Multifractal behaviour of the soil water content of a vineyard in northwest Spain during two growing seasons

Abstract

Soil processes are characterized by a great degree of heterogeneity, which may be assessed by scaling properties. The aims of the current study were to describe the dynamics of soil water content at three depths in a vineyard under rain-fed and irrigation conditions and to assess the multifractality of these time data series. Frequency domain reflectometry (FDR) sensors were used for automatically monitoring soil water content in a vineyard located in Leiro (Ourense, northwest Spain). Data were registered at 30 min intervals at three depths (20, 40, and 60 cm) between 14 June and 26 August 2011 and 2012. Two treatments were considered: rain-fed and irrigation to 50 % crop evapotranspiration. Soil water content data series obeyed power laws and tended to behave as multifractals. Values for entropy (D1) and correlation (D2) dimensions were lower in the series from the irrigation treatment. The Hölder exponent of order zero (α0) was similar between treatments; however, the widths of the singularity spectra, f(α), were greater under irrigation conditions. Multifractality indices slightly decreased with depth. These results suggest that singularity and Rényi spectra were useful for characterizing the time variability of soil water content, distinguishing patterns among series registered under rain-fed and irrigation treatments.