Research On Distribution Characteristics Of The Submerged Plants And Its Environmental Impact Factors In Some Wetlands Of Poyang Lake

This paper choose Nanjishan、Baishazhou、Longkou and Wucheng wetland of the Poyang Lake as the research area. By periodic investigation in all the year round,the paper studies the species, distribution and community structure of submerged plant in Poyang Lake. And the study collects water samples and sediment samples to measure main environmental factors of soil and water by laboratory experiments analysis. The paper also studies the temporal and spatial variations of water and sediment samples of environmental factors according to the characteristics of different lakes in different seasons; and discusses the key environmental factors that affects the growth and distribution of submerged plant in different seasons using CCA based on data of the submerged plant species abundance and soil environmental factors; Finally, some suggestions and countermeasures about the recovery and protection of the submerged plant are put forward according to the results. This research paper get the support and funding by the national natural science foundation of China(D41161035): "The community structure of submerged plant in Poyang Lake wetland and its typical factor of water environment quantitative research". The main conclusions are as follows:(1)Twelve species of submerged plants were recorded in wetland in Poyang Lake. They are distributed in 6 families, 8 genera. Nanjishan wetland distributes all kinds of typical submerged plants. The Hydrilla verticillata and Vallisneria natans are the dominant species, and also widely distributed species, which appeared in the whole investigation area. then the widely distributed species are followed by Najas minor, which is widely ditributed in the Nanjisan wetland. Hydrilla verticillata and Vallisneria natans have strong environment adaptability and can be selected as the pioneer species for submerged vegetation recovery engineering work.(2) The submerged plant of Poyang Lake wetland in spring are clustering analyzed by two-way indicator species sorting method(TWINSPAN), they can be divided into six associations: Hydrilla verticillata+ Vallisneria natans group, Najasminor + Vallisneria natans group, Ottelia alismoides group, Potamogeton crispus group, Ceratophyllum demersum group, Vallisneria spinulosa group.(3) The water environmental factors of typical wetland in Poyang Lake are different in time and space. The results show that: the Total Nitrogen(ρ(TN)) showed a rule that,winter > spring > summer > autumn; Total Phosphorus(ρ(TP)), spring >autumn > winter > summer; Chemical Oxygen Demand(ρ(COD)), autumn > spring >winter > summer, Dissolved Oxygen(ρ(DO)),winter > spring > autumn > summer.The water environment factors change are not consistent in different lakes even though in the same season. In the spring, ρ(TN) of Bang Lake in Wu Cheng is the highest, reached(1.262±0.776 mg/L), the maximum value of ρ(TP) is in Longkou,ρ(COD) of Nanjishan is at the top, ρ(DO) in Bang lake of Wu Cheng is the highest; in the summer, the highest content of ρ(TN) is in Longkou, as(0.937 ± 0.304) mg/L, the highest value of ρ(TP) is still in Longkou, maximum of ρ(COD) is in Zhushi lake in Wucheng town, ρ(DO) of Baisha Lake in Nanjishan Wetland is the highest. In the autumn, ρ(TN) of Bang Lake in Wucheng is the highest, for(0.383 ± 0.042 mg/L,maximum of ρ(TP) is still in Longkou, the highest content of ρ(COD) appears in Bang Lake of Wu Cheng, highest content of ρ(DO) is in Zhushi Lake of Wu Cheng; In winter, highest total nitrogen content is in Zhushi Lake of Wucheng Town, for(3.914± 0.769 mg/L, ρ(TP) and ρ(COD) in Dahuchi in Wucheng are the highest, ρ((DO) of Changhu Lake often as the highest.(4) Seasonal change rule of Total Nitrogen and Total Phosphorus in the sediment is consistent, the highest Total Nitrogen(w(TN))is in the spring, with the Total Nitrogen value of(0.080±0.035 mg/g) and Total Phosphorus( w(TP)) value of(0.630-0.020 mg/g),while they are falling down in the summer and autumns, when in the winter,the Total Nitrogen and Total Phosphorus are between in summer and autumn. But when it comes to the total organic carbonw w(TOC), the highest value is in summer, with the value of(1.452 ± 0.680) mg/g, and the lowest. Appears in autumn. From the aspect of different lakes, in spring, the highest value of w(TN),w(TP) and w(TOC) are all in Nanjishan, and the change tendency of three sediment indexes is consistent; in summer, change tendency of w(TN)and w(TOC)is consistent,Wu Cheng > Nanjishan> Longkou >Baishazhou, the maximum value of w(TP)is in Longkou, and there is little difference among other lakes, with the same distribution trend as w(TP)in water; in autumn, except to the Zhushi Lake of Wu Cheng, the difference of the three sediment indexes in other lakes is not obvious; in winter,w(TN)、w(TP)and w(TOC)in Zhushihu are the highest, while in Dahuchi is the lowest.(5) The analysis results of Model corresponding(CCA) reflect that: The impact on submerged plants of different environmental factors in different seasons is different. In spring, all the water and soil environmental factors have significantly effects on submerged plants, especially the depth of the water(D), total phosphorus of sediment w(TP), p H, water temperature(T) and water transparency(Trans); in summer,effects of environmental factors on submerged plant are not same, the main factors are the water transparency(Trans), total nitrogen of water ρ(TN), p H and temperature(T);in autumn, the environmental factors, such as the dissolved oxygen ρ(DO), total phosphorus of water ρ(TP), sediment organic carbon w(TOC) and water transparency(Trans), all have influence on the submerged plant; in winter, the difference of the environmental factors influence is obvious, the key influence factors are total phosphorus of water ρ(TP), total nitrogen of sediment w(TN)and water transparency(Trans).