Abstract: Open-topped chamber method was used to study the effects of elevated CO2 concentration (700 μmol mol-1) on the superoxide anion (O〖SX(B-*3〗-〖〗·〖SX）〗2) generation rate, hydrogen peroxide (H2O2) content, and activities of superoxide dismutase (SOD) and crucial enzymes in AsA-GSH cycles in the needles of Pinus tabulaeformis in Shenyang urban area. After a short period (2 months) exposure to the elevated CO2, the superoxide anion generation rate and H2O2 content in P. tabulaeformis needles decreased and the SOD, APX, MDAR, DHAR and GR activities increased, being helpful to the enhancement of P. tabulaeformis anti-oxidative capability. However, a longer period (> 60 days) of exposure might have reverse effects.

Key words: Limestone, Degraded ecosystem, Soil enzyme