Diversity Of Aquatic Plant Communities In Typical Shallow Lakes Of Jianghan Lake Groups

The Jianghan Lake Group is located at N 29° 30? ? 31° 12? and E 110° 48? ?116° 16?,which is formed by the river alluvium of the Yangtze and Hanshui rivers.Due to unique hydrology,climate and topographic terrain,there are higher aquatic plant diversity in Jianghan Lak.In this paper,the diversity of aquatic plant communities in the shallow lakes of Jianghan Lake Group was studied by the field investigation in the typical lakes of Jianghan Lake Group,and the main aquatic plant community types,community diversity index and the effects of environmental factors were analysed.The main results are as follow:(1)There are 26 families,38 genera and 49 species of aquatic plants distributed in the 188 surveyed communities.In terms of the life form of aquatic plants,13 families,20 genera and 24 species belonged to emergent aquatic plants,7 families,10 genera and 16 species belonged to submerged plants,6 families,7 genera and 7species belonged to floating plants,and 2 families,2 genera and 2 species belonged to floating-leaved plants.(2)Cluster analysis showed that 188 surveyed quadrats in the study area can be divided into 13 groups.There were Ass.Nelumbo nucifera-Spirodela polyrrhiza,Ass.Zizania latifolia,Ass.Polygonum hydropiper,Ass.Typha angustifolia,Ass.Echinochloa crusgalli,Ass.Phragmites australis,Ass.Polygonum hydropiper-Eichhornia crassipes,Ass.Alternanthera philoxeroides,Ass.Potamogeton crispus,Ass.Hydrilla verticillata and Ass.Ceratophyllum demersum,Ass.Lemna minor and Ass.Trapa bispinosa.(3)?-diversity analysis of aquatic plants indicated that the diversity index of Ass.Lemna.minor are low.This may be L.minor rapidly grows and occupies the whole surface.While four diversity indexes of Ass.Polygonum.hydropiper-Eichhornia crassipes are high,which may be due to the complex community environment.(4)Correlation analysis showed that there was a significant positive correlation between community species richness index and total nitrogen,as well as a significant positive correlation with total phosphorus.The Shannon-Wiener index and the Simpson index are significantly negatively correlated with transparency.However,the non obvious linear relationship between Pielou evenness index and environmental factors was found.RDA analysis showed that the first axis basically reflected the change of transparency in environmental factors,which was negative correlation.Also,p H value and total phosphorus were also correlated with the first axis,which referred negative correlation of p H and positive correlation of total phosphorus.The second axis basically reflects the correlation between latitude and total nitrogen,latitude showed positive correlation and total nitrogen showed negative correlation.From the prospective of length of each environmental factor,the influence of transparency and total nitrogen are larger.Comparing the four diversity indexes,it can be found that p H,total nitrogen,total phosphorus and longitude showed have significant correlation.Our results also showed the submerged plant community was positively correlated with transparency,total phosphorus and total nitrogen.Other plant communities were negatively correlated with total phosphorus,total nitrogen and transparency.(5)By comparing the results of SPSS correlation analysis and RDA analysis,it was found that the transparency,total phosphorus,total nitrogen,p H and longitude,had a greater impact on species diversity.Transparency had a greater impact on diversity may be due to reduced the transparency of water bodies.There was apositive correlation between total phosphorus and total nitrogen and community diversity.Because phosphorus and nitrogen are nutrient sources for the growth of aquatic plants,they promote the growth of aquatic plants within a certain concentration range,and vice versa.With the development of the economy and human activities,nitrogen and phosphorus elements are excessively input into water bodies such as lakes and rivers,resulting in a decrease in the diversity of aquatic eutrophic aquatic plants.There is a negative correlation between p H and diversity index,because most surface water is alkaline due to pollution from agricultural sources and sewage,when the water body is alkaline,the carbon dioxide in the water will be converted into carbonate,and the carbon supply will decrease,the diversity of aquatic plants is reduced.