Time-averaged dimensionless turbulent stresses (Eqs. (8) and (9)) as function of the volume and time-averaged Toomre parameter ⟨⟨Q⟩⟩_t. Each data point corresponds to one simulation. The black stars show the sum total of Reynolds and gravitational stress α = α_r + α_g for the hydrodynamical simulations (GI058, GI072, GI087, GI095). The corresponding contributions from the gravitational stress α_g are hown as red dots. Depicted as black diamonds and red crosses are α and α_g for the MHD simulations sg-mhd-1 and sg-mhd-2 (discussed in the following sections). In MHD cases, one has α = α_r + α_g + α_m, with Maxwell contribution α_m. The red dashed line is a guide to the eye (linear fit) for the trend in α_g.