The Population Dynamics of Timothy (Phleum pratense L.) in Establishing Swards

Abstract

To study the demography of timothy (Phleum pratense L.) in the process of the various establishing swards, both the simulated swards and the monoculture swards experiments were carried out. In the simulated swards, seeds were hand-broadcasted on plastic flats (41.5×26.5×8.0cm). The monoculture, the mixed culture with orchard grass, the one with kentucky-bluegrass, the one with white clover, and the one with these three species were set up. They were grown under uncutting (control), cutting and waterlogging conditions. We observed the demography of all species, and measured the number of tillers and height of timothy plants for a half year in both experiments. The results were as follows: In the simulated swards, both the number of timothy plants and total number of plants over all species decreased rapidly during first three months in control and cutting plots, but this tendency was not conspicuous in waterlogging plots. The survivorships in the final observation decreased in the order of waterlogging, cutting, and control plots. The dominance-suppression relationships between timothy and orchard grass varied among the various environments. Timothy showed high mortality in the plots mixed with orchardgrass under control and cutting conditions, but low mortality under waterlogging one. Timothy plants increased their tiller number only by one or two in all plots, particularly almost none in cutting plots. Plant height was higher in control than in waterlogging plots. In the monoculture swards of timothy established in field, the number of plants decreased rapidly, but the mean number of tillers per plant increased continuously during the course of the experiment. The plants with many tillers and tall height had higher survival rate, more tillers and taller height than those with few tillers and short height as time passed. These results might suggest that the population dynamics of timothy in the establishing swards varied among the various environments, and that the relationships of dominance and suppression among the members in a monoculture population of timothy are established during the early growing stage.