Abstract:In order to investigate the effects of acid rain on forest soil respiration, a simulated acid rain experiment was conducted in a northern subtropical secondary forest from March 2009 to January 2010. Acid rain treatments included CK(pH 6.4,deionized water), T1(pH 4.5), T2(pH 3.5) and T3(pH 2.5). A portable soil CO2 fluxes system was used to measure soil respiration rates. Results showed that soil respiration among all treatments had significant seasonal variation patterns. Mean soil respiration rates for CK, T1, T2 and T3 treatments were (3.20±0.21), (3.34±0.30), (3.51±0.06), (2.99±0.23)μmol/(m2·s), respectively. The experimental period was divided into three parts, which were non-growth period 1 (from February, 2009 to April, 2009), growth period (from Mary, 2009 to October, 2009), non-growth period 2 (from November, 2009 to January, 2010), respectively. A paired t-test analysis showed that simulated acid rain did not inhibit soil respiration, T1 and T2 tended to promote soil respiration in the non-growth period 1; T3 significantly inhibited soil respiration during growth period; simulated acid rain also promoted soil respiration during the non-growth period 2.Only T3 significantly inhibited soil respiration during the whole experimental period. During the whole experimental period, soil respiration showed an exponential relationship with soil temperature for each of the treatment. The Q10 (the respiratory flux at one temperature over the flux at a temperature 10 oC lower) values were 3.04, 2.73, 2.83 and 2.51 for CK, T1, T2, T3 treatments, respectively. Simulated acid rain significantly reduced the temperature sensitivity of soil respiration in the northern subtropical secondary forest.