Effects of elevated CO₂ on growth of Pinus densiflora seedling and enzyme activities in soil

Atmospheric CO₂ concentrations have increased exponentially over the last century and, if continued, are expected to have significant effects on plants and soil. In this study, we investigated the effects of elevated CO₂ on the growth of Pinus densiflora seedling and microbial activity in soil. Three-year-old pine seedlings were exposed to ambient as well as elevated levels of CO₂ (380 and 760 ppmv, respectively). Growth rates and C:N ratios of the pine seedlings were also determined. Dissolved organic carbon content, phenolic compound content, and microbial activity were measured in bulk soil and rhizosphere soil. The results show that elevated CO₂ significantly increased the root dry weight of pine seedling. In addition, overall N content decreased, which increased the C:N ratio in pine needles. Elevated CO₂ decreased soil moisture, nitrate concentration, and the concentration of soil phenolic compounds. In contrast, soil enzymatic activities were increased in rhizosphere soil, including β-glucosidase, N-acetylglucosaminidase and phosphatase enzyme activities. In conclusion, elevated CO₂ concentrations caused distinct changes in soil chemistry and microbiology.