Spatial scaling of soil salinity indices along a temporal coastal reclamation area transect in China using wavelet analysis

<p>High spatial variability of soil salinity in coastal reclamation regions makes it difficult to obtain accurate scale-dependent information. The objectives of this study were to describe the spatial patterns of saline-sodic soil properties (using soil pH, electrical conductivity (EC<sub>1:5</sub>) and sodium ion content (<i>SIC</i>) as indicators) and to gain knowledge of the scaling relationships between those variables. The soil pH, EC<sub>1:5</sub> and <i>SIC</i> data were measured at intervals of 285 m along a 13,965-m temporal transect in a coastal region of China. The spatial variability of soil pH was weak but it was strong for soil EC<sub>1:5</sub> and <i>SIC</i> at the measurement scale. There was a significant positive correlation between soil EC<sub>1:5</sub> and <i>SIC</i>, while correlations between soil pH and either EC<sub>1:5</sub> or <i>SIC</i> were weak and negative. For each saline-sodic soil parameter, the variability changed with the decomposition scales. The high-variance area at the larger scales (≥570 m) occupied less than 10% of the total area in the local wavelet spectrum, which meant that the spatial variations of the salinity indicators were insignificant at these scales. For local wavelet coherency, at a scale of 1500–2800 m and a sampling distance of 0–4500 m, the covariance was statistically significant between any two of the saline-sodic soil parameters.</p>