盐城海滨湿地景观演变关键土壤生态因子与阈值研究

Abstract

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 nitrogenavailable potassiumorganics. 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.