Large mammals help regulate the spatial structure of plant communities and keep a balance between areas with different levels of productivity. Credit: Joo Krajewski.
A study conducted by researchers affiliated with So Paulo State University in Brazil shows that large mammals have a major impact on the understory of Neotropical forests. The lowland tapir and white-lipped peccary are two species that help keep an ecological balance in areas with different levels of productivity. An article on the study was published.
The authors show that the two key herbivore species perform together. Plants are regulated by tapirs and peccaries, while understory seedling density is contributed by peccaries. The jussara palm plays a key role in the process of spatial regulation by attracting animals with its enormous quantity of fruit.
The animals eat the fruit and leave a trail of droppings behind them as they move through the forest. It increases seedling productivity by up to 185% in less productive areas, while reducing it by 190% in more productive areas. The differences in productivity between habitats are evened out.
The tapirs chew only the fruit's pulp. The seeds pass through their system and reach the soil. They range over large areas and often defecate far away from the plants whose fruit they eat, carrying seeds from one side of a forest area to another, and changing the composition and diversity of the plant communities that live there.
The trampling of the soil with their sharp hooves is caused byeccaries. Primary productivity is understood to be the production of new biomass in response to carbon flows among other factors.
"This spatial structuring phenomenon is poorly understood and hasn't been studied in depth, but it's a fundamental part of these species' role as forest engineers." Scientists consider them to be important species in Neotropical forests. The study shows how mammals affect forest dynamics. The author of the article told Agncia FAPESP that the number of palm trees affects productivity and biodiversity.
Villar's research was supported by a scholarship. He is working at the Institute of Biosciences in Rio Claro.
In the Neotropical forests such as the Atlantic Rainforest and the Amazon, palms are the dominant plant. The Neotropics have tapirs and peccaries. Villar said that the findings probably apply to many other forests in the south and center of the American continent.
The Atlantic Rainforest is important for its biodiversity and productivity because of its mutual relations between the two animal species. The importance of their preservation. The forest's capacity for carbon capture is affected by the decline in populations of top predator and herbivores. According to his group's research, large mammals can cause primary productivity to increase in tropical forests as well as in tallgrass prairie. Major changes in the structure, biomass and diversity of Neotropical forests are caused by the extinction of large mammals and illegal cutting of jussara palms for human consumption.
The original vegetation of the Atlantic Rainforest is only 12.4% left according to a nonprofit founded in 1986. In So Paulo State, the number of hectares of forest that was destroyed rose from 43 hectares to 218 hectares. There are two species of tapirs in the state. The manager of a state park in So Paulo told us that many adult palm trees were felled in a single week in 2019. The forest ceases to exist as we know it after that. Climate change is similar to this because people feel nothing is happening. Villar said it was a tragedy.
The findings from the study were published during the 15th Conference of the Parties to the Convention on Biological Diversity (CBD COP15), which was held in October of 2021. A fund was set up to allow the implementation of actions for the protection and rehabilitation of ecosystems. The 26th Conference of the Parties to the UN Conference on Climate Change (COP26), held in Glasgow, Scotland, from October 31 to November 13, 2021, focused on the impact of climate change and ways to mitigate it.
Accumulation of knowledge.
The UNESP research group has been studying these topics for a decade. The importance of tapirs and peccaries to the nitrogen cycle in tropical forests was shown for the first time in an article in a publication. The group's findings on the impact of interactions between palms and large mammals on the nitrogen cycle can now be placed alongside its research on primary productivity in the latest study.
A previous paper by the group showed the contribution of tapirs and peccaries to plant diversity and abundance.
An article signed by Villar and Patrcia Medici, a Brazilian biologists who focuses on tapirs, showed that diversity loss was lower in Atlantic Rainforest areas used by these animals than in areas from which they are excluded.
The world's largest database on the Lowland Tapir is led by Medici. She received the 2020 Whitley Gold Award, which was given to support grassroots conservativism in the global South.
Method.
The group conducted a number of exclosure experiments in two areas of Atlantic Rainforest to analyze the effects on tropical plant communities and primary productivity. Exclosure experiments are designed to determine how areas will develop if animals are excluded.
Medium- and large-bodied mammals are not allowed in the experimental plots. The northern part of the Serra do Mar State Park contains both sites. A heavy-traffic highway runs between them.
There are fifteen pairs of plots at every site, with one open plot for control and one exclosure plot. The plots were 5 m x 3 m. The area of damage to artificial seedlings, seedling recruitment, plant biomass and species richness was measured in three separate plots. The forest structure was measured from the center of the plots.
The landscape-scale consequences of the functional loss of large mammal herbivores could be compared in defaunated areas without tapirs or peccaries. Small animals such as agoutis, collared peccaries, brocket deer, and pacas did not affect the environment.
Villar said that the article shows how the animals structure primary productivity and the forest spatially, not how communities change over time.
Large herbivores have positive and negative effects on the spatial structure of plant communities, as a result of their interactions with palms in non-defaunated forest areas. They did not have a consistent effect on plant recruitment or species richness across the palm density, but they did have a negative effect on seedling productivity.
The analysis of camera trap data pointed to a key role played by T. peccari.
Next steps for the research line will include analyzing the influence of large mammals on these cycles, on the links between soil, understory and canopy, on the vertical and horizontal structure of the forest, and on other important functional groups.
The spatial structure of seedling communities and productivity in Neotropical forests are affected by large herbivore-palm interactions. The article is titled "pecon.2021.10.005".
A study shows that tapirs and large peccaries are key to ecological balance in Neotropical forests.
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