even gotten started on the role fire ecology plays with it...



Sources: http://fwp.mt.gov/mtoutdoors/HTML/articles/portraits/nutcracker.htm
http://www.fs.fed.us/database/feis/plants/tree/pinalb/all.html
http://www.whitebarkfound.org/Nutcracker.html
Retrieved on June 9, 2011
CFLRP Proposal Greater Yellowstone Whitebark Pine Restoration