To obtain basic information for evaluating resistance of soil acidification for growth, net photosynthesis, $N_2$ fixation rate and nutrient status of Alnus firma and Alnus hirsuta seedlings grown in brown forest soil acidified with $H_2SO_4$ or $HNO_3$ solution were investigated (control (pH=5.9), LN (pH=5.0; Low levels of Nitric acid), HN (pH=4.0; High levels of Nitric acid), LS (pH=5.0; Low levels of Sulfuric acid), and HS (pH=4.0; High levels of Sulfuric acid)). The shoot dry weight of Alnus firma and Alnus hirsuta and the root dry weight of Alnus hirsuta seedlings grown in the HN, LS and HS were significantly less than that of the seedlings grown in the control. The Chlorophyll a/b ratio in leaves of Alnus firma at LN, LS and HS was significantly lower than that of control. The concentration of N in leaves of Alnus hirsuta at HS was significantly higher than that of control. The net photosynthetic rate of Alnus firma and Alnus hirsuta seedlings at LN and HN was higher than that of control. Based on the results, we concluded that the negative effects of soil acidification due to sulfate deposition are greater than those of soil acidification due to nitrate deposition on growth, net photosynthesis and $N_2$ fixation rate of Alnus firma more than Alnus hirsuta.