Growth and Demography of Trifolium repens Stolons in Grazed Hill Pastures

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Abstract
Elongation rates, node appearance rates and axillary bud development of T. repens stolons in hill pasture were studied for 16 mo. under 3 grazing managements, set stocked with sheep, rotationally grazed with sheep and rotationally grazed with cattle. Growth and survival of branch stolons and long-term survival of parent stolon material were also assessed. Stolon elongation was greatest under cattle grazing; this difference between managements had both a genetic and environmental compoennt. Node appearance rates, however, were similar under all managements. Stolon elongation, node appearance and axillary bud development occurred throughout the year but at varying rates depending on season. The frequency of branch and adventitious root production per node was low and not widely different between managements. Frequencies were lowest in winter and highest in the first of 2 summers studied. Few inflorescences were formed per stolon. There was considerable variation within the sample in axillary bud development and rooting frequency. On an area basis many branches are formed but their initial mortality is high. The large number of apical meristems (average .apprx. 4000 m-2) ensures the maintenance of the population despite only a low proportion of potential branches developing. Few stolon nodes or branches survived more than a year though branch stolon survival, elongation rates and node production were positively related to the occurrence of a root at the node of origin on the parent stolon. Node and branch death occurred continuously but at varying rates during the year. Knowledge of the fate of axillary buds and the demography of nodes and apical meristems of T. repens is crucial to an understanding of the dynamics of the species and allows identification of specific plant breeding objectives for the improvement of T. repens contributions in grazed pastures.