New palynological records from the Upper Cretaceous Yezo Group in the Obira and Teshionakagawa areas of northern Hokkaido provide evidence for a revision of the first appearance age of four angiosperm pollen types (triporate, tetracolporate, triprojectate and oculate) and one characteristic genus (Cranwellia). The study shows that the triporate type pollen is present from the mid Cenomanian, Cranwellia is present from the Lower Turonian, tetracolporate pollen from the mid Turonian, triprojectate pollen from the upper Coniacian and oculate pollen from the upper Campanian. These first appearance ages, which more or less correlate with similar records from China and Russia, indicate that the first appearances in eastern Asia of triprojectate pollen and of Cranwellia are considerably earlier than the records for similar pollen types in North America. This suggests that the plants which produced these pollen types may have first occurred in eastern Asia, and then gradually migrated to North America.

View full abstract

We assessed the main factors: temperature, precipitation rate, number of daylight hours and afforestation conditions, which might affect the Cupressaceae pollen count in Okayama prefecture. The Cupressaceae pollen count data were collected from four observation sites and the climate data from the two weather stations in Okayama prefecture. It was found that the Cupressaceae pollen count correlated inversely with the total precipitation in previous rainy seasons at all observation sites. Followed by the number of non-daylight hours (the total number of daylight hours is less than 0.1) from June to August in the previous year. However, the Cupressaceae pollen counts were not correlated with the temperature for the previous July. Based on our results, plus the climate characteristics and the conditions of afforestation in Okayama prefecture, it was observed that the pollen count for Cupressaceae was highest when the total precipitation during the previous rainy season was low and the number of non-daylight hours from June to August in the previous year was low in the pollen production area. The results of multiple correlation coefficient analyses indicate that predicting the pollen count for Cupressaceae can be estimated more accurately based on the data from the total precipitation of the previous rainy season and the number of non-daylight hours from June to August in the previous vear.

View full abstract

A mature community of Someiyoshino cherry (Prunus x yedoensis) was studied to ascertain the production rates of pollen, flowers and fruits. The study community, which is in Yamazaki-Shoten or Kannonji Temple (Ooyamazaki-cho, southern Kyoto), was originally planted for ornamental and recreational purposes. The number of tree trunks in the 473.2-m^2 plot is 17, and the mean trunk diameter is 33.8 cm with a range of 21-46 cm. The fall rates (in terms of number and dry weight) of flowers and fruits in the study community were measured in 1993 and 1994 using 20 litter traps, each 0.08553 m^2 (33 cm in diameter) in trap mouth area. Mean pollen yields per flower were 51.69-65.08 (mean, 58.38) x 10^3 grains and 1.084-1.341 (mean, 1.213) mg. The numerical ratio of pollen grains to an ovule (P/Ov ratio) was 25.8-32.5 x 10^3 , as there are two ovules in each flower. The dry weight of a single pollen grain was 1.67-2.66 (mean, 2.17) x 10^<-6> mg. Total number of open flowers, obtained from the fall rates of open flowers with ovaries plus fruits, were 82.088-98.620 x 10^6/ha. The number of open flowers was triple that of P. lannesiana var. speciosa. Pollen production rates, obtained by multiplying the pollen yield per flower by the number of open flowers in a 1-ha community, were estimated to be 4.24-5.76 (mean, 5.00) x 10^<12> grains/ha and 110-120 (mean, 115) kg/ha, which were several to ten times larger than that of P. lannesiana var. speciosa. When comparing pollen production in terms of grain number with other tree species, Prunus x yedoensis has a production level similar to Pinus densiflora, Abies firma, Juglans ailanthifolia, Carpinus tschonoskii, C. laxiflora and Quercus mongolica var. grosseserrata. Most fruits fell in the early stage of development in both years. Therefore, the production rates of fruit were one-fourth to one-tenth of the rates for P. lannesiana var. speciosa. The investment of photosynthates (dry matter) in sexual reproduction was 786-1,202 kg/ha, of which pollen allocation accounted for about 10%

View full abstract

The progress of the Cryptomeria japonica pollen front in 2008 was monitored by tracking the first day of pollen release using either a Durham sampler (102 sites), or an IS-Rotary sampler (14 sites) in areas geographically ranging from Kyushu to Hokkaido. In late January a Durham sampler was used to record the pollen front in Matsuyama City which faces the landward facing Sea of Japan and in early February, the pollen front in the northern part of Kyushu to the western part of Yamaguchi prefecture was observed. In mid to late February, the pollen front arrived at Kyushu, Chugoku, Shikoku, and the southern regions of the Kinki, Tokai and Kanto districts which face the Pacific Ocean. By late February to early March, the pollen front was observed in the northern Kinki and Hokuriku districts which face the Sea of Japan and also in the northern part of the Kanto areas of central Honshu. By early to mid March, the pollen front had advanced to southern and central Tohoku; subsequently reaching northern Tohoku by mid March. The pollen front finally arrived in the western part of Hokkaido by late March to early April.

View full abstract