Studies Reveal Some Trees "Pine" For Greenhouse Gases, According To University Of Georgia Forester

January 09, 1997

ATHENS, Ga. -- The steady warming of the Earth's atmosphere, along with increased concentrations of carbon dioxide, could one day bring cataclysmic changes to the planet, some scientists believe. They have suggested global warming could cause anything from the widespread elimination of species to the melting of polar ice caps.

But new studies in USDA's Southern Global Change Program indicate there is at least one hidden advantage to increased CO2 concentrations: much better tree growth due to improved photosynthesis. Four separate groups of scientists in the South agree that managed timber stands will actually benefit from higher levels of CO2 in the atmosphere.

"What we've found so far is that pine trees are better adapted to increases in CO2 than most species, but others respond positively as well," said Dr. Bob Teskey, a professor in the University of Georgia's Warnell School of Forest Resources.

Teskey, along with colleagues in North Carolina, Alabama, Mississippi, and Oklahoma, studied the response of loblolly pines to increasing concentrations of CO2 and provided detailed and extensive measurements of photosynthesis, respiration and growth under a variety of experimental conditions.

The research will be published this spring in the book The Sustainability and Productivity of Southern Forest Ecosystems in a Changing Environment. Co-authors of the chapter outlining the research are Dr. Phillip Dougherty of the Westvaco Timber Co. of Sumter, S.C., and Dr. Robert Mickler of the U.S. Forest Service.

Teskey and his colleagues wanted to know if the benefits from elevated CO2 levels would last and if these beneficial effects might be modified by other stresses on the trees, such as increasing air temperatures. In both cases, the preliminary news is good. The researchers believe it will take hundreds of years for slowly increasing CO2 levels to reach the maximum benefits for growing pine trees. And the benefits of increased CO2 are apparently greater than harm caused by rising global temperatures.

Carbon dioxide is a natural part of the Earth's atmosphere, but it has been steadily increasing over the past 100 years, largely due to air pollution from burning fossil fuels. By measuring gases trapped in ice, researchers know that a century ago the air contained about 280 parts per million of CO2. Now, that level is up, on average, to more than 350 ppm and is climbing by about 1.5 ppm a year. While 80 percent of the increase is due to the use of fossil fuels, tropical deforestation also adds to the problem. (Oddly enough, Teskey said, cement production is responsible for about 3 percent of the atmospheric CO2 increase annually.)

Carbon dioxide is the engine that drives photosynthesis in plants, so in a sense the new findings are logical. But the researchers were surprised at the steady, increasing effect that more CO2 had on loblolly pine trees.

"There are many things we don't know about global warming," said Teskey, "such as whether or not elevated temperatures may cause shifts in precipitation patterns; however, if these patterns are the same, there is no doubt in my mind that we will see increasing production in both managed and natural stands of trees."

Teskey's own research has examined the interaction between levels of CO2 and increasing atmospheric temperatures.

While the studies focused on loblolly pines, a greenhouse experiment at the University of Georgia examined the sweetgum, and a Mississippi study measured responses in the flowering dogwood. For these species, the effect of elevated CO2 concentrations on net photosynthesis was almost always positive, but the magnitude of the response was quite variable, depending on species and growth conditions.

Other effects in pine trees included large increases in branch length, dry stem weight, total plant biomass and root growth. Leaf area was also increased, but the growth of individual needles was the same.

One surprise in the studies was the discovery that the effects of elevated CO2 on physiological processes primarily adds to, rather than interacts with, other processes.

"This is remarkable because it means tree growth in the field (on sites of high growth potential as well as sites of low growth potential) is likely to benefit from elevated CO2 concentrations in the atmosphere," said Teskey.

While the studies point toward benefits for managed stands of loblolly pines, concerns remain for native forests. Indeed, global warming could play havoc with forest ecology, leading to the loss of biological diversity among plants and trees and among the animals that live on and around them. Another worry is the attendant increase in ozone during global warming, since ozone does decrease productivity, according to Teskey. Levels of ozone in the Earth's atmosphere are more than twice what they were a century ago.

Still, the beneficial effects of higher CO2 on tree growth far outweigh the negative effects of increasing ozone, Teskey said.

University of Georgia

Related Global Warming Articles from Brightsurf:

The ocean has become more stratified with global warming
A new study found that the global ocean has become more layered and resistant to vertical mixing as warming from the surface creates increasing stratification.

Containing methane and its contribution to global warming
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term.

Global warming and extinction risk
How can fossils predict the consequences of climate change? A German research team from Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), the Museum of Natural History Berlin and the Alfred Wegener Institute compared data from fossil and marine organisms living today to predict which groups of animals are most at risk from climate change.

Intensified global monsoon extreme rainfall signals global warming -- A study
A new study reveals significant associations between global warming and the observed intensification of extreme rainfall over the global monsoon region and its several subregions, including the southern part of South Africa, India, North America and the eastern part of the South America.

Global warming's impact on undernourishment
Global warming may increase undernutrition through the effects of heat exposure on people, according to a new study published this week in PLOS Medicine by Yuming Guo of Monash University, Australia, and colleagues.

Global warming will accelerate water cycle over global land monsoon regions
A new study provides a broader understanding on the redistribution of freshwater resources across the globe induced by future changes in the monsoon system.

Comparison of global climatologies confirms warming of the global ocean
A report describes the main features of the recently published World Ocean Experiment-Argo Global Hydrographic Climatology.

Six feet under, a new approach to global warming
A Washington State University researcher has found that one-fourth of the carbon held by soil is bound to minerals as far as six feet below the surface.

Can we limit global warming to 1.5 °C?
Efforts to combat climate change tend to focus on supply-side changes, such as shifting to renewable or cleaner energy.

Global warming: Worrying lessons from the past
56 million years ago, the Earth experienced an exceptional episode of global warming.

Read More: Global Warming News and Global Warming Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to