Changes in soil water repellency in a pine–beech forest transformation chronosequence: Influence of antecedent rainfall and air temperatures

Soil water repellency often exhibits pronounced temporal variation, which can hamper the assessment of repellency levels at a site when samples taken on only one date are evaluated. These temporal variations are often correlated to the season of the year, although the factors which govern seasonal repellency trends and the pertinent time scales are often unknown. Our objective has been to elucidate the year-to-year temporal variability of soil water repellency and the relationships of soil water repellency to soil moisture, antecedent rainfall, and temperatures prior to sampling at a forest transformation chronosequence in the climatic conditions of Central Europe. The forest transformation practice of underplanting beech trees into monospecies Scots pine forests is interpreted as a “disturbance” of the established pine ecosystem. Soil water repellency of samples taken in two consecutive years during summer was assessed using the water drop penetration time and the ethanol percentage methods.The results indicated extremely high repellency, but also pronounced differences for both years. Much higher levels of repellency were observed in 2001 than in 2002. This difference could only partly be ascribed to higher soil water content in 2001. In the 5 days before sampling, rainfall and maximum daily temperatures were clearly higher in 2001. However, no differences in averaged weather conditions between the 2 years were observed for the 60 days before sampling. This suggests that the time scale pertinent to changes in repellency levels could be short, i.e. on the order of a few days.