Abstract
The changes in spatial pattern of pasture plant species and spatial relationships among them were examined for half a year after seeding in five simulated swards. A pure sward of timothy, and four mixed swards (with orchard grass, kentucky bluegrass, white clover, and all these species, respectively) were set up in a greenhouse, and two permanent quadrats (15×15cm^2) were placed in each sward (41.5×26.5×8.0cm). Spatial distribution patterns and spatial relationships among species were analysed by means of Morisita's Iδ-index and Rδ-index, respectively. The spatial pattern of broadcasting seeds of all species was random to weakly aggregated one, but that of each species was random to aggregated one. No relations in distribution among species were found in many cases. On 18 days after seeding, total germinated seeds of all species were distributed more aggregatedly and positive relations were found in several plots. Distribution of surviving plants became more random 4 months later, and little shift was observed after that. Spatial patterns were considerably different among species at the last recording date, dominant species were distributed regularly to weakly aggregatedly but suppressed species were distributed more aggregatedly. These results suggest that spatial pattern of total plants of all species in a sward becomes rapidly more random even if it was aggregated immediately after seeding, and spatial pattern of dominant species becomes more random but that of suppressed species becomes aggregatedn the process of development of dominance-suppression relationship within a sward.
