The changing plant and tiller populations of timothy and meadow fescue swards. 1. Plant survival and the pattern of tillering.
Pure swards of S48 timothy and S215 meadow fescue, grown from seed in large concrete containers out of doors, were cut (a) every 4 weeks during summer, or (b) after ear emergence followed by 2 aftermath cuts. All tillers arising within small fixed areas of the swards were labelled monthly and their life-histories were studied over 3 years. During establishment, plant numbers fell markedly in both species and both treatments until the first defoliation; after an initial increase a similar fall occurred in tiller numbers per unit area. Thereafter plant numbers declined slowly, apart from more marked falls between Apr. and June. Tiller numbers fell similarly at the same time but were almost restored by Aug. These seasonal variations depended on the balance between the appearance of new tillers and the death of old ones. During the experiment the swards, which initially contained many plants with few tillers, were changed to swards of few plants with many tillers. There was an approximate inverse relationship between numbers of tillers per plant and plant numbers per unit area. Timothy was affected more by cutting treatments than meadow fescue, but in both species there were more plants and tillers per ft2 when the swards were cut frequently. These changes are interpreted in terms of a changing pattern of competition for light within each species, imposed by cutting treatments and the incidence of flowering. F. s.-R.B.