Influence of Water Level on Cynodon dactylon Population in Water-Level-Fluctuating Zone of the Three Gorges Reservoir

To research influence of water level changes on vegetations restoration in water-level-fluctuating zone of the Three Gorges Reservoir, Cynodon dactylon in Changshou area was respectively investigated in 2008 and 2009. The results show that germination rate in 2009 is 45.3% lower than that in 2008. Total rhizome length and total node number of rhizomes in 2009 significantly increase by 303.5% and 411.1%, respectively. However, stem length, node number, leaf width and leaf number of ramets decrease by 60.1%, 55.1%, 28.6% and 33.8%, respectively. Meanwhile, total buds number, germinated buds number and buds number to rhizome length ratio in 2009 increase by 500.7%, 228.5% and 50.9%, respectively. Compared with 2008, fresh mass of ramats, rhizomes and roots reduce respectively 65.6%, 23.4% and 70.0%, and their dry mass reduce respectively 65.9%, 18.8% and 64.5%. Therefore, water level changes accelerate rhizomes extension and the formation of buds and ramets, and inhibite ramets growth.