Soil organic C (SOC) accumulation is known to increase by practices of increasing plant residue C inputs, while the SOC stabilization efficiency relative to C inputs is variable. The SOC stabilization efficiency in a Kastanozem soil (up to 21% of C inputs) is much greater than the global average (0.7%). To test whether litter is preserved by transformation into the mineral-associated SOC pool in a Kastanozem soil, we conducted a four-year incubation study of ¹³C-labeled maize residue in Saskatchewan, Canada. We monitored whether litter residue inputs are transformed and stabilized into the mineral-associated heavy fraction (>1.60 g cm⁻³). The litter decomposition rates in our study were the lowest among the global dataset due to the limited microbial activities under cold and arid climate. Fractionation of SOC into light and heavy fractions (< or >1.60 g cm⁻³, respectively) and subsequent analysis using nuclear magnetic resonance spectroscopy indicated that both the light and heavy fraction pools of transformed maize litter were enriched by microbial lipids, along with aromatic and carboxylic groups. The heavy fraction exhibited the lower decomposition rates than the light fraction due to selective loss of cellulose. This leads to the greater SOC stabilization in the heavy fraction (14% of the litter input) after the 4-year incubation period, compared to the light fraction (7%). Global temperature-dependency of microbial activities can account for slow litter decomposition under semi-arid and cold prairie, while the high stabilization efficiency of the litter-derived C is supported by microbial transformation and the relatively high capacity of mineral association in Kastanozem soils.

众所周知，通过增加植物残渣碳输入量，土壤有机碳（SOC）积累会增加，而相对于碳输入量的SOC稳定效率却是可变的。Kastanozem土壤中的SOC稳定效率（高达C输入的21％）远高于全球平均水平（0.7％）。为了测试垃圾是否通过转化成Kastanozem土壤中与矿物相关的SOC库而得以保留，我们在加拿大萨斯喀彻温省进行了为期四年的对^13种C标记玉米残留物进行孵化研究。我们监测了垃圾残留物输入是否被转化并稳定为与矿物相关的重质馏分（> 1.60 g cm ^-3）。在我们的研究中，凋落物分解率在全球数据集中是最低的，因为在寒冷和干旱的气候下微生物活动有限。将SOC分为轻质和重质组分（<或> 1.60 g cm ^-3分别）和随后使用核磁共振波谱的分析表明，转化后的玉米凋落物的轻质和重质组分库均富含微生物脂质以及芳香族和羧基基团。由于纤维素的选择性损失，重组分显示出比轻组分更低的分解速率。与轻质部分（7％）相比，在孵化4年后，重质部分（垫料输入的14％）的SOC稳定性更高。微生物活动的全球温度依赖性可以解释半干旱和寒冷大草原下凋落物的分解缓慢，而微生物转化和Kastanozem土壤中较高的矿物缔合能力支持了凋落物衍生的C的高稳定化效率。