The hydrological regime is the dominant factor associated with the degradation and restoration of inland salt marshes in Northeast China. As a typical distributed areas of soda saline-alkaline land in the world, Phragmites australis saline-alkaline marsh in western Songnen Plain degrade to saline meadow or even alkaline spots progressively in the past 20 years, due to the interruption of the water supply. In order to understand the hydrology regimes effected on Phragmites australis saline-alkaline marsh, four months of pot experiments were designed to determine the growth and physiology changes of plants. Three groups of hydrological regimes were set. (1) combined drought and flooding treatments: five levels were considered as 0+4,1+3,2+2,3+1 and 4+0 meant month for drought plus month for flooding; (2) flooding duration treatments: four levels were considered as 0, 1, 2, 3 and 4 months; (3) alternate drought and flooding treatments: five levels were considered as drought, flooding, moisture, alternate drought and flooding treatments. The Plant height, biomass, saline ions, photosynthetic parameters were determined.
Results/Conclusions
Some results were concluded: (1) Compared with four months flooding, the combined drought/flooding treatment that drought for 1 month and flooding for subsequent 3 months obtained the largest biomass and lower Na+ absorption by plant shoots, although the later give rise to the highest population height. Subsequently, the accumulation of sodium ion in plant shoots increased significantly with the delay of flooding and increased drought periods, and the significant enhanced photosynthetic activity imply the evident physiological responses to drought stress. (2) With the increase of flooding duration, plant height reached to the highest value in full time flooding but the biomass reached to the largest in the treatment that only flooded 2 months. Although the Na+ and K+ did not show a regular change, they was the lowest in this treatment. (3) Plants in alternate flooding–drought conditions exhibited substantially more biomass accumulation and less Na+ absorption compared with the single treatments of moisture, flooding, and drought. Photosynthesis physiology served as regulating and adaptive responses to different water regimes, with increased values after the short-term flooding, long-term drought, and flooding–drought cycles. Comparing all these changes in the growth, photosynthetic physiology and saline ions contents under different hydrological regimes, the growth of P. australis was promoted by flooding–drought cycles, which suggests that this may be an effective approach for restoration inland salt marshes.