Featured Research

from universities, journals, and other organizations

Soil Fertility Limits Forests' Capacity To Absorb Excess CO2

Date:
May 28, 2001
Source:
University Of Michigan
Summary:
A field study on the effects of elevated carbon dioxide (CO2) on forest ecosystems raises doubts about the ability of trees to absorb excess CO2 accumulating in the earth's atmosphere.

ANN ARBOR -- A field study on the effects of elevated carbon dioxide (CO2) on forest ecosystems raises doubts about the ability of trees to absorb excess CO2 accumulating in the earth's atmosphere.

Results of the seven-year study, to be published in the May 24 issue of Nature, show that some forests will not increase the amount of carbon they sequester—at least not enough to compensate for increasing atmospheric CO2. Soil fertility is a key factor in determining the long-term growth response to elevated CO2, according to co-principal investigator David S. Ellsworth, assistant professor of plant physiological ecology in the School of Natural Resources and Environment at the University of Michigan.

Prof. Ram Oren of the Nicholas School of the Environment and Earth Sciences, Duke University, also was a principal investigator on the project.

"When we exposed trees in low-nutrient soil to elevated CO2, they maintained growth increases only with added nutrients," said Ellsworth. "While CO2 initially acts as a stimulus to the tree's physiology, our experiments suggest that short-term increases in growth are not sustainable over the long-term in low-nutrient environments."

The open-air field study described in Nature is the first of its kind to examine the effects of elevated CO2 on forests growing in nutrient-limited environments over many years. The study included the longest running forest-based Free Air CO2 Enrichment (FACE) experiment. By exposing trees to elevated CO2 in an otherwise natural setting, the researchers were able to simulate conditions predicted for 50 years from now.

"Other recent studies have shown that elevated CO2 increases growth, measured as the amount of carbon sequestered in the tree's biomass, and increases nutrient uptake as well," Ellsworth said. "But what happens if the tree does not take up soil nutrients in proportion to that growth increase, or the nutrients are not available?"

That is the case for many northern mid-latitude forests, which comprise much land in the United States and Europe, Ellsworth noted. Forest soils tends to be low in nutrients because most of the nutrient-rich soil has been used for agriculture.

"The debate over how much CO2 trees will absorb should consider the limitations of soil fertility or other key resources in low supply."

The FACE experiment was conducted on a moderately fertile site at the Duke Forest of Duke University. A second field experiment used CO2 enrichment in chambers on an infertile site in the sandhills of North Carolina. Both experiments exposed maturing loblolly pine trees to levels of CO2 predicted to accumulate in the earth's atmosphere 50 years from now.

In the FACE experiment, the researchers compared growth of CO2-treated trees with untreated trees in an adjacent plot. Averaged over the first three years of the experiment, the elevated CO2 plot showed a 34 percent increase in growth relative to the ambient CO2 (untreated) plot. However, that increase dropped to 6 percent over the following four years.

To test whether nutrient limitations reduce the tree response to elevated CO2, the researchers added a balanced fertilizer to half the FACE area. Averaged over 1999 and 2000, trees grown under elevated CO2 without nutrient addition increased growth at an annual rate of only 7 percent while the fertilized trees grown in ambient CO2 increased annual growth by 15 percent.

The combination of improved nutrition and elevated CO2 increased growth by 47 percent at the site. This clearly indicates a synergistic effect of CO2 and nutrient supply, the researchers concluded. At the infertile site, trees without added nutrition showed virtually no growth response to elevated CO2 in two years. Under optimal nutrition and ambient CO2, growth increased 21 percent. In trees subjected to the combination of improved nutrition and elevated CO2, growth was 74 percent—more than three times the sum of separate responses.

These findings suggest that growth responses of pine forests to elevated CO2 will be highly variable and depend on site fertility, to the point that trees growing on nutritionally poor sites may not respond at all. Moreover, other factors, such as water deficits, also could limit forest response to atmospheric CO2.

"Trees can sustain increases in biomass only as long as they find enough water and nutrients in their ecosystems," Ellsworth said. "I don't think we can assume existing forests, with their fertility limitations, will completely offset rising CO2 without soil amendments. We will more likely find solutions in measures such as burning less fossil fuel and planting more trees in high-nutrient soils." The research team included collaborators from Brookhaven National Laboratory, Boston University, and the U.S. Forest Service.

The study was funded primarily by the U.S. Department of Energy and the U.S. Forest Service.


Story Source:

The above story is based on materials provided by University Of Michigan. Note: Materials may be edited for content and length.


Cite This Page:

University Of Michigan. "Soil Fertility Limits Forests' Capacity To Absorb Excess CO2." ScienceDaily. ScienceDaily, 28 May 2001. <www.sciencedaily.com/releases/2001/05/010524061936.htm>.
University Of Michigan. (2001, May 28). Soil Fertility Limits Forests' Capacity To Absorb Excess CO2. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2001/05/010524061936.htm
University Of Michigan. "Soil Fertility Limits Forests' Capacity To Absorb Excess CO2." ScienceDaily. www.sciencedaily.com/releases/2001/05/010524061936.htm (accessed August 21, 2014).

Share This




More Earth & Climate News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

California Drought Stings Honeybees, Beekeepers

California Drought Stings Honeybees, Beekeepers

AP (Aug. 21, 2014) California's record drought is hurting honey supplies and raising prices for consumers. The lack of rainfall means fewer crops and wildflowers that provide the nectar bees need to make honey. (Aug. 21) Video provided by AP
Powered by NewsLook.com
Thousands Of Species Found In Lake Under Antarctic Ice

Thousands Of Species Found In Lake Under Antarctic Ice

Newsy (Aug. 20, 2014) A U.S. team found nearly 4,000 species in a subglacial lake that hasn't seen sunlight in millennia, showing life can thrive even under the ice. Video provided by Newsy
Powered by NewsLook.com
Unsustainable Elephant Poaching Killed 100K In 3 Years

Unsustainable Elephant Poaching Killed 100K In 3 Years

Newsy (Aug. 20, 2014) Poachers have killed 100,000 elephants between 2010 and 2012, as the booming ivory trade takes its toll on the animals in Africa. Video provided by Newsy
Powered by NewsLook.com
Charter Schools Alter Post-Katrina Landscape

Charter Schools Alter Post-Katrina Landscape

AP (Aug. 20, 2014) Nine years after Hurricane Katrina, charter schools are the new reality of public education in New Orleans. The state of Louisiana took over most of the city's public schools after the killer storm in 2005. (Aug. 20) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins