Abstract: Submerged macrophytes are the key component of lake ecosystems. Studying the distribution of submerged macrophytes and the influencing factors of water environment is of significance for the establishment of vegetation restoration strategies. Field surveys for submerged macrophytes were carried out at 25 different sites in typical wetlands of Poyang Lake in May, 2013. Systematic sampling was conducted within the field sites and the water environment factors concentration values were determined in the laboratory. The biomass distribution map of the submerge plants were derived based on the field investigation data by using GIS methods, and the main influencing factors were analyzed by using Principal Component Analysis(PCA)and Canonical Correspondence Analysis (CCA). The results indicated that Vallisneria natans is one of the main submerged plants and the widespread species in the wetland of Poyang Lake. Hydrilla verticillata is the dominant species in Banghu Lake and Baishahu Lake, and V.natans is also the dominant species in Baishazhou Lake and Longkou Wetland. The major associated species included Ceratophyllum demersum, Potamogeton malaianus, P.crispus, Najas minor, N.marina, V.spinulosa, and Ottelia alismoides. The submerged plant communities in the study areas were divided into six classes by Two-way indicator species sorting methods. Most submerged macrophytes were still in the initial stage of growth and the biomass was still relatively low in the early of May, only the biomass of P.crispus was relatively high. The phenomenon of submerged and floating-leaved plants coexisting in the study areas was obvious. The results from PCA showed that the large coefficients of the first principal components included water depth, total phosphorus, and dissolved oxygen, while the large coefficients of the second principal components included pH value, chemical oxygen demand, and water transparency, which were the key factors affected the distribution of submerged plants. The results from CCA showed that the effects of water depth, total phosphorus and total nitrogen on V.natans and H.verticillata were obvious, and water transparency was the main factor which affected P.malaianus.

Key words: Poyang Lake Wetland, Submerged Plants, Distribution Pattern, Water Environmental Factors, two way indicator species analysis ( TWINSPAN ), Principal Component Analysis (PCA), Canonical Correspondence Analysis (CCA)