Effects of submergence on photosynthesis and growth of Pterocarya stenoptera (Chinese wingnut) seedlings in the recently-created Three Gorges Reservoir region of China

Chinese wingnut (Pterocarya stenoptera) is the dominant native tree species in the riparian zone of the Three Gorges Reservoir region of China. Water treatments of continuous wet soil (WS) and submergence of the soil (SS) were imposed on 4-month-old Chinese wingnut seedlings for 12 months. The effects of water treatment on photosynthesis and growth were investigated after 2 and 12 months compared to a control (C). Submergence of the soil resulted in significant reductions in net photosynthetic rate (Pn), and stomatal conductance (g (s)) as compared to C. However, stomatal conductance in wet soil treatment was maintained comparable to that of C, although net photosynthetic rate was reduced significantly. Overall, intrinsic water use efficiency (WUE (i) ) under submergence of the soil was not significantly different from that of C, but significantly higher than that of the wet soil treatment. The intrinsic water use efficiency in the wet soil treatment was also significantly decreased compared to that in the control. During the entire experiment, growth and biomass of Chinese wingnut seedlings were significantly reduced due to adverse impacts of the submergence of the soil or wet soil treatment. These results suggest that Chinese wingnut seedlings less than 1-year-old would probably need intensive soil water management for sound growth. In the Three Gorges Reservoir region, adequate draining activities should be considered for this species' regeneration.