Understanding the relationship between tree phytolith composition and vegetation is indispensable for the reconstruction of past forest vegetation by phytolith analysis. To examine the relationship between modern tree phytolith assemblages and the compositon of lucidophyllous forests in the southern part of Miyazaki Prefecture, we studied six types of phytolith, i.e., Quercus subgen. Cyclobalanopsis type, Castanopsis type, Distylium type, Lauraceae type, Pinaceae type, and Sabiaceae type, derived from leaves of major tree species in these forests. Concentration of Quercus subgen. Cyclobalanopsis type and Castanopsis type phytoliths in modern assemblages reflected the dominance of Quercus subgen. Cyclobalanopsis and Castanopsis species in the study sites. Occurrence of Lauraceae type and Sabiaceae type phytoliths in modern assemblages corresponded to the distribution of Litsea acuminata and Meliosma rigida in the study sites, respectively. Pinaceae type phytoliths tended to appear in secondary lucidophyllous forests with Pinus trees. Distylium type phytoliths in modern assemblages concentrated highly in the study plots including those without Distylium racemosum trees. The exceptional abundance of Distylium type phytoliths in modern assemblages implied an overestimate of Distylium trees by phytolith analysis.
Recent analyses of fossil woods and fruits revealed the growth of Rhus verniciflua trees in Japan since the Early Jomon Period. Distribution of this plant around archaeological sites, however, could not be clarified with these analyses, because woods and fruits may have been brought to the sites from far away by Jomon people. Previous descriptions indicated that the pollen sculpture of Rhus verniciflua was slightly different from that of other Rhus species. To clarify the basis of distinction, the pollen sculpture of six Japanese Rhus species were studied with optical microscopy and image analysis. The results revealed that, distinct from the other species, Rhus verniciflua pollen have reticulate sculpture with lumina which are regular in shape and size. Re-identification of Rhus fossil pollen at three sites of the Early Jomon Period in Aomori Prefecture showed that Rhus verniciflua appeared at ca. 5600 yr BP with the establishment of the Castanea forest around settlements and disappeared at ca. 4500 yr BP with the elimination of the Castanea forest caused by the expansion of the Aesculus forest.