Growth of Japanese Cedar Clone Godai1

One-year-old rooted cuttings of a Japanese cedar plus-tree clone, Godai1, were planted from March to April 2013 at nurseries in three locations, Yamagata (Higashine City, Yamagata Prefecture, Japan [38°23’53"N, 140°22’47"E]), Ibaraki (Hitachi City, Ibaraki Prefecture, Japan [36°41’28"N, 140°41’21"E]), and Kumamoto (Koshi City, Kumamoto Prefecture, Japan [32°52’53"N, 130°44’5"E]) (Fig 1A). The clone ‘Godai1’ was selected from Kimitsu, Chiba (35°13’12.0"N 140°07’48.0"E) as a first-generation plus tree. We have been studying ‘Godai1’ as a model clone of Japanese cedar [14 (link)], as it shows average growth and high rooting ability for propagation [22 ]. A total of 10, 6, and 8 rooted cuttings were planted at more than 25-cm intervals at the respective sites. No obstacles hindered sunlight from reaching the rooted cuttings at the nurseries at the three sites. Data regarding air temperature and day length at the three sites are shown in Fig 1B and 1C. Yamagata is located in northern Japan, which is a cold region with snow cover in winter; Ibaraki is located along the coast of the Pacific Ocean and has a mild climate; and Kumamoto is located in southern Japan, which has a warm climate. Throughout the year of the study, Kumamoto exhibited the highest mean air temperature and Yamagata the lowest mean air temperature among the three sites. The mean air temperature in Ibaraki was intermediate between that of Yamagata and Kumamoto. In Ibaraki, the temperature in summer (June to September) was similar to that in Yamagata, and the temperature in winter (January to March) was similar to that in Kumamoto.
A 10-cm-long apex portion of sunny upper branches (S1 Fig) was randomly collected each month from two of the planted trees at 10:00-11:00 am from February 2014 to February 2015 (S1 Table). All sampling at the three sites was performed within 7 days. Meteorological data for the sampling days are shown in S2 Table. The height of all cuttings at the three sites was also measured at each sampling time point and other times, and growth rate was calculated by dividing the height growth differential from April 2014 by the initial height in April 2014. The significance of differences in annual growth rate (growth rate from April to December 2014) among the three sites was tested using one-way analysis of variance (ANOVA).