Saturday, November 20, 2010

Roots

For some reason I know not why, one of my favorite lines in Lord of the Rings is when an Orc shuffles in to tell Saruman, "The trees are strong my Lord. Their roots go deep." Of course the next part is my least favorite, when they rip out all the trees, but then later the Ents take care of the Orcs and Saruman, so that part ends rather well. Trees are indeed strong, but do their roots really go deep?

When we lived in Minnesota a good friend who was a prairie ecologist spent a lot of time educating people on the beauty, diversity, and importance of prairies. She would go into classrooms and ask the kids, "Which has deeper roots, a pine tree or big bluestem?" Everyone said a pine tree of course, a pine tree is so tall compared to a grass. But is that so?

A big bluestem cultivar, growing in my garden

Prairie soils are deep and rich and the roots of native prairie plants go surprisingly deep. Big bluestem (Andropogon gerardii), the most common prairie grass, sends roots down ten to twelve feet. How about a pine tree? Despite their great height and mass, their roots extend less than two feet down. Instead, like most trees, their roots extend laterally some distance rather than vertically. This becomes obvious when you see a large white pine uprooted; we have many such fallen trees in the region as a result of major storms in recent years.

The following series of photos capture one such fallen white pine. The side shot shows a very shallow root system -- less than one foot deep. No wonder many of these trees are uprooted during major wind and rain storms.



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