| Sanjiang Plain is the largest and most concentrated marsh area in China.In this paper,studies and analyzes the characteristics of plant communities and soil elements after natural restoration in the adjacent natural wetland,the returned wetland of different restoration years and the reclaimed farmland of the wetland ecological experimental station in Sanjiang Plain.Using the method of quadrat investigation,the characteristics of species composition and structure of natural wetland,8-year restored wetland and 16-year restored wetland plant communities were studied.The results showed that:(1)compared with the natural wetland,the splant functional group had changed significantly.The functional group of natural wetland is mainly composed of species of Cyperaceae.After 16 years of restoration,the functional group of farmland plant community was mainly composed of Gramineae,and gradually developed into a plant community dominated by Calamagrostis angustifolia.(2)After 8 years of restoration,the species richness of the wetland was the highest,which is 9.3species / m2,and there were significant difference(n = 3,P < 0.05)with the natural wetland and the 16-yearrestored wetland,but there was no significant difference between the natural wetland and the 16-yearrestored wetland.(3)The Sorenson similarity index was used to analyze the richness and similarity index of natural wetland plant community,The results showed that the similarity of the plant community between the restored wetland and the natural wetland was 60.5% and 29.4% respectively.With the increase of the restoration time,the community similarity between the natural wetland and the restored wetland decreased gradually,and the community succession direction changed.The soil samples of surface layer(0-10 cm depth)were collected from the natural swamp wetland,the 16 year restored farmland and the farmland reclaimed from the wetland.The 55 elements,pH,conductivity and organic matter content of the soil samples were determined,and the correlation between the soil elements and the physical and chemical indexes of the surface soil was further analyzed.The results showed that:(1)there were significant differences in the content of physical and chemical indexes of surface soil between natural wetland and farmland,indicating that the reclamation of natural wetland into farmland significantly changed the pH,conductivity and organic matter content of surface soil.Compared with farmland,after 16 years of natural recovery,the content of organic matter in surface soil increased,the conductivity and pH of soil decreased;there was no significant difference in conductivity and organic matter between farmland and natural wetland,but the pH of soil was still different.(2)After 16 years of restoration,only Ni,N,P and k elements in the surface soil of the wetland were significantly different from those in the surface soil of the natural swamp(n = 3,P <0.05).The content of Ni,N,P in natural wetland is significantly higher than that in restoration wetland,and K content is significantly lower than that in restoration wetland.(3)the results of redundancy analysis show that the surface soil conductivity is the main index affecting the content of 55 elements in soil. |
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