EFFECTS OF LONG-TERM SUBMERGENCE ON SURVIVAL AND RECOVERY GROWTH OF FOUR RIPARIAN PLANT SPECIES IN THREE GORGES RESERVOIR REGION, CHINA

Aims Ficus tikoua, Triarrhena sacchariflora, Hemarthria altissima and Cynodon dactylon are four riparian plants in Three Gorges Reservoir Region that are naturally distributed on riverbanks of different elevations. Our objective was to determine their survival and growth after long-term submergence in the water-fluctuation zone in Three Gorges Reservoir Region. Methods We studied survival and biomass increase of plants subjected to 30, 60, 90, 120, 150 and 180 d submergence and in a control (no submergence). We measured total shoot length, total shoot number and total leaf number during the post-submergence recovery period. Important findings Survival of the plants after long-term submergence was associated with their distribution pattern on riverbanks. Ficus tikoua, mainly occurring on high-elevation sites, died after 30 d submergence. Triarrhena sacchariflora, from intermediate-elevation sites, died after 150 and 180 d submergence. 90% and 100% of submerged plants of H. altissima and C. dactylon, respectively, survived after 180 d submergence. Submergence inhibited the growth of all plants, and the total biomass increase of each species was significantly lower than that of control plants. The aboveground biomass of all submerged plants decreased significantly. After 60 and 120 d submergence, the belowground biomass of T. sacchariflora decreased significantly, but that of H. altissima and C. dactylon did not change during submergence. All surviving plants grew. After 30, 60 and 90 d submergence, the relative grown rate (RGR) in total shoot length of all submerged plants was not significantly different with that of control plants, but after 120, 150 and 180 d submergence, the RGR in total shoot length of submerged H. altissima and C. dactylon was higher than that of control plants. The RGR in total leaf number was always higher than that of control plants after all submergence durations. After long-term submergence, this might be an effective way for plants to generate more new leaves and accelerate photosynthesis.