Abstract
AimsRoots are essential drivers of soil structure and pore formation. This study aimed at quantifying root induced changes of the pore size distribution (PSD). The focus was on the extent of clogging vs. formation of pores during active root growth.MethodsParameters of Kosugi’s lognormal PSD model were determined by inverse estimation in a column experiment with two cover crops (mustard, rye) and an unplanted control. Pore dynamics were described using a convection–dispersion like pore evolution model.ResultsRooted 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 of the pore system as dominant process of root induced structure formation.ConclusionsPore 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.
Highlights
Soil hydraulic properties are the common result of particle size distribution and aggregation
We quantified the changes in the pore size distribution (PSD) of soil rooted by mustard and rye compared to a non rooted soil
Based on a column drainage experiment parameters of the lognormal Kosugi PSD model were determined by inverse optimization
Summary
Soil hydraulic properties are the common result of particle size distribution (texture) and aggregation (structure). Bio-macropores and root-induced micropores are formed (Cresswell and Kirkegaard 1995; Mitchell et al 1995; Wuest 2001; Horn and Smucker 2005; Ghestem et al 2011). These pores have high connectivity (Pagliai and De Nobili 1993; Whalley et al 2005), thereby facilitating water transport through the soil (Gish and Jury 1983; Murphy et al 1993; Suwardji and Eberbach 1998). E.g. Disparte (1987) measured an increase of infiltration with higher rooting density after decomposition of roots. Gyssels et al (2005) confirmed this finding by establishing a direct relation between root density and reduction of soil erosion
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