[MCN] PDF: A reality check on the CO2 "fertilization effect"

[Lance Olsen]

Study finds that plant growth responses to high carbon dioxide depend 
on symbiotic fungi
INDIANA UNIVERSITY PUBLIC RELEASE: 30-JUN-2016

I have the pdf of the Science article. Feel free to ask

In the meantime, you can see the abstract here:
http://science.sciencemag.org/content/353/6294/72

=============      Excerpt from press release        =================
"In some ways, our research represents encouraging news in that many 
of our forests may continue to slow climate change by soaking up 
carbon dioxide," he added. "On the other hand, it is sobering in that 
the CO2 fertilization effect may occur on a relatively small fraction 
of the Earth's surface. And if climate change also increases the 
frequency and intensity of disturbances such as droughts and floods, 
the magnitude of the plant growth response to high carbon dioxide 
will be diminished."
================================

Research by an international team of environmental scientists from 
the United Kingdom, Belgium and United States, including Indiana 
University, has found that plants that associate with one type of 
symbiotic fungi grow bigger in response to high levels of carbon 
dioxide, or CO2, in the atmosphere, but plants that associate with 
the other major type of symbiotic fungi do not.

The study, which appears online today in the journal Science, calls 
into question whether the 'greening of the Earth' that results from 
carbon dioxide stimulation of plant growth -- often called the "CO2 
fertilization effect" -- will persist as fossil fuel emissions 
continue to rise globally.

"Pumping extra carbon dioxide into a greenhouse is a common tactic to 
stimulate plant growth, but nature is much more complex than a 
greenhouse," said Richard Phillips, associate professor in the IU 
College of Arts and Sciences' Department of Biology, who is a 
co-author on the study. "So, there is great debate about whether 
pumping carbon dioxide into the atmosphere through fossil fuel 
combustion stimulates plant growth in nature, where soil nutrient 
levels are typically much lower than in a greenhouse."

Fungi that form symbiotic relationships with plants are called 
mycorrhizal fungi. Over 90 percent of all plant life on Earth 
associates with mycorrhizal fungi, which provide plants with soil 
nutrients in exchange for plant carbohydrates.

"While researchers have long known that mycorrhizal fungi play an 
essential role in the growth and health of plants, their role in 
helping ecosystems store carbon has never been investigated on such a 
broad scale -- until now," said second-year PhD student Cesar Terrer 
of Imperial College London, who is first author on the paper. "Our 
analysis is the first to demonstrate that only plants that associate 
with a certain type of fungal partner - one that helps them acquire 
nitrogen from soil - are likely to grow bigger as carbon dioxide 
levels rise."

Other authors are on the study are Colin Prentice of Imperial College 
London; Sara Vicca of the University of Antwerp, Belgium; and Bruce 
A. Hungate of the Northern Arizona University.

The research team examined 83 experimental studies of plant responses 
to CO2 levels equivalent to those expected by the year 2050, assuming 
an increase of about 2 percent each year globally.

They found a marked difference in the ability of certain plants to 
take advantage of increased CO2 levels. Plants that grew in 
nitrogen-rich soils were able to grow bigger and sustain high levels 
of growth throughout the experiment, following expectations. In 
nitrogen-poor soils, however, only plants that associate with a 
certain type of symbiotic fungi were able to keep growing larger.

The group of fungi that enabled plants to grow bigger under high CO2 
levels is ectomycorrhizal fungi - a type of fungi that helps plants 
access soil nutrients by decomposing organic matter, such as the 
remains of dead plants and microbes.

Plants that associate with the other major type of mycorrhizal fungi 
- arbuscular mycorrhizal fungi - were unable to maintain high levels 
of growth under elevated CO2. While these fungi also increase plant 
access to nutrients, they cannot access nutrients locked up in soil 
organic matter.

"Nearly all plants associate with only a single type of mycorrhizal 
fungi," said Phillips. "And since the type of fungal associates are 
known for most plant species, we can begin to predict which 
ecosystems may respond favorably to high levels of CO2 and which ones 
will not."

Ectomycorrhizal fungi associate only with woody plants, such as trees 
and shrubs, and tend to dominate in forests at high latitudes. 
Arbuscular mycorrhizal fungi associate with all forms of plant life 
and dominate in nearly all ecosystems, aside from the boreal forest. 
In temperate forests, about the half the tree species associate with 
each type of fungi.

About 30 percent of human CO2 emissions are currently absorbed by 
land-based ecosystems, without which climate change would be 
happening even faster than it is now.

The results of this study should enable climate scientists make more 
accurate predictions of the effects of CO2 in the future, Phillips 
said.

"In some ways, our research represents encouraging news in that many 
of our forests may continue to slow climate change by soaking up 
carbon dioxide," he added. "On the other hand, it is sobering in that 
the CO2 fertilization effect may occur on a relatively small fraction 
of the Earth's surface. And if climate change also increases the 
frequency and intensity of disturbances such as droughts and floods, 
the magnitude of the plant growth response to high carbon dioxide 
will be diminished."
###

-- 
  *******************************************************************************************
"Our results suggest that climate policy need not reduce happiness in 
the long run, even when it reduces income and carbon-intensive 
consumption. Climate policy may even raise life well-being, if 
accompanied by compensatory measures that decrease formal working 
hours and reference consumption standards, while maintaining 
employment security."

Filka Sekulova, Jeroen C.J.M. van den Bergh. Climate change, income 
and happiness: An empirical study for Barcelona, Global Environmental 
Change 23 (2013) 1467-1475
-------------------------------------------------
"He who knows he has enough is rich."
Lao-Tzu

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://bigskynet.org/pipermail/missoula-community-news_bigskynet.org/attachments/20160702/29e37797/attachment-0002.html>