Abstract:

Litter input influences the soil organic carbon (SOC) mineralization process, with its effect primarily governed by litter C/N, soil fertility, and temperature conditions. However, the combined impact of these three factors remains unclear. This study used low-fertility soil (LF) and high-fertility soil (HF), adding seven different C/N ratio litters and setting incubation temperatures of 23 ℃ and 33 ℃, with constant temperature and no light exposure. CO₂ emissions were dynamically monitored to investigate how SOC mineralization responds to the three factors. Results showed that litter addition significantly increased peak CO₂ emission rates, and litter with a C/N ratio less than 30 had a more pronounced effect on peak CO₂ emission rates compared to litter with a C/N ratio greater than 30. The peak CO₂ emission rate was also affected by soil fertility and incubation temperature, with the highest peak CO₂ emission rate observed under the HF-33 ℃ condition. Litter with a C/N ratio below 30 significantly increased cumulative CO₂ emissions, with maximum increases of 407%, 304%, 345% and 160% under LF-23 ℃, LF-33 ℃, HF-23 ℃ and HF-33 ℃ conditions, respectively. Correlation analysis showed a negative relationship between SOC mineralization rate and litter C/N ratio, suggesting that lower-quality litter inhibits SOC mineralization. Under LF-23 ℃, LF-33 ℃, HF-23 ℃ and HF-33 ℃ conditions, compared to litter with the lowest C/N ratio (CN1), adding litter with the highest C/N ratio (CN7) reduced SOC mineralization rates by 3.53, 3.04, 1.71 and 2.06 times, respectively. Soil fertility influenced SOC mineralization, with the SOC mineralization rate in HF being 1.29 to 2.66 times higher than in LF. The effect of incubation temperature on SOC mineralization showed significant differences in HF, and compared to the CK, litter addition in HF significantly reduced the temperature sensitivity (Q₁₀) of SOC mineralization. Using the PLS-PM model, the study concluded that SOC mineralization results from the combined effects of litter C/N, soil fertility, and incubation temperature. Specifically, the litter C/N ratio exerted a significant negative effect on SOC mineralization, while soil fertility had a major positive effect, and the effect of temperature was relatively minor. The results contribute to a better understanding of how the input of exogenous organic matter with different C/N ratios affects SOC mineralization under various soil fertility and temperature conditions, as well as the underlying combined effects.

Key words: litter input, litter C/N ratio, organic carbon mineralization, CO₂ release rate, indoor cultivation, temperature sensitivity

摘要：

凋落物输入会影响土壤有机碳（SOC）矿化过程，其影响程度主要受凋落物C/N、土壤肥力和温度条件的影响，然而，这三因素的综合影响仍不清楚。以低肥力土壤（LF）和高肥力土壤（HF）为研究对象，分别添加7种不同C/N的凋落物，并设置培养温度为23 ℃和33 ℃，进行恒温避光培养，期间动态监测CO₂排放的变化，以揭示SOC矿化过程应对三因子的响应机制。结果显示，凋落物添加显著增加CO₂峰值排放速率，且与C/N>30的凋落物相比，添加C/N<30的凋落物对CO₂的峰值排放速率的促进作用更显著。CO₂峰值排放速率同时受土壤肥力和培养温度影响，HF-33 ℃条件下的CO₂峰值排放速率最高。添加C/N<30的凋落物显著增加了CO₂累积排放量，在LF-23 ℃、LF-33 ℃、HF-23 ℃和HF-33 ℃条件下，最大增幅分别为407%、304%、345%和160%。相关分析显示，SOC矿化率与凋落物C/N间呈负相关关系，这说明低质量凋落物会抑制SOC矿化。在LF-23 ℃、LF-33 ℃、HF-23 ℃和HF-33 ℃处理下，与凋落物C/N最低的CN1相比，添加C/N最高的CN7后，SOC矿化率的降幅分别达3.53、3.04、1.71和2.06倍。土壤肥力影响SOC矿化，HF的SOC矿化率较LF高1.29－2.66倍。培养温度对SOC矿化的影响在HF中表现出显著差异，与CK相比，在HF中添加凋落物显著降低了SOC矿化温度敏感性（Q₁₀）。综合PLS-PM模型可知，SOC矿化是凋落物C/N、土壤肥力和培养温度综合作用的结果。其中，凋落物的C/N比对SOC矿化产生显著的负效应，土壤肥力则对SOC矿化产生主要的正效应，而温度的正效应则相对较小。研究结果有助于进一步理解不同土壤肥力和温度背景下，C/N不同的外源有机物输入对SOC矿化的影响及其背后的综合效应。

关键词: 凋落物输入, 凋落物碳氮比, 有机碳矿化, CO₂释放速率, 室内培养, 温度敏感性