Betula papyrifera, Argilus anius and Temperature

A field venture a few days before the current cold spell took me through a wetlands restoration project, past thickets of Nootka rose, and an effort to push back on invasive canary reed grass.  

One challenge of environment restoration plantings is keeping the rodent and deep nibblers at bay; hence, the blue plastic tubes and fencing around plantings. 

The forest stand I passed through was a very mixed stand. This tree is a tree that has a limited range in Washington State, but is a common tree in the northwest Puget lowlands.

The bark pattern of this species in northwest Washington is often dark and can be mixed up with wild cherry, another local native tree. However, some do develop the more classic white bark. There is some variability in the species that early fur trappers noted - west of the Rocky Mountains the birch do not have the same quality of bark for the building of canoes, a bit of a disappointment for the river and lake traveling that fur traders relied on.

In Washington State, Betula papyrifera is limited to the northern reaches of the Puget lowlands in western Washington and far northern and eastern edges of the state.

Distribution of Paper Birch from USGS ( “Atlas of United States Trees” by Elbert L. Little, Jr. )

The distribution of the species limiting factor is likely strongly associated with Argilus anius (bronze birch borer). Muilenburg and Herms (2012) provide an overview of the relationship of the borer and birch trees. Temperature plays a partial role. Deep freezes may slow the maturation of the borer. 

In northwest Washington, the paper birch is limited mostly to norther Puget lowlands. In the Birch Bay and Drayton Harbor area, the tree is one of the predominant species in the forest. These areas are cooler in the summer and perhaps the occasional bast of arctic air out the Fraser River canyon like today puts a bit of a check on the borer. Today, was a good example. While snow arrived in the Seattle area, the temperature in Seattle as I write this is 30 F, while the temperature at Birch Bay is 15 F. In addition, the northwest portion of the state is substantially cooler in the summer and thus a bit less stress for these cool weather wet ground trees.