Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Reforestation using exotic plants can disturb the fertility of tropical soils

30.05.2008
In many regions of the world, the impact of human activity on the environment intensified considerably over the past century.

The high world population growth rate and the expansion of areas given over to crop production associated with climatic changes (longer periods of drought, irregular rainfall patterns) induced by global warming, have contributed to the acceleration of desertification.

According to World Soil Information (ISRIC) rate, in the space of 50 years, 12.8 million km2 of soils have thus experienced diminished fertility. With the aim of limiting such land impoverishment, which is hitting the intertropical and mediterranean zones particularly harshly, a range of reforestation programmes using rapid-growing forest species (such as eucalyptus, exotic pine or Australian acacias) was undertaken from the mid 1970s. Establishment of bacterial and mycorrhizal symbioses provides these trees with the adaptation ability necessary for growth on virtually barren, mineral-deficient soil.

Although no proof is needed as to their effectiveness for producing plant biomass in harsh environmental conditions and their utility as windbreaks to control erosion, there is little information on their potential impact on the genetic and functional biodiversity of the soil microorganisms. A research programme run since 2005 in Senegal and Burkina Faso by an IRD team and its partners1 yielded clues for understanding the influence of exotic plants on the structure and biodiversity of these communities of fungi and bacteria. In Burkina Faso, controlled experiments showed that the development of E. camaldulensis, the eucalyptus species most often planted in the world, outside its area of origin, significantly reduced the diversity of the mycorrhizal fungi communities essential for the healthy functioning of the ecosystem. This negative effect was also found in the soil of a Senegalese plantation of Acacia holosericea where, scarcely a few months after its introduction, the soil’s microbial characteristics had completely changed.

This quick-growing species had effectively selected certain species of mycorrhizal fungi and bacteria of the genus Rhizobium, ending in a reduction in the species diversity of these symbiotic communities. The soil sampled from areas surrounding the A. holosericea plantation had a balanced distribution of mycorrhizal fungi species, whereas the breakdown of the fungal spore content in soil from the plantation showed a predominance of one species and therefore a strong imbalance in the composition of the mycorrhizal fungi community. In the knowledge that a plant ecosystem’s productivity is closely dependent on a soil’s mycorrhizal diversity, there is a risk that the Australian acacia might create a new ecosystem whose physical, chemical and biological characteristics will not necessarily be favourable to a recolonization of the habitat by native species. The research also demonstrated that the environments generated by this species were less resistant to water and heat stress. In a context of global climate change, such habitats could therefore experience a drastic fall in their microbial activity and thus lose their ability to be the basis of proper development of the plant cover.

The conclusions of the study conducted in Senegal in a precisely defined environment cannot, however, be generalized to tropical soils as a whole. Indeed, investigations on another A. holosericea plantation, in Burkina Faso, yielded the observation of an increase in microbial functional diversity. The contradictions between these sets of results should prompt the organizations involved in natural resources management to plan for possible introductions of exotic species case by case, taking account not only of potential impacts of the plant species under consideration for introduction, but also of the nature of the soils they are to colonize. For although this practice can yield highly satisfactory results, such as increases in the species richness of severely degraded environments, such as old mining areas, it can also upset for a long time the organization of the microbial communities which guarantee the fertility of a soil.

Grégory Fléchet – DIC

1. This research work was conducted with the support of scientists from the Département de biologie végétale of the Cheikh Anta Diop University of Dakar (Senegal) and from the Laboratoire Sol-Plante-Eau of the Institut de l'Environnement et des Recherches Agricoles (Inera) of Ouagadougou (Burkina Faso)

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/us/actualites/fiches/2008/fas296.pf

More articles from Ecology, The Environment and Conservation:

nachricht Scientists team up on study to save endangered African penguins
16.11.2017 | Florida Atlantic University

nachricht Climate change: Urban trees are growing faster worldwide
13.11.2017 | Technische Universität München

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Lightning, with a chance of antimatter

24.11.2017 | Earth Sciences

A huge hydrogen generator at the Earth's core-mantle boundary

24.11.2017 | Earth Sciences

Scientists find why CP El Niño is harder to predict than EP El Niño

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>