Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The Energy Budget of a Forest Includes Significant Heat Reserves

25.01.2010
The simple formula we’ve learned in recent years – forests remove the greenhouse gas carbon dioxide (CO2) from the atmosphere; therefore, forests prevent global warming – may not be quite as simple as we thought. Forests can directly absorb and retain heat, and, in at least one type of forest, these effects may be strong enough to cancel out a good part of the benefit in lowered CO2. This is a conclusion of a paper that will be published January 22 in Science by scientists in the Weizmann Institute’s Faculty of Chemistry.

For the past 10 years, the Weizmann Institute has been operating a research station in the semi-arid Yatir Forest, a pine forest at the edge of the Negev Desert. This station is part of a world-wide project composed of over 400 stations, called FLUXNET, which investigates the relationship between forests, the atmosphere, and climate around the globe.

The contribution of the Yatir station, says Prof. Dan Yakir of the Department of Environmental Sciences and Energy Research, is unique as it “is one of very few in the semi-arid zone, which covers over 17% of the Earth’s land surface, and it has the longest record of the processes taking place in semi-arid forests.”

Forests counteract the greenhouse effect by removing heat-trapping CO2 from the atmosphere and storing it in living trees. Over the years of measurement, Prof. Yakir’s group has found that the semi-arid forest, even though it’s not as luxuriant as the temperate forests farther north, is a surprisingly good carbon sink – better than most European pine forests and about on par with the global average. This was unexpected news for a forest sitting at the edge of a desert, and it indicated that there is real hope for the more temperate forests if things heat up under future global climate change scenarios.

But forests do more than just store CO2, and Prof. Yakir, together with Dr. Eyal Rotenberg, decided to look at the larger picture – the total energy budget of a semi-arid forest. The first hint they had that other processes might be counteracting the cooling effect of CO2 uptake came when they compared the forest’s albedo – how much sunlight is reflected from its surface back into space – with that of the nearby open shrub land. They found that the dark-colored forest canopy had a much lower albedo, absorbing quite a bit more of the sun’s energy than the pale, reflective surface of surrounding areas. In a cloudless environment with high levels of solar radiation, albedo becomes an important factor in surface heating.

Next, the researchers looked at the mechanisms for “air conditioning” within the forest itself. To cool down, trees in wetter areas of the globe use water-cooled systems: They open pores in their leaves and simply let some of the water evaporate, drawing heat away in the process. But the semi-arid pine forest, with its limited water supply, is not built for evaporation. The scientists found that it uses an alternative, efficient, air-cooling system instead. As semi-arid forests are not as dense as their temperate counterparts, the air in the open spaces between the trees comes into contact with a large surface area, and heat can be easily transferred from the leaves to the air currents. This semi-arid air cooling system is quite efficient at cooling the treetops, and this cooling, in turn, leads to a reduction in infrared (thermal) radiation out into space. In other words, while the semi-arid forest can cool itself well enough to survive and take up carbon, it both absorbs more solar radiation energy (through the albedo effect) and retains more of this energy (by suppressing the emission of infrared radiation). Together, these effects turned out to be stronger than the scientists had expected. “Although the numbers vary with location and conditions,” says Prof. Yakir, “we now know it will take decades of forest growth before the ‘cooling’ CO2 sequestration can overtake these opposing ‘warming’ processes.”

Prof. Yakir and Dr. Rotenberg then asked one more question: If planting semi-arid forests can in fact lead to warming over a good part of the forests’ life cycles, what happens when the opposite process – desertification – takes place? By applying what they had learned to existing data on areas that have turned to desert, they found that desertification, instead of hastening global warming, as is commonly thought, has actually mitigated it, at least in the short term. By reflecting sunlight and releasing infrared radiation, desertification of semi-arid lands over the past 35 years has slowed down global warming by as much as 20%, compared with the expected effect of the CO2 rise over the same period. And in a world in which desertification is continuing at a rate of about six million hectares a year, that news might have a significant effect on how we estimate the rates and magnitude of climate change. Says Prof. Yakir, “Overall, forests remain hugely important climate stabilizers, not to mention the other ecological services they provide, but there are tradeoffs, such as those between carbon sequestration and surface radiation budgets, and we need to take these into consideration when predicting the future.”

Prof. Dan Yakir’s research is supported by the Avron-Wilstaetter Minerva Center for Research in Photosynthesis; the Sussman Family Center for the Study of Environmental Sciences; the Angel Faivovich Foundation for Ecological Research; and the Cathy Wills and Robert Lewis Program in Environmental Science.

The Weizmann Institute of Science in Rehovot, Israel, is one of the world’s top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians, and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials, and developing new strategies for protecting the environment.

Jennifer Manning | Newswise Science News
Further information:
http://www.acwis.org

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

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...

Im Focus: Studying fundamental particles in materials

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...

Im Focus: Designing Architecture with Solar Building Envelopes

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>