The remarkable soil carbon sequestration and greenhouse gas mitigation effects of biochar have spurred great interest in exploring ways to maximize its benefits. However, it remains unclear how biochar application depth impacts soil carbon dioxide (CO₂) emissions and methane (CH₄) uptake in upland soil. Therefore, we carried out a 16-month field experiment in a dryland agricultural system to answer the above questions. Woody biochar (20 t ha⁻¹) was mixed into three soil layers: 0–10 cm (BC_0-10cm), 10–20 cm (BC_10-20cm), and 0–20 cm (BC_0-20cm). Soil without biochar addition was used as the control (CK). We monitored soil CO₂ and CH₄ fluxes continuously and determined the metabolic quotient (qCO₂) and the sensitivity of soil respiration to temperature (Q₁₀). The results indicated that CO₂ emissions, CH₄ uptake, qCO₂ and Q₁₀ were significantly affected by biochar application depth. Overall, compared with CK, BC_0-10cm increased total CO₂ emissions by 10.13%, while BC_10-20cm and BC_0-20cm showed no significant effect. BC_0-10cm and BC_0-20cm exhibited greater soil CH₄ uptake enhancement than BC_10-20cm, but the enhanced CH₄ uptake resulted in limited net greenhouse gas mitigation. BC_10-20cm and BC_0-20cm had a lower qCO₂ than the other treatments, which likely increased the carbon use efficiency and decreased the stress on soil microbes, but BC_0-10cm showed the opposite effect. In addition, BC_0-10cm significantly reduced Q₁₀ mainly due to the enhanced lability of the native carbon and microbial activities. Changes in environmental factors in the 0–10 cm soil largely explained the variations in CO₂ emissions, CH₄ uptake and Q₁₀ (>88%). Nevertheless, the enhanced microbial biomass in the 10–20 cm soil helped lower qCO₂ in the whole 0–20 cm layer. In summary, adding biochar to surface soil (0–10 cm) likely accelerates carbon loss, due to the strong shift in the environment of the surface soil caused by complex interactions among hydrothermal conditions, nutrient levels (i.e., N, NH₄⁺, NO₃⁻ and available P) and labile carbon. However, adding biochar to subsurface soil (10–20 cm) can effectively avoid severe disturbance of the surface soil environment and thus benefit soil carbon sequestration in the long term.

生物炭在土壤碳固存和减少温室气体方面的显着效果激发了人们对探索最大限度地利用其效益的兴趣。但是，目前尚不清楚生物炭的施用深度如何影响旱地土壤中的二氧化碳（CO ₂）排放量和甲烷（CH ₄）吸收量。因此，我们在旱地农业系统中进行了为期16个月的田间试验，以回答上述问题。木本生物炭（20吨公顷^-1）混合成三个土层：0-10厘米（BC _0-10cm），10-20厘米（BC _10-20厘米），和0-20厘米（BC _0-20CM）。未添加生物炭的土壤用作对照（CK）。我们监测了土壤中的CO ₂和CH ₄连续地通量，并确定代谢商（qCO ₂）和土壤呼吸对温度的敏感性（Q ₁₀）。结果表明，生物炭施用深度对CO ₂排放，CH ₄吸收，qCO ₂和Q ₁₀有显着影响。总体而言，与CK相比，BC _0-10cm的总CO ₂排放量增加了10.13％，而BC _10-20cm和BC _0-20cm则无明显影响。BC _0-10cm和BC _0-20cm比BC _10-20cm表现出更大的土壤CH ₄吸收增强，但是增加的CH ₄吸收导致有限的净温室气体减排。BC _10-20厘米和BC _0-20CM具有更低QCO ₂比其他处理，这可能增加了碳的利用效率和对土壤微生物的应力减小，但BC _0-10cm表现出相反的效果。此外，BC _0-10cm显着降低了Q _10，这主要是由于天然碳的不稳定性和微生物活性增强。0–10厘米土壤中环境因素的变化在很大程度上解释了CO ₂排放，CH ₄吸收和Q _{10的变化。}（> 88％）。然而，在10–20 cm的土壤中增加的微生物生物量有助于降低整个0–20 cm层中的qCO ₂。总之，由于热液条件，养分水平（即N，NH ₄ ⁺， NO ₃ ^-和可用P）和不稳定的碳。但是，在地下土壤（10-20厘米）中添加生物碳可以有效避免严重破坏表层土壤环境，从而从长远来看有利于固碳。