Effects of drought and re-flooding on growth and photosynthesis of Carex schmidtii Meinsh: Implication for tussock restoration

Drought and flood are two common stresses on the growth and photosynthesis of wetland plants. Wetland plants experience the alternating drought-flooding conditions over an irregular time-scale. In order to investigate the effects of hydrological fluctuations on plant growth and photosynthesis, we subjected Carex schmidtii (a tussock-forming species) to five alternating drought-flooding conditions: consecutive drying treatment (D), moist treatment (W) and re-flooding treatments (RT) after 30 days (DF30), 40 days (DF40) and 60 days (DF60) of drought. Results showed that both D and RT had positive or negative interactive effects on the growth and photosynthesis of C. schmidtii. D treatment increased leaf area (21.69%) and plant mass (24.40%) by the 60th day; plant height and chlorophyll content decreased by 18.03% and 17.93% compared with those obtained under W conditions, respectively. RT were found to successfully recovery plant mass, chlorophyll content and photosynthesis of C. schmidtii, whereas flooding condition inhibited plant performance in the late growth stage. DF30 conditions contributed to C. schmidtii tussocks having a rapid in response to alternating drought-flooding conditions compared to DF40 and DF60 treatments. Compared to plant traits and photosynthetic parameters in the early growth stages, C. schmidtii is much more sensitive to consecutive drying and re-flooding in the middle growth stages. Results indicated C. schmidtii to be suitably-adapted to hydrological fluctuations in the early growth stage, and RT initiated in the first 60 days can effectively recover plant growth and photosynthesis. The findings provide invaluable supporting information for the restoration and management of C. schmidtii tussocks in sedge wetlands.