Abstract <p>Peatlands in permafrost regions store vast carbon reserves; however, their responses to enhanced nitrogen availability remain insufficiently understood, particularly regarding the contrasting responses of rhizosphere and bulk soils. The field study investigated the impact of different nitrogen addition levels (0, 12, and 24 g N m^–2 yr^–1) on soil organic carbon (SOC) fractions in the 0–20 cm layer of both rhizosphere (with plants) and bulk (without plants) soils associated with <i>Eriophorum vaginatum</i> L. in a permafrost peatland located in the Greater Khingan Mountains, Northeastern China. Short-term nitrogen addition had no significant effect on total SOC in either rhizosphere or bulk soil. During the early growth stage, nitrogen addition significantly increased dissolved organic carbon content in both rhizosphere and bulk soils by 17.8–40.8%. Low and high nitrogen treatments reduced particulate organic carbon (POC) in the rhizosphere by 29.8 and 33.0%, respectively, but increased POC in bulk soil by 49.6 and 49.8%. High nitrogen addition significantly decreased light fraction of organic carbon in bulk soil by 14.7%. In the late growth stage, POC in rhizosphere soils showed no significant differences among treatments; however, in bulk soils, low and high nitrogen additions increased POC by 25.0 and 25.3%, respectively, relative to the control. High nitrogen addition enhanced LOC by 17.4 and 12.9% in rhizosphere and bulk soils, respectively. DOC is primarily influenced by soil variant and growth stage, while POC is mainly regulated by growth stage. LFOC and LOC exhibit greater sensitivity to nitrogen addition.</p>