Scale- and location-specific relationships between soil available micronutrients and environmental factors in the Fen River basin on the Chinese Loess Plateau

- Wavelet coherence successfully unraveled scale- and location-specific correlation.
- Scale-location relationships of Cu or Zn with influencing factors were similar.
- The relationship of Fe with environmental factors was local at different scales.
- The correlation of Mn with SOM was significant at scales > 32 km at all locations.

Efficient scale- and location-specific soil micronutrients management is important for crop yield and environmental quality. This usually requires knowledge on scale- and location-specific control of soil micronutrients, which is not readily available from the traditional correlation analysis. The objective of this study was to analyze the scale- and location-specific relationships between surface (0-20 cm) soil available micronutrients (Cu, Fe, Mn, and Zn) and environmental factors by wavelet coherency analysis. For this purpose, soil available micronutrients, soil pH, soil organic matter (SOM), and topographic factors were obtained at 1 km interval along a 117 km-transect in the arable land of Fen River basin, China. The results showed that Cu, Mn, and Zn were positively correlated with SOM at scales 32-40 km at all locations, while Fe was positively correlated with SOM at scales 7-16 km at locations 75-117 km. Soil pH had negative influences on Cu and Zn at scales 25-40 km at all locations and on Fe at scales 12-21 km at locations 1-64 km. Both Cu and Zn had significantly negative relationships with aspect at scales 15-32 km at all locations, which cannot be detected at the sampling scale by the traditional correlation analysis. Wetness index had a significant impact on the distribution of Zn at scales 24-38 km at all locations and at scales 14-24 km at locations 1-60 km. Although elevation and slope showed significant correlations with Cu, Mn, and Zn at the sampling scale, wavelet coherence did not show any significant correlations in the scale-location domain. Therefore, the relationships of soil available micronutrients and influencing factors were scale- and location-dependent, which implies that different management practices are needed at different scales and locations to improve the global level of soil available micronutrients in the arable land of Fen River basin.