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Journal of Arid Land  2020, Vol. 12 Issue (3): 462-472    DOI: 10.1007/s40333-020-0068-8
Research article     
Factors determining soil water heterogeneity on the Chinese Loess Plateau as based on an empirical mode decomposition method
GONG Yidan1, XING Xuguang2, WANG Weihua1,*()
1 Faculty of Agriculture and Food, Kunming University of Science and Technology, Kunming 650500, China
2 Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling 712100, China
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Soil water is a critical resource, and as such is the focus of considerable physical research. Characterization of the distribution and spatial variability of soil water content (SWC) offers important agronomic and environmental information. Estimation of non-stationary and non-linear SWC distribution at different scales is a research challenge. Based on this context, we performed a case study on the Chinese Loess Plateau, with objectives of investigating spatial variability of SWC and soil properties (i.e., soil particle composition, organic matter and bulk density), and determining multi-scale correlations between SWC and soil properties. A total of 86 in situ sampling sites were selected and 516 soil samples (0-60 cm depth with an interval of 10 cm) were collected in May and June of 2019 along the Yangling-Wugong-Qianxian transect, with a length of 25.5 km, in a typical wheat-corn rotation region of the Chinese Loess Plateau. Classical statistics and empirical mode decomposition (EMD) method were applied to evaluate characteristics of the overall and scale-specific spatial variation of SWC, and to explore scale-specific correlations between SWC and soil properties. Results showed that the spatial variability of SWC along the Yangling-Wugong-Qianxian transect was medium to weak, with a variability coefficient range of 0.06-0.18, and it was gradually decreased as scale increased. We categorized the overall SWC for each soil layer under an intrinsic mode function (IMF) number based on the scale of occurrence, and found that the component IMF1 exhibited the largest contribution rates of 36.45%-56.70%. Additionally, by using EMD method, we categorized the general variation of SWC under different numbers of IMFs according to occurrence scale, and the results showed that the calculated scales among SWC for each soil layer increased in correspondence with higher IMF numbers. Approximately 78.00% of the total variance of SWC was extracted in IMF1 and IMF2. Generally, soil texture was the dominant control on SWC, and the influence of the three types of soil properties (soil particle composition, organic matter and bulk density) was more prominent at larger scales along the sampling transect. The influential factors of soil water spatial distribution can be identified and ranked on the basis of the decomposed signal from the current approach, thereby providing critical information for other researchers and natural resource managers.

Key wordsbulk density      loess plateau      soil water      soil organic matter      soil texture      spatial variability     
Received: 03 July 2019      Published: 10 May 2020
Corresponding Authors: Weihua WANG     E-mail:
About author: *Corresponding author: WANG Weihua (E-mail:
Cite this article:

GONG Yidan, XING Xuguang, WANG Weihua. Factors determining soil water heterogeneity on the Chinese Loess Plateau as based on an empirical mode decomposition method. Journal of Arid Land, 2020, 12(3): 462-472.

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Fig. 1 Location of the study area on the Chinese Loess Plateau (a) and overview of the Yangling-Wugong-Qianxian transect (b)
Soil depth
Mean (%) Maximum (%) Minimum (%) Standard deviation (%) Variability coefficient
0-10 23.00 38.05 16.22 4.21 0.18
10-20 25.47 48.43 18.13 4.40 0.17
20-30 24.55 41.85 17.61 3.62 0.15
30-40 24.05 34.38 19.24 2.69 0.11
40-50 23.32 35.73 19.38 2.45 0.10
50-60 21.55 26.55 16.61 1.31 0.06
Table 1 Statistical characteristic values of soil water content (SWC)
Fig. 2 Intrinsic mode functions (IMFs) and residues of soil water content (SWC) at various soil depths. The numbers in each square bracket, in order, represent the characteristic scale value (m) and the contribution rate (%) of each IMF or residue. -, no value.
IMFs/residue 10-20 cm 20-30 cm 30-40 cm 40-50 cm 50-60 cm
Decomposition of SWC at the 0-10 cm depth IMF1 0.852** 0.528* 0.128 0.105 -0.082
IMF2 0.707* 0.450* 0.055 0.124 -0.055
IMF3 -0.398 0.467 -0.033 0.111 -0.082
IMF4 0.569 0.555 0.467 0.250 -1.138
IMF5 0.463 0.025 -0.074 -0.071 0.051
Residue 0.362 -0.387 -0.290** -0.132 -0.238*
IMFs/residue 20-30 cm 30-40 cm 40-50 cm 50-60 cm
Decomposition of SWC at the 10-20 cm depth IMF1 0.787** 0.191 0.031 0.035
IMF2 -0.494 -0.199 -0.042 -0.072
IMF3 -0.698** -0.154 -0.040 -0.050
IMF4 0.268 0.184 -0.029 -0.034
IMF5 0.196 -0.155 -0.186 0.021
Residue -0.397 -0.309** -0.164 -0.273*
IMFs/residue 30-40 cm 40-50 cm 50-60 cm
Decomposition of SWC at the 20-30 cm depth IMF1 0.654** 0.517 0.117
IMF2 0.628* 0.551* 0.055
IMF3 0.627 -0.524 0.117
IMF4 0.273 0.342 -0.183
IMF5 0.137 0.331 0.138
Residue 0.322* 0.139 0.159
IMFs/residue 40-50 cm 50-60 cm
Decomposition of SWC at the 30-40 cm depth IMF1 0.517** 0.340
IMF2 0.413 0.248
IMF3 0.423 -0.233
IMF4 0.641* 0.145
Residue 0.546* 0.329
IMFs/residue 50-60 cm
Decomposition of SWC at the 40-50 cm depth IMF1 0.349*
IMF2 0.156
IMF3 -0.143
IMF4 0.024
IMF5 0.342**
Residue -0.079
Table 2 Correlation coefficients of measured SWC with intrinsic mode functions (IMFs) and residues of SWC at different soil depths
Fig. 3 Intrinsic mode functions (IMFs) and residues of mean SWC and soil properties (soil particle content, organic matter and bulk density) at the soil depth of 0-60 cm. The numbers in each square bracket, in order, represent the characteristic scale value (m) and the contribution rate (%) of each IMF or residue. -, no value.
IMFs/residue Clay Silt Sand Soil organic matter Soil bulk density
IMF1 0.520** 0.508** -0.514** 0.411* 0.159
IMF2 0.589** 0.605** -0.592** 0.501* 0.431*
IMF3 0.672** 0.669** -0.665** 0.545** 0.363
IMF4 0.714** 0.705** -0.706** -0.582** -0.689**
Residue -0.847** -0.840** 0.433** 0.463** -0.973**
Table 3 Correlation coefficients of soil properties with IMFs and residue of mean SWC at the depth of 0-60 cm
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