Re: Why Is The Ground Brown
> Why Is The Ground Brown
> by Staff Writers
> Irvine CA (SPX) Apr 03, 2006
> 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
> 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
> "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."
> Founded in 1867, The American Naturalist is one of the world's most
> renowned, peer-reviewed publications in ecology, evolution, and
> population and integrative biology research. AN emphasizes
> sophisticated methodologies and innovative theoretical syntheses--all
> in an effort to advance the knowledge of organic evolution and other
> broad biological principles.
> Steven D. Allison "Brown ground: a soil carbon analog for the green
> world hypothesis," The American Naturalist 167:5.
> Related Links
> University of California, Irvine
> University of Chicago Press Journals