垦殖与自然条件下黄河三角洲土壤盐分的时空演化特征研究

为探究人为垦殖与自然条件下黄河三角洲土壤盐分的时空演化特征,实现黄河三角洲后备土地资源的高效开发,保障生态和环境安全,利用空间变换推演时间演替,沿黄河入海方向,自利津县北宋镇至黄河三角洲保护区内黄河入海口布设采样带,研究当地典型作物(小麦、棉花、水稻)和自然条件下土壤盐分的时空演化特性,随机选取28个主采样区,采集140个样点,每个样点以20cm为1个土层,测定0—100cm土层土壤含盐量。研究表明:整个研究区域0—20cm土壤平均含盐量为3.58g/kg,显著高于60—100cm土层(p0.05),属于中度盐化土,空间表现为强变异性(CV=131%),随着土层深度的增加,不同土地利用类型间盐分空间变异减小;土壤盐分剖面的空间分布特征体现了人为垦殖和自然条件的协同影响,表聚型盐分剖面主要分布在采样带的近海端(1972年后冲积区域中此类剖面占83.3%),作物以低产棉田和自然植被为主,85.7%的自然植被和45.5%棉花为表聚型,平均型主要分布在采样带的中部及内陆区域,1855年之前及1855—1972年间的冲积区域中此类剖面各占40.0%,作物主要以水稻、小麦和滩涂为主;底聚型主要分布在采样带的内陆地区,1855年之前的区域中此类剖面占31.3%,主要以农作田为主,棉花、小麦、水稻均衡分布;人为垦殖管理、植被类型等随机因素是导致0—80cm土层土壤含盐量变异的主要原因,随着土层深度的增加,随机因素影响减弱,地形、地下水位等结构性因素影响增强;基于盐分的空间分布,绘制农作物布局区划图,可为黄河三角洲地区盐渍土资源合理开发利用提供参考。该研究揭示了垦殖与自然条件下土壤盐分时空演化特征,自滩涂至内陆,土壤盐分剖面由表聚型向底聚型过渡,人为垦殖在一定程度上可以降低土壤的盐渍化程度,但人为垦殖与土壤盐渍化之间互为因果、相互推进。

Time-spatial Revolution Characteristics of Soil Salinity in the Yellow River Delta Under Different Land Cultivation and Natural Conditions

In order to explore the temporal and spatial variations in soil salinity under human cultivation and natural conditions in the Yellow River Delta,to realize the efficient development of the reserved land resources and ensure the ecological and environmental safety,in this study,spatial transformation was used to deduce the time succession.A sampling zone was set from Lijin County Beisong town to the Yellow River Estuary in a protected area (118°10′50″E to 119°09′02″E,37°26′37″N to 37°49′36″N) along the Yellow River to reveal the temporal and spatial characteristics of soil salinity in the farmland of typical crops (wheat,cotton,rice) and under natural conditions.28 main sampling areas were randomly selected and 140 samples were collected,with every 20 cm as a soil layer,and the salt content of 0-100 cm soil layer was determined.The results showed that the average soil salinity in the 0-20 cm soil layer was 3.58 g/kg in the sampling belt,which was significantly (p＜0.05) higher than that in the 60-100 cm and soil layer,and these soils were of moderate salinity.The salinity distribution showed a strong spatial variability (CV =131％) in the 0-60 cm soil layer,but with the increase of soil depth,the coefficient of variation decreased continuously.The spatial distribution characteristics of soil salinity profile reflected the temporal effect of cultivation and natural conditions.Inverted salinity profiles were mainly distributed in the coastal zone,which accounted for 83.3％ of the alluvial area formed after the year of 1972,and the main vegetation types were low-yield cotton crops and natural vegetation,which accounted for 45.5％ and 85.7％,respectively.The average salinity profiles were mainly distributed in the middle and inland regions of the sampling area,which both accounted for 40.0％ in regions formed before 1855 and during 1855 to 1972,respectively,and the main vegetation types were rice,wheat and intertidal zone.The normal salinity profile types were mainly distributed in the inland regions of the sampling zone (which accounted for 31.3％ of the area formed before 1855),and the main vegetation types were farming field,with cotton,wheat,and rice fields being distributed equally.Random factors such as,cultivation management and vegetation were the main factors that caused the variation in soil salinity in the 0-80 cm soil layer,with the increase of soil depth,the effects of these random factors weakened,but the effects of structural factors such as drainage and groundwater level became stronger.Based on the spatial evolution characteristics of soil salinity,a map of crop distribution was made to provide a support for the development and utilization of saline soil in the Yellow River Delta.In conclusion,the study revealed that the time-spatial evolution characteristics of soil salinity in the Yellow River Delta under different land cultivation and natural conditions,i.e.from coastal to inland,the soil salinity profile changed from inverted salinity profile to normal salinity profile.Cultivation can reduce soil salinization so some degree,but cultivation and soil salinization are reciprocal causations and can promote the development of each other.