This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A study published in the journal Ecological Monographs indicates that large mammals, such as tapirs, peccaries, agoutis and deer, alter the chemical composition of litter and soil in tropical forests of the Brazilian Atlantic Forest. As a result, they increase nutrient availability and, possibly, soil fertility.
The study was conducted by members of the Center for Research on Biodiversity and Climate Change (CBioClima), a Research, Innovation and Dissemination Center (RIDC) based at the Institute of Biosciences of São Paulo State University (IB-UNESP) in Rio Claro. The findings underscore the critical role of these animals, which are heavily targeted by poachers and experiencing population decline, in the long-term survival of the biome, even within areas where forest cover remains intact. "Most of the mammalian biomass in contiguous areas of the Atlantic Forest consists of peccaries, native wild pigs that live in herds that can exceed 100 individuals," says Letícia Gonçalves Ribeiro, the lead author of the study.
Ribeiro conducted the research as part of her Ph.D. at IB-UNESP. "They arrive in an area and spend a lot of time trampling and rooting around in the ground, searching for fallen fruits and seeds, as well as defecating and urinating. As a result, they end up influencing nutrient cycling, altering soil chemistry and the diversity of the litter—the layer of leaves, twigs and fruits on the soil surface," the scientist explains.
Other large herbivorous mammals that inhabit the biome include tapirs, deer, and agoutis. To better understand the importance of these animals to the Atlantic Forest ecosystem, the researchers compared soil and litter samples from areas where the mammals roam freely with samples from fenced-off areas where they were temporarily eliminated. The results revealed substantial differences in acidity (pH)—less acidic with animals present and more acidic without—as well as in the availability of nutrients, such as calcium and aluminum.
"Aluminum, which is harmful to plants at high levels, was reduced where there was a greater presence of animals. This nutrient has a special relationship with pH and calcium. A balance between the two is necessary for greater soil fertility," says Ribeiro.
In practice, this means that the presence of large mammals increases forest soil fertility. In areas with mammals, a reduction in lignin was observed in the leaf litter. Lignin is a complex molecule that coats plant cells and hinders their decomposition.
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