Friday, May 3, 2013

Desert Adaptations in the Northwoods?

A vivid blue sky stretched overhead as the intense spring sun rose above the twiggy treetops. The thick blanket of fresh, white, snow reflected bright rays up and under the brim of my cap. Ski tracks that had been crunchy with ice just 30 minutes ago were now softening as the temperature rose steeply from a nighttime low of 18 degrees, to a daytime high of 45. The one thorn in my day was an uncomfortable crack in the winter-dry skin of my left heel.

It was amazing to be skiing in late April, in Wisconsin, and it is amazing that I can begin yet another Natural Connections by describing an experience on the ski trail. This particular day, with its bluebird sky, bright sun, and warm temperatures, also reminded me of another spring ski in a faraway land called Utah.

Back in 2005, I did an internship with the National Park Service leading school field trips and working in the visitor center in the Needles District of Canyonlands National Park. I lived in the tiny little town of Monticello (very similar to Cable!) at the base of the Abajo Mountains. Even though their name means “low,” the mountains tower above the intricately carved sandstone canyons of the park.

One weekend, my roommate and I took our skis and drove up the mountain road to where the snowplows stopped. From there, we skied up and over the snow-packed pass, and stood breathless at the view. From the midst of winter, we looked out on a sunbaked summer landscape of red rock canyons below fluffy white clouds. The view fueled our anticipation for spring. The only thorn in my day was cracked lips from the desert-dry air.

You might not think that Wisconsin and the desert southwest have much in common, but I found enough similarities in Utah to feel at home there, too. The snow, for one, was a nice connection. And half-buried in that snow were manzanita bushes with small, waxy, evergreen leaves on short woody stems. They bore a family resemblance to their cousins, other plants in the family Ericaceae, who are some of my favorite residents of Wisconsin bogs.

If you’ve ever explored a bog, you may have noticed that quite a few plants have those small, waxy evergreen leaves. Leatherleaf’s name advertises its tough appendages, while the lovely names of bog rosemary, bog laurel, small cranberry, and snowberry contrast with their hardy leaves. All are in the Ericaceae family.

Down in the desert canyons, the fuzzy leaves of sagebrush, Indian paintbrush, globemallow, and the in-rolled leaves of mountain mahogany also reminded me of my Wisconsin home. That might seem odd, but have you looked at the underside of a Labrador tea leaf from your local bog lately? The leaf margins roll in on a dense patch of wooly orange hair, and hairs also carpet the tightly-curled leaves of its neighbor, bog rosemary.

Why might desert plants and bog plants have some characteristics in common? For one thing, they both deal with a lack of water and desiccating winds during at least part of the year. But aren’t bogs soggy? Well, yes, but not when they are frozen, a condition that can extend late into spring. Plus, sometimes the peat in bogs builds up so much that plants are elevated above the water table. Deserts and bogs are also poor in nutrients due to slow decomposition rates.

Evergreen leaves are great for contending with low nutrient availability and short growing seasons, because plants do not need to grow new leaves each year, so they are less dependent on nutrients getting recycled. However, unlike deciduous leaves, evergreen leaves must deal with the absence of liquid water in winter (or in the summer for that matter.) The thick, waxy cuticle is a plant’s first defense, since it reduces water loss from evaporation. It serves the same purpose as the beeswax-based salve I massage into the cracked, dry skin of my heel and lips. This protective wax is as useful in Wisconsin winters as it is in Utah!

Although waxy leaves help protect them from drying out, plants still need to exchange some gases through their stomata to carry out photosynthesis. Stomata are pores in the leaf that allow gas exchange. Along with taking in the carbon dioxide necessary for photosynthesis, water vapor can also escape during transpiration. To reduce this loss, plants – both here and in the desert – try to create a “boundary layer.”

The boundary layer is a thin zone of calm air hugging the surface of the leaf. In this layer, the conditions are less harsh (less hot and dry) than in the wider world, and the temperature and moisture gradient is less steep. Therefore, the larger the boundary layer, the slower the rate of water loss. Hairy and in-rolled leaf margins increase the size of the boundary layer and slow water loss from transpiration. Humans create our own boundary layers with fuzzy wool sweaters and fleecy mittens.

Today we stand in Wisconsin – on the edge of winter – admiring the view of a distant spring. Although it may look quite different from southeast Utah, similarities can be found across all communities if we are willing to look a little closer. This holds true in our human communities just as much as in our natural communities. Where can you see our own Midwestern toughness and resilience reflected around the globe?

“It is a wholesome and necessary thing for us to turn again to the earth and in the contemplation of her beauties to know of wonder and humility.”
--Rachel Carson

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