长江干流宜昌-监利段洲滩湿生植物群落特征及其驱动因子分析

Assemblage Structure Characteristics of Hygrophytic Plants and Their Driving Factors in Sand Bars in Yichang-Jianli Section of the Yangtze Mainstem

为了解长江干流洲滩湿地植物的群落结构特征及其驱动因子,于2018年3~5月对干流宜昌-监利5个江段洲滩的湿生植物开展了调查。共采集湿生植物88种,隶属于26科73属,其中菊科(Compositae)、禾本科(Gramineae)、蓼科(Polygonaceae)占优势,狗牙根、薹草、牛鞭草、虉草为主要优势种。采集样方平均种类数为6种,平均密度为88.9 ind/m^2,平均生物量(地上部分干重)为55.8 g/m^2。采集洲滩湿生植物群落结构时空差异较大。枝城江段洲滩样方物种数、密度和生物量均为最大,荆州洲滩均最小。样方密度在3~5月间呈下降趋势,生物量则呈上升趋势。划分了薹草、狗牙根、牛鞭草-紫菀等10个稳定群落。典范对应分析表明湿生植物群落组成主要受到黏粒比例、相对水面高程、土壤含水率以及土壤总有机质含量的影响,其中影响最大的是黏粒比例。样方总生物量沿相对水面高程、总有机质、土壤含水率的变化趋势一致,即先增大后减小;而与黏粒含量的关系不明显。分析认为洲滩湿生植物分布格局是在水文过程影响下,由底质、水分及营养共同作用的结果。

In order to understand assemblage structure characteristics of hygrophytes and their driving factors in the Yangtze mainstem,we carried out field investigations of hygrophytes in five sand bars in Yichang-Jianli section during March-May 2018.A total of 88 species of hygrophytes,belonging to 26 families,73 genera were collected.Among them,Compositae,Gramineae,Polygonaceae were dominant,Cynodon dactylon、Carex leiorhyncha、Hemarthria altissima、Phalaris arundinacea were the predominant species.The average species number in plots was 6,the average density was 89 ind/m2 and average biomass(above ground part,dry mass)55.8 g/m2.Assemblage structure characteristics of hygrophytes varied in space and time.Plot species number,density and biomass in the Zhicheng section were the largest,while those in Jingzhou section were the smallest.Density of hygrophytes decreased from March to May,while biomass increased.Ten dominant assemblages were identified including Carex leiorhyncha,Cynodon dactylon,Hemarthria altissima-Aster tataricus and the others.Canonical correspondence analysis indicated hygrophytic plant assemblages were mainly affected by clay proportion(Clay),elevation above water(ELEV),soil moisture(SM)and total organic matter content in soil(TOM),and the most important one was Clay.Moreover,plot total biomass changed with ELEV,SM and TOM in a similar way,i.e.it increased first and then decreased along these factors.The relationship between plot biomass and Clay was insignificant.We concluded that hygrophytic assemblages in sand bars were driven by hydrological regimes under which substrate,soil moisture and nutrients acted together to shape the assemblages.