| The Yellow River Delta is an important reserve resource base for low-yielding fields in China,which has great potential for development,but the field yield is greatly restricted under the influence of salinization.As an important saline-alkali land improvement measure,agricultural drainage ditches have been widely used in the Yellow River Delta region,forming a unique landscape of coastal saline farmland.In the process of use,a series of phenomena such as erosion,collapse and siltation appeared in the drainage ditches of farmland,which greatly restricts the function of the drainage ditches and destroys the landscape of farmland.In this paper the typical farmland drainage ditches?tertiary ditch,farm ditch?in the Yellow River Delta were selected,studed the dynamic change law of spatial of temporal characteristics of different seasons?Spring,Summer,Autumn?,slope directions?Eastern slope,Western slope,Southern slope,Northern slope?and slope position?Upper slope,Middle slope,Lower slope?,reveals the soil-vegetation coupling relationship through the investigation and analysis of soil and vegetation in different slopes of farmland ditches,and explores the key limiting factors for the growth of vegetation on the ditches slopes of saline-alkali soil farmlands,and then demonstrates the distribution law of ecological construction group vegetation,in order to provide reference for the ecological restoration of saline farmland.The main research results are as follows:?1?The soil characteristics of the slope of the farmland drainage ditches show significant laws of temporal and spatial variation.Soil water content is concentrated in the middle and lower slopes,and the distribution laws of different ditch types are different,and the water content of soil in autumn is higher than in spring and summer.The ditches'slope soil salt is concentrated in the middle slope in spring,and the salt table poly of the north slope of tertiary ditches is significant;in the summer and autumn,the content of soil salt is concentrated in the middle and lower slope,and reaches a relatively high value(4.74 g·kg-1)in summer.Soil p H showed significant seasonal changes that spring<summer<autumn.The content of soil organic matter and total nitrogen was showed the highest value in the middle slope,and the whole slope is showed the seasonal change law of lower in summer and higher in spring and autumn.The content of soil available phosphorus is increased significantly in summer and autumn in the surface of slope soil,and the content was accumulated in the lower slope.?2?The slope vegetation of the farmland drainage ditches showed significant differences within slope directions and positions.The vegetation Shannon-Wiener diversity index showed higher on lower slope with more concentrated soil water,and the lowest species diversity in the middle slope with the highest soil salinity.The Simpson species advantage index showed that belower slope>upper slope>middle slopes.The Pielou uniformity index re-assembles with the rich area of soil salt,and the south slope is higher than the north slope uniformity.The Margalef species richness index showed the upper slope>middle slope>lower slope.The biomass of the slope vegetation also showed significant spatial differences,and the distribution laws were significantly different among sample area.?3?The vegetation distribution of farmland drainage ditches is significantly restricted by soil characteristics,the main limiting factors are the content of soil water,organic matter,totle salt and p H.The composition of the main influence factors varies with the sample area and slope positions,and different ecological strategies are formed based on slope soil-vegetation coupling.Therefore,ecological restoration of salted soil farmland drainage ditches should be based on dynamic changes in soil characteristics and vegetation response strategies,then select the suitable vegetation types and planting methods. |
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