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Ecology

The hidden forest

Land use affects the biological diversity of the soil in the Amazon Region

PEDRO HAMDANBeetles, pseudo-scorpions, termites, bacteria, ants, fungi, spiders, acari, snails, larvae and plant roots are part of an invisible world. At least for those who walk through the Amazon Forest, bewildered by the size of the trees, the noise of the birds, the humid heat and the insect bites. Moreover, it is precisely this hidden diversity that a team of researchers, bringing together 15 institutions from several Brazilian states, has been cataloguing since 2002,  in the area of the upper Solimões River, a part of the Amazon Region near Brazil’s border with Colombia and Peru. Coordinated by the microbiologist Fatima Moreira, from the Federal University of Lavras (UFLA), in Minas Gerais, the Bios Brazil project has counted, for example, 239 species of ants, 75 species of termites and 53 species of beetles in the analyzed soil samples. “Nobody thinks about the small or invisible organisms, but the soil is a major resource,” argues the researcher.

The project arose from an initiative of the Tropical Soil Fertility and Biology Program, which, with the support of the environmental program of the UN, in 1995, brought together representatives from various countries that still have major biological diversity and forests to be protected. The idea matured slowly, and after a few years, seven countries – Brazil, Mexico, Uganda, Kenya, Ivory Coast, Indonesia and India – started working on the project, using standardized methods.

The Brazilian section involved 40 researchers and more than 100 students, who excavated 100 sampling points in the studied communities. If one adds up all these points, the sampling covers 54 hectares, an area roughly equal to 53 football pitches turned into a hole. It was necessary, in the excavations, to have on site at least one professor and one student from each of the 15 areas of specialization in the study, working in their own way. The soil experts analyzed the properties and collected samples to then conduct chemical and physical analyses; those who specialized in microscopic organisms, such as bacteria, fungi and nematodes, also collected samples to examine later under a microscope and extract genetic material capable of revealing the diversity that is invisible to the naked eye. As for those who study worms and insects, for example, they closely examined the upturned soil in search of their favorite organisms. Another team identified all the plant species found in the studied areas.

Working together provides the researchers with the assurance of relating the diversity of one type of organism with another and of looking for the corresponding diversity with the soil type and its use: forest, secondary vegetation, small plantation, larger plantation and pasture. The researchers had to overcome not only the intrinsic difficulties of the work, but also the suspicion of the local inhabitants. “At first, they thought that we were looking for gold,” Fatima comments with amusement, “but afterward they accepted us and became interested in the study.”

The Brazilians chose the upper Solimões area, in the Amazon Region, because it is still hard to reach. Therefore, it has been preserved. One can only get to it by water, after half an hour in a boat from Tabatinga, on the border with Colombia, to the town of Benjamin Constant, where the communities of native Indians from Nova Aliança and Guanabara II are found. The zone is an isolated one, but this does not mean that there are only Indians hunting with bows and arrows in the virgin forest: there are communities with about 50 families that engage in slashing and burning the forest in order to plant food.

PEDRO HAMDANPermitted deforestation
So far, the main finding of the study concerns the consequences of the method used to deforest small areas and, after a period of cultivation, allowing the forest to regenerate. “There is a notion that felling and burning are harmful procedures,” explains Fatima. However, her team has discovered that, in association with the conservation of large forest areas, small deforested segments regenerate well with secondary vegetation, a type of immature forest. Furthermore, the soil under this secondary vegetation soon re-acquires the characteristics and the level of biological wealth in the forest. “The communities that live there have been doing this for hundreds of years and it works,” she tells us, making a comparison: “However, deforesting large areas, as is the case in Acre, Rondonia and Pará, is really damaging.”

This was the theme of Ederson Jesus’s doctorate, under Fatima’s guidance, which received an honorable mention from Capes, the Coordinating Office for the Training of Personnel with Higher Education. He showed that changes in the use of the land altered the structure of bacterial communities; however, once secondary vegetation grows, these communities revert to being similar to those found in primary forests. According to a 2009 article in the ISME Journal, the bacterial community changes are tied to the chemical properties of the soil, especially its acidity and concentration of nutrients. The conclusion that the cultivation techniques of these communities do not lead to the loss of bacterial diversity is essential, as these microscopic organisms cannot be dissociated from the soil properties and help to maintain a suitable flow of nutrients.

The burning itself allows the acidity to neutralize and reduces the concentration of available aluminum, which is naturally high in the region’s soil and is toxic for plants. However, the soil improvement is merely temporary, as Fatima’s team showed in a 2009 article in the journal Science of the Total Environment. Once the cultivated plants consume the nutrients, the soil becomes depleted quickly without the production and depositing of organic matter, which occurs when the forest grows. That is why the group found the worst conditions, high acidity and a low concentration of nutrients, in pastures.

In collaboration with bacteria and fungi, arthropods, although minuscule, are the major factor of soil enrichment through the decomposition of organic matter. This is particularly true of oribatid mites and of collembolans. A study led by José Wellington de Morais, from Inpa (the National Institute of Research into the Amazon Region), published in 2010 in Neotropical Entomology, showed that the set of organisms of the cultivation systems is not very different from that which characterizes the primary forest. As for the agro-forest system, with more extensive deforestation, the result is soil that is more similar to that in the pastures, which is quite poor. The work also indicated that the mites seem to be more resistant to adverse conditions, as they are the dominant organisms in pasture soil.

The Bios Brazil researchers are still puzzling over how to fit all these parts together and understand the cyclical relations that connect the soil, the organisms that live in it and the type of use human populations make of it. “Everything is related,” stresses Fatima, “but it’s like the chicken and the egg enigma.”

PEDRO HAMDANFor the researchers, the findings are worth gold: many novelties arise from the exploration of this little known world underneath their feet. “We have described new species of nematodes, ants, termites and fungi,” celebrates the project coordinator. Some of the termites found are actually of a new genus, described in Zootaxa by Reginaldo Constantino, from the University of Brasília, and Agno Acioli, from the Federal University of Amazonas. The name of the insects, Ngauratermes, comes from the Ticuna language spoken by the most common Indians of the region. It means a termite that inhabits forest-ground residue.

Local action
Besides yielding a large number of scientific publications, that are far from reaching their end, the group has also produced a primer to show their results to the local communities. This can be found at the project site. “The researcher’s work is essential,” highlights Fatima, “but those who are going to actually engage in conservation are the local population, which is why we need to show the importance of this wealth in such a way that they can understand it.” The primers, in Portuguese, Spanish (because the region borders on Colombia and Peru) and English (the official language of the international project) have been put to good use by the team. They were the teaching material used on courses in which the researcher presented their data to the population and they are now being used in schools, to explain environmental notions using terms that are integrated with the children’s day-to-day lives.

Keeping this wealth intact is much more than sentimentalism. Fatima clarifies that the region produces important sources of food, such as the pupunha heart of palm, the cupuaçu fruit and several types of typical local vegetables. Agrobiodiversity is being exploited not only as a means of cultivating these plants and making them available in other regions, but also to understand the natural partnerships that make them healthier and more productive. One example is the bacteria and fungi that are associated with the roots of plants and that help them with their nutrition. The group of the UFLA researcher has been using Amazon Region bacteria to improve the productivity of the Vigna unguiculata bean in other regions. This way of looking at these matters comes from Fatima’s master’s degree at Inpa, with Johanna Döbereiner, who is renowned worldwide for her pioneer work on nitrogen-fixing bacteria.

Gláucia Alves e Silva, under the guidance of José Oswaldo Siqueira, from UFLA, and Sidney Stürmer, from the Regional University of Blumenau Foundation, has tested the efficiency of the association between fungi and the aforementioned beans. She found, as published in Acta Amazonica, that the most efficient fungi in terms of phosphorus absorption are more common in small plantations and pastures. Furthermore, Fatima reminds us that biological diversity is a natural form of protection: no pest manages to decimate a forest; they are only efficient against monocultures.

Fatima believes that another major benefit of this project was bringing together researchers who otherwise would have continued to work in isolation. “We formed a cohesive group that is growing.” The work is not expected to cover only the Amazon Region. A R$2.5 million project has just been approved by the company Vale, as part of a joint call with FAPESP and Fapemig, to conduct a similar type of study in the states of Minas Gerais and São Paulo, which will probably start this year.

For the researcher, conserving the Amazon Region is a matter of global interest and she advocates a forest grant to help the local communities preserve the Amazon forest and avoid the drastic transformations that have already taken place, with no possibility of being reversed, in other parts of the world. “The Iran and Iraq region, the cradle of civilization, used to be all woodlands; today, it’s a desert.”

Scientific articles
JESUS, E. da C. et al. Changes in land  use alter the structure of bacterial  communities in Western Amazon soilsThe ISME Journal. v. 3, p. 1.004-11. 2009.
MOREIRA, D. M. de S. et al. Differentiation in the fertility of Inceptisols as related to land use in the upper Solimões river region, western Amazon. Science of the Total Environment. v. 408, p. 349-55. 2009.
MORAIS, J. W. de et al. Mesofauna  do solo em diferentes sistemas de uso da terra no alto rio Solimões, AM. Neotropical Entomology. v. 39, n. 2, p. 145-52. 2010.
SILVA, G. A. et al. Eficiência de fungos micorrízicos arbusculares isolados de solos sob diferentes sistemas de uso na região  do alto Solimões na Amazônia. Acta Amazonica. v. 39, n. 3, p. 477-88. 2009.

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