Effects Of Different Water Depths On The Growth,vegetative Reproductive And Interspecific Interaction Among Domiant Wetland Vegetation In Lake Poyang

In recent years,the wetland plant community of Poyang Lake have changed dramatically,which was induced by the hydrological changing in this area..For example,the lower range of Carex community have moved down by 3m of elevation and Phragmites australis and Miscanthus lutarioriparius community have moved down by1 m.However,the mechanism of these changes are still not well understood.Many studies have shown that the alter plant competition ability under environment changes is one of the main reasons for the change of distribution of plant species.In this study,I conducted four experiments to reveal the mechanism of the plant community changes under hydrological changing.Specially,I aim to test whether the wetland plant competition ability change along different water level,thus ultimately determine the distribution of these species.The results showed that:1.The responses of growth and vegetative reproduction of wetland plants in Poyang Lake to duration of submergence1)After 120 days submergence,the survival rate of M.lutarioriparius began to decrease and all the individuals died after 180 days submergence,while all C.cinerascens and P.arundinacea could re-grow after 180 days submergence.2)Submergence significantly reduced the total biomass of C.cinerascens at the end of the experiment,while short duration of submergence was not significantly affect total biomass of P.arundinacea.3)After removing the submergence,C.cinerascens tended to allocate more biomass to leaves at the beginning of re-grow phase,while P.arundinacea did not change the allocation among the treatments.2.Effects of different water depths on the growth and vegetative reproductive characteristics of wetland vegetation in Lake Poyang1)Water depth had the most significant influence on the total biomass of C.cinerascens,and the biomass of C.cinerascens was concentrated in the underground parts during the flooding;the biomass of M.lutarioriparius gradually decreased as the water depth increased.On the other hand,water depth had no significant impact on the biomass of P.arundinacea.In terms of biomass,P.arundinacea had greater adaptability to flooding than the other two plants.2)Plant height of C.cinerascens was significantly reduced under flooding conditions.Plant height of M.lutarioriparius was reduced only under a water depth of 2 m.These findings suggest that in low flow years,the decreased water level may help M.lutarioriparius to migrate to a lower elevation.3)The water depth had no obvious impact on the ramets of C.cinerascens(P>0.05).However,the number of ramets of P.arundinacea was greatest when grown under a water depth of 2 m.These results demonstrate that in high flow years,the elevated water level has less impact on the reproduction of P.arundinacea.3..Effects of different soil moisture on the germination of the bud of wetland vegetation in Lake Poyang1)The germination rate of P.arundinacea is significantly higher than the M.lutarioriparius and C.cinerascens in different soil moisture.2)The germination rate of C.cinerascens decreased significantly with the increase of soil moisture,but different soil moisture had no significant effect on the initial time of germination of C.cinerascens.3)The germination potential of M.lutarioriparius is significantly higher than the P.arundinacea and C.cinerascens in different soil moisture,and the biomass of M.lutarioriparius also is significantly higher the P.arundinacea and C.cinerascens in the early growth.4.Effects of different water depths on the interspecific relationship of wetland vegetation in Poyang Lake.1)The competition ability of M.lutarioriparius is stronger than the C.cinerascens in the absence of water flooded condition.But with the increase of water depth,the competition relation between species would change.The competition ability of M.lutarioriparius is the weakest in the semi-submerged and begin less than C.cinerascens.2)The competition ability of C.cinerascens is stronger than the P.arundinacea in the absence of water flooded condition.And the C.cinerascens is mainly under pressure from intraspecific competition.With the increase of water depth,the competition ability of P.arundinacea is gradually strengthen.The response strategy to flood and the germination capacity of the bud of species were two significant factor which affected the interspecific relationship in poyang lake.And a large number of studies show that the change of inter-species competition ability is an important factor affecting the distribution boundary of vegetation in wetlands ecosystem.Therefore,the study which the change of the vegetation competitiveness under different water levels provides an important theoretical basis for the prediction of the vegetation dynamics and distribution patterns in the Poyang Lake shoal.