Effects of Simulated Acid Rain on Soil Respiration of Pinus massoniana

In order to understand the impact of acid rain on soil respiration of P. Massoniana, a field study with 3 simulated acid rain levels (pH2. 5, 4. 0 and 6. 0) were conducted. Measurement of soil respiration was made using a LI-8100 soil CO2 emission system, the soil temperature at 10 cm depth also was recorded. Results show that: (1) The soil respiration of P. Massoniana under different acid rain levels fluctuated with distinct seasonal patterns and the soil respiration rate was influenced significantly by soil temperature. The mean rate of soil respiration under pH2.5 level were 1.79μmol m-2s-1, and increased 16% under control level (pH6.0) respectively. The mean rate of root respiration under pH2.5 level were 1.03μmol m-2s-1, and increased 12% under control level (pH6.0) respectively.(2) Significant relationships between soil respiration and soil temperature at 10 cm under different acid rain levels of P. massoniana found, which could be best described by exponential equations. The regression equations had more predicative capability than those using only temperature as a single independent variable. (3) The Q10 (temperature sensitivity coefficient of soil respiration) values at pH2.5, 4.0 levels of P. Massoniana were 1.40, 2.05, respectively. Compared with which at control level, the Q10 values tended to increase.