【目的】探究三江平原湿地水文因子与湿地植被群落类型的关系以及水位梯度与湿地植被生态特征的耦合关系,分析水文情势对湿地植被群落的影响,为湿地生态恢复与生态系统的科学管理提供依据。【方法】以东北三江平原洪河国家级自然保护区湿地为研究区,基于野外调查选取水位梯度明显的9条样线共90个样点数据,建立以物种为横坐标、样点为纵坐标的21×90的矩阵。采用PC-ORD 5对矩阵数据进行双向指示种分析(TWINSPAN),对保护区湿地植被群落进行数量分类并分析群落类型与水位梯度的关系,使用CANOCO 5对矩阵数据进行除趋势对应分析(DCA),探究湿地植被群落分布与水位梯度的关系。最后利用Origin 2018对典型湿地植被的株高及生物量与水位数据进行高斯拟合,探究水文梯度变化对湿地植被生态特征的影响。【结果】TWINSPAN结果显示,洪河自然保护区湿地植被可划分为12个群落类型,群丛类型沿水文梯度的变化体现了植被类型由湿生植被向旱生植被演替的变化趋势,表明水位变化对湿地植被群落的演替与分布具有重要作用。样地DCA分析结果表明,湿地植被群丛的分布呈现一定的规律,植被群落类型及分布主要受水位梯度的影响。物种DCA排序结果显示,湿生植被、湿中生植被、旱生植被在排序图上均有明显的分布范围和界限,影响植被分布的主要环境因子是水位梯度。高斯拟合结果表明,3种典型湿地植被的高度和生物量随水位的变化趋势均为先增加后减少。小叶章(Calamagrostis angustifolia)、毛果苔草(Carex lasiocarpa)、漂筏苔草(Carex pseudocuraica)的最适水位生态幅分别为:[4.46 cm,20.04 cm]、[8.30 cm,28.40 cm]和[40.87 cm,48.71 cm],3种湿地植被的高度及生物量对应最大水位排序均为:小叶章<毛果苔草<漂筏苔草,此结果与分类和排序结果相符合。小叶章的高度及生物量对水位梯度的变化最敏感。【结论】水位梯度为洪河国家级自然保护区湿地植被群落类型与分布的首要环境因子,优势种的分布体现了所属植被群落的分布特征,并且具有指示生境的作用。水位梯度对湿地植被的生态特征有极显著影响,不同湿地植被对淹水水位适应性的差异导致其最适水位生态幅的差异明显。

【Objective】There are few quantitative researches concerned about the relationships between the ecological characteristics of wetland plant and water level which could probably be key to solving the environmental issues in Sanjiang Plain, Northeast, China. Therefore, the purpose of this paper is to analyze the influences of the hydrological regime on the wetland plant community by exploring the relationships between the hydrological factors and the types of wetland plant community, as well as the coupling relationships between hydraulic gradient and wetland plant’s ecological characteristics in the wetland of Sanjiang Plain.【Method】Our team chose the Honghe National Nature Reserve (HNNR) in the Sanjiang Plain of Northeast China as our research area. We had conducted several field surveys to select 9 line transects with the obvious hydraulic gradient, totally 90 sampling spots as the experimental data. The data were further measured to establish a matrix with the size of 21×90 that the sampling spots as ordinate and the species as abscissa. The major analyzing approaches consist of three main steps. The first thing was to use the PC-ORD 5 to analyze the matrix data by Two-Way Indicator Species Analysis (TWINSPAN) in order to execute the quantitative classification of wetland plant communities and analyze the relationship between the plant community and hydraulic gradient in the HNNR. Secondly, we used the CANOCO 5 to execute the Detrended Correspondence Analysis (DCA) with the matrix data to explore the relationship between the distributions of the wetland plant community and hydraulic gradient. Finally, we used the Gaussian logistic regression model to determine a relationship between the plant height, biomass of typical wetland vegetation and water level. The aim of the last step is to explore the influences of the hydraulic gradient on the ecological characteristics of wetland vegetation.【Result】The results of TWINSPAN indicated that the wetland plant in HNNR can be divided into 12 different types of community. The trend of plant types is transited from the hygrophilous vegetation to xeromorphic vegetation with the hydraulic gradient. This experimental result proved the change of water level is critical to succession and distribution of wetland plants. Moreover, the sequencing diagram of DCA reflected that the distribution of the sample showed certain regularity. The types and distributions of wetland plants were affected by the hydraulic gradient as well. Furthermore, the sequencing consequences of DCA species also showed that the hygrophilous vegetation, the wet mesophytic vegetation and the xeromorphic vegetation were all distributed obviously with exact scopes and boundaries. These results could probably be the strong evidences to prove that the main environmental factor affecting the distributions of the wetland plant in HNNR is the hydraulic gradient. Moreover, the results of the Gaussian logistic regression model demonstrated that the height and biomass of the three typical wetland plants all increased first and then decreased with the changing trends of water level. The most suitable ecological amplitude of water level of Calamagrostis angustifolia, Carex lasiocaropa and C. pseudocuraica were: [4.46 cm, 20.04 cm], [8.30 cm, 28.40 cm] and [40.87 cm, 48.71 cm], respectively. The height and biomass of the three wetland plants corresponding to the maximum water level were all sorted as: Calamagrostis angustifolia < Carex lasiocaropa < C. pseudocuraica which was consistent with the classification and sequencing results. So, the height and biomass of Calamagrostis angustifolia were most sensitive to the hydraulic gradient.【Conclusion】We concluded the hydraulic gradient is consequently the major environmental factor influencing the types and distributions of wetland plant communities in HNNR. The distributions of dominant species represented the distributing characteristics of the plant community and have functions as indicator habitats. Finally, our results also proved that the hydraulic gradient also has extremely significant impacts on the ecological characteristics of wetland plants in the reserve area and differences of the adaptability to the flooded water level among different plants could resulted in the obvious differences of their most suitable ecological amplitude of water level. Importantly, this study is to provide a scientific basis for the ecological restoration and ecosystem management of the wetlands in HNNR.