Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ancient pollen yields insight into forest biodiversity

05.06.2003


By analyzing data on tree pollen extracted from ancient lake sediments, ecologists have sharpened the understanding of how forests can maintain a diversity of species. Their findings indicate that stabilizing processes have been more important than previously thought, and that the human-caused loss of species could upset that stability in ways that remain poorly understood.

"Quantifying the link between stability and diversity, and identifying the factors that promote species diversity, have challenged ecologists for decades," said Saran Twombly, program director in the National Science Foundation (NSF)’s division of environmental biology, which funded the research. "The contribution of this study is unique, as the scientists used a clever blend of long-term data and statistical modeling to test the opposing hypotheses of neutrality and stability as key factors promoting community assembly and diversity."

Scientist James Clark and graduate student Jason McLachlan of Duke University, published their findings in this week’s issue of the journal Nature.



According to Clark, the purpose of their study was to address a central scientific problem in explaining the diversity of tree species in a forest.

"In the mathematical models ecologists use to describe how different species compete for resources such as light, moisture and nutrients, it can be difficult to get species to coexist," he said. "In models, slight advantages allow one species to ’outcompete’ the other, leading to extinction, that is, loss of biodiversity. And so, ecologists have put a lot of effort into trying to understand the differences among species that would allow one species to coexist with another species."

Explaining such coexistence is critical, if ecologists are to truly understand forest biodiversity and the forces that sustain or reduce it, said Clark. According to Clark, two basic hypotheses have arisen to explain forest biodiversity. One theory holds that stabilizing forces are required for many species to coexist.

"For example, one might imagine that, if one species is limited by light, and another by moisture, they could coexist because they’re not really competing that much," said Clark.

"An alternative ’neutral model’ hypothesizes that species are so similar it just takes a long time for winners and losers to be sorted out by competition," said Clark. "But eventually the better competitor would drive the other to extinction."

Direct observations to distinguish which model is correct would take centuries, said Clark, "So in this study we came up with a way to test the neutral model based on long-term changes in species abundance that are evident in the pollen record."

So, Clark and McLachlan examined existing data on pollen from red maple, birch, beech, ash, oak, hemlock and elm trees isolated from cores of lake sediments in southern Ontario.

"This record covers about 10,000 years, so if we look at the relative abundance of different species over that time--which encompasses perhaps several hundred generations of trees--we can estimate long-term growth rates," said Clark.

According to Clark, the neutral model would predict that the variation among the sites would increase over time, as random chance caused different species to go extinct in some areas but not others.

Some sites, just by chance, should come to be dominated by one species, while others would come to be dominated by another species.

However, the researchers found that variance among the sites did not increase over the millennia, leading them to conclude that stabilizing forces were maintaining forest diversity.

"Our findings indicate there are factors that regulate populations at relative abundances that are consistent from one place to another," said Clark." The variation from place to place is not ’neutral.’ Ecologists have long known that, within a region, some species tend to be more abundant and some species less abundant. Our study doesn’t identify what those stabilizing forces are, but it clearly shows they do not arise from neutral dynamics." Indeed, said Clark, a major challenge for ecologists is to attempt to understand what the stabilizing forces are in forest biodiversity.

"Ecologists have devoted a lot of research to that understanding, but substantial challenges remain," said Clark.

"A long-held view that there are tradeoffs among species, in which each has a unique set of competitive advantages and disadvantages that determines its abundance, is often not supported by data."

"What we are seeing is huge variability within populations," said Clark. "And this variability means they overlap in ways that determines who’s going to win and who’s going to lose. And that variability might itself represent a stabilizing mechanism."

Clark emphasized, however, that even though the role of stabilizing mechanisms remains unknown, the results from his and McLachlan’s studies offer cautionary lessons.

"Our findings suggest that forest biodiversity has probably been stabilized in some important ways, so extinction of species should cause us greater concern than if we believed that biodiversity was maintained in the past by continual replenishment of random extinction by generation of new species," he said.

"So, there’s a lot for ecologists to do to really understand the extent to which differences among species are responsible for diversity."


Duke University Media Contact: Dennis Meredith, (919) 681-8054, dennis.meredith@duke.edu,

NSF Program Contact: Saran Twombly, (703) 292-8481, stwombly@nsf.gov

Cheryl Dybas | NSF
Further information:
http://www.nsf.gov
http://www.nsf.gov/home/news.html
http://www.nsf.gov/sbe/srs/stats.htm

More articles from Ecology, The Environment and Conservation:

nachricht International network connects experimental research in European waters
21.03.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

nachricht World Water Day 2017: It doesn’t Always Have to Be Drinking Water – Using Wastewater as a Resource
17.03.2017 | ISOE - Institut für sozial-ökologische Forschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>