盐城海滨湿地景观演变关键土壤生态因子与阈值研究

文章以盐城海滨湿地典型区域为案例，以2011年4月和2012年4月对海滨湿地土壤数据为基础，结合2011年ETM 遥感影像，运用灰色关联分析、线性回归模拟和地统计学方法，辨识海滨湿地景观演变的关键生态因子，并确定其生态阈值。得出基本结论如下：(1)海滨湿地土壤理化性质海陆差异明显：从米草沼泽—碱蓬沼泽—芦苇沼泽，土壤水分和盐度表现出递减的趋势；土壤有机质、营养盐总体上从米草沼泽—碱蓬沼泽—芦苇沼泽，表现出两头高中间低的特征；湿润年份土壤水分高于干旱年份，湿润年份土壤盐度低于干旱年份。(2)灰色关联分析表明:干旱年份,水分＞盐度＞铵态氮＞速效钾＞有机质＞有效磷；湿润年份为：盐度＞水分＞有效磷＞铵态氮＞速效钾＞有机质，因此把土壤水分和盐度确定为海滨湿地景观演变的关键生态因子。(3)土壤水分和盐度在东西海陆方向上的变异大于南北海岸延伸方向上的变异。(4)将景观类型图和海滨湿地土壤水分与盐度分异图叠加分析，得出：芦苇滩土壤水分阈值＜42.332%，盐度阈值＜0.745%；碱蓬滩土壤水分阈值为38.836%～46.593%，盐度阈值为0.403%～1.314%；米草滩土壤水分阈值＞39.475%，盐度阈值＞0.403%；光滩的土壤阈值＞41.550%，盐度阈值＞0.656%。

The studying of key ecological factors and threshold of landscape evolution in Yancheng Coastal wetland

The key ecological factors influencing the evolution of coastal wetland landscape were investigated by soil sampling and analyzing, and analyses on data from ETM+ by methods of grey relative analysis, linear regression and geostatistics in the Yancheng national natural reserve as an example. The ecological thresholds were defined based on the analyses on the relationship between the spatial distribution and landscape types. (1) The physiochemical properties of soil at the coastal wetland exert distinct continental and oceanic difference, depending on their specific location and corresponding vegetation types. Soil water content and salinity shows a trend of decrease from Spartina marsh to salsa, and to reed. The soil water content was higher in wet season than in dry season, in contrast, the salinity exhibited lower average value in wet season than in dry season. The soil organics and nutrient content show higher values in Spartina marsh and reed, while lower in salsa, and generally higher in wet season than dry season, with an exception for the soil available phosphorus. (2) Through the grey relative analysis, the rank of the correlation between the wetland soil physicochemical characteristic and landscape evolution follows: in the dry season water > salinity > ammonium nitrogen > available potassium > organics > available phosphorus; in the rainy season water > salinity > available phosphorus > ammonium nitrogen > available potassium > organics. Therefore the soil water content and salinity were identified as the key ecological factors that influence the evolution of coastal wetland landscape.(3)The spatial distribution of soil water content and salinity show the same trend and was classified into five grades, with the variation higher in the eastern-western direction than in the southern-northern direction. (4) Combined with analyzing distribution of soil water content and salinity and the correlated landscape types, the range of thresholds of soil water content and salinity were defined. The soil water content and salinity were less than 42.33% and 0.745% respectively for reed soil; 38.836%-46.593% of soil water content and 0.403%-1.314% for salsa soil; Spartina marsh soil had water content of above 39.475% and salinity above 0.403%; with the soil water content and salinity of more than 41.550% and 0.656% for optical flat soil.