长江河口九段沙下沙湿地植物N、P、K的分布特征与季节动态

Distribution characteristics and seasonal dynamics of wetland plant N,P,and K in lower shoal of Jiuduansha at Yangtze River estuary

2005年4—12月逐月对长江河口九段沙下沙湿地生态系统主要湿地植物群落进行样方调查与样品采集,通过对海三棱藨草(Scirpus mariqueter)、互花米草(Spartina alterni-flora)和芦苇(Phragmites australis)3种植物样品中N、P、K元素含量分析与生物量测定,揭示了下沙主要类型湿地的植物N、P、K元素的含量、分布、贮量与动态变化特征。结果表明:3种湿地植物N、P、K元素含量、分布、贮量与动态特征均各具特点。不同植物以及同一植物不同构件营养元素含量与分布均存在较明显的差异。营养元素在不同植物与同一植物不同器官含量排序的差异明显。N、P、K贮量分布特征因湿地植物种类、构件以及生物量不同而异。植物中营养元素含量与贮量的分布特征存在差异,其原因在于,与营养元素含量相比,生物量是制约植物营养元素贮量的主要因子。下沙湿地3种湿地植物及其构件的营养元素含量与贮量一般都低于上沙湿地。3种湿地植物营养元素均表现出明显的季节动态,一般生长初期营养元素含量高,生长停滞期含量低。3种湿地植物N、P、K含量的动态特征存在差异,总趋势为N、P、K含量随生长过程的进行而下降,相对下降速度排序为:K>N>P。受局地环境条件影响,上沙与下沙湿地的植物N、P、K元素的含量、分布、贮量与动态变化特征存在差异。

From April to December 2005,an investigation was made on three main types of wetland plant community composed of Scirpus mariqueter,Spartina alterniflora,and Phragmites australis,respectively in the lower shoal of Jiuduansha at Yangtze River estuary,with their plants sampled monthly,and the N,P,and K contents and biomass determined.The three species had different characteristics in their N,P,and K contents,distribution,storage,and dynamics,and the nutrient contents in different species and in different organs of same species differed with plant growth.The order of N,P,and K contents was obviously different in different species and in different organs of same species.The storages of N,P,and K were mainly affected by plant species,their organs,and biomass,among which,biomass was the main limiting factor.The nutrient contents and storages of the three species and their organs were generally lower in lower shoal wetlands than in upper shoal wetlands.The nutrient contents of the plant species showed obvious seasonal dynamics,i.e.,higher at the initial stage of plant growth and lower at the withered stage.The dynamic characteristics of N,P,and K contents differed with plant species,but had an overall tendency of decreasing with plant growth and in the order of KNP.Under the effects of local environmental factors,there existed differences in the characteristics and patterns of N,P,and K contents,distribution,storage,and dynamics in the wetland plants between lower and upper shoals of Jiuduansha.