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The Douglas-fir is native to the west coast of North America, found everywhere from Mexico to Canada.
The tree is tolerant of drought. It loves rain. It is fire-adapted: depending on fire to get started, able to survive all but the most severe fires when it reaches maturity.
It can live a thousand years.
We have no typhoons, no hurricanes, so these strong trees can grow tall.
Even so, the biggest firs, like this one, often have a broken top, succumbing often enough to the more moderate storms we do have.
When that happens, apical dominance ends, and side (“epicormic”) branches pop out below the crown, often growing large and tangled, reaching out for sunlight.
A severe fire ravaged the Puget Lowlands in 1508, burning everything to the ground here at Seward Park.
A less severe fire burned here in 1701, killing most of the trees. A cohort of 200 year-old doug firs survived; each had developed thick fire-resistant bark. You can see burned bark on this tree, and on many others throughout the forest. (These dates are documented here.)
A few large cedars also survived the fire. Perhaps sword ferns as well, their woody rhizomes nestled below ground, protected by soil.
There are a thousand kinds of smaller creatures in the forest hungry for that food. Many of them – doug fir predators – have short life spans. Which means they can quickly evolve cunning new ways to get at Big Tree’s carbon chains, in its needles, sap, and roots.
And Big Tree has only the defenses with which it was born. How does it survive?
We hear a lot these days about below ground fungal networks connecting and protecting trees in the forest.
Endophytes are not so well known, tiny microbes that live in the leaves and needles of most plants. Including our long-lived firs.
We introduce you to Rhabdocline Parkeri. Millions of years ago, this tiny fungus struck a deal with doug-firs. In exchange for some of the energy the tree acquires from the sun, and packages up into long carbon chains, the fungus emits insecticides. These protect the tree.
A key piece of this symbiois is that R.parkeri, like the predators, reproduce quickly, one or more times per year. So as predators invent new strategies to get at the doug fir, R.parkeri can keep pace, inventing new defenses.
It is likely that R.parkeri was originally an antagonist, going after the tree’s food without offering anything in return. Related Rhabdocline fungi do exactly that, causing disease in some doug-firs. But as with many other microbes, a symbiotic relationship evolved over time. Mutual aid, mutual benefits ensued.
Which we see here in this old and beautiful tree
This symbiosis is exceedingly common in the forest and, indeed, in all of us mammals- humans included. Many symbiotic microbes live in our bellies. They take a small share of the food we eat, offering digestive help and some disease protection in return.
Life is indeed a community affair.