Publications - Brett Robinson

Root strategies - where trace elements occur heterogeneously in soil

Trace Elements (TE)s occur heterogeneously in soil. Depending on the soil’s origin, TE concentrations may change by an order of magnitude or more over just a few centimetres. The total concentration and distribution is a function of the parent material plus subsequent atmospheric or water-borne deposition.

The heterogeneous distribution of TEs in soil affects plant root growth. In some tree species, the roots avoid hotspots contaminated with TEs. Conversely, roots of the hyperaccumulator plant Thlaspi caerulescens actively forage zinc-rich hotspots in soils. The response of roots to heterogeneously distributed TEs may profoundly affect uptake as well as leaching of the trace element through the soil profile. The principles of how heterogeneously distributed TE affects root development is poorly understood.

Until recently, a lacuna of non-destructive measurement technologies has hampered the visualisation of the growth and activity of living roots. The Paul Scherrer Institut, Villigen, Switzerland has developed a facility to visualise roots in soil using neutron radiography and tomography. Using this technique, we can investigate the response of roots to heterogeneously distributed TEs in soil. Neutron radiography can also reveal the water flux in the root zone. We are developing experimental techniques and image processing tools to obtain quantitative data from such neutron radiographs.

Using neutron radiography, we endeavour to elucidate TE-root interactions on the single plant scale with the aim of producing more accurate whole system models of contaminant transport. However, to be useful in the real world, such models require validation at larger scales. We are investigating the role of roots in preferential flow using large lysimeters covered with both shallow and deep-rooting vegetation. Following a rain event, we will intensively measure drainage from the lysimeters to investigate preferential flow and TE leaching.

Publications - Brett Robinson

Root strategy or root inhibition? A neutron radiograph of a lupine growing in a 150 x 150 x 10 mm aluminium slab containing soil partitioned with 20 mg/kg added B in a 50 mm vertical strip on the right hand side of the image. The left hand 100 mm contained no added B.