Use of the Chilling Requirement in the Estimation of the Effects of Warming on Shifts of Warmside Boundaries in Certain Types of Trees

抄録

A preliminary study was carried out in order to examine whether evaluations of effects of global warming on the cold requirment of certain types of trees could be of some use in predicting migration of vegetation belts or shifts of cultivation limits of fruit trees. The so called chilling requirment (CR) was chosen as an index for this purpose and the shifts of warmside boundaries of several kinds of trees are examined. Comparisions between CR and other thermal indexes such as the warmth index (WI) and the coldness index (CI) are made. In the study area, i. e., eastern and northern Japan, the correlation between CR and WI is very high so that the regions in which there are trees of a type under consideration are possible with both indexes or not possible with both indexes. It is shown that a uniform warming scenario may destroy the present CR-WI relationship. It is pointed out that flowering data suggests that the warmside boundary of Prunus yedoensis could be determined by CR. Finally, a general discussion on problems associated with use of the thermal indexes predicting the impact of warming on the distribution of vegetation or trees is given.