Abstract
To examine the relative importance of genotypic and environmental effects in determining differences in life-history traits such as survival rate, plant size and fecundity within a pasture population of timothy, the tiller- and seedling-transplanting experiments were carried out in a small area (40×45m). The adjacent subpopulations of timothy were transplanted in each experiment. The survival rate and the size of plants were examined among the tiller-transplants for three years, and among the seedling-ones for two years. The results were as follows: 1. The survival rate and the plant size were different among the transplanting plots. These variations were closely related to those for grazing pressure and vegetational structure. 2. Life-history traits were different between the tiller-transplants and the seedling-ones. The plant size and the seed reproduction in first year were lower in the seedling-transplants than the tiller-ones. 3. No differences in life-history traits were found among the adjacent subpopulations in both transplanting experiments. 4. These facts suggest that environmental differences were much more important than genotypic ones in determining differences in life-history traits of timothy in this pasture.
