Yellowstone's migrating bison manipulate springtime green-up

phys.org | 8/23/2013 | Staff
Kota79Kota79 (Posted by) Level 4
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On a typical June day in Yellowstone, it's not unusual to see hundreds of bison grazing in the Lamar Valley. The herds appear to aimlessly move back and forth through meadows threaded by a winding river, just passive figures in an idyllic scene. But, as it turns out, that's far from the full picture.

In fact, with every blade of grass that bison bite off and swallow, they are fundamentally manipulating the landscape to maintain the best forage for themselves. They even change the way spring green-up occurs in Yellowstone's vast grasslands.

Bison - Landscape - Springtime - Season - Plant

Without bison moving freely on the landscape, the springtime season of plant growth in Yellowstone would be shorter, the habitat would not be as green, and the grasses would not be as nutritious.

Remarkably, that allows bison to migrate differently than other species.

Bison - Move - Elevation - Mid - Summer

When bison move to higher elevation by mid to late summer, the herd's small army of hooves and hungry mouths causes the grasslands to revert to earlier stages of plant growth. In effect, the bison graze with such intensity that they turn back the clock on forage green-up, hitting reset on springtime.

The effect of bison on Yellowstone's plant growth is so strong that sensors on NASA satellites can detect from outer space how grassland dynamics differ between areas that are lightly or heavily grazed. Where Yellowstone bison congregate, plant green-up is different, and it's not some fluke of local weather—the bison and their intense grazing are the cause.

Discovery - Bison - Range - Benefit - Research

The discovery that bison engineer the range to their benefit arose through research by a team led by Yellowstone National Park scientists Chris Geremia and Rick Wallen. They worked in partnership with biologists at the University of Wyoming, the University of Montana and the U.S. Geological Survey.

The team wrote a paper, titled "Migrating bison engineer the green wave," published today (Nov. 18)...
(Excerpt) Read more at: phys.org
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