Multifractal and joint multifractal description of available nutrients concentrations extracted by two methods along short transects

Abstract

Spatial variability of available P, K, Ca and Mg, sampled along two short transects and determined by two different extraction methods, was characterized using multifractal and joint multifractal analysis. Sixty-six soil samples were collected every 0.8 m, both in a vineyard and in a polyculture field. Available nutrients were extracted with an ion exchange resin and the Mehlich 3 solution. Shape and width of singularity, f(α) versus α, and generalized dimension, Dq, spectra, showed that spatial distributions obtained by the two tests behaved as quasi-monofractals in the vineyard, but were fitted with multifractal models under polyculture. Joint multifractal analysis demonstrated positive correlations between the scaling indices of P, K, Ca and Mg, extracted by resin and Mehlich 3, which were stronger under polyculture. Pearson correlations between available nutrients determined by two tests at the single scale ranged from R2 = 0.54 to 0.95 and were weaker than those of the respective scaling indices across the range of scales studied, which varied from R2 = 0.63 to 0.97. The joint multifractal approach showed that single scale analysis may be insufficient to compare relationships between available nutrient tests. Moreover, multifractal analysis may be useful to upscaling/downscaling nutrient availability.