Latitudinal Variation in Radial Growth Phenology of Cryptomeria Japonica D. Don Trees in Japan

We investigated the latitudinal variation in radial growth phenology (onset, cessation, and duration of radial growth) of Cryptomeria japonica D. Don trees in Japan. The radial growth was observed using dendrometers in 16 stands at multiple latitudes throughout Japan. The onset of radial growth showed a clear latitudinal gradient: at high-latitude sites, C. japonica growth started later than at low-latitude sites. However, cessation of radial growth was independent of latitude. Consequently, the duration of radial growth (defined based on the onset and cessation dates) showed a weak but significant latitudinal gradient: at high-latitude sites, C. japonica trees grew for a shorter period than trees at low-latitude sites. The onset and duration of growth were respectively strongly and weakly affected by temperature, although growth cessation was not explained by temperature or precipitation. The latitudinal gradient for duration of radial growth weakly but significantly supports the hypothesis that regional variation in growth phenology is a key factor responsible for the regional variation in long-term growth. Furthermore, we found that growth duration was more variable at low latitudes than at high latitudes.