As the planet warms, soils are becoming an increasingly important part of the climate story. Soil organic carbon is one of the largest carbon stores on land, but higher temperatures can speed up microbial decomposition and release more carbon dioxide into the atmosphere. A new study published in Biochar suggests that the type of fertilizer used in forest soils may influence how strongly this process responds to warming.
Researchers tested a nanozeolite-coupled biochar-based phosphate fertilizer, known as NanoBP, in soil collected from an intensively managed Moso bamboo forest in subtropical China. Moso bamboo forests are highly productive and cover millions of hectares, making them important for regional carbon storage. However, their fast nutrient and carbon cycling also makes them sensitive to warming and intensive fertilization.
"Our study shows that not all phosphorus fertilizers affect soil carbon in the same way," said corresponding author Yongfu Li. "Although both fertilizer types supplied comparable phosphorus, the biochar-based nanozeolite fertilizer reduced carbon mineralization, while conventional phosphorus fertilizer increased soil-derived carbon dioxide emissions."
In a 56-day laboratory incubation, the team compared three treatments: no fertilizer, conventional chemical phosphorus fertilizer, and NanoBP. Soils were incubated at 25 °C and 35 °C to examine how fertilization affected soil organic carbon decomposition under warmer conditions. The researchers also measured Q10, an indicator of how sensitive carbon mineralization is to temperature change.
The results showed a clear contrast. Conventional phosphorus fertilizer increased cumulative soil-derived carbon dioxide emissions by 31 to 36 percent compared with unfertilized soil, suggesting that easily available phosphorus stimulated microbial decomposition of soil organic carbon. By contrast, NanoBP reduced soil-derived carbon dioxide emissions by 11 to 18 percent. Warming increased emissions across all treatments, but the increase was smaller under NanoBP.
The biochar-based fertilizer also reduced Q10 by about 8 percent across bulk soil, active carbon pools, and slow carbon pools. This means that soil carbon decomposition under NanoBP was less responsive to warming than in the control and conventional fertilizer treatments.
To understand why, the researchers looked beyond total phosphorus availability. They found that NanoBP increased microbial biomass and available phosphorus, but still suppressed key enzymes involved in cellulose breakdown, including β-glucosidase and cellobiohydrolase. NanoBP also reduced the abundance of two carbon-degrading functional genes, GH48 and cbhI. These microbial traits were among the strongest predictors of Q10.
"The mechanism appears to be microbial functional constraint rather than simply phosphorus supply," Li said. "NanoBP may create a soil environment where microbes have more available phosphorus, but their ability to decompose carbon-rich plant material is limited."
The study suggests that the composite structure of NanoBP, which combines nanozeolite, biochar, phosphate, and mineral components, may help regulate nutrient release and reduce the accessibility of organic carbon to decomposers. This differs from conventional soluble phosphorus fertilizer, which can rapidly stimulate microbial activity and carbon turnover.
The authors caution that the study was conducted under controlled laboratory conditions and that field-scale validation is needed. Still, the findings provide a mechanistic basis for exploring biochar-based smart fertilizers as tools for carbon-conscious forest management.
"Fertilizer design is usually discussed in terms of crop productivity and nutrient efficiency," Li said. "Our results highlight another important dimension: how fertilizer form can shape microbial processes that determine whether soils lose or retain carbon under warming."
The study provides new insight into how advanced biochar-based fertilizers may support both nutrient management and soil carbon protection in subtropical bamboo forests.
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Journal Reference: Jiang, Z., Tang, C., Fang, Y. et al. Nanozeolite-coupled biochar-based phosphate fertilizer dampens warming-induced soil carbon loss by microbial functional constraints in Moso bamboo forests. Biochar 8, 112 (2026).
https://doi.org/10.1007/s42773-026-00620-0
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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.
