Nitrogen (N) deposition is a major environmental issue that affects global climate change. Study of the rhizosphere has become a research frontier in underground ecology. However, the effects of N deposition on N and phosphorus (P) supplies, and organic carbon (OC) mineralization in the rhizosphere of trees in subtropical China remains unclear, and whether the underlying mechanisms differ between tree species need to be determined. In the present study, a coniferous tree (Cunninghamia lanceolata) and a broadleaf tree (Liquidambar formosana) each 15 years of age were selected at the Qianyanzhou Experimental Station of the Chinese Academy of Sciences to evaluate in situ N deposition. Trees were treated with 10 g N m^-2 a^-1 and compared to the control. After 3 years, rhizosphere and bulk soils for both tree species were collected to assess pH value, mineral N, available P, water-soluble organic carbon (WSOC), and the dynamic of OC mineralization following 34 days incubation. Rhizosphere effects of all measured variables were assessed using ratios of rhizosphere to bulk soil, and OC mineralization parameters at early (0-9 d), middle (9-19 d), and late stages (19-34 d) were obtained using the traditional dynamics model. N deposition significantly decreased rhizosphere and bulk soil pH, available P in rhizosphere soil of C. lanceolata, and OC mineralization intensity in bulk soil of L. formosana. N deposition also increased NO₃^--N in bulk soil of L. formosana and WSOC in bulk soil of C. lanceolata (P < 0.05). In contrast, NH₄⁺-N, mineral N, and the ratio of mineral N to available P in rhizosphere and bulk soils did not differ significantly between both species. N deposition significantly increased OC mineralization rates in C. lanceolata rhizosphere and bulk soil by 71.2% and 41.2%, respectively; but decreased OC mineralization rates in L. formosana rhizosphere and bulk soil by 10.6% and 44.1%, respectively. N deposition significantly decreased both the rhizosphere effects of NO₃^--N and the early OC mineralization rate in L. formosana, but increased its late OC mineralization rate; whereas the rhizosphere effects of all measured variables in C. lanceolata showed no significant differences between control (CK) and N treatments. N deposition significantly altered soil nutrient supply and OC stability, and the synchronicity of responses to N deposition between rhizosphere and bulk soil was stronger for C. lanceolata than for L. formosana. We concluded that response of rhizosphere processes to N deposition differs between conifer and broadleaf tree species. The response of rhizosphere OC mineralization to N deposition showed a positive effect for C. lanceolata, and a negative effect for L. formosana, as their rates preferentially increased and decreased, respectively with N deposition. This difference could be attributed to their nutrient requirements and root traits, because C. lanceolata prefers fertile soil and are not associated with mycorrhizal fungi, whereas L. formosana can tolerate infertile soil with roots that are associated with mycorrhizal fungi. To our knowledge, the present study is the first to report on the effects of N deposition on the interactions between supplies of N and P in soil, and the stability of OC in different tree species of subtropical China, and reports divergent mechanisms in coniferous versus broadleaf tree species.