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Why Is The Ground Brown?

Date:
March 31, 2006
Source:
University of Chicago Press Journals
Summary:
Ecologists have long asked, Why is the world green? In other words, why aren't herbivores, such as insects and grazing animals, more successful at eating the world's green leaves, also known as plant biomass? In the May 2006 issue of American Naturalist, Steven D. Allison (University of California, Irvine) asks the same questions a different way: Why is the ground brown? Why don't the organisms that break down the carbon in the soil consume it all?
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Ecologists have long asked, Why is the world green? In other words, why aren't herbivores, such as insects and grazing animals, more successful at eating the world's green leaves, also known as plant biomass? In the May 2006 issue of American Naturalist, Steven D. Allison (University of California, Irvine) asks the same questions a different way:

Why is the ground brown?

Why don't the organisms that break down the carbon in the soil consume it all?

Some of the same ecological factors make the world green and the ground brown, especially the carbon in plant material, the role of herbivores and decomposer organisms in consuming that carbon, and the role of predators in eating the consumers of the carbon. As it turns out, as Allison observes, "the chemical structure of soil carbon makes it far more difficult to consume than plant carbon."

There is about three times as much carbon in soil than in plant biomass. In addition, minerals in the soil can block decomposers from feeding on soil carbon. Allison also points out that most decomposers are of relatively small size compared to the animals eating green leaves.

"Instead of digesting material in their guts, decomposers depend on enzymes to partially digest their food sources outside their bodies," Allison explains. "This strategy is a major constraint on the breakdown of soil carbon that helps make the ground brown."

Steven D. Allison "Brown ground: a soil carbon analog for the green world hypothesis," The American Naturalist 167:5.


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The above post is reprinted from materials provided by University of Chicago Press Journals. Note: Materials may be edited for content and length.


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University of Chicago Press Journals. "Why Is The Ground Brown?." ScienceDaily. ScienceDaily, 31 March 2006. <www.sciencedaily.com/releases/2006/03/060331151723.htm>.
University of Chicago Press Journals. (2006, March 31). Why Is The Ground Brown?. ScienceDaily. Retrieved August 30, 2015 from www.sciencedaily.com/releases/2006/03/060331151723.htm
University of Chicago Press Journals. "Why Is The Ground Brown?." ScienceDaily. www.sciencedaily.com/releases/2006/03/060331151723.htm (accessed August 30, 2015).

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