黑土层不同粒级结构下有机碳矿化的模拟研究

东北黑土坡耕地侵蚀沉积分异明显，且冻融交替频繁，但各坡位土层结构以及通气孔隙度随含水率和温度的季节性变化对有机碳矿化和CO₂扩散效率的影响机理尚不清楚。以典型黑土坡耕地为研究对象，采集未侵蚀区表土风干、筛分后，选取粗(0.5～1 mm)、细(<0.125 mm)两种粒级，分层回填，全粗、全细、上粗下细、上细下粗4种土柱模拟典型坡位土层结构，对比分析冻融与非冻融不同温度梯度下，各土层结构CO₂释放速率变化特征。结果表明：非冻融变温(5～30℃)条件下，各土层结构CO₂释放速率存在显著差异，其中上粗下细土层CO₂释放速率均值为14.45μg/(kg·h),显著高于其他土层，增幅达20%～59%,说明不同土层间土壤颗粒大小和上下堆叠关系对CO₂传输效率有重要调控作用。经两次冻融作用后，0～15℃变温培养中，各土层间无显著差异，上粗下细土层CO₂释放速率均值为4.17μg/(kg·h),略高于其他土层，说明冻涨融缩效应削弱了不同土层结构之间孔隙结构和联通性差...

Simulation of Organic Carbon Mineralization in Black Soil Layers with Different Particle Size Structures

On the rolling slopes in northeast China, erosion and deposition often result in distinct soil layer structures at different soil slope positions where frequent freeze-thaw cycles can further alter soil water and porosity distribution. However, how different soil layer structures with distinct porosity and connectivity respond to varying water and temperature changes, and how they affect soil organic carbon mineralization and CO₂ emissions are far from being fully understood. The Mollisol samles were collected from the farmlands with gentle and extended slopes in the northeastern China, air-dried and then sieved. Soil particles of two sizes, coarse(0.5～1 mm)and fine(<0.125 mm), were refilled into different soil columns to simulate four typical slope soil structures: all coarse structure all fine structure, upper coarse + lower fine structure, and upper fine + lower coarse structure. The soil columns were incubated and their CO₂ emission rates were measured at different temperature gradients to compare the different responses of the four soil structures to non-freeze-thaw and freeze-thaw conditions. The results show that under non-freeze-thaw conditions(over 5～30℃), CO₂ emission rates among the four soil structures differed significantly, the average CO₂ emission rate of the upper coarse + lower fine soil layers was 14.45 μg/(kg·h)which was 20%～59% higher than those of the other three soil structures, illustrating that the CO₂ transfer efficiency was profoundly influenced by soil particle size and their overlaying patterns; after two freezing-thawing cycles, the differences of CO₂ emission rates among the four soil structures became insignificant over 0～15℃, the average CO₂ emission rate of upper coarse + lower fine soil column was 4.17 μg/(kg·h)which was merely slightly higher than those of the other three soil structures implying that freeze-thaw could change the structure and connectivity of soil pores, thereby weakening the differences of soil layer structure on CO₂ emissions. These findings highlight the potential impacts of soil structure, especially the overlaying patterns and pore connectivity, onto CO₂ emissions, which can help advance the current understanding on carbon source potentials in erosion-deposition settings.