Root induced changes of effective 1D hydraulic properties in a soil column

Aims Roots are essential drivers of soil structure and pore formation. This study aimed at quantifying root induced changes ofthe pore size distribution (PSD). The focus was on the extent of clogging vs. formation of pores during active root growth. Methods Parameters ofKosugi’s lognormal PSDmodel were determined by inverse estimation in a column experiment with two cover crops (mustard, rye) and an unplanted control. Pore dynamics were described using aconvection–dispersion like pore evolution model. Results Rooted treatments showed a wider range of pore radii with increasing volumes of large macropores >500 μm and micropores <2.5 μm, while fine macropores, mesopores and larger micropores decreased. The non-rooted control showed narrowing of the PSD and reduced porosity over all radius classes. The pore evolution model accurately described root induced changes, while structure degradation in the non-rooted control was not captured properly. Our study demonstrated significant short term root effects with heterogenization ofthe pore system as dominant process of root induced structure formation. Conclusions Pore clogging is suggested as a partial cause for reduced pore volume. The important change in micro- and large macropores however indicates that multiple mechanic and biochemical processes are involved in root-pore interactions.