Analysis of scale-specific factors controlling soil erodibility in southeastern China using multivariate empirical mode decomposition

Abstract

Soil erodibility (K) is a key factor in predicting the erosion of soil by water. K is spatially influenced by many environmental factors, but studies of the scales of factors influencing K are rare. The objective of this study was to identify the scale-dependent relationships between K and various environmental factors using multivariate empirical mode decomposition (MEMD). K and nine environmental factors were investigated at 101 locations along a 4200-km sinuous transect in southeastern China and then they were decomposed and analyzed using MEMD. Mean K was 0.043 ± 0.008 t ha h MJ−1 mm−1 ha−1 and had a weakly moderate spatial variability. Six intrinsic mode functions (IMFs) and a residue were obtained for K and the environmental factors after decomposition. The mean scales for IMF1 to IMF6 were 123.4, 192.4, 347.0, 598.9, 1268.3 and 1559.2 km, respectively. IMF1 for each variable explained most of the spatial variability for the variable, and IMF1 and IMF2 or IMF1 and IMF3 explained half of the spatial variability of the variable. K was mainly associated with soil-particle composition and soil organic-matter content at small scales (IMF1-IMF2), with soil-particle composition and pH at moderate scales (IMF3-IMF4) and with elevation, saturated hydraulic conductivity and clay content at large scales (IMF5-IMF6). Modeled prediction functions of K at each scale of decomposition were accurate, but the total prediction accuracy at the sampling scale was slightly lower than for multiple linear regression. The MEMD method was nevertheless valuable and provided detailed information about the factors influencing K at different spatial scales.