Table 1.

Fixed parameters: model parameters determining characteristics of soil, water uptake and biomass, with description, units (where relevant) and the value used in this study; these parameters are kept fixed during evolutionary simulations

Model parameter	Description*	Units	Value
dsoil	Soil depth	mm	250
cwater	The volume of water that can be held in a cubic millimetre of soil that is available for uptake by the roots	mm3	0·1
pwc	Probability of a given voxel at the top of the impermeable layer containing the entrance to a wet crack		0·005
umax	Maximum water uptake per root length	mm3 d−1 mm−1	10
etrans	Water transport efficiency of roots per cross-sectional root area	mm3 d−1 mm−2	0·002
kbm	Root biomass per volume	g mm−3	0·001
econ	Water to biomass conversion efficiency	g mm−3	0·00001
lwatervoxel	Edge length of cubic voxels used for water calculations	mm	25
tsim	Time represented in simulation, i.e. the length of the wet growing season	days	180
dwu	Implementation parameter controlling resolution of water uptake calculation	mm	0·5
Pmroot	Potential main root elongation rate	mm d−1	5

*Further details in text.