Dynamic Changes Of Seed Bank In Changhu Wetland Before And After Removal Of Enclosure Culture

Aquatic plants are the first producers of lakes,providing food sources and habitats for the rest of the life,and promoting the material cycle,improving water quality,effectively maintaining the ecological balance and coordinated development of lakes,So it has important ecological value in lake ecosystem.With the increase of social population pressure and unreasonable exploitation and utilization of wetlands,most lakes in our country are generally reduced,plant community structure is simplified,function is weakened,lake water ecosystem is degraded,and aquatic plant diversity is gradually lost.The water quality of the lake deteriorated rapidly.Soil seed bank is the sum of viable seeds in soil matrix.Because the seed bank accumulates seeds produced by surface plants in different periods and environmental conditions,it reflects the vegetation status in the past to a certain extent,and also anticipates the future vegetation structure and succession dynamics.In areas with severe and frequent disturbances,seed bank has a particularly significant impact on surface vegetation.In this study,the changes of seed bank before and after the removal of seine net in Changhu wetland were studied,and combined with the change of vegetation on the ground,some constructive suggestions and protection strategies were put forward for the protection of Changhu wetland.The results show that:1.From 1985 to 1999,the enclosure culture area of Changhu Wetland was established by the original ecological lake.By 2008,the enclosure culture area had accounted for more than 45% of the total Lake area.The enclosure was dismantled in June 2016.In April 2017,the enclosure of Changhu Lake had been completely dismantled.The water quality of Changhu Lake changed from poor eutrophication to severe eutrophication to moderate eutrophication,and the water quality of Changhu Lake became worse.2.Before the removal of purse seine,there were 23 germinating species in seed bank,8 submerged plants,2 emergent plants,7 wet plants,2 floating plants,2 amphibian tolerant plants,2 terrestrial herbs.After the removal of purse seine,only 16 species germinated in seed bank,3 submerged plants,3 emergent aquatic plants,5 wet plants,2 floating plants,2 amphibian tolerant plants,1 terrestrial herb and 1 long plant.The seed bank in the sediment of Lake wetland is not rich,and the species richness of vegetation in the seed bank decreases.3.With the deepening of water level,the species richness and evenness of aquatic plants in Changhu Wetland Seed Bank decreased.The change of hydrological conditions affected the germination,growth and development of wetland seed bank.4.In 1989,there were ten aquatic flora clusters in Changhu Lake area,with abundant species.By 2008,aquatic flora had been reduced to six,mainly composed of Potamogeton maackianus A.Benn,Potamogeton wrightii Morong and Hydrilla verticillate.In this survey,Potamogeton crispus L.has become the dominant group in the Changhu Lake region.The community diversity of Changhu Lake is gradually disappearing,and individual species are gradually evolving into the dominant species in this area.5.Before the establishment of the enclosure in Changhu Lake,there were 34 families and 104 species of surface plants in Changhu Wetland,19 species of wet plants and emergent plants.After the establishment of the enclosure,there were 32 families and 81 species of surface plants in Changhu Lake,including 7 species of emergent aquatic plants and 6 species of wet plants.In the vegetation survey of Changhu Lake in 2018,there were 21 families and 40 species of surface vegetation in Changhu Lake.There are 22 species of terrestrial plants,6 species of emergent aquatic plants and only 3 species of wet plants.The plant diversity and species richness on the Changhu Lake are greatly reduced.