Claire Grierson

Claire Grierson ( Biological Sciences ), co-applicants T Quine and Sarah De Baets (College of Life and Environmental Sciences, University of Exeter) recently won funding from the Cabot Institute Annual Open Call for a project looking at how roots stabilise soils.  This has implications in the growing of food, fuel, timber and fibre and also impacts on water, air and carbon cycles.  Here they explain their project.

Humans have degraded almost a quarter of the vegetated land on Earth, most by soil erosion. Soil loss on conventionally managed agricultural land dwarfs soil production with around 12 million fertile hectares lost annually. Plant roots produce soil cohesion, retain soil on slopes, and cycle nutrients into soils, amongst the largest carbon sinks on Earth.

However, we don’t know how roots stabilise soils. This ignorance could prove costly as population growth demands more food, fuel, timber and fibre production from plants and soils, impacting on water, air and carbon cycles. Climate change may compound the problem by bringing more frequent extreme weather likely to exacerbate soil loss.

When rills or gullies develop during water flow, large portions of the soil are lost. Previous small-scale research has shown that root architecture matters (e.g. De Baets et al., 2007, De Baets et al., 2010, Geomorphology) and that fine roots are very important (Li et al., 1991) for preventing concentrated flows of water erosion.

Still, the reason why fibrous root systems seem to be more effective than tap root systems is not completely unravelled yet. Presumably, the occurrence and proportion of fine root hairs matters. With regards to the effect of tap rooted species, more research needs to be done on larger scale samples, in order to better understand and model their erosion-reducing potential.

By conducting concentrated flows of water experiments on bare and root-permeated topsoil samples (0.5 m x 0.3 m x 0.1 m), the relative loss of sediment, nutrients and water from soil plots containing a range of existing Arabidopsis root mutants (fibrous root system with root hairs, fibrous root system without root hairs, less branched tap-root like system) will be assessed.

The aim is to compare the erosion-reducing potential of root permeated soils of fibrous root systems with and without root hairs (relative to bare topsoils) and to compare and model the erosion-reducing potential of fibrous and more tap-root like Arabidopsis (relative to bare topsoils).