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Birches — A Gift to the Forest

By Sara Wright


Paper birch with its distinctive peeling bark

Every winter I expect to lose more birches to windthrow than any other tree because gray and white birches (Betula populifol, B. papyrifera) are for the most part a short-lived pioneer species, some of the first trees to colonize an abandoned field or recently logged area. Gray birches often grow in crowded clumps; white birches are more solitary. After all these years of watching a young birch/white pine forest grow out of what once was a large field, I initially felt dismay when birch trees bent their crowns to the ground and eventually broke off at their trunks.


Now all I can think of is the gifts the birches are bringing to earth when they arc and fall. Bent low with thick spidery brooms for branches, they provide immediate cover for grouse and other birds. Thousands of birch seeds pepper the snow-covered ground providing protein rich treats for my regular winter birds. Chickadees, titmice, nuthatches, goldfinches, pine siskins, cardinals, juncos, doves, grouse, and turkeys are a few of the birds around here that love birch seeds. Deer, rabbits, and hares feast on the twigs. In spring, birch catkins attract many insects, which in turn attract large numbers of migrating warblers.

Downed birches support and enrich mycelial networks that connect the forest underground.

Birches can also be important nesting sites for red-tailed hawks and vireos as well as for cavity nesting birds like chickadees and woodpeckers. Small strands of (white) birch bark are the key materials used by vireos in their hanging nests. Birch strips also line the nests of wrens, and last year I found shreds of bark woven into my phoebe’s nest. Squirrels and other small mammals also incorporate this material into nest and den linings. Yellow-bellied sapsuckers regularly drill into birches to allow sap to run out. Boring holes into birches attracts ants for others to feast upon. As the reader can discern, birches are important to a wide variety of species.


Gray birch with their distinctive dark "mustaches"

When the trees come down in storms, the rotting logs break down so rapidly that, before long, they are covered with polypores including turkey tails that, besides being prime players in decomposition, are fascinating fungi to look at. Downed birches support and enrich mycelial networks that connect the forest underground. These pathways allow for nitrogen, carbon, water, phosphorous, and other minerals to be exchanged. Around here, the downed birches have let more light into my young forest, and ground covers like wintergreen and princess pine are springing up in these areas along with young winterberry bushes. I also have a new crop of lady slippers and pyrolas.


Standing gray birch are hosts for eastern and tiger swallowtails, white admiral, mourning cloaks, and tortoiseshell butterfly caterpillars. Many birds and animals eat the early spring leaves and buds. The wind pollinated flowering catkins provide a feast for early pollinators. Black bears love these catkins, too.


A number of years ago, scientist Suzanne Simard discovered that, in the Northwest when paper birch was allowed to grow along with red cedar and Douglas fir, the birch protected the other trees from Armillaria, an aggressive root pathogen which can eventually kill any tree in its path. Paper birches also contain bacteria with antibiotic properties that help protect conifers from other diseases. Because gray birch and paper birch share almost identical DNA structures, I suspect that the former protects our Eastern forests in similar ways.

Chickadees, titmice, nuthatches, goldfinches, pine siskins, cardinals, juncos, doves, grouse, and turkeys are a few of the birds around here that love birch seeds

Gray and white birches are native to North America, and both are frequently found growing with poplar and willow. These first succession trees that germinate first provide much needed shade for second succession trees like oaks, beech, hemlocks, and firs.


Gray and paper birches are easily confused as most have white bark (or whitish bark in the case of gray birch), and they often grow together in the same habitat. I have one of each that tower over the brook that look so white that if paper birch wasn’t peeling, it would be hard to tell them apart from a distance. The leaves of both species remind me of poplars. Not surprisingly, these birches also hybridize. Although birches aren’t long lived trees, some do seem to thrive for many years if planted in protected places that have adequate moisture. 


These days when I walk by the logs and branches that crisscross the ground in my woods, all I can think of is that these trees are caring for the forest as a whole. Even in their dying, they are actively participating in the Circle of Life.


 

Photo Credits:

Paper Birch: Peter Balcerzak, 2016,  Creative Commons Attribution-Share Alike 3.0 Unported




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