Featured Research

from universities, journals, and other organizations

Repeated Fire And Drought: A Menace For Mediterranean Forests

Date:
May 26, 2009
Source:
Cemagref
Summary:
Is fire an enemy of Mediterranean forests or a natural regulating factor of the ecosystem? What is the effect of climate change on the interactions? Researchers have found that it is a question of frequency, itself related to the stock of organic matter which determines life in soil. The results obtained have created new possibilities for better management of the most fragile ecosystems.

Plane dropping water on a forest fire in the Corsican mountains.
Credit: iStockphoto/Jean Schweitzer

Is fire an enemy of Mediterranean forests or a natural regulating factor of the ecosystem? What is the effect of climate change on the interactions? Thanks to the IRISE1 program, coordinated by Cemagref, we now know that it is a question of frequency, itself related to the stock of organic matter which determines life in soil. The results obtained have created new possibilities for better management of the most fragile ecosystems.

Fires represent one of the most serious disturbances to Mediterranean forest ecosystems, where 600,000hectares burn every year. However, it is not so much the size of the burnt zones that worries the Cemagref researchers as the impact of fires on plant communities and the capacity of the ecosystem to regenerate itself.

Thanks to the IRISE program, coordinated by Cemagref, we now know that forests are not destroyed by a single fire, but when the frequency of fires is too high. This three-year, multi-disciplinary project brought together scientists from three research institutes (Cemagref, CNRS, INRA) and three universities from the Aix-Marseille and Lyon regions. It was possible to determine the critical frequencies above which the ecosystem is no longer balanced and its regenerative capacity is reduced. Key mechanisms involved in the regeneration or collapse of fragile ecosystems were identified. Taking advantage of the reduced rainfall from 2003 to 2008, the scientists also studied the interaction between repeated fires and droughts.

50 years to repair the effects of a fire

In areas regularly subjected to fire, biological activity in the soil is concentrated in the first centimetres where most of the organic matter is found and is exposed to combustion and erosion. Following a fire, most physico-chemical parameters of forest soils return to their initial levels after 15 to 25 years.

But a full 50 years are required before the ecosystem regains is overall and qualitative resilience. Before the 50 years have elapsed, the bacterial communities and soil fauna, essential elements in the regenerative process, are less diversified and active. What is more, after a fire, the organic matter contains high levels of poorly degradable or toxic substances that are likely to partially inhibit the biological activity of the soil. It is only after 150 to 200 years without a fire that the carbon stored in the soil increases significantly and the structure and composition of the vegetation improve.

The first and fourth fires are critical

A single fire is sufficient to interrupt the restoration process, however it cannot compromise the long-term regenerative capacity. The latter is also not affected by one or two additional fires over a 50-year period. However a fourth fire over the same period, or two fires within a very short time span (less than ten years) can be fatal. If a fourth fire occurs, species and communities that are essential for ecosystem operation become more rare and the stock of organic matter is reduced in both quantity and quality. The fire releases a large quantity of CO2 and the forest can no longer play its role as a carbon sink, which, in the end, contributes to the greenhouse effect. The plant community changes and the forest can gradually give way to shrubs and bushes.

When drought chimes in

An increase in the frequency of dry periods, as in 2003 to 2008, combined with a high frequency of fires, leads to a collapse of the biological operation of the ecosystem. A long dry period after a fire slows or even stops regeneration of the forest. Similarly, the impact of a fire is greater on an environment that has recently suffered a long dry period. Four successive dry years would appear to constitute a critical threshold in the resistance of forests to fire. Climate change, by intensifying the combination of fire and dryness, can only increase the fragility of ecosystems, which makes it difficult to foresee their condition over the mid and long term.

Taken together, the above work provides the means to formulate priorities for the management of Mediterranean forests. Zones that have suffered a number of recent fires and that could be irreparably damaged by another fire must receive priority attention, before other forests that have not burned for decades and are more resilient. The rare old forests (over 150 years) must also be protected at all costs. Due to the importance of the stock of organic matter in soil for forest resilience, the adjunction of compost to enhance the fertility of forest soil and environmental dynamics could be a solution in the most fragile zones. Experiments have been launched in order to assess the effectiveness of such a policy.

(1) The IRISE program (2005-2008) took place thanks to the European Forest-Focus regulation, via the French Agriculture ministry and with the support of the "Mediterranean centre for environmental sciences" federative research institute.


Story Source:

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


Cite This Page:

Cemagref. "Repeated Fire And Drought: A Menace For Mediterranean Forests." ScienceDaily. ScienceDaily, 26 May 2009. <www.sciencedaily.com/releases/2009/05/090519080045.htm>.
Cemagref. (2009, May 26). Repeated Fire And Drought: A Menace For Mediterranean Forests. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2009/05/090519080045.htm
Cemagref. "Repeated Fire And Drought: A Menace For Mediterranean Forests." ScienceDaily. www.sciencedaily.com/releases/2009/05/090519080045.htm (accessed April 24, 2014).

Share This



More Earth & Climate News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Fungus Killing Bats, Spreading in US

Deadly Fungus Killing Bats, Spreading in US

AP (Apr. 24, 2014) A disease that has killed more than six million cave-dwelling bats in the United States is on the move and wildlife biologists are worried. White Nose Syndrome, discovered in New York in 2006, has now spread to 25 states. (April 24) Video provided by AP
Powered by NewsLook.com
New Pictures of Ship That Sank in 1888

New Pictures of Ship That Sank in 1888

AP (Apr. 24, 2014) Federal researchers have released new images of the City of Chester, a steamship that sank in San Francisco Bay in 1888. Researchers recently found the shipwreck while mapping shipping routes. (April 24) Video provided by AP
Powered by NewsLook.com
Risk of Asteroid Hitting Earth Higher Than Thought, Study Shows

Risk of Asteroid Hitting Earth Higher Than Thought, Study Shows

Reuters - US Online Video (Apr. 23, 2014) A group of space explorers say the chance of a city-obliterating asteroid striking Earth is higher than scientists previously believed. Deborah Gembara reports. Video provided by Reuters
Powered by NewsLook.com
UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
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