Effects of seed size and emergence time on tree seedling establishment: importance of developmental constraints

To evaluate the importance of developmental constraints in the determinatio n of the relative importance of seed size and emergence time, early seedlin g performance of two woody species with contrasting growth phenology were o bserved under competitive conditions with tall herbs in an early succession al habitat. The oak, Quercus mongolica var. grosseserrata, with determinate shoot development (a single leaf flush), showed a marked influence of seed size on subsequent seedling height growth and survival. Because of determi nate growth, emergence time had negligible effects. The walnut, Juglans ail anthifolia, which continued to produce new leaves throughout the growing se ason (indeterminate development), showed a marked influence of time of emer gence on seedling performance, because it affected the amount of growth tha t could be achieved; seed size, however, had negligible effects as the seed lings grew. These results suggest that relative importance of seed size and emergence time for early seedling performance is closely associated with d evelopmental constraints (growth phenology).