Abstract:

Characteristic parameters of photosynthesis in response to irradiance of 13 naturally-regenerated tree species, which were used for vegetation restoration in the dry-hot river valley of the Jinsha River, were studied and several main conclusions were drawn. It was theoretical and feasible to determine the weak light range by the descending point of light using efficiency on light response curve. The subsection functions provided a well-fitted simulating curve for photosynthetic response to irradiance. The determination of weak light region had significant effect on apparent quantum yield of photosynthesis (α) and dark respiration rate (R_d), however it had not obvious effect on light compensation point (LCP), light saturation point (LSP) and maximum apparent photosynthesis rate (P_max) . The variation ranges of α, R_d, LCP, LSP, P_max of 13 tree species in dry March respectively were 0.020 7～0.059 2 μmol CO₂·m^-2s^-1/μmolphotons·m^-2s^-1, -2.07～-0.31 μmol CO₂·m^-2s^-1, 14～37 μmolphotons·m^-2s^-1, 1 015～1 648 μmolphotons·m^-2s^-1, 3.09～19.32 μmol CO₂·m^-2s^-1. There were similar rank of the 13 species among the bases of the maximum apparent photosynthesis rate, the saturation light using efficiency and apparent quantum yield of photosynthesis, which suggested that if the tree species had a higher light using efficiency in weak light region and under the saturated light, they often had a higher maximum apparent photosynthesis rate.

Key words: dry-hot river valley, vegetation restoration, light response curve of photosynthesis, apparent quantum yield of photosynthesis, subsection function