Intraspecific variation of acorn traits of Quercus serrata Thunb. in Kanto region, central Japan

Abstract

Acorns (nuts and cupules) of 88 Quercus serrata Thunb. individuals in central Japan were collected in 2000 and 2001, and the relationships between twelve acorn traits and several environmental factors, such as altitude, warmth index (WI), annual mean temperature and precipitation were examined. All nut traits, three cupule traits and a peduncle trait were correlated negatively with altitude and precipitation during the acorn growing season, and positively with WI and annual mean temperature. These results indicated that the higher the precipitation was and the lower the WI, the smaller were the size and volume of nuts and cupules. This suggests that the differences in the length of the acorn growing season among the sampling sites may be responsible for the trends in acorn size and volume. The acorn size traits of Q. serrata were negatively correlated with precipitation during the acorn growing season, especially within the latter part of the growing season. Thus, we conclude that acorn size of Q. serrata had some strong relationship to less precipitation in the latter part of the acorn growing season. However, it was difficult to separate the effects of precipitation from those of temperature on acorn traits in our analysis. Moreover, Q. serrata nut length was more dependent on thermal conditions than was nut width. This difference may be caused by the different developmental patterns between these two dimensions, especially after August when the width stopped increasing but the length did not.