Abstract: The objective of this study was to apply multivariate empirical mode decomposition (MEMD) in revealing scale-specific characteristics of soil organic carbon (SOC) and total nitrogen (TN) and their main affecting factors. Using the transect method (20 m interval), 50 soil samples were collected from the peak-cluster depression. SOC and TN and environmental factors were separated into different intrinsic mode abductions (IMFs) and residues represented different scales. The multicharacteristic scales were IMF1, IMF2, IMF3 and IMF4 for SOC, and IMF1, IMF2, IMF3, IMF4 and IMF5 for TN. The dominant scales for SOC were similar with for TN. The dominant scales were IMF1 and IMF2 (scale: 68.6 and 140.9 m) for SOC, and IMF1 and IMF2 (scale: 73.2 and 141.1 m) for TN. IMF1 and IMF2 presented the main contribution to overall prediction of both SOC and TN. At each scale, SOC and TN were controlled by one or multiple factors. Significant correlations between rock ratio and SOC and TN were found both at measured scales and all IMFs. However, the relations between SOC and TN and the other environmental factors were complex. The significant correlations between SOC, TN and topographic wetness index and soil water at smaller scales (141.0 m) were strongest. The significant correlations between SOC and TN and pH at moderate scales (229.2 m) were strongest. The significant correlations between SOC and TN and elevation and slope at larger scales (362.9 m) were strongest. Our results showed that SOC and TN were controlled by different environmental factors at different specific scales. Our findings provide a better understanding of the relationships between SOC and TN and their main affecting factors at specific scales, and provide scientific basis for adaptive landscape pattern design and land-use structure adjustment.

Key words: grape, drip irrigation, rootshoot, regulation.