A Madrone Forest and other Orcas Island Observations

I did some more tree ring counting notes-on-tree-rings-and-old-forests and again on Orcas Island. This rather modest diameter Douglas fir trunk on the southwest side of Mount Constitution had approximately 100 rings.  

The small diameter but old age does cause me to wonder about the age of stands of large Douglas firs that are scattered about the island.

Old growth Douglas fir

The more interesting aspect of my ventures was finding myself in a forest stand where the predominant tree was Arbutus menziesii.   



Mount Constitution is not a dry spot. While it shares the alignment of other dry areas in the Olympic Mountains rain shadow, it is a bit too down wind and subject to weather events approaching from elsewhere. Its sharp rise above sea level also enhances rainfall locally. However, soils are very thin with shallow bedrock and hence water retention is limited creating a bit of a dry like habitat despite the 40+ inches of rain on parts of the peak. Being on a southwest facing slope added to the dryness. Good habitat for the madrone.

But this forest stand of  Arbutus menziesii also benefitted from anthropogenic forces.

Douglas fir stump

I suspect that the madrones were present prior to logging, but post logging allowed the madrones to flourish over a larger area.

The appeal of this tree is sometimes easy to see. Or perhaps the appeal is simply that its bark habit is so contrary to most trees.

The tree was well established with lots of seedlings.

Arbutus menziesii and lodge pole pine seedling

Of course my purpose was geology so I had to check out the slopes and the bedrock. This is an area of Orcas where the geologic formations are a bit chaotic as units are shuffled in a series of thrust faults. In this case the bedrock was mostly Turtleback Complex with a bit of East Sound Group. Alas, despite the large number of outcrops the exact contact was obscured.