Tiller dynamics of grazed swards.

Topics discussed in this review, mainly of the major forage grasses include tiller morphology, canopy leaf area optimization for continuously and rotationally grazed swards, and tiller population demography including its manipulation and the effects of mixed species swards. It is considered that the primary driving principle for tiller dynamics is the optimization of leaf canopy area in relation to defoliation intensity and available resources, such as light and water. The concept of a multiphase size-density compensation relationship along an environmental boundary may rationalize otherwise conflicting observations on tiller density and on tiller appearance and death rate and are relevant to issues such as carrying capacity or sustainability. There remain substantive complex differences in tillering behaviour, often unique to a particular species, which are best explained from a tiller demography basis. A well-directed understanding of tiller demography may result in significant improvements in productivity in some situations.