Relations Between Genet and Tiller Population Dynamics: Survival of Phalaris Tuberosa Tillers After Clipping

Abstract

(1) Glasshouse populations of Phalaris tuberosa were established from seed at four different genet densities, and allowed to grow until all four populations had similar tiller density. The tiller populations were then clipped at four different heights. (2) The population with highest starting density retained a higher tiller density than the other three. Its tiller survival under all clipping treatments was lower, so that the density of surviving tillers was independent of initial genet density. (3) At the three highest sowing densities, tiller survival was independent of clipping height, but at the lowest sowing density it depended strongly on clipping height, because the lowest sowing density produced a size-class distribution with fewer small and more large tillers. Small tillers survived well at all clipping heights, while large tillers survived less well and were particularly susceptible to close clipping. (4) Survival under clipping in these tiller populations can be understood in terms of their size-class distribution and their density. The genet structure of the populations had only an indirect influence, via the size-class distribution.