Effects of different climatic conditions on soil water storage patterns

Abstract

The soil water storage (SWS) defines the crop productivity of a soil and varies under different climatic conditions. Pattern identification and quantification of these variations in SWS remain difficult due to the non-linear behaviour of SWS changes over time. Wavelet analysis (WA) provides a tool to efficiently visualize and quantify these patterns by transferring the time series from the time domain into the frequency domain. We applied WA to an 8-year time series of SWS, precipitation (P), and actual evapotranspiration (ETa) in similar soils of lysimeters in a colder and drier location and in a warmer and wetter location within Germany. Correlations between SWS, P, and ETa at these sites might reveal the influence of altered climatic conditions but also of subsequent wet and dry years on SWS changes. We found that wet and dry years exerted an influence over SWS changes by leading to faster or slower response times of SWS changes in relation to precipitation with respect to normal years. The observed disruption of annual patterns in the wavelet spectra of both sites was possibly caused by extreme events. Extreme precipitation events were visible in SWS and P wavelet spectra. Time shifts in correlations between ETa and SWS became smaller at the wetter and warmer site over time in comparison to at the cooler and drier site, where they stayed constant. This could be attributed to an earlier onset of the vegetation period over the years and, thus, to an earlier ETa peak every year. This reflects the impact of different climatic conditions on soil water budget parameters.