Doubling the amount of carbon dioxide in the air significantly reduces the number of plant species that grow in the wild, according to a newly released study on climate change in California.
The results, published in the Proceedings of the National Academy of Sciences (PNAS), are the latest findings from the Jasper Ridge Global Change Project at Stanford University – a multiyear experiment designed to demonstrate how grassland ecosystems will respond to predicted increases in temperature and precipitation caused by the continual buildup of CO2 and other greenhouse gases in the atmosphere.
Writing in the June 16 edition of PNAS Online, researchers found that exposing open grasslands to large doses of CO2 gas for three years caused a nearly 20 percent reduction in wildflower species and an eight percent decline in plant diversity overall. The addition of excess nitrogen and other predicted climate changes caused diversity to plunge even further, the study found.
To study the environmental impact of such future global changes, researchers monitored 36 circular plots of land, each about six feet in diameter, between 1998 and 2001. Four circles were left undisturbed as experimental controls. Each of the remaining 32 circles was divided into four quadrants – like a birthday cake cut into equal pieces – for a total of 128 experimental plots.
Different treatments were applied to different plots. Some were given a single application, such as excess carbon dioxide gas, while others received various combinations of elevated CO2, heat, water and/or nitrogen fertilizer.
Initially, each plot contained between five and 20 varieties of grasses and wildflowers. The goal of the experiment was to see how different combinations of treatments would affect species diversity over a three-year period.
The results were dramatic. Plots that received all four treatments lost more than one-fourth of their wildflower species, while those given elevated nitrogen or CO2 suffered a 10 to 20 percent decline.
However, plots treated with excess water experienced a 10 percent increase in wildflower diversity and a 3 percent gain in the number of annual grass species.
"We found that elevated CO2 caused a loss in species, while added precipitation caused an increase. We were surprised they had such opposite effects," said study co-author Christopher B. Field, a professor by courtesy of biological sciences at Stanford and director of the Carnegie Institutions Stanford-based Department of Global Ecology. "One hypothesis is that elevated CO2 added moisture to the soil, which tended to extend the growing season of the dominant plants, leaving less room for other species to grow."
On the other hand, he noted, increasing precipitation by 50 percent may have encouraged growth in late-season plants that normally stop growing during the dry California summer: "We think the effects of elevated CO2 and increased precipitation were more or less the same, but because they were separated in time by a couple of weeks, they actually produced opposite results. In our ecosystem here, things that happen at different times in the season are really important."
The study also revealed that heat in the absence of other treatments had no significant impact on diversity. However, when experimental plots were exposed to higher temperatures along with excess nitrogen, carbon dioxide and water, the number of wildflower species plummeted.
"One take-home message of our study is that certain kinds of species are much more sensitive to climate and atmospheric changes than others," Zavaleta observed.
"It turned out that wildflowers were much more sensitive to the treatments than grasses were, no matter what combination of treatments we tried," she added, noting that a large-scale change in diversity could diminish the ability of grasslands to support birds, deer, butterflies and other wildlife – as well as commercial grazing.
The researchers discovered that they could make remarkably accurate predictions of species diversity in plots where multiple treatments had been applied simply by adding up losses and gains observed under single treatments. For example, in quadrants receiving excess nitrogen, heat and CO2, wildflower diversity decreased by about 27 percent -– almost exactly what would be expected if you added up the percentages of loss in quadrants given single treatments of CO2 (18 percent), nitrogen (8 percent) and heat (2 percent).
"One possible reason we see this overall additive response is that the mechanisms that are driving the changes are not interacting," Field said – a finding that could prove beneficial in forecasting how global environmental changes will affect plant diversity in other ecosystems.
"We hope to move into the domain where we can predict responses rather than just record them and report them," he added.
Other coauthors of the PNAS study are Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford; Nona R. Chiariello, research coordinator of the Jasper Ridge Biological Preserve; and M. Rebecca Shaw of the Nature Conservancy.
The study was supported by the National Science Foundation, the David and Lucile Packard Foundation, the Morgan Family Foundation, JRBP, the Carnegie Institution of Washington, the U.S. Department of Energy, the U.S. Environmental Protection Agency, the Switzer Foundation, the A.W. Mellon Foundation and the Nature Conservancy.
Mark Shwartz | EurekAlert!
Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences