Blog Number 12, August 2022
When I moved to Rocky Brook in 1999, the Washington DOT was in the process of removing a vintage steel bridge on Highway 101, replacing it with a much less interesting concrete structure. I dreamt about keeping that rusting relic, maybe converting it into a community meeting place or at least repurposing it as a bike and pedestrian crossing for the adjacent Dosewallips State Park. I might have been able to get them to rethink the project and save this historic structure, but I was too late in the process and too new to the community. So, it was torn down, sold as scrap metal, lost forever.
Right next to the bridge were some cottonwood trees which also had to be removed in order to allow construction activities to proceed. These were big trees, tall and wide. Eagles nest every year on one giant just downstream. They are the tallest things along the river, approaching 200 ft. high. I stopped one day to count the rings as I often do when I come across fallen giants such as these.
To my astonishment, they were not even fifty years old. A fir or cedar with that kind of height and girth would be five times that age.
Three miles upriver from this site is where I now live, along both the Dosewallips and Rocky Brook which flows into it. Both are anadromous (salmon spawning). The “Dosey” as locals refer to it, has the distinction (for the moment) of being the only river that flows into Hood Canal, on the east side of the Olympic Mountains, with glaciers at its source. They sit on Mt. Anderson, 7,321 ft., the 4th highest peak in the Olympics. Because of the glaciers (which, like glaciers nearly everywhere, are retreating fast) the Dosewallips runs high and milky with silt in the spring and summer.
When I bought my 40 acres of floodplain and steep rocky headland, I was pleased to find some big cottonwoods amongst the predominantly alder floodplain woodland. For almost twenty years I watched and waited to see signs of young cottonwoods popping up in places to replace these old giants. Alders continued to thrive. Cedars and grand fir sprung up along the streambanks. The few existing conifers kept getting larger. But no young cottonwoods to speak of. And, all my large cottonwoods appeared to be about the same age.
I wondered why this was.
Black cottonwoods (populus trichocarpa) are considered to be short-lived trees (50 to 100 years), though they might reach tie ripe old age of 200 on occasion. Compare this to red alders (less than 100 years), big leaf maple (300+ years), Douglas fir (750 +years) … and the grand daddy of Pacific Northwest forests; Western red cedar (1000+ years).
Black cottonwoods are well adapted to riverine conditions. they thrive and depend on the constant availability of water. In the late spring I can see their reddish roots exposed, right in the middle of the river. They “sucker” readily (sending up new trees from their base or along roots), and a broken branch will, like a willow, establish itself and start a new tree if it is washed downstream and is stuck into a muddy bank.
I have a basic understanding of forest succession in this landscape. Given time, the forest here should be dominated by cedars, hemlock and aging Douglas fir. They are what are called the “climax” species. They make up an “old-growth” forest. They are shade tolerant, meaning that they grow well in the shadow of other trees. Douglas fir is the exception, it needs sunny, more open exposure to get started, and once it does, it grows tall and straight, constantly reaching for the sunshine.
Cottonwoods, on the other hand are what are referred to as “pioneer” species; trees that inhabit disturbed areas such as floodplains. They thrive in full sun and help create the conditions conducive to the longer lived trees; building up the bare soil with carbon and nutrients through leaf drop and creating some shade for those less tolerant of open conditions.
For twenty years I noticed virtually no young cottonwoods along these floodplains. Then two years ago a cottonwood forest began to appear along the floodplains of both the Dosewallips and Rocky Brook.
I can only guess at why this is happening now. Here are some possibilities
A really good seed year
While the May air is filled with the drifting cottony seeds every year, I know from my fruit trees that there are good years and less productive years. Maybe cottonwoods also have years when seeds are more viable and the success rate is high?
The ever changing rivers
Both the Dosey and Rocky Brook’s main channels have migrated to the other side of the floodplain; their former rocky bed is where the cottonwoods are thriving.
2020 and 2021 were exceptionally dry years. There were few high water flood events than usual. This contributed to making the newly exposed river banks better suited to trees since they were rarely underwater or scoured clean by raging water.
Alders dominate this landscape, the result of significant soil disturbance (logging and flooding). Maybe they simply do so well under these conditions that cottonwoods cannot become established.
Elk and Deer Browsing
One of the more enlightening books I have come across in recent years is Wolves in the Land of Salmon by David Moskowitz. He describes populations of wolves to the north on Vancouver Island which feed on salmon along beaches, tide flats and the lower reaches of rivers there. This came as a surprise to me; like most people I associate wolves with deer, elk and other land-based mammals, not fish. But wolves are smart and, like bears, recognize a good opportunity when it appears.
In this book Moskowitz discusses elk and deer populations and how they contribute to a wolf’s diet. He notes how elk and deer prefer cottonwood, willow and cedar and tend to avoid alder. Thus, in areas where there are no wolves, where deer and elk populations explode without a natural check, elk may browse out cottonwoods in a manner which favors alder. I am pretty sure this is part of what is happening here along the Dosey and Rocky Brook since we have a large (60+ animals) resident elk herd.
Probably the most important thing that I have learned in my nearly seventy five years of paying attention to the world around me is that there usually is no simple answer to most questions. Nature is complex. Most likely the absence of young cottonwoods here for twenty plus years and all of a sudden their appearance is the result of multiple factors. It may be some combination of the above considerations, or it just well might be something completely different, something I have no awareness of. We constantly improve our understanding of this world we all share, and are often surprised at what we learn.
In any case, these young cottonwoods provide yet another fascinating thing for me to pay attention to.
And cottonwoods certainly are good for salmon. Young forests stabilize river banks, preventing erosion and silting. Big old trees create shade and calm pools for young fish to hide out. Fallen giants last for years, further creating protected areas for salmon of all ages.
While cottonwoods may take years to appear, the salmon arrive every year. Like cottonwoods they have good years and not so good years. I am hopeful that this will be the former.
Stay tuned … the salmon are coming!
Dennis Lloyd Kuklok
Rocky Brook, August, 2022.