Ryoji Hashimoto

Comparative study of leaf carbon gain in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool-temperate deciduous forest

Seasonal courses of leaf CO2 gas exchange in a growing season were examined in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool temperate deciduous forest. Between the two tree species there were no large differences in the light compensation point of leaf photosynthesis, except for the season of new leaf expansion. However, light-saturated rates of net photosynthesis were obviously high inT. dolabrata var.hondai. EvergreenT. dolabrata var.hondai saplings had large photosynthetic production in two seasons, before the emergence of new foliage and after foliage fall of the overstory deciduous trees, because of the significantly high solar radiant energy penetrating under the forest canopy during the seasons. Saplings of deciduousQ. mongolica var.grosseserrata were heavily shaded throughout the growing season by foliage of the overstory trees, which resulted in a low daily surplus production. The annual surplus production of leaves in the growing season was estimated to be 2300 mmol CO2 m−2 inT. dolabrata var.hondai and −100 mmol CO2 m−2, slightly negative, inQ. mongolica var.grosseserrata. These results supported the high survivability ofT. dolabrata var.hondai saplings and the high mortality ofQ. mongolica var.grosseserrata in the deciduous forest.

Microsatellite variation and differentiation among local populations of Castanopsis species in Japan

Microsatellite variations in Castanopsis species in Japan were examined to clarify the genetic relationships among 25 local populations according to the difference in the number of layers of adaxial epidermis in the leaves. Six microsatellite loci were assayed for 629 seedlings from the populations, and these seedlings were classified into five types according to the state of the leaf epidermis. Remarkable differences in the allele frequency of the six microsatellite loci were observed among these local populations. The coefficients of genetic differentiation, RST, of each locus ranged from 0.209 to 0.388. An unweighted pair-group method (UPGMA) phenogram constructed on the population pairwise RST over the loci revealed three clusters (A–C), and six sub-clusters. These clusters reflected the differences in the occurrence frequency of seedlings in each epidermis type within a population. Our findings suggest that clusters A and C are the local populations dominated by Castanopsis sieboldii and Castanopsis cuspidata, respectively, while local populations of cluster B are composed of the two Castanopsis species and/or include many individuals derived by hybridization. The six sub-clusters were found to reflect the geographic relationship among the populations, suggesting a different process for geographic population dynamics during the postglacial period.