We studied the soil organic carbon ( SOC) content distribution patterns of Betula albo-sinensis forest on the southern slope of the Qinling Mountains and determined the factors affecting those patterns .The average SOC content was (32.11± 3.77)g· kg-1 in the soil under Betula albo-sinensis forest, the average SOC content in virgin forest was (33.11±32.3 )g· kg-1 , in secondary forest was 31.59±3.94 g· kg-1 , and the average SOC content was significantly different between virgin forest and secondary forest .The same change appeared in different forest regions , however, there was no significant differ-ence on two slope aspects and three slope positions .By correlation analysis , the SOC content was positively correlated with elevation, stand age, shrub biomass and herb biomass , and negatively correlated with slope gradient , forest density and canopy density .By principal competent analysis , the elevation and gradient were the first principal competent affecting SOC content, the canopy density and the forest density were the second principal component , the shrub biomass and the herb biomass were the third principal component , and the stand age was the fourth component principal component accounting for 88.15%of the variance of SOC content .By stepwise regression analysis , the elevation , gradient, canopy density , shrub biomass and herb biomass were the primary factors affecting the SOC content .%以秦岭南坡红桦林为研究对象，利用标准地调查获得林分、地形、土壤和植被相关数据，分析红桦林土壤有机碳质量分数空间分异特征及其与林分因子和地形因子间的关系。结果表明：秦岭南坡红桦林土壤有机碳质量分数总体均值为（32．11±3．77）g· kg－1，变异系数为11．74％，其中原始红桦林土壤有机碳质量分数（33．11±3．23）g· kg－1，次生红桦林（31．59±3．94）g· kg－1，原始红桦林比次生红桦林高4．81％（p＜00．5）。差异分析结果表明：红桦林土壤有机碳质量分数在不同坡向和坡位未表现出显著差异。相关分析、主成分分析和逐步回归结果表明：红桦林土壤有机碳质量分数与海拔、林龄、灌木生物量和草本生物量呈显著正相关，与坡度、郁闭度和林分密度呈显著负相关，上述林分因子和地形因子转化的主成分方差累积贡献率为88．15％，其中海拔、坡度、郁闭度、灌木生物量和草本生物量是影响红桦林土壤有机碳质量分数的主要因子，并拟合出利用这5个因子估算秦岭南坡红桦林土壤有机碳质量分数的模型方程。
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