Figure 4. Root growth observed through minirhizotron tubes.

(a) Root length production over time (m m⁻² image) of Festuca rubra (Fr) and Plantago lanceolata (Pl) in mixtures, obtained from minirhizotron observations at 10 cm depth. Solid lines are for observed values, dashed lines for expected values from monocultures (½ of monocultures). On each date, t-test were run separately to detect significant differences between observed and expected values in each species. P-values were then adjusted using the Sidak correction for multiple comparisons. After correction, * P<0.009; ** P<0.002; *** P<0.001. (b) Linear regression of expected versus observed root length of Plantago and Festuca in mixtures over the whole experiment, and null expectation expected = observed (1∶1). Significance of deviation of slopes from unity is shown by p-values. Data are means ± SE, N = 3–4.