[Gasification] TREES THAT THREATEN FORESTS

[Benjamin Domingo Bof]

Trees that threaten forests 04/03/2008 Agency FAPESP - For a forest in danger, nothing as the birth of new trees. At least it is this what the common sense allows to imagine, but the reality is not this well. To the list of threats to the tropical forests a new can be added: trees. According to a study made for researchers of the United States, not native trees when entering tropical forests provoke alterations in the found basic biological structure in the places. Or either, they make with that the forest if becomes less hospitable the myriad of plants and species of animals that of it depend. The study printed of the Proceedings magazine will be published this week in the site and briefing in the edition of the National Academy of Sciences (Pnas). The group, led for Gregory Asner, of the Department of Global Ecology of the Carnegie Institute, used an innovative technology for remote sensoriamento. By means of the Aerial Astroroof Carnegie, installed in an aircraft, the
 researchers had drawn three-dimensional maps to more than evaluate the impact of invading species in an area of 220 a thousand hectares of forest in the Havaí. "invading Species of trees frequently present properties biochemists, physiological and structural different of the native species. We combine these ` fingerprints ' with three-dimensional images to see as these trees are modifying the forest ", said Asner. In the Havaí, they esteem themselves that half of all the organisms is not native and that about 120 species of plants they can be considered as highly invasive. Areas of original vegetation in tropical forest in the archipelago generally are dominated by the ohia (Metrosideros polymorpha), but this species that grows very slowly are losing land for the other news in the place, as the Morella faya, originary of the Canaries Islands. In accordance with the researchers, trees also introduced can open way for invading from the alteration of the fertility of the
 ground. The moluccana Falcataria, for example, considered one of the species invading, fixes nitrogen of the atmosphere, concentrating it in the ground, what it stimulates the speed of growth of another invasive and lesser species, the Psidium cattleianum. The P. cattleianum, in turn, forms a dense covering that prevents that most of the solar light reaches the ground and promotes the growth of young native plants. The researchers stand out that the analyses had been made in reserves protected for the government. Or either, the scene still can be worse. "These espécias obtain to spread for protected areas and without the aid of alterations promoted for the activities human beings. This suggests that the traditional boardings of conservation are not enough for the survival in the long run of the forests ", said Asner. Three-dimensional the Invasive article plants transform the structure of rain forests, of Gregory Asner and others, could be read in briefing for subscribers
 of the Pnas in www.pnas.org.
       
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