Researchers studying the ant Formica japonica found that rice straw biochar applied at moderate levels, especially 2.5% to 5%, improved several colony behaviors linked to soil health. Ants in moderately amended soils showed stronger habitat preference, built larger and more complex nests, found food more quickly, and maintained more effective social recognition. However, when the biochar dose reached 10%, the benefits declined and ant survival dropped sharply.
"Soil restoration is not only about improving nutrients or pH," said corresponding author Bo Pan. "It is also about protecting the living engineers that keep soil ecosystems working. Our results show that ants can respond very positively to biochar, but only within an appropriate application range."
Biochar is produced when biomass is heated under limited oxygen. Because it can improve soil structure, increase carbon storage, and help retain nutrients, it has attracted global interest as a tool for sustainable agriculture and ecological restoration. Yet most studies have focused on plants, microbes, or chemical properties of soils. The effects of biochar on soil animals, especially social insects that shape ecosystem processes through collective behavior, remain less understood.
Ants are among the most important soil animals. By digging nests, moving food, redistributing nutrients, and interacting with other organisms, they influence soil aeration, water movement, seed dispersal, and community balance. In this study, the researchers tested how different biochar concentrations affected the behavior of F. japonica, a common Asian ant species.
At 5% biochar, ants showed the strongest overall performance. Their nest tunnel area increased to more than twice that of many other treatments, suggesting enhanced soil engineering activity. Their maze success rate reached 87.5%, compared with 57.5% in the control group, and their food-finding time was greatly reduced. Ants exposed to moderate biochar also showed stronger defensive behavior toward invasive red fire ants and maintained peaceful behaviors, such as antennation and grooming, with nestmates.
"These behaviors matter because they are directly connected to ecological functions," said first author Sha Liu. "When ants build more complex nests and forage more efficiently, they can improve soil porosity, nutrient cycling, and biological interactions in ways that support ecosystem recovery."
The study also revealed a clear warning. At 10% biochar, ant survival fell to about 55% after 10 days, and foraging and social behaviors were weakened. The researchers linked this decline to a combination of high soil alkalinity and environmentally persistent free radicals, which may create physiological stress for soil organisms.
The findings suggest that biochar effects follow a dose-dependent pattern: beneficial at moderate levels, but potentially harmful when overapplied. This has practical importance for restoration projects, farmland management, and large-scale biochar deployment.
The researchers emphasize that soil animals should be included in future biochar safety assessments. Instead of evaluating biochar only through plant growth or soil chemistry, restoration planning should also consider how amendments affect organisms that actively maintain ecosystem functions.
"As biochar use expands, we need application strategies that support whole ecosystems," Pan said. "Our study shows that ants can serve as sensitive indicators of whether biochar is helping soil life or placing it under stress."
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Journal Reference: Liu, S., Xiong, D., Zeng, L. et al. Biochar application enhances ant (Formica japonica) ecological functions as indicated by their social behaviors. Biochar 8, 77 (2026).
https://doi.org/10.1007/s42773-026-00594-z
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
