Biochar modulates temperature sensitivity of soil N2O emissions: soil-specific mechanisms

Abstract Biochar is increasingly promoted as a strategy for mitigating soil nitrous oxide (N 2 O) emissions, yet its effect on the temperature sensitivity (Q 10 ) of N 2 O emissions remains poorly understood. In this study, short-term incubation experiments were conducted using two contrasting soils (agricultural and forest soils) amended with two biochar types (wood- and rice husk-derived) at three application rates (0, 1%, and 3%) under three temperatures (10 °C, 20 °C, 30 °C). We investigated how biochar alters Q 10 of N 2 O emissions and explored the underlying mechanisms. Results showed that cumulative N 2 O emissions increased with temperature in both soils, with higher Q 10 values in forest soils (1.63–2.84) than in agricultural soils (1.13–1.63). Only high-rate wood biochar (WH) significantly changed Q 10 , decreasing it in agricultural soils but increasing it in forest soils. In agricultural soils, WH strongly reduced NO 3 − –N availability and minimized its temperature response, intensifying substrate limitation and lowering Q 10 . In forest soils, biochar accelerated the decline of NH 4 + –N and slowed the increase of NO 3 − –N with temperature, suggesting tighter coupling between nitrification and nitrate-consuming processes. Although WH and high rate rice-husk biochar showed the smallest NO 3 − -temperature slopes, the unique properties of WH (e.g., low ash content, higher aromaticity, and larger pore size) may have promoted short-term NO 3 − retention, thereby strengthening temperature-coupled nitrification–denitrification turnover, which likely contributed to the higher Q 10 observed under WH. Partial least squares path modeling (PLS-PM) confirmed that temperature exerted stronger total effects on N 2 O emissions than biochar through changes in substrate availability, pH, and functional genes, while biochar acted as a secondary modulator. Overall, biochar regulated N 2 O Q 10 through soil-specific pathways, highlighting the need for soil-specific biochar application strategies under future climate change scenarios. Graphical Abstract