Litter plays a crucial role in the formation and turnover of soil organic carbon (SOC). However, its impact on SOC in black soils with varying degradation levels remains unclear. With the typical black soils in northeastern China with different simulated degradation levels (slight, moderate, and severe), we comparatively analyzed the changes in total organic carbon (TOC), easily oxidizable organic carbon (EOC), particulate organic carbon (POC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) under silver poplar litter addition (LP) and maize straw addition (MS) versus a treatment without litter addition (CK) at 45 days (early stage), 90 days (mid stage), and 135 days (late stage) after litter addition in a field in-situ experiment. The results showed that: 1) For black soils at different degradation levels, TOC content generally followed the order of LP>MS>CK. The increase in TOC was relatively greater in moderately degraded black soils. Compared with the early stage, TOC content in both LP and MS treatments were significantly increased during the mid and late stages. 2) At the early stage of litter decomposition, in slightly degraded black soils, the LP treatment significantly reduced EOC and DOC contents by 35.8% and 7.7%, respectively. In moderately and severely degraded soils, LP treatment significantly increased both POC and DOC contents. MBC was significantly increased across black soils with different degradation levels. Under MS treatment, EOC increased by 32.7% only in moderately degraded soils, while POC and MBC increased significantly only in severely degraded soils respectively. At the mid stage of litter decomposition, DOC content significantly decreased while MBC significantly increased in slightly degraded black soils, with POC significantly reduced by 36.7% in MS treatment. In moderately degraded soils, LP significantly increased DOC by 41.9%, and MS significantly increased MBC by 29.2%. In severely degraded soils, LP and MS significantly increased MBC by 17.3% and 16.0%, respectively. EOC content increased significantly under both LP and MS only in moderately degraded soils. At the late stage of litter addition, POC content decreased by 13.7%-21.4% in slightly degraded black soils, increased by 25.0%-25.3% in moderately degraded black soils, while EOC in LP treatment significantly increased only in slightly degraded soils. In moderately degraded soils, DOC significantly decreased and MBC increased. In severely degraded soils, LP significantly increased DOC by 6.0%, and MS significantly increased MBC by 28.6%. 3) Total nitrogen was a key factor influencing SOC and its active components in black soils with different degradation levels. In conclusion, the response of soil organic carbon and its active components to litter addition varied across soils with different degradation levels. High-quality litter (LP) was more conducive to the formation of TOC. The transport and accumulation of SOC and its active components were jointly regulated by both litter type and soil quality.
凋落物对土壤有机碳的形成与周转具有重要作用,但凋落物对不同退化程度黑土土壤有机碳的影响尚不清楚。本研究在东北典型黑土区模拟不同退化程度(轻度、中度和重度)的黑土,通过田间原位控制试验,以不添加凋落物为对照(CK),对比分析了银中杨凋落物添加处理(LP)和玉米秸秆添加处理(MS)在凋落物添加45(前期)、90(中期)和135 d(后期)的土壤总有机碳(TOC)、易氧化有机碳(EOC)、颗粒有机碳(POC)、可溶性有机碳(DOC)、微生物生物量碳(MBC)的变化特征。结果表明:1)不同退化程度黑土TOC含量总体上表现为LP>MS>CK,其中,中度退化黑土的TOC增加幅度相对较大;与添加前期相比,后期LP和MS处理的TOC含量显著增加。2)在凋落物添加前期,LP处理在轻度退化黑土中EOC和DOC含量分别较CK显著降低35.8%和7.7%,在中、重度退化黑土中POC和DOC含量显著增加,MBC在不同退化程度黑土中均显著增加;MS处理EOC含量仅在中度退化黑土中显著增加32.7%,POC、MBC仅在重度退化黑土中显著增加。在凋落物添加中期,轻度退化黑土中两个凋落物添加处理DOC含量显著降低,MBC显著增加,MS处理POC含量显著降低了36.7%;在中度退化黑土中,LP处理DOC含量显著增加了41.9%,MS处理MBC显著增加了29.2%;在重度退化黑土中,LP、CS处理MBC分别显著增加了17.3%、16.0%;LP、MS处理EOC含量仅在中度退化黑土中显著增加。在凋落物添加后期,轻度退化黑土中两个凋落物添加处理POC含量降低了13.7%～21.4%,中度退化黑土中提高了25.0%～25.3%;LP处理EOC含量仅在轻度退化黑土中显著增加;两个凋落物添加处理在中度退化黑土中DOC显著降低,MBC显著增加;在重度退化黑土中LP处理DOC含量显著增加了6.0%,MS处理MBC显著增加了28.6%。3)全氮是影响不同退化程度黑土土壤有机碳及其活性组分的关键因子。综上,不同退化程度黑土土壤有机碳及其活性组分对凋落物添加的响应存在差异,高质量凋落物(LP)更有利于土壤TOC的形成,土壤有机碳及其活性组分的转运积累受凋落物种类及土壤质量的共同调控。.
Keywords: degraded black soil; litter addition; organic carbon fraction; soil organic carbon.