土壤碳氮沿海拔梯度变化及其耦合关系是山地生态系统碳氮循环研究的重要内容。为分析不同土层土壤有机碳，土壤全氮及有机碳活性组分在海拔梯度上的分布规律及相互之间的耦合关系，选取亚高山物种岷江冷杉（Abies faxoniana）原始林为研究对象，以卧龙邓生野牛沟岷江冷杉原始林2920-3700 m的样地调查数据为基础，分析不同土层土壤碳氮及活性组分沿海拔的变化规律，总结土壤有机碳稳定性沿海拔主要规律，从土壤有机碳活性组分和碳氮关系的角度揭示其对土壤有机碳沿海拔变化的影响。结果表明：1）腐殖质层土壤有机碳（SOC）随海拔升高逐渐增加，与温度显著负相关，轻组有机碳（LFOC）及颗粒态有机碳（POC）随海拔上升均表现先增加后降低的趋势，土壤全氮（TN）随海拔变化不显著，但林线处LOFC、POC和TN均显著增加；0-10 cm土壤有机碳及全氮则表现为双峰特征，峰值分别在3089 m和3260 m处，与年均温度无显著关系。2）LFOC及POC在腐殖质层和0-10 cm土层中所占比例较大，是表征土壤有机碳含量沿海拔变化规律的主要活性组分，腐殖质层LFOC/SOC和POC/SOC随海拔上升逐渐增高，0-10 cm层则逐渐降低，暗示腐殖质层有机碳稳定性沿海拔逐渐降低，0-10 cm有机碳稳定性逐渐升高。3）SOC与TN显著正相关，SOC是影响TN的主要因子，但腐殖质层TN与有机碳活性组分无显著相关关系。4）土壤C/N和微生物量C/N在3177 m大于25：1，是引起土壤有机碳含量显著降低的主要因素。
Distribution characteristics of soil organic carbon (SOC) and total nitrogen, as well as the coupling relation between SOC and TN are important areas for research in the carbon and nitrogen cycling in mountain ecosystem. In this study, vertical transects in Abies faxoniana forests at altitudes between 2920 m to 3700 m in Wolong were investigated to determine the distribution of soil organic carbon (SOC), soil total nitrogen (TN), and labile soil organic carbon fractions (LFOC) along the altitudinal gradient, as well as the coupling relationships among them. The results showed that: i) SOC content in the humus layer increased along the altitudinal gradient and had a negative relationship with temperature. LFOC and particle state organic carbon (POC) increased followed by a decrease along the altitudinal gradient. TN did not significantly change with increasing altitude, whereas LOFC, POC, and TN significantly increased near the forest line. TN and SOC in the 0-10 cm depth layer were double-peaked as altitude increased, with peaks at 3089 m and 3260 m, respectively. ii) The major fraction of LFOC and ROC were observed in the humus layer and the 0-10 cm depth layer of soil. In addition, LFOC/SOC and POC/SOC in the humus layer increased along the altitudinal gradient, whereas LFOC/SOC and POC/SOC decreased in the 0-10 cm layer of soil along the altitudinal gradient, indicating the stability of SOC in the humus layer decreased along the gradient, whereas the stability of SOC in the 0-10 cm soil layer increased as altitude increased. iii) SOC was significantly and positively correlated with TN, and SOC content was the main factor affecting the TN. However, TN did not exhibit a significant relationship with the labile fractions of SOC in the humus layer. iv) The ratio of C/N in soil and that in microbial biomass were higher than 25 at an elevation of 3177 m, which was the main factor causing the significant decrease in the SOC content.