Scientists revise long-held beliefs about plant biodiversity and biomass
For decades, scientists have believed there is a particular relationship between the biomass produced by plants and the number of different plant species in a given habitat. Based on a 1970s study, it has long been taken as fact that as plant biomass (also known as plant productivity) increases, the number of different plant species (or plant richness) also increases. Up until it reaches a peak, that is. Afterwards, both parameters were believed to decline. Plotted on a graph, this relationship resembled a hump, with maximum plant richness poised at the top of the curve.
But according to new research published in the journal, Science, this model is pure fancy. "This hump pattern that everyone thought was true . . . it just isn't there," said Stanley Harpole, assistant professor in the Department of Ecology, Evolution, and Organismal Biology at Iowa State University. "This hump was the hypothesis for a long time, but it just isn't supportable."
The issue has repercussions for a number of disciplines. Biomass is a key component of any given ecosystem, so Harpole expects the new finding will spark worldwide interest. "Hundreds of papers have talked about this and it has become fixed in researchers' heads that this is a true pattern," said Harpole.
Now they will need to revisit their preconceptions and make adjustments to models that may figure in calculations relating to the relationships among area, biomass and species diversity.
Data for the present study were compiled by a variety of researchers, working at 65 different sites on five continents. The cooperative ecological research effort, dubbed Nutrient Network (or more colorfully, NutNet), for the first time made use of standardized collection and measurement methods.
In essence, the data was meaningful because there was no comparison of apples to oranges, figuratively speaking. Harpole says he and his collaborators weren't out to prove anyone wrong. "We are just trying to figure out what is going on," said Harpole. "How the world works. That is what we really wanted to know."
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