黄土丘陵区治沟新造耕地土壤的水盐分异特征

目的] 黄土丘陵区“治沟造地”工程形成的部分新造耕地面临着土壤盐碱化的风险,探究新造耕地土壤水盐空间分异特征及其影响因素,为预防和防治土壤盐碱化,促进新造耕地可持续利用提供理论依据。方法] 选择该区典型新造耕地,沿沟头至沟口设置6个试验小区,依次为采样点1,2,3,4,5,6,利用网格法获取每个小区0—20,20—40 cm深度的土壤样品,采用多重分形方法分析新造耕地土壤水、盐空间分异特征。结果] 新造耕地土壤水、盐含量沿沟头至沟口皆逐渐降低,采样点1,2,3地块的平均土壤水分和平均盐分含量分别为17.6%和0.81 g/kg,分别比采样点4,5,6地块的平均值高23.0%和14.1%（p<0.05）。采样点1,2,3地块土壤水、盐的多重分形参数D₁小于采样点4,5,6地块,而ΔD表现出相反的结果,表明采样点1,2,3地块土壤水、盐的空间变异性均较高。浅的地下水影响深度是促进采样点1,2,3地块盐分在表层土壤积累的主要原因（p<0.05）;地形特征也是一个重要原因,采样点1,2,3地块地形狭窄,不利于排水,易发生涝渍,加剧了盐分积累（p<0.05）。此外,采样点1,2,3地块可能受到较高盐分含量的坡面径流和泥沙侵入,提高了该区域土壤水、盐分含量及其变异性。结论] 地下水影响深度、地形特征及坡面径流泥沙是造成采样点1,2,3地块土壤水、盐含量及其空间变异性较高的重要原因。因此,靠近沟头位置的新造耕地是未来土壤盐碱化预防的重点区域。

Spatial Distribution Characteristics of Soil Water and Salt in Newly Cultivated Farmland Under Gully Control in Loess Hilly Region

Objective] Part of the newly cultivated farmland formed by the "Gully Control and Land Reclamation" project is facing the risk of soil salinization in the loess hilly region. The spatial distribution characteristics of soil water and salt and their influencing factors were studied for preventing and controlling soil salinization, and promoting sustainable utilization of newly cultivated land. Methods] A typical area of newly cultivated land was selected, and six experimental plots were established along a gully head to the gully mouth, with sampling points numbered sequentially from 1 to 6. The grid method was used to obtain soil samples from the 0-20 and 20-40 cm layers in each plot. The multifractal method was used to analyze the spatial distribution characteristics of soil water and salt. Results] Soil water content and salt content gradually decreased from the gully head to the gully mouth. The mean soil water contents and salt contents at sampling points 1, 2, and 3 were 17.6% and 0.81 g/kg, respectively, which were 23.0% and 14.1% higher than the respective values at sampling points 4, 5, and 6. Meanwhile, the multifractal parameters D₁ of soil water and salt at sampling points 1, 2, and 3 were less than the respective values at sampling points 4, 5, and 6. ΔD values showed the opposite result, indicating that the spatial variability of soil water and salt at sampling points 1, 2, and 3 were higher. The depth of groundwater influence was the main reason for increased accumulation of salt in the surface soil at sampling points 1, 2, and 3 (p<0.05). The terrain characteristic was also an important reason (p<0.05). The narrow terrain was not conducive to drainage, was prone to waterlogging, and exhibited exacerbated salt accumulation. In addition, sampling points 1, 2, and 3 may be invaded by slope runoff and sediment with high salt content that increased soil water, salt content, and variability in the area. Conclusion] The depth of groundwater influence, terrain characteristics, and slope runoff sediment were important reasons for the high soil water content, salt content, and their spatial variability at sampling points 1, 2, and 3 in newly cultivated farmland. Thus, newly cultivated farmland near the gully head location would be a key area for preventing soil salinization in the future.