Seed and Seedling Demography of Four Co-Occurring Carpinus Species in a Temperate Deciduous Forest

In order to clarify regeneration traits and their fitness, we compared seed fall, seedling emergence, and first-year seedling survival of four co-occurring species, Carpinus tschonoskii, C. japonica, C. laxifiora, and C. cordata, in an old-growth temperate deciduous forest in Ogawa Forest Reserve, central Japan. Seedling emergence ratio of C. cordata (5.5%), whose seeds mostly germinated 1.5 yr after seed fall, was lower than the other species (8.5-11.2%). First-year seedlings of Carpinus tschonoskii and C. japonica had much lower survival rates (2.7%, both species) than C. laxifiora and C. cordata (7.5- 8.5%) under closed canopy, suggesting that the former two are more disturbance dependent than the latter two. They are characterized by their seed and seedling performances as seed rain type fundamentally; however, C. cordata and C. laxiflora are able to establish a seedling bank, and C. cordata has a seed bank too. These regenerative strategies partly explain the abundance and population structure of the four species in this old-growth forest. Multiple regression analyses showed that topography was important for survival of all species but C. cordata. This result was consistent with the adult distribution of these species in this forest. Wind dispersal of Carpinus is effective, both to escape from density- or distance- dependent high mortality and to increase the chance of arriving at canopy gaps, where seedling survival rate is high. However, escaping high mortality seems relatively more important for C. laxifiora and C. cordata (seedling bank strategy), and arriving at a canopy gap is relatively more important for C. tschonoskii and C. japonica (seed rain strategy).