New approach challenges old ideas about plant species and biomass

Sep 22, 2011

For decades, scientists have believed that a relationship exists between how much biomass plant species produce and how many species can coexist.

This idea comes from a 1970s study that showed as plant produced – called plant productivity - in a system increased, so did the number of plant species – referred to as plant richness - to a point. After that point, the number of is thought to decline.

When plotted on a graph, the resulting line forms a hump shape, with maximum species richness occurring at the point of intermediate productivity.

Now it's time to get over the hump, according to new research in the current issue of the journal Science.

Stanley Harpole, assistant professor in the Department of Ecology, Evolution, and Organismal Biology at Iowa State University, was part of the team researching productivity and richness, and he says the research doesn't support that relationship.

"This hump pattern that everyone thought was true ... it just isn't there," said Harpole. "This hump was the hypothesis for a long time, but it just isn't supportable."

Harpole says that the amount of biomass is one of the more important components of an ecosystem, so there will be worldwide interest in this research.

"Ecologists have long been interested in this relationship between how many plants there are and how much they produce," said Harpole. "For years they [scientists] have been plotting correlations looking at the relationship of biomass to species richness."

There was no 'hump' shape, according to Harpole. In fact, after plotting the data from all the sites, only one of the 65 sites showed a hump-shaped pattern.

"And that is supposed to be the 'true' pattern?" said Harpole.

Harpole believes the original work that led to the predictions for a hump shape was good research, and it showed a correlation between richness and productivity. But it didn't show cause-and-effect relationships.

"Hundreds of papers have talked about this and it has become fixed in researchers' heads that this is a true pattern," said Harpole.

The lead author of the paper is Peter Adler from Utah State University who is part of a Nutrient Network (NutNet) team that he, Harpole and others established.

The study is the first major paper produced by NutNet, a worldwide, ecological research group of more than 70 scientists on five continents that works cooperatively on studies of this kind.

Previous studies with global implications were often limited because disparate groups used different methods to collect data, leading to sometimes different conclusions.

NutNet's standardized methods eliminate those inconsistencies.

"We use the same experiment, the same design, the same measurements were taken, the species were counted in the same way, and the biomass was clipped in the same say," said Harpole. "It is important that you do everything in the same way."

When the results from NutNet's 65 research sites came in, the results were clear.

Harpole said the NutNet group wasn't trying to prove anyone wrong, but just hoped for clearer understanding.

"This is exciting science to me," he said. "We are just trying to figure out what is going on. How the world works. That is what we really wanted to know."

Explore further: Seals forage at offshore wind farms

Related Stories

Too much water, fertilizer bad for plant diversity

Mar 26, 2007

Too much of multiple good things -- water or nutrients, for example -- may decrease the diversity of plant life in an ecosystem while increasing the productivity of a few species, a UC Irvine scientist has discovered.

Recommended for you

Seals forage at offshore wind farms

14 hours ago

By using sophisticated GPS tracking to monitor seals' every movement, researchers have shown for the first time that some individuals are repeatedly drawn to offshore wind farms and pipelines. Those man-made ...

Study provides insights into birds' migration routes

16 hours ago

By tracking hybrids between songbird species, investigators have found that migration routes are under genetic control and could be preventing interbreeding. The research, which is published in Ecology Le ...

Technology tracks the elusive Nightjar

18 hours ago

(Phys.org) —Bioacoustic recorders could provide us with vital additional information to help us protect rare and endangered birds such as the European nightjar, new research has shown.

User comments : 0