Revealing the scale‐ and location‐specific variation and control factors of soil salinity using bi‐dimensional empirical modal decomposition

Abstract

AbstractThe key to saline land management and soil salinity control is to clarify the dynamics of soil salinity and the characteristics of environmental factors. However, due to the high heterogeneity of soil salinity, the influence of environmental factors on soil salinity variation at specific scales and locations is still unclear. The purpose of this study is to reveal the variability characteristics and controlling factors of soil salinity in the Wei‐Ku Oasis during different seasons. One hundred and eighty‐two topsoil samples (0–20 cm) were acquired during the irrigation and non‐irrigation seasons (IRRS and NIRRS) in the study area. This study predicted soil surface salinity at 90 m spatial resolution from randomForest (RF) models and measured data. Based on the mapping, a bi‐dimensional empirical modal decomposition (BEMD) algorithm was applied to extract the variation of the soil salinity at different scales and locations in the IRRS and NIRRS. Subsequently, correlation analysis, semi‐variance functions, and redundancy analysis were applied to dissect the correlation and main control factors between soil salinity and the environment at three different scales. The results indicated that soil salinity was greater in the NIRRS at the Weiku Oasis. Soil salinity was decomposed into five intrinsic modal functions with spatial variability scales of 6.20–50.61 km and 7.93–50.18 km during the IRRS and NIRRS, respectively. The relationships between environmental factors and soil salinity were scale‐ and location‐specific, suggesting a complex interrelationship between topography, temperature, vegetation cover, and soil salinity. The normalized difference vegetation index was found to be the main factor affecting small‐scale seasonal variation in soil salinity, whereas the large‐scale spatial distribution of soil salinity was most affected by evapotranspiration and temperature. These findings highlight the effectiveness of BEMD in revealing the scale and location control of soil salinity.