Abstract: A pot experiment was conducted with 2-year-old Guadua amplexifolia to study its NaCl tolerance. The results indicated that NaCl stress had significant effects on the physiological and biochemical characteristics of the plant. The salt injury was divided into 3 degrees, based on the leaf-abscission rate after 40-days exposure, i.e., noninjury (<10%), mild injury (10%-50%), and serious injury (>50%). The ion leakage and MDA content increased considerably over time, the relative conductivity of the plant exposed to 0.30% and higher salinity for 40 days was >50%, and the MDA content was higher than that at lower salinity. Both POD and SOD activities increased in the early days and then decreased with extended NaCl exposure. On the 40th day exposure, POD activity was the highest at 0.20% NaCl, while SOD activity was the highest at 0.30% NaCl. Osmoregulation substance such as free proline and soluble protein had the same trend. After 40 days exposure, the contents of free proline and soluble protein kept increasing in the plants exposed to 0.20% and lower salinity, while kept decreasing in those exposed to 0.30% and higher salinity. In summary, 0.30% and higher soil salinity was not suitable for the growth of G. amplexifolia.

Key words: Cunninghamia lanceolata, Mixed forest, Soil quality assessment, Soil function