File:Whitebark pine, Pinus albicaulis, branches and male cones (28468464347).jpg

whitebark pine, Pinus albicaulis, branches and male cones, Nevada, Sweetwater Mountains, East Sister, Dalzell Canyon - Smith Valley drainage, elevation 3147 m (10325 ft).

Finally finished up 2016 with some whitebark pine research. This western North American endemic is currently a candidate for Endangered Species listing, because of widespread declines and mortality from white pine blister rust and pine beetles. Most of the mortality has been in the main part of its range in the northern Rocky Mountains. I have been helping to survey less impacted populations near the southern edge of its range.

whitebark pine is unique among North American white pines in having cones that remain closed until torn apart by animals, or falling apart on their own. The animals (mostly Clark's Nutcracker and various small mammals) are very efficient at this, and if you aren't there while cones are still on the tree, often all you find is a litter of disarticulated cones scales on the ground. The species depends almost entirely on Clark's Nutcracker to disperse its seeds. Vegetatively the species is virtually identical to limber pine (Pinus flexilis), which causes ID problems where they grow together, unless cones are present.

Here in the Sweetwater Mountains the two species grow together, and the whitebark pine cones look a little different, being lighter colored and less readily falling apart, which are traits of limber pine. I have seen the same kind of variation in other places where the two species grow together, suggesting the possibility of some genetic mixing. Or, this could just be natural variation in whitebark pine populations.