Figure 4.

¹³C excess (in mg ¹³C m⁻²) after pulse-labelling in (a) aboveground plant biomass, (c) fine-root bulk biomass, (b) bulk soil and (d) the extractable organic carbon (C) pool in control (closed circles) and drought (open circles) plots; ¹³C excess in (a) followed an exponential decay function (y = a × e^(−λ*x); with a = initial pool size, λ = decay constant and x = time; control, solid line; drought, dashed line; mean residence time of ¹³C (MRT) = 1/λ). ¹³C excesses for (b) and (d) were calculated for the uppermost 10 cm of soil. Light grey lines indicate mowing, and black lines indicate rewetting. Effects of drought on ¹³C excess were analysed separately before and after cutting by two-way repeated-measures ANOVA with time and drought treatment as factors (ns, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001; for further details see Table 2).