The Strange Tale of the Deciduous Conifer

We have a long list of native conifers here: red, white, and jack pine, black and white spruce,¬†balsam fir, eastern hemlock, eastern red cedar, and… tamarack. Tamarack is different. Tamarack is the only one that does this.

I really like tamaracks. I’ve written about them before. I keep wondering about them, though. Why are they deciduous, losing their needles every autumn, while every other species of conifer found here is evergreen? Things like this usually don’t just happen at random – there must be some of sort of adaptive advantage to shedding their needles, right?

Boreal forests are mostly dominated by evergreens. Keeping your needles year-round cuts down on the amount of nutrients you need (you don’t need to manufacture new leaves as often) and lets you photosynthesize during the winter, instead of relying on the short northern growing season. So why are tamaracks and other larches among the most successful boreal trees of all, growing far north of the Arctic Circle? Some Googling led me to a 1990 paper on the subject by S.T. Gower and J.H. Richards.

According to the paper, the longer a leaf lives, the lower its photosynthetic rate: individual tamarack needles don’t live as long as those of evergreen conifers but they can photosynthesize like crazy in the long days of the northern summer. What’s more, since tamarack needles don’t have to survive the cold, dry conditions of winter, tamaracks don’t have to invest nutrients in constructing thick protective cuticles them. Ever stroke the foliage of a tamarack? It’s very soft. Tamaracks still get the advantages of having a conifers’ needles-shaped leaves and cone-shaped canopy, though, so they can compete where spreading, broad-leaved deciduous trees like maples and birches can’t. (Among other things, being cone-shaped helps conifers get the maximize their access to sunlight.)

Everything in nature is a trade-off. I still have a zoology department t-shirt from my undergraduate days featuring a drawing of a giraffe bending down to drink captioned with the words “Life is a Compromise.” Tamaracks are a compromise between two different tree lifestyles, and it must work well for them, because they thrive in some of the harshest environments around.

The Tamaracks are Blushing Green

Oh tamaracks, those quirky deciduous conifer with the bunches of silky soft needles. I’ve written about them before – first last August, then again in October to show them turning golden in the fall. In the winter they drop their needles completely, and now…

 Small point of interest: it was snowing lightly while I took these photos yesterday morning!

My Birding Badge Has Been Revoked

If you are walking in the woods in winter and come across a section of trail freshly littered with tamarack cones…

…look up. Chances are there’s a flock of crossbills in the vicinity. Of course, if you’re me, you’ll have neglected to bring your binoculars along on your walk, and the Birdchick herself will tell you to hand in your birding badge.

For those not in the know, crossbills are very cool finches whose beaks are criss-crossed in a unique way that enables them to pry open cones to get at the seeds within, and they are especially fond of tamaracks. Oh well. Next time.

Tamarack Attack!

Jack, who always leaves such lovely comments, asked about tamarack, and I took a couple photos of tamarack a while ago that have been sitting on my hard drive, so the topic of my next post is obvious.

Larix laricina, commonly known as tamarack, American larch, or hackmatack. (Gesundheit on that last one.) Where I am now in northern Wisconsin seems to be a sort of transition zone between the harsh boreal forests to the north and the more diverse forests to the south, with boreal species like tamarack, spruce and aspen found side-by-side with maple, oak, birch and basswood. Some species I was familiar with in Ohio, like sycamores, are missing entirely, and some, including most of the conifers, are new to me. Tamarack ranges north to the very limits of the tree line.

Its needles, which grow in tuft-like bunches, are incredibly soft to the touch. During a portage on my canoe trip over the weekend, I leaned back to let someone pass me on the trail, and when I felt something silky brush my arm I didn’t have to turn around to know the tree behind me was a tamarack. What’s even more interesting is that this is a deciduous conifer. These needles will turn gold in the autumn and then fall.

When old lakes fill in and turn into bogs, like the one above, moisture-loving tamaracks will be one of the pioneering tree species (along with spruce). Although I can’t rationally explain why, I have a lot of fondness for these slightly oddball trees. Come autumn I’ll have to take some photos to show you the color change.