Fig. 5. Shoot necromass above cutting height (a) and below cutting height (b) during regrowth of perennial ryegrass swards from 21 July to 15 Sept. 1997 at ambient (36 Pa) and elevated (60 Pa) pCO₂ and after an infrequent (4 cuts yr^-1) and frequent (8 cuts yr^-1) cutting treatment before the beginning of the experiment (Error bars = SE, n = 6).