Understanding the process of carbon (C) sequestration under biochar amendment is crucial to mitigate climate change. However, the actual annual C sequestration rates after biochar application and underlying mechanisms at a scale of soil aggregates remain unclear. Thus, the C sequestration rates based on a net ecosystem C budget approach were investigated during a consecutive 6 years paddy field (2012–2018). Further, soil samples were collected in 2018 to identify the effects of long-term biochar (20 or 40 t ha⁻¹ applied in 2012) amendment on 1) C sequestration by determining C hydrolyzing activities and mineralization in aggregate size classes and 2) C sequestration between aggregates using the ¹³C natural abundance. The results showed that biochar-induced annual C sequestration rate decreased during the first two years, whereas it increased during the following four years. The lower ecosystem respiration (-4%) and higher crop yield (+9%) explained the latter C sequestration, compared to N treatment. Relative to N treatment, six years aged biochar decreased soil total organic C (TOC) mineralization in the bulk soil (-12 %), macroaggregate (MacroA, 250−2000 μm, -38 %) and microaggregate (MicroA, 53−250 μm, -19 %) size classes, but increased in silt (2−53 μm, +5%) and clay (0.1−2 μm, +24 %) size classes. Partial least squares path modeling revealed that the decrease in activities of β-glucosidase (-13 %), α-glucosidase (-20 %), cellobiohydrolase (-17 %) and xylanase (-2.5 %) and the improvement in soil structure increased C accumulation. The ¹³C natural abundance showed that Δ¹³C (δ¹³C of aggregates – δ¹³C of bulk soil) decreased by increasing aggregate size. Biochar increased probability of C flow from MacroA to MicroA, relative to without biochar amended treatment. Thus, biochar protected low molecular weight C compounds in the MacroA, with subsequent fast transfer into MicroA, which having long storage and the highest stable C content among the aggregate size classes. Consequently, increase in C protection via transferring C from MacroA to MicroA and decrease in soil hydrolases activities induced by biochar in MacroA and MicroA contribute to the high C sequestration potential.

了解生物炭修正过程中的碳固存过程对于缓解气候变化至关重要。但是，尚不清楚在施用生物炭后的实际年固碳率和潜在的机制。因此，在连续6年的稻田（2012-2018年）中，研究了基于净生态系统碳预算方法的碳固存率。此外，在2018年收集了土壤样品，以确定长期生物炭（2012年使用20或40 t ha ^-1）修正案对1）固碳的影响，方法是确定骨料尺寸类别中的C水解活性和矿化作用，以及2）C使用^13的集合体之间的隔离C自然丰度。结果表明，生物炭引起的年固碳率在头两年下降，而在随后的四年中上升。与氮处理相比，较低的生态系统呼吸（-4％）和较高的农作物产量（+ 9％）解释了后者的碳固存。相对于氮处理，六年生物炭使散装土壤中土壤总有机碳（TOC）矿化减少（-12％），大型骨料（MacroA，250-2000μm，-38％）和微骨料（MicroA，53-250μm （-19％）大小等级，但淤泥（2-53μm，+ 5％）和黏土（0.1-2μm，+ 24％）大小等级有所增加。偏最小二乘路径模型表明，β-葡萄糖苷酶（-13％），α-葡萄糖苷酶（-20％），纤维二糖水解酶（-17％）和木聚糖酶（-2.5％）的活性下降以及土壤结构的改善均增加C积累。的¹³ Ç天然丰度表明，Δ ¹³ C（δ ¹³集料的Ç - δ ¹³土体的C）降低，通过增加的聚集体尺寸。相对于未经生物炭改良的处理，生物炭增加了从MacroA到MicroA的C流动的可能性。因此，MacroA中的生物炭保护了低分子量的C化合物，随后又迅速转移到MicroA中，该化合物具有较长的存储时间，并且在总尺寸类别中具有最高的稳定C含量。因此，通过将C从MacroA转移到MicroA来增加C保护作用，并降低由MacroA和MicroA中的生物炭引起的土壤水解酶活性，这有助于高C螯合潜力。