Dynamics of soil CO₂ profiles of Pinus sylvestris var. sylvestriformis seedlings under CO₂ concentration doubled

The gas-well system permanently installed in the soil was adopted for studying the dynamic relationship between CO₂ profiles and seedling root growth of Pinus sylvestris var. sylvestriformis (Takenouchi) Cheng et C. D. Chu. The study was conducted in the Open Research Station of Changbai Mountain Forest Ecological System, The Chinese Academy of Sciences from 1999 to 2001. Four treatments were arranged in the rectangular open-top chambers (OTCs) : ambient CO₂ + no-seedling, 700 μmol/mol CO₂ + no-seedling, ambient CO₂ + seedlings, 700 μmol/mol CO₂ + seedlings. By collecting and analyzing soil gas synchronously, it was found that the dynamics of CO₂ profiles were related to the biological activity of seedlings. There were more roots distributed in the top soil and the boundary layer across soil and sand, which made more contributions to the CO₂ profiles due to respiration root. Compared with the ambient CO₂, elevated CO₂ led to the peak of CO₂ concentration distribution shifted from soil surface layer to the boundary layer as seasonally growing of seedling roots. It is suggested the gas-well system is an inexpensive, non-destructive and relatively sensitive method for study of soil CO₂ concentration profiles.