Difference in ¹³⁷Cs in needles between main and lateral shoots of Japanese fir growing in natural forests 5 years after the Fukushima accident

ABSTRACT

Japanese fir (Abies firma Sieb. et Zucc.) usually shows a trifurcated branching form, differentiated into main and lateral shoots. We compared the radiocesium (¹³⁷Cs) concentration in needles between the terminal main shoot and two terminal lateral shoots of Japanese fir in order to examine whether the shoot position (main or lateral) affected ¹³⁷Cs concentration in needles. The ¹³⁷Cs in needles of main shoot was significantly higher than that of the two lateral shoots, suggesting that differences in shoot positions are a factor affecting the ¹³⁷Cs in needles. To examine the relationships between ¹³⁷Cs in needles and shoot morphological traits, the dry mass of needles and branches and the length of branches were measured. The main shoots had statistically significant heavier needles and branches and longer branches than lateral shoots. However, the ¹³⁷Cs in needles was not significantly correlated with the morphological traits of shoots. Our results suggest that the difference in ¹³⁷Cs in needles between main and lateral shoots cannot be attributed to the difference in shoot morphology (dry weight and branch length). We recommend that when sampling needles for the evaluation of contamination of ¹³⁷Cs, the shoot positions should be considered to eliminate ¹³⁷Cs variation arising from these traits.

KEYWORDS:

• The Fukushima Daiichi Nuclear Power Plant
• Abies firma
• shoot position
• shoot morphological differences
• intraindividual variation

Acknowledgments

We thank Prof. K. Shizuma at the Graduate School of Engineering, Hiroshima University for his support in sample measurements and data analysis. The present research was supported through the Hiroshima University Phoenix Leader Education Program for the “Renaissance from Radiation Disaster”, funded by the Ministry of Education, Culture, Sports, Science and Technology.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Hiroshima University Phoenix Leader Education Program and Ministry of Education, Culture, Sports, Science and Technology.