With summer comes the weekly ritual of mowing the lawn. While this is often considered a mundane task, mowing is in fact holding back a forest. If nature had her way, almost all of our cleared land would be woodland — not grass and crops.
To keep it from happening takes a lot of work: Lawn mowers, bush hogs, herbicides, fire, plowing; all are needed to keep a phenomenon called forest succession from taking place. Succession is a series of vegetation stages a piece of ground will go through to convert from open land back to forest. It happens all the time, and is nature’s way of surviving natural disasters like tornadoes or wildfire.
So let’s mind trip a little. Imagine you’re riding lawn mower is a time machine and you’re going to ride it through the different stages your yard will go through to become a forest. So rev up the engine, put it in gear and don’t engage your mower blade.
Year 2015: You’ve just quit mowing, and so the yard is still just like you’re used to. This is stage one succession, bare dirt or short grass.
Year 2016: The grass has grown tall, thick and there’s several broad leaf weeds sticking up here and there like chicory and thistle; still stage one.
Year 2017: There’s now some woody stuff starting to move in, especially blackberry briars and honeysuckle brought in by birds pooping out seeds. This this vegetation is getting hard to walk through. Rabbits are making themselves at home, and deer are sneaking through the neighborhood to browse on your honeysuckle, grapevines and weeds. This brushy phase is called stage two succession.
Year 2020: Tree seedlings are starting to appear, especially cedar, pine and yellow poplar. All of these trees are called pioneer species, requiring full sunlight, and are usually the first to appear on abandoned land. It’s getting hard to see through the trees and brush to see your neighbors’ house.
Year 2040: The branches of the cedar, pine and poplar have grown together and shaded out the grass, weeds and briars. Your lawn is now a layer of pine needles and leaves; Deer are browsing on small saplings of oak and hickory, and using your yard for thermal shelter during hot summers and cold winters. This is stage three succession, a forest dominated by pioneer tree species.
Year 2050: Your yard is still a mixed pine/hardwood forest, but other trees have seeded in and beginning to grow into gaps in the forest ceiling, which foresters call the canopy. These trees include oak and hickory, which can tolerate some (but not a lot) of shade.
Year 2080: The cedars and pine have died from age or shaded out by the oaks and hickories, and your lawn is now a heavily shaded deciduous hardwood forest. Mast (acorns and hickory nuts) is attracting deer, turkey, grouse and squirrel. Underneath this forest is a layer of young maple and beech saplings, both able to grow in deep shade. This is stage four succession, a forest dominated by mid-shade tolerant tree species.
Year 2170: Some of the oak are beginning to get old and die out, opening up holes in the canopy. The maple and beech trees have been patiently growing slowly underneath, waiting for a chance at some sunlight. As holes in the forest canopy form, maple and beech occupy them.
Year 2300: The oak/hickory forest has died out and been replaced by a maple/beech forest. As these species die of old age, more maple and beech will replace them, because they are able to grow under heavy shade. Your yard has now reached stage five succession, a stage where the tree species will not change over time, until some event occurs that takes the forest back to an earlier stage. This could be a storm, a timber harvest, or a lot of fire. Stage five supports some wildlife, but not as much as any of the earlier stages.
So in around 30 years your lawn transforms into a forest in transition, and in around 300 years it becomes a forest that’s pretty much unchanging. Mowing grass can seem to be mediocre work, but when you keep in mind it’s holding back a forest, it seems a more impressive act.
Steve Roark is the area forester in Tazewell, Tenn. for the Tennessee Department of Agriculture, Forestry Division.