A new field study reveals that biochar, a carbon-rich material made from plant residues, can significantly restore soil health and nitrogen availability in forests affected by acid rain. The findings highlight a promising, nature-based solution for protecting ecosystems under increasing environmental stress.
"Soil nitrogen is the foundation of ecosystem productivity, but acid rain disrupts this balance," said lead author Yuanyuan Feng. "Our results show that biochar can not only counteract soil acidification but also actively rebuild the biological processes that sustain nitrogen cycling."
Acid rain has long been recognized as a major environmental challenge, especially in forest ecosystems. It lowers soil pH, depletes nutrients, and disrupts microbial activity, ultimately reducing the availability of nitrogen needed for plant growth. One critical component of this process is acid-hydrolyzable nitrogen, a key pool of bioavailable organic nitrogen that responds quickly to environmental change.
To investigate how biochar influences this nitrogen pool, researchers conducted a two-year field experiment in a plantation forest dominated by oak trees. They simulated acid rain conditions and applied biochar derived from forest litter, allowing them to observe real-world interactions between soil chemistry, microbes, and nutrient cycles.
The results were striking. Under acid rain conditions, biochar increased soil pH and boosted total acid-hydrolyzable nitrogen by nearly 65 percent. Several important nitrogen fractions also rose substantially, including acid-amino acid nitrogen and acid-amino sugar nitrogen, both of which play essential roles in nutrient storage and slow release.
Beyond chemical improvements, biochar triggered major biological changes in the soil. It enhanced microbial biomass and increased nitrogen use efficiency, meaning soil microbes were better able to retain and recycle nutrients. The study also found that biochar reshaped microbial communities, promoting more complex bacterial networks while simplifying fungal interactions.
"These biological shifts are key," Feng explained. "We found that microbial processes, rather than purely chemical factors, were the dominant drivers of nitrogen accumulation. Biochar works by reprogramming the soil ecosystem."
Advanced statistical modeling confirmed that biological factors accounted for a larger share of changes in nitrogen pools than chemical properties alone. In particular, microbial nitrogen use efficiency and microbial biomass were identified as the strongest predictors of how nitrogen fractions responded to biochar.
Importantly, the influence of biochar exceeded that of acid rain itself. While acid rain typically reduces soil nitrogen availability, biochar reversed this trend and established a more resilient system capable of maintaining nutrient balance.
The findings suggest that biochar offers a dual benefit. It neutralizes soil acidity while simultaneously enhancing the biological machinery responsible for nutrient cycling. This combination makes it especially valuable for managing forests exposed to long-term acid deposition.
As climate change and industrial emissions continue to alter atmospheric chemistry, strategies that improve soil resilience are becoming increasingly important. Biochar, produced from agricultural or forestry waste, also provides a sustainable option that can contribute to carbon sequestration.
"Our study provides a mechanistic understanding of how biochar regulates nitrogen under acid stress," Feng said. "This opens new opportunities for using biochar in sustainable forest management and ecological restoration."
The researchers emphasize that future work should explore how different types and application rates of biochar perform across diverse ecosystems. Still, the current findings offer strong evidence that this low-cost material could play a vital role in safeguarding soil health and supporting long-term ecosystem stability.
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Journal Reference: Feng, Y., Liu, Y., Liu, J. et al. Biochar-driven biological regulation dominates acid-hydrolyzable nitrogen accumulation in plantation soils under acid rain stress. Biochar 8, 55 (2026).
https://doi.org/10.1007/s42773-026-00572-5
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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.
