Abstract
It is important to study the mechanisms associated with the spatial
distribution of soil water and salt to control soil salinization and
promote the sustainable development of farmland. In this study, six
plots in gully farmland in the loess hilly region with different spatial
locations were selected to determine the spatial distributions of soil
water and salt and their correlation using the multifractal method. A
grid method (15 m 15 m, 3,600 m2) was applied in the 0–20 and 20–40
cm soil layers where each sampling site was located at the center point
coordinates. The results showed that the spatial variability of the soil
water and salt were 1.41 and 1.73 times higher, respectively, in the
upstream farmland than the downstream farmland. The uneven runoff and
sediment distributions from gullies in the upstream farmland increased
the spatial variability of the soil water and salt. In addition, the
vulnerability of upstream farmland to waterlogging caused further in
their spatial variability due to narrow landform features. Analysis
using the joint multifractal method showed that the spatial variability
of the soil water and salt was strongly correlated (P < 0.05)
because of the coupling between soil water and salt. In addition, the
spatial variability of the soil water and salt was strongly correlated
in the 0−20 and 20−40 cm layers because of the spatial autocorrelations
of the soil properties (P < 0.05), thereby indicating that the
spatial distributions of soil water and salt in the whole soil layer
could be represented by those in the 0−20 cm layer. Thus, we recommend
using the 0−20 soil layer to sample the distributions of the soil water
and salt. Our results provide a theoretical basis for studying the
interactive mechanisms associated with the distributions of soil water
and salt, and for optimizing the sampling method in the study area.