| The Yellow River Delta is located in the coast of Yellow River estuary, the south of the Bohai Sea, and its area changed fastest in our country, but with the influence of the river the sea and the land, there are many complex wetland types and ecological environment in this area, and the natural ecological system is fragile. With the rapid development of economic and society in the Yellow River delta, the degradation of its native natural wetland is serious, and to restore the regional vegetation is very important to the natural ecosystemand to social sustainable development.The interaction between species has an important effect on the population dynamics and on building the plant community, and it is one of the center of the plant community ecology. In the past, the study of interactions between species focused on the competition, but in recent years, the positive interaction gradually aroused people’s attention. In this paper, to make a study of the typical communities in the Yellow River Delta, we take the community survey and neighbour removal method, select plant height, stem, leaf number, biomass, leaf nitrogen and phosphorus content and related indicators, use relative interaction index value as the intensity and direction measurement of species interactions, and compare different treatments.Through the survey of the Yellow River Delta plant communities we found that the region’s ecosystem is instable and primordial, the ecological environment is fragile and the species composition is monotonous. According to the results of the survey, we divided 53 kinds of plants into seven plant communities in which the dominant species are determined, and measured soil physical and chemical properties, then we calculated the important value of the dominant species, species richness and Shannon-Wiener index, then on this basis we did the neighborhood removal experiment.The results of the neighborhood removal experiment showed that in the study of the plant communities, plants showed positive interaction in height, leaf number, pitch number and the survival rate, and showed competition in stems, the index of the biomass are quite different in different communities. The data analysis showed that: the positive interaction is universal in the experimental plant communities in the Yellow River Delta, but the intensity of the effect is different; there are differences among different traits and different species, that told us that the positive interaction is species specific and traits specific, which also showed that for the study of positive interaction, the choice of the traits is determined; neighbour removal experiment changed illumination, soil moisture and temperature, soil salinity content of microhabitats, which offers the possibility of the occurrence of positive interaction.In the five Phragmites australi plant communities, the intensity of the positive interaction enhanced with the increasing of the salt stress. But the direction of the interaction did not changed; community positive interaction has a positive correlation with the species richness, which also provides a theoretical support for making use of the positive interactions to the vegetation restoration; the intensity of the interaction in different periods is different, both positive and negative interactions show the highest intensity when the Phragmites australi growing rapidly, then the intensity gradually decreased, there is no transforming between positive and negative interactions through the whole period.The formation and distribution of the typically plant communities in the Yellow River Delta within the study can be considered as the result of the plant transformation and adaptation to the environment. The study of the positive interactions and the interactions effect in different period in the typical plant communities in the Yellow River Delta will help to deepen the understanding of the typical meadow communities, and provide a theoretical reference for the natural ecosystemand social sustainable development. |
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