White barked Pseudotsuga menziesii (Douglas fir)

Although my field ventures are typically focused on geology, I do note the flora around me. However, I lack education and ongoing learning to provide astute explanations - there are a lot of gaps in my understanding of plant biology and ecosystem. A fair bit of self learning and I remain very humble about just what I am seeing and what it means.

I came across a set of evergreens with very white back while visiting a site in the North Cascades.  

What were these white barked evergreens? I started going through a list of possibilities. The site was a low elevation site, but well within the mountains. Climate wise yearly rain fall is very high at 80 plus inches per year. The site is low enough that winters are generally mild, but inland enough that periods of hard freezes should be expected. The site was in one of the deep valleys with valley ridges on the order of 5,000 feet or more. Hence, nearby areas have very different growing conditions and tree species. Avalanche hazard zones are located on the slopes with evidence of periodic avalanches all the way to the valley floor in places.

It was pretty easy to tell just what the trees were by finding cones.

 Pseudotsuga menziesii (Douglas fir) cone.

So not an unusual tree species at all. Douglas fir can and does often have light colored bark as young trees. I can not be entirely sure of the age of these trees, but based the site was disturbed in the late 1970s and early 1980s so these trees may be 30 years old.

I can say that the growing conditions are very harsh. The site essentially had no soil and was underlain by cobbles and boulders. The excessive drainage has created a somewhat out of place dry ecosystem that has stunted the trees throughout the area. Indeed many were dead perhaps not able to survive once attaining larger size with a couple of hot long dry summers thrown in the mix.