Earthworm effect on root morphology in a split root system
Abstract
Plants respond to their environment through adaptations such as root proliferation in nutrient-rich
patches. Through their burrows and casts production in soil, earthworms create heterogeneity which could
lead to local root adaptations or systemic effects. To investigate the effect of earthworms on root system
morphology and determine whether earthworm effect is local or systemic, we set up two independent
split root experiments with rice or barley, (i) without earthworm (CC), (ii) with earthworms in both
compartments (EE), and (iii) with earthworms in one single compartment (CE). Earthworms had an effect
on belowground plant biomass. The relative length of thick roots decreased with an increasing abundance
of earthworms. Some root diameter classes responded to earthworm number in a linear or curvilinear
way, making simple conclusions difficult. We found no difference in root biomass or morphology between
the two compartments of the split root system in the CE treatment, but a positive effect of earthworm
biomass on root biomass, volume, surface area, and length at the whole plant level. Results supported a systemic effect dependent on earthworm abundance. Modification of nutrient mineralization, soil physical structure, and/or the concentration of signal molecules could all be responsible for this systemic effect.