Comparison of climatic effects on radial growth of evergreen broad‐leaved trees at their northern distribution limit and co‐dominating deciduous broad‐leaved trees and evergreen conifers

Abstract

AbstractUsing dendrochronological techniques, this study examined whether tree‐ring width of two evergreen broad‐leaved species (Cleyera japonica, Eurya japonica) at their inland northern distribution limit in central Japan is more limited by low temperature compared with two co‐dominating deciduous broad‐leaved species (Fagus japonica, Magnolia hypoleuca) and two evergreen conifer species (Chamaecyparis obtusa, Abies firma), whose distribution limits are further north. The two deciduous broad‐leaved species and the two evergreen conifers are tall tree species. Evergreen broad‐leaved Cleyera japonica is a sub‐canopy species and Eurya japonica is a small tree species. The tree‐ring widths of four of the six species (except for Eurya japonica and Magnolia hypoleuca) correlated positively with the March temperature just before the start of the growth period. For deciduous broad‐leaved Magnolia hypoleuca, the tree‐ring width was correlated positively and negatively with July temperature and precipitation, respectively. However, the other deciduous broad‐leaved Fagus japonica showed no such relationships. For the evergreen broad‐leaved Cleyera japonica and evergreen conifers Chamaecyparis obtusa and Abies firma, tree‐ring widths correlated positively with winter temperatures, probably because evergreen species can assimilate during warm winters. The tree‐ring width of Cleyera japonica also correlated positively with temperatures of many months of the growth period. By contrast, the tree‐ring width of the other evergreen broad‐leaved Eurya japonica showed no positive correlation with the temperature in any month. Most Eurya japonica trees were suppressed by tall trees, which might disguise any climate effect. Thus, there were species differences in response to climate for each life form, and the tree‐ring width of Cleyera japonica at the northern distribution limit was more limited by low temperatures compared with co‐dominating species. It is suggested that growth of Cleyera japonica is increased by global warming at the latitudinal ecotone.