Creuser pour découvrir le monde des racines

samedi 8 avril 2017
par  Marie-José Turquin
popularité : 3%

Digging Deep Reveals the Intricate World of Roots |

If you’ve ever driven past wild prairie grasses swaying in the Kansas breeze and felt a wave of appreciation for America’s heartland, you should know that those visible grasses are just the tip of the iceberg.

“We’re pretty blind to what’s going on beneath the soil,” says photographer Jim Richardson, who became well acquainted with the world of dirt while working on “Our Good Earth,” a 2008 National Geographic magazine story.

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Dr. Jerry Glover works in a soil pit at the Land Institute in Salina, Kansas. On the left, the deeper roots of wheatgrass are displayed, while the more shallow roots of wheat are visible on the right.
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The bulk of a prairie grass plant, it turns out, exists out of sight, with anywhere from eight to fourteen feet of roots extending down into the earth. Why should we care ? Besides being impressively large, these hidden root balls accomplish a lot—storing carbon, nourishing soil, increasing bioproductivity, and preventing erosion.

Unfortunately, these productive, perennial grasses (which live year round) are more rare than they once were.

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Compass Plant
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“When [you] say the American Midwest is a breadbasket, essentially what you mean is that you have taken out the prairie grasses. You went out with Willa Cather and the plow that broke the plains, plowed up the grassland, and started planting annual grasses like wheat, sorghum, corn, any of the big grains that supply most of our calories,” says Richardson.

A challenge in raising the profile of this tallgrass ecosystem is that so much of it is underground and therefore difficult to visualize. Enter photography.

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Missouri Goldenrod
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Richardson wanted to reveal these roots to the world, highlighting not only their productive attributes but also their surprising scale and intricacy. Logistically speaking, he had to get creative, because if you were to try and dig up the roots of switchgrass from any old prairie, you would destroy them in the process.

“You can’t get them out of the ground. You’d be going down ten feet and trying to excavate all around them to get them out. It just wouldn’t work,” he says.

So Richardson collaborated with Dr. Jerry Glover, an agroecologist and a National Geographic Emerging Explorer who developed a method of growing tallgrasses in “root-tubes” (made from PVC pipes) while he was working at the Land Institute in Salina, Kansas. It takes a year or two to grow the plants. When they’re ready, the tube is split and, after a good wash, the roots come out intact and ready for their close up.

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Dr. Jerry Glover stands next to a 14-foot tangle of Indian grass, compass plant, and big bluestem grass that he grew. He welded together two 55-gallon drums, laced the inside with a wire frame, filled the tall container with soil and seed, and then watered and waited. Three years later, he cut open the barrels and laid bare a giant’s bouquet of native prairie plants.
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Then came the second hurdle : how to capture the scale and the texture of these roots at the same time. Remember, some of these roots are twice as tall as an NBA basketball player.
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Detail of Indian grass roots, which reached 10 feet into the earth.
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“[Glover] basically brought the roots over to the gallery here, rolled them out on the floor, and said, ‘How can we photograph this ?’” says Richardson.

He describes their solution as being similar to that of a flatbed scanner. They put a long piece of plexiglass on a platform and laid the roots out. Then they put a camera up above the plant on a ladder so that they could look straight down on the roots. Starting at the top, they photographed an approximately 12” x 18” section of the plant, then moved it 12 inches and photographed another section, working their way down the plant as the camera stayed still.

They then took those photos (usually between eight and fourteen per plant) and stitched them together into a super high-resolution image, like a vertical panorama. The main problem now, he says, “is finding walls high enough for the print job.”
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Richardson has a well-known, one-liner piece of advice about photography : “If you want to be a better photographer, stand in front of more interesting stuff.” I found it funny that he’s become so invested in a story about roots and soil, something that at first glance seems kind of boring. So I asked him about it. He explained : “What I mean is that, as a photographer, you need to do the work of discovery … Do the grunt work of research to find gems in unsung places. The worth of the photograph depends on the intrinsic value of what is being seen.”

Interested in how perennial grains might be developed to produce more food ? Read on, here.

See more of Jim Richardson’s photographs of soil (which prove that soil is actually really interesting) here.

Hear Jim talk about “standing in front of interesting stuff” in this interview on Proof.