鄱阳湖南矶湿地优势植物群落及土壤有机质和营养元素分布特征

Distribution characteristics of plant communities and soil organic matter and main nutrients in the Poyang Lake Nanji Wetland

湿地植物和土壤是承担湿地诸多生态功能的主要基质和载体,相互之间有着强烈的影响。湿地土壤影响植物的种类、数量、生长发育、形态和分布,湿地植物又影响土壤中元素的分布与变化。鄱阳湖湿地的植物和土壤的特征及由他们带来的候鸟栖息地价值都受到他们之间的相互作用以及湖泊水位不同频率和幅度波动的影响。研究鄱阳湖湿地植物和土壤的特征及其形成原因和相互关系。为此,从2010年10月到2011年10月,对鄱阳湖湿地不同水位梯度下分布的芦苇、南荻、苔草、虉草和刚毛荸荠5个优势植物群落中57个定点样方展开了月度植被调查并且对5个不同植物群落下的135个土壤样品进行了实验室分析,研究了鄱阳湖优势植物群落及湿地土壤中有机质、全氮、全磷、全钾含量的分布特征及其相互关系。研究结果表明,鄱阳湖湿地优势植物群落分布特征受湿地土壤元素分布特征、湖面水位波动及植物生长特性和土壤沉积及土壤养分的综合影响,呈现了沿水位和海拔梯度明显的条带状或弧状分布、从湖岸到湖心依次分布为:狗牙根群落、芦苇群落、南荻群落、苔草群落、虉草群落、刚毛荸荠群落,最后是水生植物。同时植物群落的组成和分布特征也随季节性水位涨落的变化而变化;土壤有机质及其他各元素含量特征受植物群落分布、水位波动规律及湿地土壤特性等各种因素的影响,呈现出相对一致的分布规律,在0—20cm土壤层含量较高,20cm层后随土壤深度的增加含量逐渐减小,减小的速度先快后慢直至40cm层后趋于稳定;不同植物群落对土壤有机质、全氮、全磷、全钾的含量及变化具有很大的影响,不同植物群落下同种元素含量差异显著,并且各自随土壤深度和植物群落的变化呈现出层状、带状或弧状富集特征。不同植物群落对土壤养分元素含量影响程度不同,苔草群落对各元素吸收和滞留能力最强、影响最大,刚毛荸荠群落对土壤营养元素影响最弱。湿地植物群落和土壤之间彼此有着强烈的影响,其中植株的重量和土壤的SOC、TN及TP含量有非常显著的负相关关系,与土壤TK含量则有较强的正相关关系,同时,植株的重量和高度与土壤地下水埋深也有微弱的负相关关系。

Wetland plants and soils are essential for ecological functions of wetlands and have strong interactions,e.g.wetland soils affect the distribution and abundance of plants species,especially the quantity,growth,development and morphology,as well as the distribution of plant communities.On the other hand,wetland vegetation also affects the distribution,dynamics and variation of chemical elements within the soil.The diversity of wetland plant communities and wetland soil in the Poyang Lake wetland and the resultant habitat for migratory birds are dependent on plant-soil interactions and Lake water-level fluctuations of varying frequency and amplitude.Much qualitative research had described the response of vegetation to alternating high and low lake levels in Poyang lake wetland,but few quantitative studies have documented the changes that occur.In response to recent concerns over the relationship among the lake water level,wetland vegetation and the habitat for migratory birds,we collected a quantitative data set from Poyang lake wetland and do some analyzes.Aimed to（1） study the characteristics of plant communities and（2）study the characteristics of wetland soil organic matter,total nitrogen,total phosphorus and total potassium,and（3） infer some hypotheses about the relationships between all of these variables in Poyang Lake wetland,we did monthly continued vegetation survey from October 2010 to October 2011 in 57 fixed quadrats in the Phragmites australis（Cav.） Trin.ex Steub.）,Triarrhera lutarioriparia L.Liu,C.cinerascens Kükenth.,Phalaris arundinacea Linn and E.vallecuIosa Ohwi communities along different water level gradients,and did laboratory analysis of 135 soil samples under the 5 dominant plant communities in Poyang Lake wetland.The results showed that,the distribution of plant communities present cluster distribution in population,present banded or arc-shaped distribution along the water level and elevation gradient in communities,and some species present mosaic distributions;plant community composition and characteristics also changed with the seasons and hydrological fluctuations.These characteristics may be due to the combined effects of the distribution of soil elements,Lake Water Level Fluctuations and the plant growth characteristics.There were relatively similar distribution patterns of organic matter and total nitrogen,the concentrations of soil organic matter and total nitrogen in the 0—20cm layer were significantly higher than those in the 30—90cm layers,and the content of nutrients in the soil decreased slowly with the soil depth and kept stable below 30 cm.Obviously,there are strong correlations between plant communities and soil characteristics,e.g.the content and change of soil organic matter,total nitrogen,total phosphorus and total potassium,for there are large significant differences with the chemical elements content and diversification between different plant communities.There was a significant negative correlation between Plant weight and soil SOC,TN and TP content,however,a strong positive correlation with TK content.Meanwhile,the plant′s weight and height have a weak negative correlation with depth of groundwater.This study provided quantitative evidence that lake-level fluctuations drive vegetative change and soils′ changes in Poyang Lake wetlands and it may assist in making decisions regarding Poyang lake management for government.