Soil Science Society Belgium Thematic Day 2014: Soil-plant interactions in a changing world. location:The Royal Academies for Science and the Arts of Belgium, Hertogstraat 1 Rue Ducale, Brussels date:5 December 2014
Natural vegetation is frequently used in ecological restoration programs to prevent or
reduce the severe impact of soil erosion processes. Over the last two decades the focus of
research on controlling soil erosion by vegetation gradually shifted from aboveground biomass
towards the role of belowground biomass. Several case studies reported on the effects of plant
roots in controlling concentrated flow erosion, however a global analysis of these root effects is
still lacking. The objectives of this study are therefore: 1) to provide an overview of the empirical
studies reporting the effects of root variables on soil erosion rates, 2) to establish a global
dataset and to analyse the erosion‐reducing effects of plant roots and 3) to investigate the
influence of soil texture and root system architecture on soil erosion‐reducing effects of roots.
An extensive literature review resulted in 34 publications on the effects of plant roots in
controlling soil erosion by water. Data from respectively 13 and 6 studies for root density (RD,
kg/m³) and root length density (RLD, km/m³) were pooled resulting into two global datasets
containing 822 and 274 observations of the relative soil detachment rate (RSD, ‐). Non‐linear
regression analysis resulted in the Hill curve model (RSD=(R(L)D)^(‐b)/(c+(R(L)D)^(‐b)); with
b and c model parameters) as best fit model in order to estimate the erosion‐reducing potential
of plant roots. Both datasets showed a large variability due to differences in root characteristics
of tested plant species, soil characteristics and experimental set ups which resulted into a low
predictive accuracy. By means of a Monte Carlo simulation this uncertainty was quantified
allowing us to use the models as a first assessment of the erosion‐reducing effects of plant roots.
Minimal values for RD and RLD at which plant roots have a positive erosion‐reducing effect at
95% confidence interval amount to 1.3 kg/m³ and 16 km/m³ respectively. Efforts to improve the
model by using additional variables (soil texture and root architecture) were not effective.
However it is likely that a high percentage of sand as well as a tap root system negatively
influence the erosion‐reducing effect of roots. Preference is given to the global model based on
RLD to estimate RSD as RLD takes into account the effect of root system architecture which is
not the case for RD.