Significance of tree roots for preferential infiltration in stagnic soils

摘要

It is generally recognized that roots have an effect on infiltration. Inthis study we analysed the relation between root length distributions fromNorway spruce (Picea abies (L.) Karst), silver fir (Abies alba Miller), European beech (Fagus sylvatica L.) andpreferential infiltration in stagnic soils in the northern Pre-Alps inSwitzerland. We conducted irrigation experiments (1 m2) and recordedwater content variations with time domain reflectometry (TDR). A rivuletapproach was applied to characterise preferential infiltration. Roots weresampled down to a depth of 0.5 to 1 m at the same position where theTDR-probes had been inserted and digitally measured. The basic properties ofpreferential infiltration, film thickness of mobile water and the contactlength between soil and mobile water in the horizontal plane are closelyrelated to root densities. An increase in root density resulted in anincrease in contact length, but a decrease in film thickness. We modelledwater content waves based on root densities and identified a range of rootdensities that lead to a maximum volume flux density and infiltrationcapacity. These findings provide convincing evidence that tree roots instagnic soils represent the pore system that carries preferentialinfiltration. Thus, the presence of roots should improve infiltration.