Effects Of Salinity And Hydrological Interference On Individuals And Populations Of Suaeda Salsa

Suaeda salsa is one of the most important pioneer species and it plays an important role in the succession and stability of ecosystem in the Yellow River Delta with a strong salt tolerance. In recent years, the fragile ecosystems of this area are degraded due to the intensification of salinization and saltwater intrusion, which makes the habitat of wildlife and vegetation under threat. The effects of salinity gradient and hydrological interference on seed germination rate, individual form, biomass and population of S. salsa were investigated. There is a regular effect of salinity on S. salsa: with the increase of salinity gradient, seed germination rate of S. salsa decreased gradually. The germination rate of S. salsa was 70% at 3g/kg salinity. When the salinity rose to 12g/kg,the germination rate was about 65%. The germination rate was50% when the salinity up to 20 g/kg. It is suggesting that the salt stress can inhabit the germination of S. salsa and the degree of inhibition increased with the increase salinity gradient. The effects of hydrological interference on seed of S. salsa are as follows: river flooding not only improved the germination rate also improved the uniformity. And seawater flowing reduced the seed germination rate. The germination rate of 3 different salt treatments in the river flooding group all reached 70% finally, which means that river flooding can weaken the inhibitory of salt stress on germination of S. salsa.The effects of salinity on S. salsa in the growth period is apparent: with the increase of salinity gradient, the height, leaf area, crown area and biomass were reduced gradually. Under slight salinity gradient, the height of S. salsa can reach more than 25cm; under moderate salinity gradient, the height was 10cm; and under the high salinity gradient, the height was only 5cm due to the late emergence and slow growth. The biomass of S. salsa under slight salinity gradient was 10 times higher than that under high salinity gradient. The effect of hydrological interference on individual form of S. salsa was not obvious, but the change in the distribution of plant biomass was significant. Especially for the changes of root and leaf biomass. No matter river flooding and seawater flowing were obviously promoted the growth of root and leaf of S. salsa under different salt environment.The status of populations of S. salsa were different in different salinity gradient: the population density of S. salsa was big and productivity was high in the slight salt environment. And the competition turned to intensify gradually with the growth of plants. The population densities in the moderate salt environment and slight salt environment were similar, but the population productivity and intensity of intraspecific competition was obviously different. The population density was only 400 per square meter and productivity was very low in the high salt environment. There was no obvious change in intraspecific competition in the whole growth process. The effects of hydrological interference on S. salsa population are as follows: no matter river flooding or seawater flowing all reduced the population density in different salt environment and also weakened the intensity of intraspecific competition at the same time. As a whole, the effect of flooding on the productivity of population was not significant, but there was an increasing tendency in productivity under slight salt environment.In addition, according to the effects of individual form and population of S. salsa in different salt treatments, a new calculation method of niche was established based on the data obtained from the experiment. According to the new calculation method of niche, the intraspecific niche of S. salsa was calculated. The intraspecific niche of S. salsa was different in different salinity gradient in the initial period of growth. With the development of population, the intraspecific niche of S. salsa gradually converged in 3 different salinity gradient. The effects of hydrological interference on intraspecific niche of S. salsa are as follows: there was an expanding tendency in intraspecific niche of S. salsa in short time flooding in different salinity gradient. The intraspecific niche can explain the characteristics of distribution of S. salsa, which means that this method of calculation of niche is scientific. There are also some limitations and further research is required to get more extensive application.