Changes in selected physico-chemical properties of floodplain soils in three different land-use types after flooding

Abstract

This article provides information on selected physico-chemical properties, including soil colour, texture, electrical conductivity, pH<sub>H</sub>2O, pH<sub>CaCl</sub>2, content of total carbon and Q<sub>4/6</sub> quotient, of the topsoil and subsoil of former flood sediments at three diverse vegetation plots in a floodplain and in two reference plots unaffected by floods, and changes of some soil properties caused by a new subsequent flood. Aggradation of flood sediments in the area was controlled both by local terrain morphology and vegetation type cover. Differences in the properties of sediments in the individual plot types were caused by the different production of litter, root biomass and carbon cycling before the new flood. Vertical distributions and inventories of <sup>137</sup>Cs in soils revealed the position and proportion of modern sediments in soil profiles, man-made filling of former erosion grooves and ploughing depths. The new flood of a lower hydrological power aggraded a thin layer of organo-clay sediment on the soil surface but showed minor effects on the investigated soil properties. The lowest dry bulk density and highest total porosity values were found in the topsoil of woody and grassy plots after the flood implying no substantial break down of soil aggregates by the flood. The highest dry bulk density values in the subsoil of fields indicated soil compaction from agricultural machinery. No increased soil salinity was found after the flood. The flood did not significantly affect the pH<sub>H</sub>2O of the topsoil and subsoil; however, a significant increase in pH<sub>CaCl</sub>2 was found for the topsoil of grassy plots and for all topsoil samples from the park. No significant increases in total carbon (C<sub>tot</sub>) contents were found in topsoils of any plot types after the flood in spite of an accumulation of thin organo-clay material on the soil surface after the flood. However, significant increases in C<sub>tot</sub> in subsoils of all plot types indicate the vertical migration of colloidal and dissolved organic carbon in soils during the flood. C<sub>tot</sub> contents positively correlated with electrical conductivity values and negative correlated with pH values. The relatively minor changes in soil physico-chemical properties found after the flood can be explained by the short duration and small dynamic power of the flood, and the timing of sampling when the flood had receded and soil aeration was already being restored.